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An interview with Robin Marshall, ex-Epos designer

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Interview made last year by the student audio club at the university in Hong Kong. I nicked this from the Pink Fish forum.


Q - You are probably best known as the founder of Epos and for the products you designed under the Epos badge.


Is that right? Epos engaged a rather short period in my life. I’ve done other things, too.



Q - Nevertheless, people still talk about the ES14 and the various audio forums are full of posts relating to them. I’ve seen them favourably compared with the best current products on several occasions.


(Laughs) That’s very flattering. It’s always nice to have one’s ego massaged.



Q - Were you involved with any of the Epos products that came after the ES11 and ES14?


Not at all.



Q - Do you take any interest in the current direction and product offerings of Epos?


To be perfectly honest, I don’t know a thing about what goes on at Epos these days. It simply isn’t my concern. I’ve known Mike Creek, who owns Epos, for many years and I have every confidence that he is making stuff that’s right for today’s market.



Q - Do you still use Epos speakers in your own system?


No, I’ve not used them for many years.



Q - What do you use?


I have several different speakers which I use in different parts of the house. I do quite a lot of informal listening sitting in front of my computer and for this I use small nearfield monitors which I cobbled together using odds and ends that I had lying around. In my main system I usually use a JBL 1400 Array, although I sometimes pull out an old pair of Yamaha NS1000s.



Q - Are these better than your Epos designs?


Off course. If nothing else, the JBL Array has the capability to handle the dynamics available from today’s recordings.



Q - If you were back at Epos and making a speaker in the category of the ES14, would you do it differently from the original?


I designed the ES14s more than 25 years ago and things have moved on since then. Recorded music has a more bandwidth, greater dynamic range and less distortion. Reproduction systems obviously need to keep up. We have access to better materials and manufacturing technology and we have computational power that was just a dream when I was working on the ES14.


Physics hasn’t changed, of course, and all the constraints that were in place when I designed the ES14 are still there. What has changed is our ability to negotiate within these constraints and fine tune the various conflicting trade-offs. Finite element analysis, for example, would have reduced the time I spent designing the ES14 magnet system by a considerable margin and would have enabled me to do a much better job. As it was, I had to rely largely on intuition and cut-and-try evaluation. Most of the design calculations were made using a Hewlett-Packard HP41 programmable calculator and took an eternity. Today it would take just a few minutes.


My views and my engineering prejudices haven’t changed much in 25 years, but the tools available to me certainly have. I’d like to think that I could design better products today than I could yesterday.



Q - Would you use a metal dome tweeter?


(Laughs) I’m an old man and I don’t hear much above a 500 Hz any more so I’d probably leave the tweeter out.



Q - Seriously, you have often championed metal dome tweeters in the past. Are you still convinced of their merits?


All tweeters are defective in one way or another. I’m not so much a fan of metal for tweeter domes as a fan of high-modulus materials. It just happens that most of the available high-modulus materials are metals.


It seems to me to be important to avoid destructive resonances in the diaphragms of high frequency driver units if we are to have any hope of extended bandwidth and predictable dispersion characteristics. Most soft domes tweeters exhibit seriously resonant behaviour and the best we can do is to damp the Q of these resonances. Maybe that’s an acceptable solution. Maybe it’s not. All I can say is that I would prefer not to have the resonances in the first place.


I looked very seriously at beryllium when I was designing the ES14 tweeter, but I had to accept that it simply wasn’t possible to manufacture Beryllium domes without the risk of killing myself and anyone else who came into the factory. Times have changed and now I could buy ready-made beryllium domes from China for half what it cost me to make aluminium ones. Using beryllium for the dome wouldn’t be a panacea, but it would certainly give me a bit of a leg-up.



Q - Minimalist crossovers is another of your hallmarks. Would an updated ES14 follow this path?


Simple crossovers place huge demands on the drive units and in almost every respect are more difficult to engineer properly than complex ones. In a perfect world I would use first order electro-mechanical slopes because nothing else can equal their time and frequency domain performance. Lots of things need to be right to make them work and it certainly isn’t a trivial engineering exercise. It’s the fastest route I know to exposing all the deficiencies you built into your drive units!


First order electrical slopes designed in isolation of the responses inherent to the drive units are not the same thing as first order electro-mechanical slopes, as I sure you know, and may or may not provide the same performance benefits.


High order crossovers make the designer’s life easy and on the face of things allow the use of less-than-perfect drive units. I’m not convinced that they don’t add their own set of defects to the mix, however. I’m always amused when I see products with fourth order networks described as “phase coherent”. I assume that they respond to physical laws which are different from the ones that I know.



Q - The ES14 is often criticised for its bass. Do you think with hindsight that you got it wrong?


One big problem with the ES14 was that people refused to use it in the way I intended. They always wanted to believe that it was a vented box, which it wasn’t. It could certainly be seriously boomy and ill-controlled when used as one. I’ll have to leave it to your judgement to say whether I got it wrong.


Something that I might say in my defence if you decide that I did get it wrong is that much has changed in the world since I designed the ES14 and it shouldn’t really be a surprise to find deficiencies when it is exposed to today’s higher resolution program material. I certainly wouldn’t expect to step out of my current car and into one made quarter of a century ago without having to make some adjustments to my driving and to my expectations.


More important than all that is the fact that you cannot consider the low-frequency performance of a speaker in isolation. You need to consider it as part of an integrated system with the room. The room is always the dominant factor at low frequencies unless it is large enough to have resonant modes outside the bandwidth of the speaker. Any speaker with reasonably extended bass is likely to get itself into trouble in the average room and there will always be a chance of it sounding fantastic in one room and dire in another.


The best thing is probably to equalise the speaker/room system. I use four sub-woofers in my main system to try to energise the room modes coherently and I use a parametric equaliser to notch the major additive room resonances. One great thing at low frequencies is that if you take care of the frequency domain you automatically take care of the time domain.



Q - Would you have any interest in designing a product like the ES14 but updated for today’s technology?


Not really. I don’t have an awful lot of interest in hi-fi these days and have very little knowledge of today’s flavours. My attention is tuned more to professional audio.



Q - I’ve read somewhere that you had something of a reputation for the sheer scale and diversity of your recorded music collection. Is music still important to you?


Absolutely. Nothing has changed. I still see my application of technology as being nothing more than a servant of the music. How does it sound is still the most important question that I can ask myself.



Q - Is your music collection on vinyl or CD?


A mixture of both. It’s increasingly finding its way onto hard disk, too.



Q - I know that you once played your vinyl on a Linn LP12 but that you no longer do so. That came as a surprise to me because I thought that the LP12 was something of a legend. What turntable do you use now?


I owned an LP12 for several years but I became increasingly frustrated by its performance limitations. I think its true to say that the LP12’s reputation was build on a foundation of bullshit and I guess that the myth promised us more than the reality was able to deliver. I returned to a Garrard 401 which I’ve owned for at least a million years. I’m sure that the sophistication of today’s precision engineering tools could produce something better, but I’ve simply not taken the time to look around at what is currently on offer.



Q - And Naim Audio?


I’m still a big fan of the Naim products that I use in my own systems. I have one of their CD players and I have several NAP250 power amplifiers. The NAP250 is a good, solid product, even if its circuitry is not far removed from an application notes design. I’ve always thought that Naim take a lot of care to get the fundamentals right and this shows in the reliability and continuity of their products.


I’ve not shut my eyes to other manufacturers by any means. I’ve owned a raft of different amplifiers over the years and I still have a liking for tube amplifiers. This dates back to my schoolboy days when I spent all my money at H L Smith’s in the Edgware Road buying kits to build the various Mullard designs.



Q - How would you categorize yourself? Are you a physicist? An audio engineer? A product designer? What?


It would be pretentious to call myself any of these things. I’m a seeker of knowledge. With each successive year I learn a little more and then find that I know even less than I previously thought. On the day that I die I shall probably need to confess that this amazing reverse spiral has resulted in my not knowing anything at all.

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AudioEnz;63107 wrote:




Q - How would you categorize yourself? Are you a physicist? An audio engineer? A product designer? What?




It would be pretentious to call myself any of these things. I’m a seeker of knowledge. With each successive year I learn a little more and then find that I know even less than I previously thought. On the day that I die I shall probably need to confess that this amazing reverse spiral has resulted in my not knowing anything at all.


There's a great truism in this last answer.

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The interviewer goes on and on about Epos despite



Epos engaged a rather short period in my life. I’ve done other things, too.


Guess something got lost in the translation.



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Interesting he uses the JBL 1400 Array; most in the Hi-Fi press pooh-pooh these horn loading systems due to "colouration"...


Myself, I was bought up on horn loaded PA's so I'm partial to the new JBL array systems.


His main system sounds like a PA system anyways what with 4 subs and a parametric eq to correct. I'd say he likes his music LOUD.

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michael w;63117 wrote:
The interviewer goes on and on about Epos despite [...]


Keep in mind that this was an interview undertaken for an audio club. It's not surprising that the interview concentrates on Marshall's hi-fi activities.



wysper wrote:
probably didnt do their research and didnt know what else he has done.


I'm a great fan of what Marshall did with Epos. I have read every interview with him I could find and anything he's written. And even I lost track of him more than a decade ago.



got tinnitus wrote:
Interesting he uses the JBL 1400 Array


The NZ importer brought two pairs of them into NZ. I tried to get a pair at home over Christmas, when they weren't doing any good to the importer sitting in their show room. However they were not to be moved. I was offered the opportunity to "review" them in the showroom - a dubious method that another publication undertakes - but I declined as it didn't meet the standards I require from a review.

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Very interesting interview - thanks Michael - I am intrigued by the JBL 1400 Array - any one with first hand experience with them? - they seem to have alot of what I like - hope I'm not staying too far from the original thread - cheers

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