The following interview appeared, in edited form, in the November 2004 issue of the British Pro Audio magazine, Audio Pro. There had been some anticipation that Dr. Heil would tackle some of the anti-Line Array comments made by Funktion One's Tony Andrews, in Audio Pro's April 2004 issue. As it turned out these two acoustic wizards had a lot in common - not least possessing much charm and good humour.


The following interview appeared, in edited form, in the November 2004 issue of the British Pro Audio magazine, Audio Pro. There had been some anticipation that Dr. Heil would tackle some of the anti-Line Array comments made by Funktion One's Tony Andrews, in Audio Pro's April 2004 issue. As it turned out these two acoustic wizards had a lot in common - not least possessing much charm and good humour.

It is given to few men to create the sort of radical change in their industry wrought by Christian Heil, founder of L-Acoustics and the father of modern line array. While it's true that Dr Heil didn't invent the underlying theory, it was his pioneering research and design work, resulting in the revolutionary V-DOSC system, that turned the industry's conventional wisdom on its head, with implications that are still being explored, some 10 years later.

In that time, rival manufacturers, who probably sniffed when this tiny, unknown French company had the audacity to challenge the orthodoxy of live sound, have not only had to eat crow, but stand on the table afterwards and make long, loud speeches about how it was the finest thing they've ever eaten and how they'd always said so, hadn't they?

And who can blame them, when the use of a line array system is as much a part of some artists' and engineers' contracts as the provision of the right brand of mineral water and the absence of red M&Ms?

In fact, so Borg-like has been the hegemony, that voices are starting to be raised. As veteran British designer Tony Andrews of Funktion One complained in these very pages not so long ago, the situation is starting to look like a living example of Emperor's New Clothes syndrome. Most realise that it is getting out of hand - but few dare say so.

But here's a thing: Christian Heil, himself, is one of them. And what's more, he has a brand new line array that could, once again, change the very nature of the game.

But to begin at the beginning, how had Dr Heil, a particle physicist by training, originally managed to get involved in all this sound stuff and what was the genesis of his line array concept?

'Oh, history...' he laughs. 'You know, I'm not very good at looking back. I feel uncomfortable when people ask me about the past as I don't think what I do, or what we have done, is something very exceptional or rare.'

But we can't be doing with such modesty, however disarming, so I press the point about the overwhelming success of line array - only to have The Tricky Question planned for later in the interview cut down to size before it was even raised.

'Well, yes, I know. But sometimes fashion creates strange situations. You see, I'm not one of these guys who say that the line array concept is the answer to everything - the solution to every problem. There are others which are quite acceptable. Line array is not universal.'

Which, coming from the man who put it where it is today is quite something - and it is a subject to which we shall return.

'When I was in my mid-twenties (I'm about 50 now), I was doing a PhD in the physics of elementary particles, but I was very interested in sound and, not being a musician or involved in music, I was trying to find a link between physics and music and it was sound that was the link.

'As for line array, when I started my company the fashion was to multiply boxes and cabinets to create big clusters on the side of the stage and, obviously, the result of that was, as is widely recognised today, interference. But at that time, it wasn't a real issue - it was either accepted or ignored. But the fact was that these speakers were creating high SPLs close to the arrays but with very poor intelligibility at long distances and with a control of directivity that I can only describe as chaotic.

'My first idea was to simplify the configuration of speakers. When you saw one of those clusters you had speakers arranged in the vertical domain as well as the horizontal and that was something quite complex, so I started by using conventional speakers in a line array format - that was my first system, something like 20 years ago.'

What had made him think that was the way to go? In essence, good old Occam's Razor.

'It was simpler - from the physical point of view it was easier to address the problems in one plane, in one dimension, rather than in two dimensions simultaneously. In one plane, it was easier to understand the behaviour of the speaker, and it was also easier to control the horizontal directivity and avoid interference between cabinets sitting close to each other. In the vertical plane, the line array also provided more focus of energy in the vertical domain and was also creating a better throw in the lows and the mids.

'What we then came up with was WST (Wavefront Sculpture Technology), which we introduced in 1992, and which gave us control of the high frequencies. This was something that needed to be addressed, because when we produced the early line arrays, we had a good throw of the midrange, good control of the low-mid and lows, but we couldn't control the high-mids and high frequencies, because, at that time, I was still arraying conventional cabinets, using traditional horns. But already I was impressed by the capacity of the system and we were impressed by the fact that the line array offered a much smaller and easier rigging proposition, so it was much simpler and cheaper for the end-user. We could see that it could become attractive in principle, but we were facing some very difficult issues, trying to work out how to smooth the high frequencies and how to control them. That took us five years work, before we could introduce V-DOSC.

'What V-DOSC meant was technology which allowed high frequencies to couple in a way so that when you assembled two high frequency units, they behaved as a single one. It's quite impossible to do this with two traditional horns, because when you put them on top of each other they have two different origins and will never match together, even if you curve them - the two centres cannot be located at the same position, so you will inevitably create interference. The DOSC waveguide allowed us to array high frequency drivers on top of each other and create a flat isophasic wavefront and from this we discovered a new propagation mode - the cylindrical wave front.'

The work which led to Dr Heil's patented DOSC waveguide took the team into uncharted waters at times. 'When we discovered that our measurements were different from our expectations, we had to launch a new series of research programmes to try and understand what was going on - how the wavefront propagated in correlation to the shape of the waveguide. We understood then that there were quite different fields of propagation, the nearfield, the farfield and sometimes, when you don't achieve what you want - the chaotic field! So it was this experience that was translated into Wavefront Sculpture Technology.'

Which, given the usual scheme of things, was where a cynic might have expected it all to end. French scientist develops amazing technology with huge potential for Rock and Roll PA systems (among others) and is promptly ignored by the rest of the world. Indeed, given the size of the companies he was up against and the legions of grizzled sound engineers who had cut their teeth on point source systems, it seems a minor miracle that L-Acoustics not only made a breakthrough, but became one of the most important speaker makers in the world. How had it happened? How had Dr Heil managed to persuade the audio industry he was on to something and that what everyone had been doing for the past twenty years was, not to put too fine a point on it, not always the best way of doing things? How had they reacted?

'Well, at first, I would have to say that they did not react. I'm not even talking of the Americans, here - I'm talking of the Europeans. I remember I first showed this technology at Frankfurt in '93 and, although we had a year of experience in the field with some French companies and designers and I was sure it would work, there were obstacles. You see, we were not only a French company but a very French company, which means that we weren't exporting! So at Frankfurt I saw many people, whose reaction was that it just wouldn't work, that this configuration of vertically stacked boxes couldn't work because there would be too much high-mid concentration with a poor high-end. And in theory they were right, but they didn't know we were using this new technology. So at first engineers didn't react well - until they had to use it.

'What happened was that we had engineers who had had experience with the system when they were touring in France and they started talking about it, which is how it began in Scandinavia, in Germany, Holland and then the United States.

Had he found the World's biggest market, the USA, as difficult as one might imagine?

'Not really. Actually, I didn't find the United States that hard because, in a way, the United States works like a united nation, so it's easier than in Europe where, despite what we are trying to build, there are still very individual nations. In fact, we were successful in the US before we were successful in Europe. It took us two years, which I think is quite fast for a French company that was completely unknown there.

'What made the difference, I think, was that we had the support of some famous engineers such as Buford Jones, who had been Pink Floyd's engineer and who had a lot of respect. Also Jeffrey Cox, who has been my partner in the US to build the company there. That sort of support really helped.

'When we first went to the USA it was with a very small line array system, just 16 boxes, and the first demonstration we did was a shoot-out against companies using S4 systems. We were comparing four S4s and four V-DOSCs and, obviously, four V-DOSCs were about the size of a single S4, so it was a shock when we were demonstrating that these small cabinets, ok, maybe they weren't providing as much SPL, but they had more throw and more clarity than four S4-type speakers.

'People's first reaction was: "Well, you know, your system is too small for the American market" but engineers started working with it, for example Patrick Baltzell, who began using it for corporate shows. What we had was a rental inventory of around 48 cabinets in the US - we weren't selling boxes - but some companies started using it, grew confident with it and started using different configurations and what happened was that V-DOSC, which was originally perceived as a corporate system, became a Rock and Roll system with bands like Motley Crue, Van Halen and Bob Dylan, as well as a classical system used by Pavarotti - it became a system with very wide applications and it took no more than two years to get to that point.'

If all this sounds like proof that the world will, indeed, beat a path to the door of the man who invents the superior mousetrap, there is at least a suspicion of marketing expertise here, as well as the acoustic variety. For example, it has been (perhaps unkindly) suggested that Dr Heil's insistence that V-DOSC systems could only be driven by qualified engineers, endowed a little extra marketing magic and mystery. Be that as it may, he insists it was absolutely necessary.

'You have to understand the context of that time. The typical box had a directivity of 40 x 20, or 40 x 40 and you'd assemble these boxes in a not very well defined way. If you looked at those traditional clusters, you wouldn't see two boxes with the same angle, because the rigging didn't allow for that sort of precision and, even if it had, it wouldn't have helped, because it wouldn't have removed the interference between the boxes - just changed it a bit.

'When I first presented the system to engineers I arrived with my laser beam, with all these kinds of tools that looked very sophisticated for the sound reinforcement world of that time and people looked at me as if I was coming from Mars - the traditional crazy scientist. But what I was trying to show people was that making a mistake of one degree makes a big difference at 70 metres - you can miss ten rows of seats that way. It sounds obvious today, but at that time, think back 11 years, it wasn't understood, so if I had given this system even to the most talented sound engineer in the world but without a system engineer who knew how to use it, he would have made the same kind of mistakes. Adjusting wavefront sculpture means what it says - you are manipulating the wavefront. The box in itself hasn't got any vertical directivity: that is given by the shape of the array and this isn't very difficult to understand, but it needed consideration and at the time people hadn't had to think that way.

'People used to look at me and smile and say "You know, Christian, you're a very nice guy, but I've been a sound engineer for 20 years, so I know how to rig a system" and obviously they did - but not a system using this technology.'

Imitation being the sincerest form of flattery, Christian Heil and his team perhaps should have been glowing within a year or two, as the world and his wife began to play catch-up. This, as you might expect, doesn't exactly please the otherwise very affable Dr Heil.

'It didn't happen that quickly,' he says. 'But I think it started with EAW, for the Atlanta games. In fact V-DOSC had been specified for that by Patrick Baltzell, but I understood there were some hard political aspects in the US and that it would have been very difficult to accept a system that was, well - French, firstly, and secondly, not commonly accepted at the time - not one of those systems from the big guys like EAW, JBL and so on, who were fighting very hard at the political level. So, at that period, both EAW and JBL both decided to design line array systems.'

Now, taking the recent PLASA as an example, the only wonder is that the guy running the hot dog stall doesn't have his own new line array system on offer. Does that ever make Dr Heil feel like Baron Frankenstein - a man who has unleashed a rampaging monster?

'Yeah, like the golem or something,' he laughs. 'What can I say? It's about fashion, but...well... I don't regard this very positively, I have to tell you - not only because all these manufacturers have copied an idea, but because they didn't copy well! In fact it devalues the original concept. Imitating a line array concept - creating a system where boxes are lying on top of each other, well, why not? It's saving rigging and promoters can sell more seats in a venue, but I do think that's the main reason why they've done it - not because they want to create a wavefront sculpture technology, because I don't think most of the manufacturers have any idea what that is. They don't have a clue. When I see the designs, I look at them as I did ten years ago, when I didn't know anything about WST - typically, horns lying on top of each other... What can I say? I'm sure the results aren't going to be very good. It's depreciating the line array concept.

'Still, the V-DOSC technology, which is built on WST technology, is recognised as the original and sets the standard, so yes, everyone has his own line array, but all I can say is that I feel sorry for these other manufacturers that they feel they have to do it, and my belief is that they are only doing it because they have to do it. I remember one of the most reluctant was John Meyer - even after presenting the M3D system, he was saying that line array is not a good concept, and now they have four or five line arrays. I look at JBL - they had no choice, either, they had to make a line array.'

This overwhelming triumph, however, is far from comforting to Dr Heil. 'Even though we originated the design, I don't think that line array is the universal solution. But look, before we go further into this, I would like to draw a distinction between the terms "line array" and "line source". Line array may be a big problem, but line source, that uses WST criteria is, to me, a very good solution to some configurations and when I say some, I'm not talking of everything. I'm talking about configurations where you have a big gap between the close audience and the far audience, where a horn, or a conventional waveguide in a box cannot address the farfield and the nearfield easily, where you have to focus the energy for the back of the venue and the front: all these kind of configurations, like outdoors, or big arenas, or theatres or clubs with shallow audience profiles. Then the line source concept is a very good one because it allows you to focus the energy where you want. It's very much addressing the farfield with very good projection of highs, but without too much power in the nearfield. In other words, with a line source you can smooth the SPLs over the audience and that, typically, is very difficult to do with a non-line source concept.

'But when you want to use a line array in small theatre or in a venue with several levels, with balconies, or where the you have a floor under, say, 20 metres (and a lot of theatres are like that), or in a venue that is very high, like a typical opera house - then it becomes very hard to use a line source because you need too many boxes.

'The trend for line array has invaded all these theatres and they are willing to use a small line array concept, but as the system gets smaller the wavelength remains the same, so you cannot focus the low frequency or the low-mid in a small line array, so there's no advantage as far as I'm concerned in that sort of situation.

'Line source is not a universal tool and we have quite a range of speakers, based on a coaxial design, which are much less visible than line array, but for distributed applications, coaxial principles are much the best way to address reinforcement. They are easy to use, a perfect point source design. You can make mistakes and it still works and the sound - let's talk about sound! - it's very nice.

'What people possibly don't know is that the line array component of L-Acoustics is no more than 40 per cent of our turnover, if we include ARCS. 50 per cent is coaxial speakers and ten per cent is amplifiers, so, as I say, we have never pretended that line source is a universal solution.'

And so to the big news - Christian Heil and his team have been at it again. Over the 20 years that it has been making sound systems, L-Acoustics' new product introductions have been sufficiently spaced to suggest that the company only launches new systems when it genuinely feels it has something fresh to say (ARCS in 1995, dV-DOSC in 1999 being the major introductions), so any new product is unlikely to happen just because the market needed a few extra volts to keep it awake. And what the company has unveiled (more or less as this issue goes to press) is very much a grande fromage.

So, Dr Heil, what is it called? And what is it?

'Ah! Well, you picked the right day to ask as we only decided on the name this morning! That was the most difficult thing for us: KUDO. What does it mean? Not much, actually! It's a reference to the codename we had when we were developing it, which was "K". If you look at a K, it has a straight line with a v-shape and that's the clue, because this kind of v-shape is used as a movable coverage louvre, and this is the kind if technology we are introducing - an adjustable louvre. This means that from a KUDO box you can have four different directivities. You have two symmetrical, 50 degrees and 55 degrees and 110 degrees, so a narrow angle and a wider angle. You can also choose an asymmetric configuration with 25/55 Left or 55/25 Right. So each box in a line array can now be configured with a different directivity pattern, so long throw boxes at the top of the array, for example, will generally have a narrower angle in most configurations, because you don't need a very wide angle, say at a sports venue, where you need a narrow directivity for the long throw and a wide angle for the short throw. So I can imagine that in an array, some boxes will be configured in the narrow angle, with the bottom cabinets focused on the mid, and the nearfield will be in a wide angle configuration.

'For permanent installations, when you have a Left/Right system, you will use an asymmetrical configuration to avoid reflections on the side walls. I really believe that introducing this is introducing the next generation of line source arrays. This is what needed to be done - addressing the horizontal directivity.

'In effect, what we are doing with KUDO is addressing what other manufacturers should have been addressing during the past 11 years. What I didn't understand during all that time was the way in which other manufacturers are trying to imitate V-DOSC, using the same formats, the same configuration, the co-planar symmetry, the same kind of speaker arrangements. And when we created the dV-DOSC with eight inch speakers, again, within two years we've seen all these other eight inch line array systems. But no one has presented an evolution of the concept and it's very curious, because there has been a demand from users: they were actually asking for this.

'With a line source array you can very satisfactorily address the control of vertical directivity - you can focus the energy where you want. But what is a problem is the fixed horizontal plane, and engineers have been telling me that, for example, dV-DOSC having 120 degrees directivity was perfect for many corporate applications, but when you have a narrow venue, they might have problems with reflections. So the next step was to address horizontal directivity as well and that is what we are launching at AES.

'Many rental companies need a very flexible system - something can be used one day in a ballroom, the next day at an outdoor festival and the day after in a theatre and they want their main system to be the same box - they can't afford to have multiple systems and as KUDO comes between V-DOSC and ARCS, typically 3dB lower than V-DOSC and 3dB louder than ARCS, it fits well. But it is a universal box, a full-spectrum box with a very deep low end.'

So there you have it and, if history is a guide, it's a pretty reasonable bet that the next few years will see other manufacturers scrambling onto the horizontal directivity bandwagon, too. Meanwhile, no doubt, that self-effacing revolutionary, Christian Heil, will be working with his team, plotting to remain several steps ahead. Something even his rivals must admit he has been remarkably good at, to date.


2005 Gary Cooper