00:00 Julian Rodgers Welcome to the Sound On Sound Recording & Mixing Podcast channel. My name is Julian Rogers. In this episode, we're joined by a loudspeaker designer and Sound On Sound monitor reviewer, Phil Ward, to explore the compromises behind every speaker design. Phil Ward's loudspeaker career began in 1982 when he joined UK hi-fi company, Mordaunt-Short, in a junior design role. After leaving Mordaunt-Short in 1987 for a spell in audio PR, Phil joined Canon as design manager for the Japanese multinational's range of consumer and custom install speakers, and then Naim Audio as speaker designer and project manager. Since 2001, Phil's worked as a freelance consultant and writer across both the pro and consumer audio sectors. Phil plays electric and double bass and has recorded, produced and mixed numerous bands and artists. Welcome, Phil. Phil Ward Thank-you very much. I recognise some of that in your discussion on me. 01:03 Julian Rodgers Well, there we are. So we're gonna take a quick tour around loudspeaker design and defer to your superior knowledge. So we should start with, something that must have occurred to anybody who's set a pair of monitors up next to another pair of monitors and listened to them, because every monitor claims to be absolutely flat, completely neutral, reference quality and they all sound completely different to each other. So why? Phil Ward Because they're very complex. The, the function of converting electrical energy to acoustic energy is full of distortions and losses and compressions, and they're inherent to the electrical and mechanical workings of a driver. And different manufacturers and different designers decide that they want to try different methods to overcome those issues, and that means things end up sounding different. Julian Rodgers That's a good answer. Phil Ward That's it in a nutshell. Julian Rodgers So I mean, so why can't we build it? I mean, if there's, it's a mature technology. People have been making loudspeakers for an awfully long time now. What barriers are there in the way of building that idealised loudspeaker that everybody wants? Phil Ward The fundamental barrier is the impedance mismatch between the air and our means of moving the air. So the driver diaphragm and the air have very different density, and in electrical terms that's a very different impedance. So transferring energy from one to the other is difficult and very inefficient. A typical loudspeaker will be 2% efficient in power terms. So 98% of the power that you input to a loudspeaker is dissipated as heat. Only 2% of it becomes the acoustic energy that you hear. And those losses mean that, the losses come from the complexity of the impedance mismatch and that means there's a million ways of trying to overcome that. And I've lost track of the original question now, but that seemed like a reasonable answer. Julian Rodgers It's a reasonable answer to a question. 03:19 Julian Rodgers So I mean it's... I mean, circling very briefly back and I mean, I suspect that there won't be an easy answer to this, but lots of people are familiar with impedance as an electrical characteristic of stuff. You're talking about the impedance of air, which is not made of electricity. So is there a simple way you could break that down for us? Phil Ward It's why you can swim, but you can't fly. You can wave your arms in the water and you move because the density of water and the density of your physical presence is similar. You can't fly because the molecules in air are much further apart than the molecules in water, or they're much less dense. So you can't move much air when you flap your wings. A drive unit has exactly the same problem. It's very difficult to move air because the molecules are... it's low density, they're widely spaced. That's the impedance mismatch. Julian Rodgers Really neat answer. Phil Ward It's why birds can fly, we can't. Julian Rodgers Excellent. Phil Ward Because they're much lower density because they're light. 04:19 Julian Rodgers I like it. I like that a lot. Okay, so we've touched on that but like most things, any products, well, nearly every product is designed to a cost and when you're balancing compromises, one of the first ones to turn up is usually oh, that's too expensive. So how does cost affect compromise? What could we pick out as being the biggest failing of a typical budget loudspeaker compared to one that's designed with, you know, fewer compromises or, you know, virtually none? Phil Ward The two biggest compromises, I guess, are low-frequency bandwidth, because the more low frequency bandwidth you want, the deeper bass you want from a loudspeaker, the more the drive unit, the bass unit diaphragm has to move and that's difficult in terms of the electric motor that sits behind the drive unit. The further it has to move, the more distortion will result. The second compromise is cabinet panels. If you think about the potential radiating area of the cabinet panels and the radiating area of the driver, there's far more radiating area in the cabinet. So the cabinet doesn't have to move much to start producing as much output, usually in the mid-range where the cabinet panels resonate more output than the drive unit does. So if you want to have a bigger cabinet that enables you to fit a bigger driver, you've got more radiating area of the cabinet and you have to try and stiffen that to stop it moving, and that's very expensive. As soon as you start putting braces in a cabinet, shelves, or even more complex structures inside the cabinet, the costs rocket. So that usually gets taken away on a cheap loudspeaker and you end up with something that sounds coloured because the cabinet panels are moving. Julian Rodgers A really good point about the acoustic output of those panels. I mention in reviews that I do of monitors, pretty much the first thing I'll do is I do a tap test, and I just knock it like a door and that tells you a great deal. But that's interesting extra info in why that isn't a waste of time. Phil Ward No, I do it too, you know. Julian Rodgers And it should hurt on a good loudspeaker. Phil Ward Yes I've been tapping the sides of cabinet panels for forty-five years now. Julian Rodgers Absolutely. But yeah, so I mean the physical stuff costs, that's a pretty common thread that we find with pretty much any product. In terms of what's inside, would you say things are easier? Phil Ward What, in terms of the compromises? Julian Rodgers In terms of the limitations and constraints of cost. Phil Ward No, no. Nothing is easy when you're trying to take cost out of a speaker. If I go back to drive unit diaphragm area, the bigger the diaphragm, the larger the voice coil diameter you want to attach to it and bigger diameter voice coil means a bigger magnet, and a bigger magnet means bigger chunks of metal. So the magnet top plate and the pole piece and the back plate all become much bigger, and decent steel, especially nowadays, and large magnets are very expensive. So the costs multiply rapidly as soon as you try and give your loudspeaker more performance, the costs rocket. The loudspeakers, I've always thought that loudspeakers are one of the few consumer products where you do tend to get what you pay for. I know, I know there's all sorts of craziness of high-end hi-fi because I'm, you know, I'm involved in some of it. But especially in the sorts of regions that we're talking about, of the kind of monitors that we typically review in Sound On Sound. If you've got something that seems remarkably cheap, remarkably inexpensive, then there will have been some compromises made in order to achieve that cost and one of the skills of loudspeaker designers who are working with those sorts of products is managing the compromises and trying to find a solution that still works as a monitor but is affordable. That's really difficult. It's easier to design speakers that are expensive because you're not so constrained by the compromises. 09:19 Julian Rodgers So you referred to bass performance and we should talk about bass because everyone likes bass. So, lots of bass from a small box is something that everybody tries to do. I think actually I mean, sometimes remarkable amounts of bass come from remarkably small devices and there's clearly a trick in there and we can discuss that. But ultimately there's no substitute for size, correct? Phil Ward No. No. Julian Rodgers So in that case, how does it work? How do you get good bass frequency, bandwidth and level from a speaker? Phil Ward There's a law that's talked about among loudspeaker designers called Hoffman's Iron Law. I've never actually Googled who Hoffman was, but it's the law that says low-frequency extension, bandwidth, sensitivity and cabinet volume are trade-offs. They're a compromise between the three. You can't have all three. If you want more bass extension, more bandwidth, you'll have less sensitivity and / or you'll need a bigger box. The reason for that is kind of all about... well, there's many constraints. One of them that kind of goes back to what we were talking about a moment ago of compromises and cost is diaphragm excursion. The smaller the drive, the smaller the diaphragm, the further it has to move in order to create bass. The driver excursion that you need to play bass increases exponentially with falling frequency, so you need... I can't remember exactly what the maths is, but you need probably eight times the driver excursion to play 40Hz than you do 80Hz and as soon as a driver moves, you get distortions, you get errors occurring. So if you want a small box, by definition you've got a small drive unit, which by definition means it's got to move a long way. And when it moves a long way, that's when things start to fall apart. Julian Rodgers So I mean because there is a limit to how far, as well as there's the mechanical, actually constructing it, but if it's gonna move at a certain frequency and it's got to move further, then it has to move faster, correct? Phil Ward Yes, it has. Julian Rodgers And there's gonna be a limit on that surely, of kind of... Phil Ward Yeah, yeah. It's harder and harder to get a small drive unit to play bass. 11:51 Julian Rodgers So this is why headphones can do it. Phil Ward Yeah, why headphones can do it, because they're very close to your ears. Julian Rodgers So they're very quiet. Yes, I mean, that makes perfect sense. Phil Ward Yeah. 12:03 Julian Rodgers So something, to get bass I mean, anyone who's ever taken a driver out of its cabinet and just held it in free space will have experienced that, why the cabinet's there and I mean, when you read about this stuff, people talk about things like open baffles and stuff, which are interesting, but entirely impractical. There is a convergence onto bass reflex boxes, everything, well, not everything. I mean, I've got a pair of monitors over there that aren't reflex boxes, but they're overwhelmingly common. What's so attractive about porting? Phil Ward Fundamentally, it means you're not wasting the radiation that comes from the back of the driver. When you put a driver in a box, a closed box, you're saying I'm gonna lose 3dB, no, 6dB of level because I'm not going to use the rear radiation because it's out of phase with the front radiation. What you're doing with a reflex box is over a very narrow band of frequencies, reversing the phase of the rear radiation of the driver and allowing it to add to the front radiation. So effectively, it's a trick to get around Hoffman's iron law, so you get an extra 6dB of level that you can play with. You can use it either for more sensitivity, or you can trade it for bass extension. So it's using the rear radiation of the driver, which a closed box speaker doesn't use. So your compromises become easier. The compromises in terms of cost become easier. Julian Rodgers It does sound like you're describing a free lunch, which makes me very suspicious. Phil Ward Exactly. You should be. Julian Rodgers So is it actually one of those rare occasions where there is a free lunch? Phil Ward There's a free lunch in terms of bandwidth but the cost happens in the time domain, because a reflex system adds another resonance to the resonance of the driver and the box and if you're too greedy with it, that becomes audible. Julian Rodgers Yeah. We've all heard over-ported small speakers that sound horrid and one-notey. Phil Ward Yeah. Yeah. Julian Rodgers Excellent. Blowing across the top of a bottle is what always comes to mind.. Phil Ward Which is kind of the, it's a Helmholtz resonance, which is much the same thing. Julian Rodgers Yeah, okay. I mean no, lovely kind of, I mean I don't wanna go deep with these things because we would literally be here all day. There are alternatives. I've got a nice pair of sealed boxes back there, which I really like. I've got a pair of transmission line speakers downstairs as well there. That's an interesting case. Phil Ward Yeah. 14:52 Julian Rodgers What about alternative approaches? Briefly, what are the advantages and disadvantages of different cabinet designs in your opinion? Phil Ward The advantage, I've always loved a closed box in pure terms of how the loudspeaker reproduces music. I'm a big fan of closed boxes. So in purist terms, I would always first want to do a closed box. Transmission lines can be made to work extremely well, but there's an element of black magic in transmission lines. If you look at a company like PMC, who've been working on their transmission line techniques for really since the company was founded and they're still finding newer ways to optimise it. These days there's a lot of modelling software that you can use to help design transmission lines, but there's always going to be an element of black magic to transmission lines to make them work. They're a very complex beast. So they're difficult intellectually and although, as I've just said, PMC make it work very well, it's quite easy to come up with transmission line solutions that don't actually work any better than an equivalent reflex or a closed box. So there's a risk that you're gonna put all that effort into designing a transmission line and not get anything better out of it than a reflex box. So it's the complexity of transmission lines that's the downside, and that's more in commercial design of monitors and hi-fi speakers. That is more a commercial consideration than it is a technical consideration. It'll take you longer to make it work. 16:50 Julian Rodgers And as for other approaches I mean, there's the niche ones like I mean, an open baffle's theoretically possible, but good luck with that. Lots of people try full-range horns, which end up being vast. Phil Ward Yeah. Julian Rodgers Is there, have we missed any that are kind of worthy of mention? Phil Ward I don't think we have, no. As you said, that you'll go to a high-end hi-fi show, you'll see a few open baffles. They can sound amazing if you've got a big enough room, but in the real world, they're very difficult. 17:22 Julian Rodgers OK, so I mean, something I've always really liked, seeing form and function go together, something looking the way it does because of what it does. And a great example of that, that's one that really struck me was the Genelec 83 series, The Ones, as they're called, because I got it straight away. Lots of people were complaining and calling them Cyclops speakers and thinking they looked weird and I didn't care if they looked weird as long as they were weird for a good reason, and they really were. Can we touch on point source and why that's a consideration and what the alternatives are? Phil Ward Yes. Point source is a great idea and the fundamental benefit is over what we'll call a distributed source, where you've got a separate woofer, mid-range driver and tweeter, is that the drivers are radiating from the same point in space. They're coincident. That has its major advantages when you go off axis. With a conventional loudspeaker that's got a tweeter above a bass-mid unit, if you go off axis vertically, the path lengths to your ears between the two drive units changes and that means their arrival time changes and they will slowly go out of phase. When they go fully out of phase, you'll get a huge dip in the frequency response. Speakers are very sensitive to vertical on off-axis issues like that because of that path length change. The dual concentric or coincident speakers overcome that completely, because the two drivers are radiating from the same point in space. You don't get the changes in path length when you go off axis. The other significance of dual coincident speakers is the dispersion. The directivity of the tweeter is defined part or primarily by the shape of the diaphragm of the mid-range unit around it. So you don't get the dispersion, the directivity mismatch that often occurs between bass mid-range units where the directivity is increasing with frequency, and then suddenly it crosses over to a tweeter, say a 25mm tweeter that has very wide directivity at the crossover point. So as well as the vertical off-axis issue, you get a general directivity issue where there's a sudden discontinuity in directivity, the dual concentric. The coincident overcomes that too. Julian Rodgers So I mean, interesting point about the off-axis response, because you're gonna hear that even if you're sitting on axis, you'll hear that reflected back from you in your less than perfectly anechoic room. Phil Ward Yeah exactly, yeah. I mean, if you're sitting in front of near-field monitors and you stand up and sit down quite often, play some pink noise through near-field monitors and stand up and sit down, and you'll hear the sound change. And that is fundamentally the vertical directivity changing, because the path length to the drivers has changed. Julian Rodgers But it's at the high end that these things matter the most because of the shorter wavelength. So I mean if certain conditions are met, then drivers in different places can couple successfully, correct? Phil Ward Yes. The constraint is, you need to get the two drive units close enough that the wavelength at crossover frequency is significantly bigger. If you can do that, then you can substantially get over the vertical dispersion issue and you'll see some companies that are beginning to do that kind of thing. The tweeter in a waveguide, the dome tweeter in a waveguide is becoming quite popular. Amphion is probably the monitor manufacturer that's best known for doing that, but there's other companies, many other companies doing it too. The reason for doing the waveguide is that it enables you, because of the gain the waveguide gives you in the tweeter, you'll get about 10dB gain from the waveguide at the bottom end of the tweeter. That enables you... Julian Rodgers Because it's horn-loaded. Phil Ward Exactly, because it's horn-loaded, yeah. That enables you to push the crossover frequency right down and that means you vastly improve, you can put it, typically a crossover frequency in a sort of old-fashioned two-way speaker would be about 3kHz. The Amphion get it down to about fifteen hundred, so an octave lower. There was a speaker I reviewed not long ago in Sound On Sound called the AsciLab 6b. That has a very big waveguide and they've got the crossover frequency down to 1k in that. It's a 25mm tweeter, might be 29, can't remember. But they've got the crossover frequency down to 1k, and it doesn't really show any significant vertical off-axis problems. Julian Rodgers Right. Phil Ward So that whole tweeter waveguide thing is a significant new, in the last ten years or so, something significant that's changed. 22:29 Julian Rodgers Okay. And I mean, I suppose those, can think of a few examples of big changes in monitor design, but most of them I'd argue are kind of a result of, aren't physical things, put it that way. Phil Ward Yeah. Julian Rodgers] The DSP trickery and things like that. Phil Ward Yeah, yeah. Julian Rodgers But that's a good solid example of, I mean maybe it's because it's easier to model or something, do you think, or is it just a new idea? Phil Ward It's not a new idea, it's been around for quite some time, but I think there's, loudspeaker design has gone down various different paths over the past 40 years or so and sometimes those paths haven't been, in my opinion, particularly valuable. I'm thinking primarily about people that get very focused on diaphragm material. And although diaphragm material is important and things like, you know, carbon fibre tweeters or beryllium, which are heavy to work with and yeah all those, beryllium and all those sorts of things, they are interesting and it is interesting to think about diaphragm materials in terms of what would be the ideal diaphragm material. But in doing that, I think people lost sight of some of the fundamentals, like the work that the PURIFI drive unit company are doing on reducing distortion in bass drivers. That's really interesting stuff and I think it's probably more valuable than worrying too much about the diaphragm material. The PURIFI drivers have, some of them have an aluminium diaphragm, but some of them have just a paper diaphragm that could have been designed fifty years ago. The diaphragm is of secondary importance I think, to minimising the distortion that the motor system causes. I'm not sure how I got onto that soap-boxy kind of bit. Julian Rodgers That's okay. Phil Ward Diaphragm material got a lot of attention in the seventies and early eighties when the engineers at the BBC started to use plastic for diaphragm materials. And this was the new world, plastics were available. We could make diaphragms out of them, but they didn't really offer anything that paper couldn't do. Julian Rodgers No, paper was a remarkably good choice and it's been around... Phil Ward It is. It still is, yeah. Julian Rodgers And we've still got soft dome tweeters in spite of all the... Phil Ward Yeah. Julian Rodgers And this isn't new either, so I take your point. What I wanted to touch on at least was, I mean, pistonic HF drivers absolutely, we're all very used to those. There are some alternative approaches. Any comments on, I mean, there are a couple of different varieties of ribbons and some really esoteric stuff as well but I mean, ribbons both kind of folded and planar. Any comment on why we see as many of those as we do? Phil Ward They're a very interesting approach. I mean, I probably, as a speaker design consultant, I don't think I'd ever argue that anybody should use an air motion transformer or whatever they're called these days. My biggest issue them with is directivity, because they're big. The advantage they have of the diaphragm is driven over its entire area, which is a very significant advantage and it means a reduction in distortion, reduction in reflection of energy back, from the back of the dome out forwards or the back of the diaphragm out forwards. All of those things are good, but the price is significant directivity issues, simply because of their size. And I don't, I personally, although you know, I've listened to a whole bunch of speakers and reviewed speakers in Sound On Sound that have those sorts of tweeters and reviewed them well and for near-field monitors it can work. But the fundamental directivity issue makes me uneasy. Julian Rodgers So I mean, I think you've, I was wondering whether to ask you if you have a kind of like a favourite approach for HF drivers, but would I be right in saying that you've just said that you're less concerned about material and stuff, but it's how it's implemented, not what it's made of. Phil Ward It's how it's implemented. The implementation of a tweeter and whether it works or whether it's any good or not is really the stuff going on behind the dome. Julian Rodgers So wrong question. Phil Ward Not the dome material. Yeah, yeah. Julian Rodgers Fair enough. Phil Ward Hard pistonic tweeters can be made to sound great if the motor system is designed properly and things like the rear energy is dealt with properly. It's not a beryllium or whatever other material dome is not a magic bullet. You can still make a terrible sounding tweeter with a beryllium dome. 28:02 Julian Rodgers Yeah. So briefly jumping into an anecdote, I visited ATC in Stroud some years ago, spent a day at the factory having a look around. My overriding impression I came away with was that there wasn't one reason why ATC speakers are good. It was all about the drivers and it was lots and lots of tiny, tiny little, little improvements they'd made over a very long time. Phil Ward Yeah. It is all in the details. Julian Rodgers And that's why there was, you know, they were so open about yeah, you can have a look at everything, because they knew perfectly well that, you know, nobody's gonna be able to nick it because it's just doing the work. Phil Ward Yeah. Julian Rodgers Yeah. Very interesting. Phil Ward Well it's the same argument I was, or it wasn't an argument, the same thing I was saying about PMC. Yes, you could go out and design a transmission line, a monitor based on a transmission line low frequency technique, but it will take you a long time to make it as work as well as PMC have managed to make those work. But that's the work of probably three decades. Julian Rodgers And as with so many, I don't know, so many people trying to promote some idea of I'll tell you the secrets of, you know, let's say music production, there isn't one. There isn't one in loudspeaker design either by the sounds of it. When I was at that factory visit with PMC, something that I came away with was the approach to off-axis sound. We referred to this earlier when we were talking about point source and dual concentrics and stuff. But their approach was very much one of just, reflected sound is far less problematic if it sounds as similar as possible to the on-axis sound. It'll be less distracting. It was the first time that point had been made to me. It's one that I sort of carried with me. Loads of work's been done on controlling dispersion from speakers these days. Phil Ward Yeah. Julian Rodgers I mean, you're referring to waveguides, which possibly we should revisit. Also, there's approaches like, I mean I'm very familiar with K3s, which are very clever and there's some other people who are doing similar stuff like that. But where are you on that? Do you think that trying to control that dispersion so tightly is a good approach? Phil Ward Yeah, I think it's an approach that can have huge benefits, particularly in studio environments that are work critical. The products like the Kii THREE and the Kii SEVEN I think are very valuable in doing that. The reason that we, you know, and there's other manufacturers. There's Dutch & Dutch who do it passively. There's a couple of others I can't remember now. One of the reasons we don't see much more of it is it's intellectually very difficult to do. The brains behind the Kii THREE and the Kii SEVEN are brains that are working at a level well beyond mine, it's not easy stuff. There's also the point that there's all sorts of monitor manufacturers out there that could probably do it. There's very clever people at Genelec and at Adam Audio and all sorts of places, but the benefit, the advantage that Kii had was they were a startup, so they weren't weighed down by decades of we do loudspeakers like this. Bigger loudspeaker manufacturers that have the resources, the technical resources and the intellectual resources to do things like that, have to be very careful with ensuring that they don't suddenly make their entire range obsolete. So if a big loudspeaker manufacturer came out with a nearfield monitor that had directivity control and all of the rest of the range didn't, there might be a commercial issue there because people would go well, I don't wanna buy the old stuff anymore. Julian Rodgers Although if they're as expensive as Kii's, that problem might solve itself. Phil Ward Yes, there is that. Julian Rodgers Certainly, yes. Phil Ward Yeah. Julian Rodgers There is a barrier to entry involved there. Phil Ward But to get back to the technical point about that, the reason that those sorts of products work quite well, or in my opinion very well in a critical listening environment, is they effectively take more of the room out of the equation. They move the switch from the direct field to the reverberant field gets pushed back in the room and that really helps because you can increase your listening distance. So near field doesn't have to be as near. You can get more people involved, more people can listen, more people will hear the same thing and you have less a room. And we all know how rooms are so important... Julian Rodgers We haven't even gone there because that's just another podcast. Phil Ward No, we haven't gone there. Yeah. Julian Rodgers But yes, absolutely. The speaker and the room very much work together as we've all discovered. Phil Ward But one of the things, to go back a little bit to directivity in the room, the thing about, and the idea you picked up from PMC, which I very much agree with is, is that off-axis errors, the speaker, the room is driven by the off-axis, predominantly by the off-axis sound of the speaker. If you think about it, the on-axis sound is typically firing down the room or even across the room. Its first reflection is a long way away. The first reflections on the off-axis sound, be that the rear radiating sound or the side radiating sound, or the up or the down, those first reflections are much closer and much more powerful. So it's the off-axis sound that defines the sound in the room more than the on-axis, axis sound. So yeah, the off-axis sound is really important. 33:55 Julian Rodgers So I mean, all we've really talked about with controlling directivity is this idea of kind of, I mean ultimately it's like a cardioid response, but full range. It's more difficult to control directivity the lower the frequency gets. There are really interesting things happening elsewhere with kind of like beamforming technologies and, I don't know, larger scale stuff. Things like HOLOPLOT is amazing, if you've seen that, but this is PA equipment, this is large scale stuff. I suspect that a lot of these clever things that you can do possibly don't scale quite as well, although there is sort of stuff to do with beamforming for consumer use as well. Do you think that's useful in a studio environment? Will we see anything like that? Phil Ward You're right. The observation that you're right, it doesn't scale down very well, because HOLOPLOT relies on arrays of, I can't remember, is it 32 x 32 drivers? Julian Rodgers It's loads. Oh, yeah, yeah. Phil Ward It's loads, yeah. So it's very big. Julian Rodgers And you're probably using multiple cabinets as well if you're doing anything interesting. Phil Ward Yeah. And it works because you've got those discrete 32 drivers and the phase interactions of those 32 drivers can be used to control directivity and even multiplex audio, so you can use the same unit to send different audio to different parts of the current. Julian Rodgers Which is mind-boggling, I have to say Phil Ward Yeah. But that only works because of the scale, so it doesn't scale down to our sort of five by four piece of studio, with a... Julian Rodgers Exactly, exactly. So you're saying it's great, but for our kind of application, you can't see it coming down? Phil Ward It's great but no, not yet. Julian Rodgers Yeah. Phil Ward You'd have to start designing very small drivers that were able to create very high sound levels at low frequencies and that's very difficult. Julian Rodgers That's, yeah, that's getting close to a worst-case scenario from a design point of view by the sounds of it. So yeah. Phil Ward Yeah, yeah. Julian Rodgers It's everything you can't have all at once. Phil Ward Excellent. Julian Rodgers Yes. We'll park that idea. I mean, one thing that we've kind of sniffed around slightly but haven't explicitly kind of spoken about is the role of DSP, which I mean, you can't really have not seen it if you've been paying attention to speech design in the last kind of fifteen years. Any comments on that? I mean, is it a good thing? Is it just a way to do stuff cheaper? Phil Ward It's partly, it's a way of adding features, it's a way to do stuff cheaper, from my point of view as you know, my speaker design history comes from the what I, or what I consider the artistry of designing passive speakers. So I'm a bit sniffy about DSP, makes it too easy. But I think if DSP adds something that isn't available by other means and again, we go back to what Bruno Putzeys has done with the Kii THREE and the Kii SEVEN, he's using DSP to achieve something that you can't do any other way. So I think if the DSP adds significant value and pushes the design forwards, yes, it's brilliant. If it's just there to, I don't know, add a bit of EQ, then that's the point at which I get slightly sniffy because I think, with all the money you spent on that DSP, you could have had a bigger voice coil. Julian Rodgers Right. Phil Ward So if it's there to cover up the fundamental weaknesses of the drivers, then... Julian Rodgers Oh, so correctively, correctively. Phil Ward Yeah. That makes me less happy. Julian Rodgers Yeah. Phil Ward But that, you know, that might be a little bit to do with being a grumpy old speaker designer. So yes, DSP is can be incredibly valuable and incredibly useful, but I like to see it doing something interesting. Julian Rodgers Fair enough. Fair enough. Phil Ward And also in, you know, there's this sense that active loudspeakers are just a passive loudspeaker with a couple of amplifiers stuck on the end. I'd like to see much better, much closer integration between the amplifier and the drivers. The kind of things that PSI do, where the driver is incorporated. Julian Rodgers Good speakers, yeah. Phil Ward Yeah. And the driver's incorporated in the feedback loop of the amplifier and you can get a significant reduction in distortion through doing that. That's the sort of integration of electronics and acoustics that I think is really valuable. Julian Rodgers Yeah, very much a slept-on brand, PSI. I like them a lot. So what I was gonna ask is, I mean what, if anything, do you think lots of users of loudspeakers misunderstand that they might benefit from understanding better about loudspeakers? Phil Ward All of the above. Julian Rodgers Okay, all right, we can move on. Phil Ward I think people do misunderstand the fundamental problem of converting electrical energy to acoustic energy and just how inefficient it is, and just how that knocks on to the issues we've talked about and the compromises that need to be made. I think that's the fundamental misunderstanding, is it's a, loudspeakers are taken, you know, in our contemporary culture, loudspeakers are taken almost for granted. And it's kind of miraculous to me, it's miraculous that they work at all because it's such a difficult thing to do. Julian Rodgers I can remember as a kid trying to work out how it was that a single loudspeaker could make more than one sound at once. And you know, I mean, I'm there now, but it gave me something to think about. And yeah, they are pretty miraculous. Phil Ward They are, yeah. 39:47 Julian Rodgers So I mean, you're probably gonna have plenty of examples of loudspeakers you've experienced and enjoyed. Just name one. Pull one out of the air of something you've really enjoyed hearing. Phil Ward Well I've already mentioned it, the AsciLab 6b, which I reviewed I don't know, nine months, a year ago. So AsciLab is a little South Korean company who have a long history in environmental acoustics and just decided to have a go at making speakers. But the guy who's their founder is a very intensely academic engineer and he decided he was gonna do it properly. He wasn't going to engage in any of the sort of hi-fi snake oil. He was going to engineer this speaker as well as he possibly could and the results are really quite striking. So the 6b is a smallish well, medium-sized near-field monitor. It's two-way, it's got a big waveguide, it's got a PURIFI driver, it's passive and I do love a passive speaker. Again, that's because of my history, really. I love the challenge of a passive speaker and he's done an incredibly good job at engineering a speaker as well as can possibly be done, and it sounds great, it sounds really striking. You think oh, that's right. So I think that's a great product. The pair I had for review had to go back and I kind of wish they didn't. Julian Rodgers Yeah, I've had that about a couple, but there we go. Phil Ward Yeah. Yeah. Julian Rodgers Brilliant, brilliant. Anyway, thank-you so much for that. That was really genuinely enlightening. I'm glad we did it. Phil Ward Thanks Julian. Julian Rodgers And yeah, thank-you for listening. Be sure to check out the show notes page for this episode, where you'll find further information, relevant links and details of all our other episodes. And before you go, do visit soundonsound.com/podcasts, where you can explore what's playing across Sound On Sound's podcast channels. This has been a Julian Rodgers production for Sound On Sound magazine.