Not An Audiophile – The Podcast featuring episodes with Alan March, the mastermind behind March Audio. Alan’s journey from working on jet engines at Rolls Royce to designing top-tier HiFi amplifiers and loudspeakers is nothing short of fascinating.
Podcast transcript below – Episode 003.
TRANSCRIPT
S01 EP003 Alan March & March Audio & Rolls Royce jet engines
Welcome to Not An Audiophile The Podcast. This is Episode Three
Alan March: Honestly, we’re nice.
Andrew Hutchison: well, you say that, but. Hello. Welcome to Not An Audiophile the podcast. This is Episode Three, and today we’re speaking with Alan March of Alan March Audio. He knows about amplifiers, but he also knows about jet engines. Roll tape.
Welcome to the latest episode of Not An Audiophile
Welcome to the latest episode of Not An Audiophile. Today we have the, Well, some say the amazing Alan March. maybe he is. He’s here. He’s definitely connected. Alan, how are you going?
Alan March: I’m doing very well, thank you. Andrew, how are you?
Andrew Hutchison: Good, thank you. Yeah, you sound good.
Alan and Ruth march moved to Western Australia from the UK about 12 years ago
and how’s, the weather over there? It’s probably warm, actually. Is it?
Alan March: Well, it’s. It’s actually sunny at the moment, but it has been throwing it down with rain. it’s been pretty torrid here for the past few days.
Andrew Hutchison: Okay. Because the country is supposed to be having some kind of heat wave, but it seems to be a little bit of a, you know, maybe an exaggeration. It’s warm for the time of year, there’s no doubt about it, but clearly not in Albany. So, you’re in the business of designing and manufacturing, amplifiers and loudspeakers under the brand March Audio. Now, where did you get the name from?
Alan March: it is simply my name. I couldn’t think of anything better to, call it. So we just went straight with my name.
Andrew Hutchison: Name and it works. So, I think you started five, six years ago. Along those lines, yeah.
Alan March: So, sort of potted history. I, Myself and my wife Ruth, we emigrated over to Australia from the UK about 12 years ago. so we’re poms. We’re poms, but don’t hold that against us. honestly, we’re nice.
Andrew Hutchison: well, you say that, but…..
Alan March: There are varying opinions on that. I know, in the relative forums. But…..
Andrew Hutchison: Well, I mean, we’re going to obviously get to that, but, Yeah, so you. I mean, when you moved to Western Australia, there are a lot of poms, as you describe them in Western Australia. I always feel like they came by boat and they were so sick of being at sea. They just got off at Perth, which clearly is, the first port you come to when you come from, the UK or Europe or what have you. but that wasn’t the case, clearly, in your case, did you have a bit of a thing for the west or, what was the thought process there?
Alan March: Well, it’s quite simple. my wife Ruth, she’s a civil engineer by training. So she’s she’s a very technical person and, there is an awful lot of engineering, mining engineering jobs available in Perth. And we came probably about when the mining boom was hitting its peak. And, it was very simple to get a job in Perth.
Andrew Hutchison: Yeah, okay.
Alan March: We stopped.
Andrew Hutchison: Very practical decision. Yep. And, I mean, you’ve spent some amount of time on the east coast, you’re happy with the west coast.
Alan March: yeah. back in the UK we were living, out in the rural areas. So, we were probably, you know, we probably liked the rural areas more than these big cities. So, Perth is actually quite a good, introduction to Australia, if that’s your sort of, background. And we subsequently moved further into the sticks, down in Albany. So, we’re really out in the sticks now.
Andrew Hutchison: Yes, somewhat, I suppose. But I don’t know from first hand experience, because as a typical, east coaster, I’ve never been to WA, which is really kind of embarrassing and partly laziness and also partly the fault of the airlines who make it the same price to fly to Perth as they do to fly to a number of other international locations that are seemingly more, exciting. but of course they’re not. We know Perth is great. wa is great. Everyone I know who’s been there loves it. And I know I’m sounding like an east coast tosser, but I do intend to get there one day and, you know, so twelve years ago that you moved there, but only six years ago that you started, in the audio business, specifically, or at least this particular enterprise. what did you do for the six years? Were you thinking up models or were you working as an engineer? Because you are also qualified as a…
00:05:00
Andrew Hutchison:I believe a mechanical engineer. But I, you can correct me as, as required.
Alan March: No. So my professional background, so back in the UK, I spent most of my career, working, for Rolls Royce aero engines. Ah, not the cars, because everybody thinks Rolls Royce. They think the cars. No, we’re talking about jet engines here. so I started with an electrical and electronic apprenticeship.
Andrew Hutchison: well, my mistake then. So you are more on the electrical side? Apologies. I mean, that kind of makes more sense. It’s just that, people do jump engineering areas, of expertise, I guess. So it’s not, it’s not unreasonable that you could move from mechanical to electrical, although it kind of is in some ways, since electrical is obviously much harder. But so, yeah, so electrical apprenticeship at Rolls Royce, is that right?
Alan March: Yeah. So we just saw an electrical and electronic apprenticeship. So it’s covered sort of both disciplines there.
Andrew Hutchison: Yeah.
Alan March: Okay. But you talk about the mechanical.
Alan March: ultimately, what we were doing was applying that knowledge, for the manufacturer of some of the most sophisticated mechanical, objects on the planet. Jet engines are really the state of the art in mechanical engineering. So what I ended up doing was working as what they call a measurement engineer. So when you’re designing and testing jet engines and jet engine components, you, need to, gather information about how they’re performing. a typical example.
If one of those big fan blades fell off, it would destroy the engine
So those big blades you see when you’re walking up the steps into the aircraft in front of the engine.
Andrew Hutchison: Yes.
Alan March: those compressor blades. one of the things you’ve got to do is, look at the vibration in those blades. basically, There’s a very simple truism. If it rotates, it vibrates.
Andrew Hutchison: Yes. Yes. A girl told me that once.
Alan March: So you’ve almost certainly experienced this. When your wheels on your car are out of balance, you get a vibration and it comes m through the steering wheel. and they need to be perfectly imbalanced. So anything that vibrate, rotates, it vibrates. So what happens when you get a piece of metal and you vibrate it backwards and forwards? it will start to fatigue.
Andrew Hutchison: Oh, yeah, we don’t want that.
Alan March: And ultimately, if it fatigues too much, it will actually crack and then break. And one of those big blades falling off, on a jet engine while you’re flying in the sky, will seriously spoil your day.
Andrew Hutchison: Oh, yeah. I presume the whole thing would self destruct almost immediately. Would it? Because it obviously is suddenly, dramatically out of balance, or what would actually happen other than we don’t know where the bits go, obviously, they go straight through a fuel tank, I guess, and leaving a fiery trail in the sky. But, what would happen to the turbine, etc etc, do you think?
Alan March: Well, if one of those big fan blades fell off, it would definitely destroy the engine. And it’s actually one of the tests we do to pass the certification tests.
Andrew Hutchison: Yeah.
Alan March: one of those big blades deliberately exploded off.
Andrew Hutchison: Okay.
Alan March: But with an explosive bolt when the engine’s running at full power.
Andrew Hutchison: Wow.
Alan March: And that cowling must contain the blade.
Andrew Hutchison: was that right?
Alan March: Yeah, because if it comes through the, cabin space, that’s going to be catastrophic.
Andrew Hutchison: Yeah, indeed.
Alan March: so, those cowlings are very specially designed to absorb the vibration and the shock of one of those blades falling off. and just to give you a sort of an idea of, how much energy, it’s containing, when one of those blades comes off, it’s about the same energy, that would be required to throw a family sized car 100ft in the air.
Andrew Hutchison: Okay. All right.
Alan March: That’s not.
Andrew Hutchison: So what, well, they, I guess they spin very quickly and they made out of titanium or something, or what, what material do you think it is?
Alan March: it does depend
Alan March: the, like the Rolls Royce big fan blades, they’ve got a technology where it’s a titanium composite, but the blade is hollow to reduce weight. The blade is hollow. they go into the two halves, get pushed together in a furnace and sort of gases flow through the, not molten metal, but, the softened metal and expand it out into the correct shape. there’s actually lots of videos actually on YouTube about all this sort of stuff. So if people are interested, they can certainly go and see that.
Andrew Hutchison: I mean, it is as you said, it’s absolutely at the high end of human endeavour, isn’t it, really?
Alan March: Yeah,
00:10:00
Alan March: I actually believe it’s more sophisticated and higher technology than sort of space technology, because what these engines are doing, they rely, they’re running reliably you know, probably 18 hours a day, every day. and they mustn’t go wrong. No, the technology has got to that state now. where you’ve got turbine blades operating in an environment that’s hotter than the melting point of the metal, which.
Andrew Hutchison: Kind of doesn’t initially make sense, but. Yeah. Yeah.
Alan March: Okay, well, the only reason they don’t melt is the turbine blades have these tiny, thousands of tiny holes drilled in the edge of, of the blade.
Andrew Hutchison: Okay.
Alan March: And, hot gas, although it’s a lot, it’s cool, it’s cooler than the turbine temperature, but it’s, one of the compressors on the front of the engine, it’s still quite hot. It’s several hundred degrees still. It’s flowed through the blade and it puts a film of gas over the surface of the blade to protect it from the very high temperatures.
Andrew Hutchison: okay, so it really is, it.
Alan March: Really is incredible technology.
Andrew Hutchison: yeah, it’s breathtaking because, and it does make you wonder about the slow development of other areas of R and D or you know engineering, electrical, mechanical or otherwise. in some ways. You know like there’s people always offer up the example of the cardinal versus you know, aviation. If cars had increased in performance at the rate aircraft have over the last hundred years they’d obviously well they’d do a thousand miles an hour and wouldn’t use any fuel doing it because you know clearly aircraft have come so far and really the jet engine has been around for what, 70 years or something like that. Is that approximately right?
Alan March: Yeah, approximately. Yeah. Frank Whittle designed it, end of the war. So yeah it’s just got to be. Yeah, it’s got to be about, it’s got to be in that region 70, 80 years.
Andrew Hutchison: Yeah it’s progressed some in that time. And I guess part of this care, this high level of exceptionally high level of engineering is about efficiencies and because obviously from the seventies, the Boeing jets of the seventies, I mean they left this nasty black trail across the sky when they were getting airborne. yeah.
Alan March: Changed quite a bit. if you notice on those old jets they are what they call a turbo jet. So they’re not actually very wide.
Andrew Hutchison: Yeah.
Alan March: so no they were quite long.
Andrew Hutchison: And skinny I guess, versus the current.
Alan March: There’s two fundamental different type wires. There’s three, there’s more than one? Two. But two major types of jet engine. A turbojet and a turbofan. So a turbojet, most of the air goes through the core of the engine.
Most people don’t understand how jet engines actually make it go along
but as you see on, on modern engines they have that massive fan at the front.
Andrew Hutchison: Yeah.
Alan March: And if you stop to look on steps and you look through you can actually see all the way through the back of the engine. That’s because the fan is blowing it would destroy the engine, a lot of the air around the Ah, engine. so that has a
multitude of advantages. so two song concept. Most people don’t understand how jet engines actually make it go along. so if I said to you, if you could complete this sentence, every action has an equal and.
Andrew Hutchison: Opposite reaction or reaction.
Alan March: Reaction.
Andrew Hutchison: Yep.
Alan March: So jet engines work on the simple principle. If you move a ton of air backwards.
Andrew Hutchison: Yes.
Alan March: Out the back of the engine you will get a ton of thrust forwards. And that’s what pushes the engine along. The aircraft along.
Andrew Hutchison: Yep.
Alan March: It will work. Yeah. People have strange concepts about how it’s pushing against something but it’s not, it’s just simply react reactive force.
Andrew Hutchison: Yeah.
Alan March: So turbojet moves a smaller amount of air more quickly and that can be noisy. and not ah, not as efficient.
Andrew Hutchison: Yeah.
Alan March: but it’s better if you want to go fast. So you’ll still see turbo jets in more military applications these days.
Andrew Hutchison: Okay. So yeah, so is this.
Alan March: They need to go flat.
Andrew Hutchison: Yeah. Sorry, I didn’t mean to cut you off. turbo fan then, which is the modern engine for passenger civil engines is.
Alan March: Moving larger amounts of air more slowly.
Andrew Hutchison: Okay. And so is that.
Alan March: So it’s the mass of the air you move. That is the thrust.
Andrew Hutchison: And this, and this of course is this. All this is
00:15:00
Andrew Hutchison: relevant regarding your amplifier designs but we’ll come back to that. your jet powered amplifiers, the
So is this, do you think a limitation of why we’re not flying at MK II
So is this, do you think a limitation of why we’re not flying around at MK II or something? Is it because other than the airframe obviously is not appropriate for that speed, but Is it because of the jet? The sweet spot for those jet engines is at mach 0.75 or eight or whatever we travel at normally, whatever they cruise at. Is that, yeah. that’s part of the engines are part of that reason or equation?
Alan March: Yeah. It’s primarily cost.
Andrew Hutchison: Yep. Cost of.
Alan March: You want to go back to cost of fuel. And just the cost of the technology involved.
Andrew Hutchison: Yeah. Okay.
Alan March: So I mean I worked on Concorde.
Andrew Hutchison: Oh did you, you just dropped that into the conversation there as if everyone has had a crack at working on a Concorde. But so of course there’s a whole podcast right there.
Alan March: I guess so, yeah, it is, it’s a fascinating subject. So my involvement, I’m old, but I’m not quite old enough to have worked on it, Through development. But I worked on it after the crash in France.
Andrew Hutchison: Okay.
Alan March: So yeah we could, we could leave that for another one because that’s…
Andrew Hutchison: We don’t have to leave it, but yeah, I will only because I think I mean clearly we’re going to speak to you more than once at the podcast here. Podcast being Not An Audiophile. Details available at Not An Audiophile.com. and by the time this is up, available on iTunes and YouTube. I think that was an ad. so….
One of the things that appeals greatly to me about jet engines is quality control
look, this is all very impressive and very interesting and you have a skill at explaining these things in such a way that someone who knows nothing about jet engines, such as myself has half an idea, or at least I think I do, how they might work. but yeah, people don’t get exposed.
Alan March: To it, that’s why. And technology and what happens with jet engines and you know we all get on aircraft but we don’t think much about it unless there’s some horrible bangs and crashes that scare you to death. So It’s one of the things that I can absolutely assure people is the amount of quality control. I won’t speak for Boeing at the moment, but certainly the quality control of the engine builder of the engine of Rolls Royce for example.
Alan March: Ah, it was extreme. It was absolutely extreme. ah, I mean the engines are hand built, and someone doing up bolts on the engine would have someone following behind them, inspecting it. That sort of thing is going on. Every instrument you use to measure anything is calibrated, it’s traceable back to national standards and if it, then when it goes to get recalibrated it fails. There has to be a whole investigation about what that instrument was used on and could it affect product quality and so on and so forth. So That’s ah, something I’ve taken. That sort of attitude to quality control is something I have taken through into this business.
Andrew Hutchison: which leads us completely full circle, Let’s go back to jets for a second. But we will come back to amplifiers, a quick break before we do. But Yeah, that level of quality control which appeals greatly to me but I guess it comes at a cost. There’s a lot of effort put into that aspect of it and that’s one reason why the engines are expensive, I guess.
Rolls Royce has two divisions: civil and military. So, um, the civil is based in Derby
I’m also impressed by the cost of a bolt and things like that. I mean have you got any I mean I was speaking to a gentleman came in the shop with, with a repair or something and he was working out at the airport. We were not far from the airport, for Qantas I think, in their maintenance. Assuming Qantas still has a maintenance division. Haha. yeah he was giving me some examples of fastener prices and $120 for a bolt or something like that and it wasn’t a very big one. you probably have some staggering examples of parts prices. Yeah, you probably don’t know the price exactly, but the talk around the hangar kind of thing. Oh, well, of course you probably did. You work in hangers Rolls Royce, have a facility at an airport or you’re all working off, you know, somewhere.
Alan March: Well, so Rolls Royce has two divisions. the civil aircraft we all fly on to go on holiday. And the military aircraft. Military, engines. So, the civil is based in Derby in the UK. And the, military is based in Bristol, which is where I’m from. So I actually spent most of my time working on the military side of things. but I wasn’t what they called the off site measurement team for many years. we were the ones that were sent off to Timbuktu when something didn’t work. or you had to do some testing, of an engine, maybe at a customer site. So it could be, a Royal Air force site that using
00:20:00
Alan March: our engines, a lot of the american, the American Navy used to use, a lot of, Rolls Royce engines. they use the T 45 aircraft, for training. And before the F35 came along they used to use Harrier jump jets, which is another Rolls Royce engine. one should hope that it would.
Andrew Hutchison: Have a Rolls Royce.
Alan March: Surely a program. Yeah, they used to love the things. and that’s another story. But the Harrow jump jet is much better than the F35. we won’t go into at the moment.
Andrew Hutchison: We will. We’ll add that to the list. So, ah, we’ve got, Concord and we’ve got the Harrier jump for future episodes. Even though this is apparently an audio related podcast. Audio is so incredibly dull and uninteresting compared with what we’ve just spoken about, though. But, a little bit more real world, we’ll get to the relevance. Well, the real, the reality is that, none of us are going to have a harrier in our backyard, nor be capable of flying it or maintaining it. So, whereas an audio system, we can probably manage that. we’re gonna have a quick break. We’re gonna have a quick break and we’re gonna come back and talk about amplifiers. Is that all right?
Alan March: Okay. Absolutely.
Andrew Hutchison: All right. Thank you, folks. See you soon. Dellichord loudspeakers. An Australia made product designed here, manufactured here, sold worldwide, sold around Australia through various dealers, but also on display coming up at the australian HiFi show in Melbourne early to mid October. See us there. Have a chat, have a listen. in the meantime, check out delacord.com dot au. Back to the show.
Alan March was a measurement engineer before getting into amplifiers
Hello, folks. We’re back at Not An Audiophile, the, podcast about, jets and other interesting stuff and sometimes audio gear. we have Alan March from, he’s, calling in from his hq in Albany, Western Australia. Western Australia being in the western part of Australia, Australia being, in the lower hemisphere of the world. So, amplifiers of all this knowledge of testing, measuring jet engines. And you’ve applied, I guess from what you implied, you’ve applied, some of that, quality control, if you like, to your own product. But, how did you get into amplifiers? What drove you there?
Alan March: Well, I’ll explain. I’ll explain the relevance of my, previous professional background to all the electronics because people are going, what on earth have jet engines got to do with audio electronics? As I mentioned earlier, my role was a measurement engineer. So what we would need to do is, test, when you’re testing components and engines, you need to measure how they’re performing, how they’re vibrating, what pressures, what temperatures are happening. and these could be using pressure transducers, strain gauges, vibration transducers and all sorts of other different measurement measurement techniques, including x ray. We even use x ray engines.
Andrew Hutchison: did you have a, like a wooden school ruler? Did you,
Alan March: Yeah, you had a wooden school.
Andrew Hutchison: Absolutely. Keep going.
Alan March: fully calibrated, of course.
Andrew Hutchison: A calibrated one. The expensive version.
Alan March: So the, the electronics and, recording systems that we use to record those information, it’s all, it’s all a small electrical signals, that aren’t dissimilar to, audio signals, electrical signals that we have in our domestic HiFi’s. In fact, there’s no real differentiation apart from it’s not music.
Andrew Hutchison: no, I suppose not.
Alan March: yes, I mean, like strain gauges for recording the strain in a component m when an engine’s running. I mean, you can actually get strain gauge cartridges for turntables.
Andrew Hutchison: Okay?
Alan March: So they use that. They use that technique instead of moving a magnet or moving a coil.
Andrew Hutchison: Okay.
Alan March: Just, they flex a stringage.
Andrew Hutchison: As someone who works on turntables a lot, I’m not. Excuse my ignorance, because I’m clearly very ignorant. So, I’ve vaguely heard of that, but what do you see? You fit this particular cartridge instead of a normal magnetic cartridge or whatever, and you measure what with it and how.
Alan March: Just as a side, a strain gauge measures how much flex there is on a jedge, typically a metal component, how much it flexes and moves. so you can apply that technology into an audio cartridge. So, the stylus m. makes a piece of metal with a strain gauge flex on it.
Andrew Hutchison: Yeah.
Alan March: Well, it doesn’t have to be. It doesn’t have to be metal. It could be some other relevant material.
Andrew Hutchison: Yeah.
Alan March: And and it causes a resistance change in in the strain gauge. Because all a strain gauge is is
00:25:00
Alan March: a resistor.
Andrew Hutchison: Yeah.
Alan March: On a sort of plastic sheet.
Andrew Hutchison: Yes.
Alan March: Flexible plastic sheet. so that varying resistance gets changed into a varying voltage or current. and, hey, presto. You can get with us with a suitable amp amplifier, you can get a, your audio signal at the other end. So, basically, the point I’m making is that everything we were doing was no different to audio electronics.
Andrew Hutchison: No. By the sound of it.
Alan March: Yeah. We even used to use, real to reel analog tape recorders to record vibration.
Andrew Hutchison: Okay.
Alan March: Because they’re almost literally audio frequency signals. Maybe up to 80 khz. and we used to use 28 track. well, they were developed from, audio tech recorders.
Andrew Hutchison: Yeah. Yeah. Okay.
Alan March: We subsequently moved to digital, but the digital acquisition systems are, again, no different to any digital, audio acquisition system. They’re identical.
Andrew Hutchison: Yes.
Alan March: So all these signals are coming out of an engine, out of a test bed. And they have to be. They call signal conditioned, may be amplified, may be filtered. and you have a really important thing going back to the quality control. You have to make sure that the data you’re recording is absolutely accurate. Because that data goes back into the engine design.
Andrew Hutchison: Yeah.
Alan March: If you screwed something up and you’re measuring, I don’t know, 20 kilopascals instead of and m. It’s actually really, 25.
Andrew Hutchison: Yes.
Alan March: the ultimate conclusion is that something serious could happen in flight.
Andrew Hutchison: Yes.
Alan March: Because they might change based on that. They think, oh, that’s okay. That’s that pressure is okay. Yeah.
Andrew Hutchison: Yeah.
Alan March: So the quality control. So what we’re doing is sort of, like a. Like a studio recording engineer, but with much greater discipline.
Andrew Hutchison: Well, yeah.
Alan March: It’s not to get night. It’s not to get an artistic effect where you can do anything you like. You can add distortion. You can add echo and all stuff like that. It’s just to make it absolutely accurate.
Andrew Hutchison: Which is, a skill.
You used to test blades with vibration as part of your measurement work
Because, getting fake measurements out of things or not measuring something in the correct way or using the correct technique can, of course, throw up some, sort of useless data, I guess. it’s a number, but it’s as you say, you’ve got to make sure it’s the right number, and it’s consistent and so, yes, I mean, hence you were busy with that. And how many years did you do that for by the way? That measurement, roles probably a good.
Alan March: Yeah, I worked at rolls for properly about 18 years.
Andrew Hutchison: Wow. Okay. You must be older than. Yeah, you must be older than your look.
Alan March: Hey, yeah, I’m in my fifties so. Yeah, getting there.
Andrew Hutchison: Well preserved. It’s that it’s that dim, rarely seen english sun. I guess that hasn’t worn you out.
Alan March: Yeah. In measurement engineering itself, probably about twelve years, I’d have said.
Andrew Hutchison: Yeah.
Alan March: Another thing we used to. Another thing we used to. As part of the test system, I mentioned about testing blades with vibration.
Andrew Hutchison: Yes.
Alan March: we used to use these shakers that were powered, these massive shakers that would shake engine blades and you’d put strain gauges all over them and measure the stress and strain in the blades to make sure they’re not going to fail in service. But we’d be using audio amplifiers to, to shake them to drive the shakers.
Andrew Hutchison: Yeah. Right. Yeah, yeah, yeah. So you were. Yeah. You imagine you’re not, you’re not buzzing them at particularly high frequencies then, or I guess you sort of do a sweep and try to find the resonances or something and really, then really nail them.
Alan March: Yeah, that’s absolutely correct. so every object has a natural frequency. If you say flicker a wine glass with your finger, you’ll get a ding and it will resonate at a certain frequency. Ah, a jet engine blade is exactly the same.
Andrew Hutchison: Yeah.
Alan March: You flick it, it will vibrate at a certain frequency. And so you want to make sure that the end. That the. Either, The blade. The blade is designed such that it doesn’t vibrate significantly at the wrong frequencies.
Andrew Hutchison: Yeah. Within the operating range.
Alan March: range, range of the aircraft. Yeah, absolutely. So, So, yeah, and then we shake them and heat them up to the relevant temperatures with induction heaters. And you’d vibrate them. So, yeah, I used to, I used to look after repairing and very large high power, audio amplifiers. I mean we’re talking about 510 kilowatt amplifiers to drive these shakers.
Andrew Hutchison: Yeah. So they’re probably all gone class D now, I suppose. Have they?
Alan March: Well, believe it or not, we were still. You when I was there, we were still using some valve amps to do it.
00:30:00
Andrew Hutchison: Always that, right.
Alan March: These things were massive. They were, you know, they were, they were. Ah, they’re absolutely massive.
Andrew Hutchison: What? shoot, like some kind of broadcast transmitting tube or something. What,
Alan March: I can’t remember what it was, but I mean the met, the main tube tubes in that, in the amp, I’m thinking of, They were probably about 100 cm across. Yeah, sorry.
Andrew Hutchison: A hundred centimeters. A meter across.
Alan March: I’m probably about. Probably about 300 mm tall.
Andrew Hutchison: That’s a serious tube. Yeah. Okay.
Alan March: It’s a big cheap.
Andrew Hutchison: Yeah, yeah.
You spent some of your earnings on audio equipment at Rolls Royce
All right. I think I knew the three digit code for that tube once, but my memory is, not what it once was. But yeah, I did. There was a seat, there was a design or two out there with a single ended, a single ended amp out there with, with one big sort of transmitting tube in it which is possibly similar to that. All the same. They’re impressive, but most to look at.
Alan March: Most of those amplifiers. Yeah, most of those amplifiers were For those who are familiar, they just. They had 102 n 3055.
Andrew Hutchison: Oh, yeah.
Alan March: Power transfer, power transistors on the output. They were a horrible design because they. Each one had a fuse and if one of them failed, it would trip the amplifier and then you had to go and find the right one that had failed.
Andrew Hutchison: Oh dear. Oh dear. Yeah. Okay. Each, each output device had a fuse.
Alan March: Yes. Yeah. They were just literally parallel. They were paralleled up.
Andrew Hutchison: Yeah. Wow. Okay.
Alan March: And if they go, and if they go, they’ve been driven hard. And if they go short circuit, then you put very High voltage onto your shaker. So that’s not great.
Andrew Hutchison: Not great. And So yeah, two and three or double five, is the, is the workhorse of to three, you know, power transistors has been for, well, my whole career. I guess it was invented late seventies or something like that. Maybe before that, maybe mid seventies. So maybe this gear was built in the seventies anyhow, by the sound of it.
Alan March: Well, it was, it was old stuff. Yeah, yeah.
Andrew Hutchison: Yeah.
Alan March: Very expensive stuff and a lot of, a lot of. Because a lot of the stuff you couldn’t buy off the shelf. Rolls Royce had its own electronics design department that would build field specialist stuff because you just couldn’t buy it, where needed.
Andrew Hutchison: Yeah, well, indeed. I mean if you need a 10,000 what amplifier. There’s not, there’s a limited amount that you can buy. So, Wow. Okay, I’ve only got. All I’ve got is. Wow.
Andrew Hutchison: So just stepping sideways then. So you. I’m a little. The bit that we’ve left out is this is the step wherever you. I mean, I assume you spent some of your earnings, at Rolls Royce on audio equipment. Is that, what happened?
Alan March: Of course, of course, yes. I mean, I’ve been. I’ve been in, an audio file maybe, not a traditional audio file, but I’ve been.
Andrew Hutchison: You realize, just before you go any further. Sorry, before you go any further, to be on this broadcast, you need to be not. So you were, but you’re not anymore. Okay.
You were interested in audio electronics and music from the age of ten
Now, okay, so you were enthusiast. And you. So you had. What did you have? A hell of a lot. You had a lynn names, name system. Right. Of course.
Alan March: No, I did, I did, I did probably everything that everybody else has done. with. With audio electronics. you know, I was interested in audio electronics and music from the age of about ten onwards. Wow.
Andrew Hutchison: So you go way back soon.
Alan March: Yeah, so as soon as I started earning money, then. Then I started buying HiFi.
Alan March: So let me think. I mean, I had. I’ve gone through Nene gear, Meridian gear.
Andrew Hutchison: Yep.
Alan March: I mean, I started off with. With nad. I had a 30 20. Everybody had one of those.
Andrew Hutchison: Yeah. Yeah. Except me.
Andrew Hutchison: But I mean, you know, they. They were a charmer. There’s no doubt about it. You know, they were, a charmer and they were a bargain, you know. So,
Alan March: Yeah, built.
Andrew Hutchison: Built a reputation on one model. So, Yeah. Yeah.
Alan March: Ah, I had one of those very early Phillips CD players.
Andrew Hutchison: Yes. Oh, the vertical, aligned CD.
Alan March: It was. It 104. I can’t remember. M. It’s a very long time ago. That’s 40 years ago.
Andrew Hutchison: Oh, yeah. What do you mean? You haven’t got it anymore?
Alan March: No. No.
Andrew Hutchison: Okay, so you’ve.
Alan March: Actually, the kit I kept for a very long time was, I eventually got a tag McLaren Av system.
Andrew Hutchison: Okay. Right here. Yeah.
Alan March: And, That, That kept me very happy for a very long time. I mean, I went through all. Yeah, I went through all sorts of different speakers. Stoners, faber, you know, BMW also. Yeah. Lots of different things that cafs. Yeah. But yeah, I was, you know, I was serial upgrader at that point.
Andrew Hutchison: You know, Philip Swift and his partner at audio Lab would be very impressed with hearing
00:35:00
Andrew Hutchison: you say that because I’m, pretty sure the tag McLaren was. was a spin off of audio lab. The original audio lab. Yeah. you know, the various amplifier designs got rolled into the tag McLaren gear.
Alan March: That’s correct. Yeah. They, Basically, tag, McLaren decided they want to get into high end audio for some reason. Some,
Andrew Hutchison: Unusual reason. Yeah.
Alan March: Well, tag McLaren had fingers in all sorts of pies from aviation to, obviously, watches. And, you know, it’s sort of high end, esoteric stuff. so they started by, they started by buying audio lab. they then, as you say, updated the designs and brought out their av processor. that was a truly what I would call a HiFi av processor because most of them these days aren’t actually very HiFi at all.
Andrew Hutchison: no, they are not.
IAG bought, bought all the, all the designs and rights and everything
Alan March: you could you. I wouldn’t use any of them for music these days. but that tag McLaren really was high, quality for audio as well as the home theater. Yeah. And then eventually, I think the story basically is they weren’t selling at a high enough price. They were only making, they were doing high end stuff and making very little money on it. And, that, finished them off in the end.
Andrew Hutchison: That was that. Yeah. I don’t know how, whether it ended badly or they just made a decision to sell out of it, I don’t know that obviously IAG bought, bought it at auction or something, as they, as IAg tends to do, but.
Alan March: That’s right, yeah. IAG bought, bought all the, all the designs and the rights and everything and rolled them into their products.
Andrew Hutchison: Yes.
Alan March: So the loop goes around.
Andrew Hutchison: Yes, it does. it travels, to the other side of the planet and starts again. So, yeah, great. A great, I mean, I, you know, I mean, you’ve mentioned mostly what were effectively local products for yourself and. But what great local products. I mean, it was, ah, I mean, England is a great place to have an interest in HiFi because, you almost, you don’t need to, buy outside of the country, really. So much good stuff still made there, even today. Really. Perhaps not as much as there was then. So, yeah, just take, take a bit.
Alan March: Of a dive now. But, Yeah, certainly was when I was younger.
Andrew Hutchison: Yeah, it was in its heyday, I guess.
So you’ve clearly got an interest in audio and manufacturing
So you’re interested in. So you’ve clearly got an interest in audio and you have had since, the age of ten, approximately. But, what about the interest in manufacturing? Does that come from seeing it happen at Rolls Royce? Is that sort of what tweaked your interest there? Or is it just, you just wanted to create something or what, what were you, what were your thoughts there?
Alan March: Well, yeah, I mean, from a personal perspective, I love building shit. It’s, I just, you know, I’ve always say it’s not just audio, it’s audio electronics. So I’ve been interested in electronics in general. You know, I threw it through, for decades. I was playing with electronics and building my own things and done a few speakers and things.
Alan March: So yeah, the actual creative process, I love the design work. I’ve been sat this morning doing pcb design work. And it’s, I find just fine. I just love doing it. And then you see a product coming out the end of it and people like. And people like it.
Andrew Hutchison: Yes.
Alan March: It’s fantastic.
Andrew Hutchison: Yeah.
Alan March: So I wouldn’t say I’m actually, I wouldn’t say I’m actually interested so much in the manufacturing process.
Andrew Hutchison: Yeah. As the design part and development part perhaps.
Alan March: Correct. Yeah.
Andrew Hutchison: Yeah.
Alan March: That’s what’s, what my real passion is, should we say.
Andrew Hutchison: Hmm? Yeah. Well clearly. So. I mean your product looks fantastic. It’s Certainly sensibly priced. It performs extremely well. At the amplifiers I’m referring to. No, I mean it does, it’s well regarded. In fact, the amplifiers have been around for quite a while, as we said, like five or six years or something like that. But In more recent times you went off sideways, as we all do at some point in our life, and built some speakers. Do you want us to tell, do you want to, Because what I. The difference between your loudspeaker and say, the one that we do here at Dellichordt or you know, Sir Hannah Swift or proactor spendor or you know, or any, is that you’ve got these these drive units with the broken surrounds and that’s, that’s the difference. Right. So, and I suppose that product came out and you went oh, I could build a speaker out of that. That would have solve, would solve a problem. In fact, tell us why those drive units have the weird looking surrounds. Because I’m pretty sure there’s a good engineering reason for it.
Alan March: It is, it is a very good engineering.
00:40:00
Alan March: So we’re referring to the purify, Drivers. So that crinkly looking surround is. There’s a very good reason for it. The, if you think about a normal hat, what they call a half roll surround, sort of the semicircle surrounds that you get on most to most drivers. What happens when the cone moves backwards and forwards is that that cone deforms and it changes shape.
Andrew Hutchison: Okay.
Alan March: What it’s actually also doing is not just changing shape, it’s actually changing the surface area of The driver.
Andrew Hutchison: Surround is changing shape. Or the cone or both is changing shape. You said the cone is changing shape, which, which it probably is. But did you mean the surround or you mean the whole combination, the surround cone combo? Yeah.
Alan March: The surround is changing.
Andrew Hutchison: Yeah. Okay.
Alan March: The cone does. We won’t go into the modes in the cone as well.
Andrew Hutchison: Yeah.
The surround is changing shape to some subtle degree as well
But clearly it’s changing shape to some subtle degree as well. No doubt. But Yeah. Okay. So the surround is. Well it’s clearly changing shape. Yes. As the cone. I mean obviously on bass frequencies the cone is excursioning a decent distance, say plus or minus a few millimeters, Or more. And So yeah, the half round, surround is Stretching effectively, I suppose. correct.
Alan March: And that leads to the surface area, the radiating surface area of the, of the entire driver cone and surround because it’s all radiating sound.
Andrew Hutchison: Yes.
Alan March: Changing. And that change in surface area leads to distortion.
Alan March: There’s a distortion mechanism there. So what purifying did, it’s a spectacularly simple idea is that they designed the surround so half of it sticks out and half of it sticks in.
Andrew Hutchison: Ah. yes. Yeah, that makes sense now that I think of it. Yes, yes. In what, half a dozen segments or something like that. Or four.
Alan March: Oh, I’d have to, I don’t know. I’d have to. I’ve got one, I’ve got one over here. I’m just gonna buzz over and have a look. 1234 sticking out and four sticking in.
Andrew Hutchison: There you go. Okay. Yep. So. And that one balances the other something.
Alan March: Correct. So the surface area remains the same wherever it is on the travel of the, of the cone. Second thing it does is it keeps the restoring force on the cone equal. Consistent wherever, consistent wherever it is on the travel of The tent.
Andrew Hutchison: Yeah. That, that makes.
Alan March: With the house.
Andrew Hutchison: Yep.
Alan March: With a half roll, it’s. The restoring forces is very different from, from just maybe a millimeter to say 5 mm.
Andrew Hutchison: Yeah.
Alan March: And it will be different whether it’s going in or going out as well because of the nature of the shape.
Andrew Hutchison: Yeah, yeah. The, although they, they say, they say, whoever they are, that most of the stiffness of the suspension is down to the spider. Is it different with these drive units? Maybe the spider is somewhat more compliant. The surround takes more of that role on due to its complexity or something. Or do you, what, do you have any thoughts on that or is that not something? Well, you don’t need to concern yourself with to some degree.
Alan March: that’s actually a very good point because They, I mean purify, you know, what they do is they’re a technology company. They’re there sort of intellectual property. they don’t want to build stuff. They don’t want to build amplifiers. They don’t want to build speakers. they develop technology for us oems to implement. So, they don’t tell us. They don’t tell us everything about how it works. They’ll give you a good idea. So I couldn’t tell you the, relative merits of the, of, the surround versus the spider, in terms of talking here. I mean, Lars is very helpful from purify. He might. If I went and asked him, he might tell me, but it’s not something I’m. I bothered to investigate. Because it works?
Andrew Hutchison: Because it. Well, yeah. And I mean, you’re only really interested in how it works as a whole, really. It’s. Yes. Yes. But, it is. It is quite a different drive unit design because of the complexity of the surround, I guess, which surrounds. I don’t know if they’re an afterthought, but I don’t think they really are. But I mean, they are. Ah, they have. We talk about the change in aviation versus the lack of change in other areas. I mean, roll surrounds really changed once only until these weird looking ones that you’re using. probably ever when they went from some kind of ribbed fabrics around to a more compliant rubber, or foam half roll surround. But,
Alan March: Yeah, and this is what, this is what purify did.
Will: It’s polarizing. I mean, the looks, the aesthetic is somewhat polarizing
When they decided they were going to make, drivers, they just sat back and said like, well, okay, what are the problems?
Andrew Hutchison: Yes.
Alan March: Ah, they identified a number of specific
00:45:00
Alan March: problems that traditional, drivers suffer from and set about trying to solve those problems.
Andrew Hutchison: Yeah, well, they, you know, they did. They’ve, they’ve no doubt achieved it. I mean, the looks, the aesthetic is somewhat polarizing, I guess. I mean, it’s interesting for technical types. I, sometimes wonder whether the lady of the house is attracted to that slightly, insect like around. I mean, in the sense it looks a little bit like a centipede or something crawling around the perimeter of your driver. it’s not that I’ve seen it.
Alan March: I’ve, I’ve seen it likened to, Some, chinese dumplings.
Andrew Hutchison: yeah, there is a bit of that too. Yeah. Yeah. So,
Alan March: we do, we do grill to cover it up if people feel they.
Andrew Hutchison: Can’T deal with it.
Alan March: When we do HiFi shows, people, come up to me literally every five minutes. They wander in the room and go, oh, they either go, your speaker’s broken, or, What’s it all about. And We have to explain it. We do it very patiently. We have to explain it probably about 100 times a day.
Andrew Hutchison: Well, not now. Because this wide ranging broadcast that everyone. And everyone with an interest in the audio was listening to. Will. They’ve now had it explained to them. So you’ll no longer receive that question. yeah, it’s. I suppose if we just talk on the speakers for a second. And why not? although we will once again take a brief break in a second.
Baffle diffraction related issues, I guess. And you’ve addressed them as realistically as you can
But, The highly radiused, edges. Is that something you’ve. I mean, because this. There’s. Well, there’s not two schools, I thought. I mean, in reality, it must assist with. Ah. Baffle diffraction related issues, I guess. But is that. Is that a. Is that what you’re trying to deal with by going for quite a. Probably, what? A 25 mil radius on the box or something?
Alan March: Yeah. Absolutely. Absolutely. Spot on. It never ceases to amaze me how many speakers are still using, Sharp edges on the corners. It’s a very well known issue that, As the pressure wave radiates, along the baffle, from the driver. That if you hit a sharp edge, you’ll get this diffraction effect. And Really it needs a Video or some drawings to explain it. but basically the sound wave, how shall I say it sort of breaks off that corner at that sharp edge. And you get Constructive and destructive pressure, waves mixing with the. With the main sound coming from the main cone. So you’ll get. As you move around the speaker, you’ll get. You’ll get peaks. And you’ll get Dips in the amplitude of the sound. So yeah, if you’re at a particular angle, you might get a peak. And if you’re another particular angle, you’ll get a. You’ll get a. You’ll get a dip. So, the radius helps mitigate that. It won’t solve it completely. you actually need a much larger radius than that to really solve the problem. yeah, but that combined with the wave guide, the, waveguide on the tweeter does significantly help the issue.
Andrew Hutchison: Yeah. And I think. Look, certainly from a theoretical point of view, I absolutely and utterly agree with your, I mean, with your design process. I mean, there are issues with that. And you’ve addressed them as realistically as you can. Because obviously, You know, it’s impractical to have a hundred mil radius or something on the edge of the baffle. But, But, You say, you know, why do manufacturers still make pointy edge boxes and, and, you know, don’t attempt to deal with, deal with that. Is that, that’s what people want is.
Alan March: I was just about.
Andrew Hutchison: Some people just. They would, they’d like.
Alan March: Yeah. You know, they, as a manufacturer, you can’t necessarily do what technically is, is, is correct because it is aesthetically too radical.
Andrew Hutchison: Yeah. It’s a weird thing that, the same could be said. The analogy could be made for cars and other things, I think, where, I mean, if you think about cars for a second, an ideally slippery, aerodynamic shape, like one that really is good, built a little bit like a light plane, nice and narrow. people just don’t want, they would never buy it. You know, like it’s, it’s absolutely.
Alan March: All the concept car the, the manufacturers make before they bring a concept into manufacture. It gets toned down so much from what the concept, the concept of. Wow, look at, that’s amazing.
00:50:00
Alan March: Futuristic. And then it comes out looking like, a trabant or something. You know.
Andrew Hutchison: Maybe not that bad, but, yeah, I mean, it’s, you know, we, I’ve run, what would you call it, you know, what the film producing people do where they get a room full of people and, maybe play them the end of the film or part of the film and ask questions and trying to form a. I mean, it’s a terrible way to make a movie, of course, but I mean, that’s how Hollywood does it. They’re there to make money, I guess. But I mean, you know, you ask people about aspects like I once asked a bunch of people about, and I’ve said this, to mention this to Brad Suhan, who has, who is a, is a fan of asymmetric tweeter positioning and, which obviously helps with edge diffraction as well.
Alan March: But it is mostly the right thing to do.
Andrew Hutchison: Yeah, it’s a reasonable, oh, well, it doesn’t, it spreads the problem around and it’s a good thing to do. It’s certainly not as good, perhaps, as what you’ve done, but it’s, it creates a similar polarization. Some people just don’t want the tweeter off the centre line. They will not buy that loudspeaker. And then I once designed something that didn’t even have symmetrical tweeters. So I had the tweeter 15 mil off the centerline to the left, on both left and right speed. People were freaking out, leaving the room, throwing up into buckets. Like, I’m like, sorry, I quite like it. Like, it’s, I don’t have a problem with asymmetry. some people, it’s vomit inducing. So, and this is. Unfortunately, there’s this. You have to sort of balance these decisions, these engineering decisions. Yes.
Dellichord loudspeakers, an Australia made product designed here
Against people’s, expectations, I guess. But, But it’s good to understand. So that you. And, of course, you. We did mention the, Well, actually, before we get onto the. The, I’ll call it the horn loaded tweeter, just to annoy you. we’re just going to have a break and come back and discuss that horn of yours. one tick.
Alan March: Okay dokey.
Andrew Hutchison: Okay. Back soon, folks. Dellichord loudspeakers, an Australia made product designed here, manufactured here, sold worldwide, sold around Australia through various dealers, but also on display coming up at the
Australian HiFi show in Melbourne early to mid October. See us there. Have a chat, have a listen. in the meantime, check out Dellichord.com.au back to the show.
Andrew Hutchison with Alan March discussing his loudspeaker designs
So. And we’re back. Not An Audiophile is back for, possibly, session Three in this episode, which might be the last. Alan is, Alan. Alan March. Alan March of. I am going to start again. All right? So stop laughing. It’s, It’s Andrew Hutchison here with Alan March on the Not An Audiophile podcast discussing Alan’s fine, range of audio products and perhaps the reasons why they are designed the way they are and how he got both to the industry from jet engines at Rolls Royce. And, of course, we find out that, in fact, he’s had an interest in audio, for his whole life, which I guess we all probably have. And, we haven’t talked about music yet, but we’ll come back to that. But what we were talking about is, his loudspeaker designs and, the reasons for the odDBall surrounds and the benefits that they offer. And also, we touched on the large, radius, or big radius, baffle edges, in fact, cabinet edges, full stop.
M finds large horn speakers to sound colored and not natural
And, we’re going to talk about the horn loaded tweeter, which, of course, is not horn loaded, although it kind of is, isn’t it? I mean, that is how it works, is that it?
Alan March: Absolutely, I’ve been known to, state my distaste for very large, you know, those massive horn. Horn speakers that you sometimes see at HiFi shows, kind of things.
Andrew Hutchison: They use at race courses for, public address.
Alan March: Yeah, you know, they’ve got a horn that’s three or 4ft wide or maybe bigger. And
Alan March: M I’ll probably upset a few people with this, but I’ve always found them sounding.
Andrew Hutchison: You’ve never upset anyone with your comments?
Alan March: I’ve never upset anyone. I’ve always found them to sound colored and not natural.
Andrew Hutchison: Many, many do, but not all. I’ll say. That’s correct.
Alan March: Yes. It’s an unfair generalization, I do realize that. But I’ve heard many, many units at manyHiFi shows over the years, etc ete. I think I probably heard one that I went, okay, I can get on with this. I can live with it there’s a good reason, technical reason, why some of them do sound colored. And it’s, it’s directivity.
Andrew Hutchison: Okay.
Alan March: What we hear, with speakers is so much about their directivity properties. And Large horns
00:55:00
Alan March: that have got very narrow directivity, their direct sound, what you hear coming directly at you face onto the speaker is actually very different in frequency response and timbre from what’s being reflected off the walls, floor and ceiling, with narrow directivity. And there’s plenty of research on this. I’m sure you’re fully aware of Mister Floyd Toole and the research he did on subjective speaker preferences compared to sort of technical design. And one of the principles is that the timbre and frequency response coming off the reflections in the room needs to be similar to what’s coming directly at you from the speaker.
Andrew Hutchison: Indeed.
Alan March: And again, that’s all down to the directivity of the speaker.
Andrew Hutchison: Is that sort of related or is the power response or that’s part of that sort of discussion. I mean the power response being balance of sound that fills the room or what have you.
Alan March: Yeah, I suppose it’s a term we need to explain to people because if you haven’t done any acoustics work, you might not understand what that means.
So I expect most people have heard of sound pressure level, um. Well it’s measured in DB
So I expect most people have heard of sound pressure level,
Andrew Hutchison: DB.
Alan March: DB, yeah. Well it’s measured in DB. DB is not a unit. It’s just a ratio way of expressing a large ratio between two numbers. So I.
Andrew Hutchison: That’s. Yeah, in fact DB is a funny thing, isn’t it? It’s hard to grasp in a way, maybe 2 seconds on DB because it’s. Yeah, it’s quite an interesting, it’s a it’s a. Yeah. So yeah, you explain it as you will do much better than I can. So far away just, just, just briefly, for. It’s funny, I’ve listened to a lot of audio podcasts over many years. I don’t think anyone’s discussed the relationship of and maybe power. Audio acoustic power in the room or whatever, so far away. Alan. Yeah, yeah, I’ll leave it. I’ll leave it at your feet.
Alan March: Okay, so, DB. so DB is not. People think it’s a unit of measurement, of a unit of how loud something is. And it’s not actually that at all. it’s like. Okay, like a millimeter is a definitive measurement of distance.
Andrew Hutchison: Yes.
Alan March: what DB is, is a way to express a ratio between two numbers. So the thing with audio is that the human hearing animals as well, covers a, massive range of pressure levels. So what we hear is the pressure of air moving, against our eardrums. And we can hear from very tiny, tiny, low pressure measurements up to very, very high pressure measurements. And literally, our threshold of hearing in terms of pressure is, ah, 20 micro pascals.
Andrew Hutchison: Okay. it doesn’t seem like much.
Alan March: Doesn’t. Well, let’s put it this way. Atmospheric pressure is, let me see. Is it 1515 kpa? 15 kp?
Andrew Hutchison: I was hoping you had the answer to that, because I’ve forgotten it because I don’t do KPI’s.
Alan March: Well, I should know this.
Andrew Hutchison: Yeah, I think you should, because it.
Alan March: Is absolutely critical to testing jet engines.
Andrew Hutchison: well, I’m sure you did it.
Alan March: It’s 14.7 psi.
Andrew Hutchison: Yes. Well, yes, yes, that’s the. That’s the number that. Anyhow, keep going. Yeah, that was the number. It absolutely rings a bell. Yes. So in pascals.
Alan March: Yeah, kilopascals, it’s a 101 kilopascals.
Andrew Hutchison: Is that what it is?
Alan March: So that’s just atmospheric pressure.
Andrew Hutchison: Yeah.
Alan March: so you got a difference between. Between maybe, you know, you’ve got a difference between micro pascals and thousands of pascals KPA, which.
Andrew Hutchison: Yeah, well, that’s, So hang on. So, yeah, you’re talking micro pascals versus kPa. So, we’re talking, 1000 million.
Alan March: Yeah. So let me just look up. I mean, we say. They say like, 120 decibels, is the threshold of pain.
Andrew Hutchison: generally depends what music you’re listening to, really. I mean, clearly Celine Dion at probably 75 is unpleasant, but keep, going.
Alan March: I’m just looking it up. I’m trying to find a calculator on the Internet to see what it is.
Andrew Hutchison: Probably the Internet’s pretty slow and you still on dial up there, I guess, are you. What, what’s,
Alan March: Starlink? It’s fantastic.
Andrew Hutchison: Oh, okay. Yeah. So
01:00:00
Andrew Hutchison: I’ve just made a fool of myself yet again because you’re clearly faster. Internet.
Alan March: We are being in the sticks. We have no connection at all. So we’re on satellite. anyway, anyway, so going back, going back to tv.
Andrew Hutchison: Yes.
So what DB is the threshold of hearing, as I already mentioned
Alan March: So if you got to express the, audio volume levels in pascals, it would be. Yeah. You’d be using numbers with either lots of zeros up front or lots of zeros behind.
Andrew Hutchison: Indeed.
Alan March: So it becomes unwieldy.
Andrew Hutchison: Yes.
Alan March: To use. So what DB is the threshold of hearing, as I already mentioned, is 20 micro pascals.
Andrew Hutchison: Yes.
Alan March: And what is always omitted when you see like a sound pressure level m measurement, of say 95 decibels or something is the fact they should have on the end of it reference 20 micropascals. So it’s a ratio of say, 90.
Andrew Hutchison: Decibels higher, higher than 20 micro pascals.
Alan March: 20 micro pascals, yeah.
Andrew Hutchison: Okay. Which is the, which is the, threshold of portable sound, correct. Yeah. Yeah. Okay. So the lightest wisp of a hummingbird’s, well, we’ll say feathers, at a distance is 20 micropascals. You can just hear it in the middle of the night. And then. Yes, and then 95 decibels is, Clearly, Yeah, well, 95 DBa is the threshold of a DB is the threshold, might be a weighted or whatever is the threshold of where you’re supposed to wear hearing protection, I think, isn’t it? Or something like that.
Alan March: well, this is actually some of the job I used to do because when I, when we came over to, Australia, I started working in an engineering firm in their noise and acoustics and vibration department. and one of the parts of my role was being a noise officer. So I, I did do some work going to industrial sites, maybe mine sites, monitoring and assessing noise levels within, for health and safety reasons. So, basically in Australia you’re allowed to hear, 85 decibels for up to 8 hours a day, is that right?
Andrew Hutchison: Without clearly, without hearing protection. 85 for 8 hours is. Okay.
Alan March: That’s okay. So, so hearing damage.
Andrew Hutchison: Pretty loud. Yeah. Okay.
Alan March: So, so hearing, hearing, hearing damage is, is level multiplied by time? Effectively, yes.
Andrew Hutchison: Okay.
Alan March: and again, going back to the thing, a three decibels increase in volume is notionally, twice the amount of power. So what happens is if you go up three decibels, say from 85 to 88, you half the amount of time you can listen to it for.
Andrew Hutchison: Yeah. Makes complete sense. Yeah. Okay. Which then means that 95 decibels you can listen to, to it for a 10th of the time I guess that you would at 85. Yeah.
Alan March: Correct. Yeah. And you very quickly when you go up you start getting into very short periods of time before you start risking damage.
Andrew Hutchison: Yeah.
Alan March: So.
Andrew Hutchison: Well yeah, because if you’re under an hour at 95 then you’re clearly under, under probably under five minutes at 105, which helps.
Alan March: Yeah that’s it. Yes.
Andrew Hutchison: eah. And I mean 105 is loud but it’s, it’s not that loud. I mean you know a decent stereo turned up in the seated position is probably 105 decibels. And when I say decent I mean a very decent one I suppose, but And one perhaps more bias towards playing loud than, than in a high fidelity fashion. But Yeah that’s, yeah that’s Well a, that’s a great explanation because I don’t think anybody really thinks about that too much and relates the pressure of sound to the DB thing and you’ve done a nice job of that. Thank you very much.
Sound power is the difference between sound pressure and sound power
which brings us back somehow brings us back to Horn load because you’re talking about direct, you talk about directivity and you talked about. Oh yeah, tool and We’re talking about power. Well power response power. Yeah, yeah, yeah.
Alan March: So the difference between sound pressure and sound power.
Andrew Hutchison: Yes.
Alan March: So the sound pressure when you measure it with a sound level meter is literally the pressure level that you’re receiving at that point in the room.
Andrew Hutchison: Yeah.
Alan March: Sound power on the other hand. So you’ve got ah, an object that emits sound. It could be anything, it could be your fridge, it could be your speaker, it could be your car. the amount of sound power an object emits is the amount of power it’s emitting in all directions. So ideally you want to measure that in a sphere
01:05:00
Alan March: around the object.
Andrew Hutchison: Yeah.
Alan March: So it’s the total amount of energy that, that the object is emitting. Now speakers, people don’t necessarily think about it too much. emit sound in all directions, particularly at low frequencies.
Andrew Hutchison: Indeed.
Alan March: so it’s not just what’s coming forward from the speaker at you from the front because the speaker’s emitting sound in the back, it’s in the side, in the top, the bottom. And the thing that it’s doing is it’s changing how much sound power is emitted dependent on frequency.
Alan March: At very low frequencies speakers are omni-directional. So the bass goes everywhere, everywhere in all directions at ah, very high frequencies, what the tweeter is doing, it becomes directional and tends to be. When you get to 20 khz is beat. It gets to a point where it’s almost beaming depending on the design.
Andrew Hutchison: Well, yes. Size of the diaphragm, I guess to some degree. yeah, as well. Yep. So is this where the, the horn is this is this where this is this. It’s there to, to tweak the directivity then, is, that’s correct.
Directivity is dependent on how large an object is compared to wavelength
Alan March: So, so another interesting property of any object, it’s not just speaker drivers, any object is, its directivity is, if I can explain this properly, its directivity is dependent on how large, physically large the object is compared to the wavelength of the sound it’s playing.
Alan March: So if you have a very, very large object, like a woofer, trying to play a very high frequency, that is a very short wavelength, it will beam the sound.
Andrew Hutchison: Yeah.
Alan March: But a very small object like a tweeter, playing the same frequency will have a much, much wider, directivity.
Andrew Hutchison: Indeed.
Alan March: It’ll become more omni-directional.
Andrew Hutchison: Yeah.
Alan March: So that’s why we have tweeters. A single, I see sometimes these single driver, speakers and they don’t work, simply do not work because you heard it here first.
Andrew Hutchison: Well, you’re not really, I mean, they don’t work. I mean, but they can sound sort of, you know, they have their own attributes, I guess, which some people like, but yeah, I mean that, that is why the two or three way speaker was invented. Right. So just keep, keep on with the thought process because you, so to summarize, basically wider diaphragms, beam, and by beam I guess we mean have very narrow directivity, like a 1020 degree range in any direction, I guess, out into the room from the front. So you really need to be standing directly in front of the speaker to hear a broad range of, you know, an evenish frequency response. But of course, correct, yes. And now I guess maybe those full range speakers that you’re alluding to, the louthers of the world and others, I guess they do produce a bit of high frequency in their slightly ragged, uneven kind of way. on axis, they probably, they probably are full range on axis.
Alan March: That’s it, that’s, it’s possible to design a, you know, maybe a four or five, six inch driver, I think with some difficulty to be relatively flat frequency response directly on axis.
Andrew Hutchison: Yeah.
Alan March: But the moment you start moving off axis, because of the beaming effect of the large size dryer diaphragm. The high frequencies, they will be beamed and but the low frequencies will be very spread out. So, And as we listen in rooms.
Andrew Hutchison: Yes, we do.
Alan March: And what we hear is a combination of the direct sound and the reflections off of all the floor, walls and ceiling.
Andrew Hutchison: Yep.
Alan March: And as I mentioned earlier, if those reflections are radically different in timbre and a frequency response from the on axis, we hear it and we don’t like it. Now, yeah, that’s not just me saying that. This has all been The Floyd Toole research was very much about subjective, people’s subjective responses to speakers and how that tallied up to the technical measurements of speakers. so it’s not some kind of abstract technical theory,
01:10:00
Alan March: it’s not personal opinion. Floyd Toole and the guys at Harmon, they did listening tests with people, controlled listening tests, and they tested maybe 70, 80 different speakers and they got to the point where they could predict from the anecdote measurements of a speaker what people were going to say, they were going to like. So it’s, it’s back to, it’s backed up by real subjective research. yeah.
Andrew Hutchison: And look it, I’ve listened to there’s a, there’s a YouTube video of him summarizing all of his testing and R and D over the years beautifully. I mean he’s a great speaker and no pun intended. And it’s a great lecture. Well, I’m sure, you know, you’ve, you’ve seen the video I’m referring to. It’s a relatively recent one. and I remember when I looked at it maybe two years ago or something, that you had various YouTube bloggers with, you know, 200,300 thousand views. And I, you know, and I think, I think poor old Floyd had like 80,000 at that stage. Or was it 8000 or something? I’m like, how is it? This guy is a genius, more or less. And certainly, offering us this plethora of useful information. That is an enormous amount of research and testing and what have you gone into? And some guys over on another YouTube channel blithering about some piece of audio gear that he’s been gifted to write a review about and he’s getting way more gravitas. You’re like, there’s something wrong in the world, right? But yeah, he’s a, he’s a great person to listen to. And the only thing I would say though, because I agree with your thoughts on it, but Harmon not building great speakers though. So what, there’s a disconnect, is there? Or what happened there, do you think?
Alan March: well as always, as we’ve always already discussed, marketing does get in the way.
Andrew Hutchison: Yeah, yeah.
Alan March: it doesn’t so much affect maybe smaller businesses like ours because we’ve got more latitude to do what we, we as designers want. But if you’re working in a big organization like Harmon, JBL, their partner, sister company and so on, the bottom line of that business is to make money. We all need as businesses to make a, we all need as businesses to make money.
Andrew Hutchison: But they got to make lots of money.
Alan March: They got to make lots.
Andrew Hutchison: They got to pay Mister Toole’s wages for a start. I don’t know, he’s not actually there anymore, is he?
Alan March: He did, he did, no, he’s retired.
Andrew Hutchison: He did ten or 15 years there or something like that, you know.
Alan March: Yeah. So they have less attitude to do as we’ve already discussed, to do anything radical. so you know, and actually Floyd discusses this because he had his own arguments within Harmon, I believe. the marketing people getting in the way.
Andrew Hutchison: Yeah.
Alan March: And saying you can’t have that shape, you can’t have that color, you can’t have a tweeter looking like that and you can’t put it there.
Andrew Hutchison: You can just imagine he probably wheels in some hideous looking control contraption that fulfils all of the requirements, except the aesthetic ones. And and then they’re all falling about, you know, what is this? You know, but this is, you know, of course it probably sounds amazing. and the sound is uber saleable. But but yeah, getting it, I mean that is the trick, that’s the trick of loudspeaker design is to get the customer expectations and hopes to match the sound that they would aesthetically to the sound that they would like to hear. Which I’m pretty sure Mr Toole’s got that bit pegged. Even though we are using North Americans as the ears for this testing. You got any thoughts on that at all?
Alan March: Ah, oh actually yeah, because there was a very there’s one test that they did do because there’s this concept around that people from different countries have different tastes in audio, sound and whatever. so they did an experiment. They had an identical set of speakers, good set of speakers. And ah, the only difference between them was there was slightly different voiced crossover. and they did the subject the controlled listening tests in various different countries.
Andrew Hutchison: Yeah.
Alan March: And The results came out as everybody liked the same thing and disliked the same things.
Andrew Hutchison: Okay. All right. Yes. So they took two pairs of speakers that were largely this, to look at, but that they had tweaked the crossover to have it perform less. Well. Yeah. Okay. And then obviously.
It turns out it’s a complete fallacy that there’s a European sound
Alan March: And that’s. Well that’s one thing, a part of the controlled listening test. You wouldn’t be able to see the speaker.
Andrew Hutchison: Yes,
01:15:00
Andrew Hutchison: of course.
Alan March: yeah, so it turns out it’s a complete fallacy that there’s a European sound and an American sound, or an Australian sound. It’s a complete fallacy.
Andrew Hutchison: Yeah. I think it is a complete fallacy as far as the preference of the listener. But I think that those three parts of the world certainly produced different sounding products though. But I mean, I’m not sure why that is. I mean, and I guess it was a case more historic, more than current perhaps. Like I think in the seventies and eighties when sixties, seventies and eighties when, measurement wasn’t as accurate, measurements were not as easy to come by. I think that there was more character in loudspeakers in some cases. Or although I always think that the best engineered ones tend to rise to the top and be the more well loved examples of those years of production. But I think that the English speakers did sound different to American speakers and I think they did sound probably different to Australian speakers. Not that we had as many to choose from. But I think that there’s differences there. But I think, yeah, humans probably prefer the same sound. But I always wonder about some southeast Asian Chinese area type countries and their jingly jangly music and whether. Which sounds to our ear, my ear at least quite jingly jangly, to use that musically technical term. yeah. Yeah. I just wonder whether they do prefer a sort of brighter, you know, less, I don’t know, warm, sweet sound or is that just up?
Alan March: I don’t know. But I mean you could. You could suppose that that sort of high frequency content music. that I think a lot of westerners find a bit grating.
Andrew Hutchison: Yes.
Alan March: Not being Bagging it or anything.
Andrew Hutchison: No. I mean, clearly.
Alan March: Yeah. Cultural thing.
Andrew Hutchison: And we are talking historical music, I think probably mostly rather than. Yeah, they might be producing today. But, Yeah. You’ve got thoughts?
Alan March: Yeah. Maybe lots of high frequency content. will have different requirements of the speaker than, there, may be, say, western rock music, for example.
Andrew Hutchison: Yes.
Alan March: although, although that does sort of ah, conjure up a problem because I don’t believe that speakers need to be, have different sounds to suit different genres. A good speaker is a good speaker.
Andrew Hutchison: Absolutely. Yeah.
Alan March: Of course if it sounds good with jazz and accurate with jazz, it will sound good and it will sound accurate with rock or whatever. that’s another subject.
Andrew Hutchison: it is another subject. Although I have to say I agree. Although the weird thing is that, and this is a, you know, this is a thing that annoys me at HiFi shows. Lots of people get annoyed by HiFi shows. One would wonder why anyone went, but they do tend to play jingly. Okay, here I go. I’m not going to say jingly jangly again. Let me say noodley jazz. Yeah. Very lightweight, simple recordings that are almost bordering on being sound effect discs than they are pieces of music. And you, why don’t you just put Fleetwood Mac on AC DC or some rap of some description or techno and you know what? Why don’t you play the music that the people are going to play? And I think it’s because there is this in the high end, not in the real world of affordable audio equipment, but in the, in the, in perhaps in the, in the far high end in some cases they’re just, just in love with almost sound effects. You know, like, just like it’s the oddest thing. Do you find that, I mean, I don’t know if you’ve been to any shows much lately other than your favorite.
Alan March: Yeah, I mean I won’t, I won’t mention the, the brand, but I did go into one brand’s room, high end brands room. a ah, show not so long ago.
Andrew Hutchison: Yeah.
Alan March: And I really was quite curious about these particular speakers and I want to listen to them. And and they, they put on this, this, this, well it was not literally atonal noise and I couldn’t have recognize it as music. And as such, I couldn’t actually discern what the speaker sounded like.
Andrew Hutchison: Yes.
Alan March: so I, I legged it quite quickly.
Andrew Hutchison: Yeah. And that’s, that’s it. That’s an example of exactly what I’m talking about. So we, we don’t know what that’s about. I mean, do we, or do you have thoughts on why they do that?
Alan March: Well, yeah, I mean of course we’re, we’re sat with HiFi shows. Let’s be honest about this. We’re trying to sell to people.
Andrew Hutchison: Absolutely.
Alan March: We’re enthusiastic about our product. We think it’s great. We want people to love it. so we want to show it off to its best ability. So if you
01:20:00
Alan March: play bat out of hell, which sounds probably one of the worst sounding albums I’ve ever heard, it’s going to sound rubbish.
There’s a fine line between interesting and awful recordings on HiFi shows
So you want to put on, you want to put on recordings that sound good, you do. But getting that balance of finding recordings that are interesting, people are going to like. but one of the things I love about HiFi shows is people asking ah, for requests and I’m finding all sorts of different music I’ve never heard before and it’s absolutely fantastic.
Andrew Hutchison: Well some of it is
Alan March: You do get the odd customer, that comes with something that is just mind bendingly awful and you have to shut it off as quickly as possible. yes, it’s always a degree, it’s.
Andrew Hutchison: A fine line between, well there’s, and you know, we won’t talk, we’re going to talk about shows on another occasion, but because we will need to wrap this particular podcast up shortly. okay, so let me quickly go.
Directivity of a speaker is critical to how you perceive sound in a room
Alan March: Back to, back to speakers and the cones and horns just very, very quickly.
Andrew Hutchison: Yeah. Ah, we didn’t quite finish the let’s call it a, let’s call it a wave guide. So which is really just another name for a horn.
Alan March: So as we were discussing, the directivity of a speaker is critical to how you perceive the sound when it plays in a room. If you’re actually listening outdoors, all you’d be really. Although there is a reflection off the floor obviously. but because there’s no walls or ceiling, you’d predominantly, if a speaker had a good on axis frequency response, you wouldn’t actually be too worried about the directivity because you won’t be hearing it coming out the side of the back. So if it was a good on axis frequency response, you’d like it. But of course we listen inside rooms, so directivity becomes a very important influencer, to how the speaker will actually sound to us in the room. So directivity is critical, I just keep saying it. Directivity, directivity, directivity. So why do we.
Andrew Hutchison: Directivity, directivity, directivity, directivity. I’ve got it.
Alan March: So why do we have three way speakers? Well, it was one way to solve the differing directivities between drivers sizes.
Alan March: So going from a very large six, eight inch woofer to a maybe three, or four inch mid range, you could keep the directivities similar at the crossover point. Uh-huh so there’s no sudden change in directivity with two way speakers are very, very often compromised because you’re going from a very large woofer and at crossover you’re suddenly switching over to a small tweeter. So you go from a narrowing directive at, the woofers top end to a suddenly bursting out to a very wide directivity, where the tweeter takes.
Andrew Hutchison: I think I’m onto it. So, yeah, okay, you explain it, but I think, I think I know where you’re going. Yes, yes.
Alan March: So what that means on a two way speaker is that very typically the directive suddenly gets wide as you go to the tweeter. And that means there’s lots more sound power going into the room at that, at that point.
Andrew Hutchison: Yeah.
Alan March: So there’s a sudden disconnect in the amount of energy, that you’re hearing as the tweeter takes over. And that’s why so many speakers and why I started looking at, waveguides, so many speed two way speakers. To me, sound relatively bright and hard in the mid range. Yeah, it’s because they might have a, they might have a very flat on axis frequency response, but because of the extra sound power that they’re putting into the room, what you hear at, ah, the measurement point or your ears, should we say, suddenly has a lot brighter, lot more energy at that frequency.
Andrew Hutchison: Yeah. Just, just to clarify that, well, it’s not something I would normally say in regard to your explanations, but I think what you’re getting at is if you have a, say, a one inch dome tweeter, blended, attempting to blend it with a six and a half inch base bed range driver, that there is good chance at the crossover frequency without a waveguide that the output at the low end of that, one inch tweeter, diaphragm’s range is very wide. And of course the six and a half inch bass driver at that same frequency where the two are met and meeting and being crossed over, of course, has narrowed up and is to some degree not beaming, but certainly has narrowed right up because it’s at the upper end of the range of that driver’s, capability. And so yes, the disconnect is that, at say, 45 degrees off axis, the six and a half, at say, two and a half kilohertz is quite narrow and very little output at that 45 degree position.
01:25:00
Andrew Hutchison: But the tweeter at 45 degrees at that frequency has enormous output and maybe we could be talking six, eight or ten decibels more, perhaps. And so that is difficult to control. And then manage also good on axis response. so this is where your waveguide comes in. And I take it as no expert on waveguides, I’ve not experimented with them, but I’m guessing that it narrows up the tweeters response at that crossover frequency. Is that the gist of it? Yes, sort of more closely match the, that of the six and a half.
Alan March: Correct, correct. Absolutely. Spot on. So, so whereas we used to go to a three way driver system where the, the, the physical size of the mid range driver would help it match the directivity of the woofer and then match into the directivity of the tweeter, we can actually with a two way. If we add a waveguide, it does exactly what it says in the tin. It narrows up and controls the wave front coming out of the tweeter. So at the lower frequencies where it’s taking over from the woofer, it’s narrower and much more closely matches the woofer. So that means the sound power going into the room is similar from the woofer and the tweeter. So the reflections you get off the walls, are also similar.
Andrew Hutchison: Yeah.
Alan March: Which is humans like.
Andrew Hutchison: We like it, it seems, I mean, I guess, and I’m going to play devil’s advocate for a second and say, well that’s great, that makes sense. And that has got to make the crossover development, you know, the ultimate result better, one would assume, and perhaps simpler.
But what do you think, if any other trade offs of using a waveguide then, because I guess everything in science there’s a, is a compromise to some degree. So what do you think there are any real down? There’s down. Is there a downside other than cost perhaps?
Alan March: yeah. Oh absolutely. They are difficult to design.
Andrew Hutchison: Okay.
Alan March: you need some pretty sophisticated software to design a waveguide that’s going to do what you need it to do properly over the frequency range. It’s got to cover because you might need to cover from 1 khz up to 20 khz.
Andrew Hutchison: Indeed. Yeah.
Alan March: and sometimes you’ll see in wave guides at the top end and around 15 to 20 khz they can get a bit what in their terms of their frequency response. So it’s difficult to get. Right. so they are difficult to design. There’s no doubt about that. they do have some other advantages because they’re narrowing up the directivity at the low end. you can, they actually get more sense, effectively more sensitive. They get louder. So you need less power, which means. Which means you can actually cross them over lower because they don’t have to work so hard. Such a large extension on them.
Andrew Hutchison: Indeed.
Alan March: that could be very helpful. With, with two way speakers,
Alan March: Other disadvantages. Well, yes, they do, they do, they do cost more. And you have got to get them right because I say about this directivity. If you measure the frequency response with a microphone in a room, from a pair of speakers, if those pair of speakers in an anechoic setting had a perfectly flat on axis frequency response, you measure in the room, they have a sloping frequency response.
Andrew Hutchison: Yeah.
Alan March: It slopes downward. And this is very simply because the sound power falls as you go up in frequency. But this is what we used to hearing. Any, any sound producing object, whether it’s a violin, a guitar in a room will have directivity and you will always find that it will have a sloping, a sloping frequency response going down as you, as you, as you go up in frequency. So it’s what I used to hear. But with a speaker, You’ve got to get that slope right. Yeah. There’s no categoric exactly right answer. I can’t tell you that six, Degree slope is right.
Andrew Hutchison: No.
Alan March: Because it does. It’s got to be sloping. but you’ve got to get it right. And it’s a balance of the specific speaker design, its directivity. the room also plays a part that will change the slug.
Andrew Hutchison: Indeed. And you are talking about the room outcome, effectively the power response. The listener is on the lounge listening to the stereo and it is the resultant of all reflections etc. And of course every room is different. So that’s going to be hard and personal taste, I guess, is part of this. Some people prefer warmer balance or what have you, but yeah. So you are engineering for a more or less flat response on axis. Anechoically, At a, like a meter or two away from the loudspeaker. That. So that, that’s a design goal with your loudspeakers, is it? Is that,
Alan March: Yeah. The typical measurement
01:30:00
Alan March: distance is 2 meters and you normalize to 1 meter for sound pressure levels, 2 meters because it takes A certain amount of distance for the drivers to Blend from the cabinet. We won’t go into that, into too much detail.
Alan, I’d love to have you back on the show for round two
So yeah, on axis frequency response, flatter and smoother the better.
Andrew Hutchison: Yep. Yep. Okay.
Alan March: But you need a falling sound power as frequency goes up.
Alan March: Which will lead to a falling in room, what we call an in room response.
Andrew Hutchison: Yep. Well I find that, of course, I find that all very interesting. I guess I know some of it. But to have it, to have it turned around and presented to me and presented in a such an eloquent way, Alan has been a great pleasure. And I think the listener has probably enjoyed your explanations of various things from blades flying off jet engines and how the aircraft passengers are protected by some kind of scatter shield built into the engine cowling or something along those lines or however that works through to waveguide design and the fact they’re not really a horn. I’d like, I’d love to have you back on the show and I think there’s many things we could discuss. I want to discuss the Concorde and whatever you know about that because it’s probably the most amazing machine ever in, invented on the planet ever. Even though it was a seventies thing. And also those other things that you do which are amplifiers which we’ve kind of ignored. And because they, I believe they employ class D technology. And that’s something we can talk about because it can work extremely well. And in fact is probably, I mean, I mean I guess it’s the newest amplifier thing under the sun. It’s not the newest. There’s other things that have come out recently I think, that are not new semiconductor technology at least. but we’d like to talk about that more. So would you be interested in coming back for round two, sir?
Alan March: Oh, absolutely, absolutely. I wish we had. We might have to do a video podcast, because some of this needs diagrams to help you crack.
Andrew Hutchison: Does it really? Have you got a whiteboard there or something that you.
Sir Clive Sinclair released the first class D amplifier in 1967
Alan March: Oh, but just a very quick one on class, the amplifiers. Did you know, do you remember Sir Clive Sinclair who invented the zinc compute z 80? Yeah. And the and the little electric trike thing. Yeah.
Andrew Hutchison: Are you having a crack at trikes? What the hell? I think he’s might have had one wheel at the front. So that’s not, that’s never going to work.
Alan March: He actually released the first class D amplifier and I think it was 1967. Yeah.
Andrew Hutchison: Okay.
Bruno Putzey talks about amplifier topology and various classes
All right. So what, what using, well, using transistors, I’m going to guess very early what? Germanium transistors or something.
Alan March: But yeah, it didn’t last long because it was more like a radio transmitter. But yeah, it’s, it’s, it’s a concept that’s been around for a very long time.
Andrew Hutchison: Well, yeah. And I guess people don’t realize the engineering behind the whole. There’s many classes of amplifier and they’re really a description of distortion characteristics and what have you and range, you know, frequency, how broadBand they are. Otherwise. I mean there’s the whole class a b. Is there a class c? I’ve kind of forgotten whether the. There was, but it. You know there’s.
Alan March: Yes.
Andrew Hutchison: Yeah, yeah. Out of feeling there was And I think that’s used in rf applications or something. But yeah there’s this edfgh, there’s, there’s certainly h and there’s certainly g and there’s a bunch of others I think. So. Yeah. Well that’s it. That’s an exciting possible title for a new podcast. Is is amplifier topology and various classes. But we might stick to class D since you’re ahead. Product uses them and, and so do many others these days. In fact it’s a, it’s. What did I see in a newsfeed the other day? a new fancy Marantz amp and it’s going to have class D. I think your friend mister Putsy, is that his pronounce his name. He’s His ideas are in it somehow. So I mean everyone is
Alan March: Oh yeah.
Andrew Hutchison: I mean I think Marantz have done clothes d before but this is a new look at it or something. So anyhow, I’ll stop showing my ignorance and we’ll wrap this up. Thank you again, Alan. It’s been enlightening very well and a lot of fun. And thank you people for listening. And of course you know, go to the website, Not An Audiophile.com, and you know all of that, you know like and subscribe and blah blah blah. And feel free to comment on YouTube because by the time this broadcast goes up it will be on YouTube and you’ll be able to comment and say all sorts of nasty things about Alan and I. Well mainly about me. But we’ll love it because we love that sort of thing. we didn’t get onto that, Alan, how you love a good Internet discussion. But we will next time. So thank you and
01:35:00
Andrew Hutchison: we’ll talk again soon. You’re very welcome.
Alan March: Looking forward to it.
Andrew Hutchison: Thanks, Alan.
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