Coda Audio: Behind The Music

Twenty years ago, Svetly Alexandrov had an idea – a concept which, he believed, if implemented correctly, could lead to radical new standards in terms of sonic quality and sound reproduction. Now, dozens of patents later, and with a seriously strengthened global workforce, his forward-thinking company, Coda Audio, is ready to put its stamp on the loudspeaker market; and if its technology is anything to go by, in a very big way.

Svetly Alexandrov ultimately got the bug for audio after playing in bands, and not being satisfied with the sound on stage. One thing led to another, and eventually, a company was born.

Based out of Hannover, Germany, Coda Audio was born in 1997, and has been ISO-certified since 2007. The core of its manufacturing, however, is carried out in the Coda factory in Alexandrov's hometown of Sofia in Bulgaria: drivers, mechanics, voice coils, you name it – all the core elements that go inside each Coda product are made out there.

“It was more like fun at the beginning,” admits Alexandrov, with a smile. “But we really started Coda [Audio] six or seven years ago; that's when we began to create the brand.”

Now, the plan is to become the number one choice in sound systems for audio professionals around the globe, from major touring applications to installs, theatres, and house of worship. It's a hell of an ask, one might say, but Coda has a series of curveballs in terms of philosophy, outlook, and most impressively, its technologies. The company is under no illusion that conventional methods will cut it – and one thing these guys are not, is conventional.

“We're a vertically orientated company, which means we produce really almost everything,” Alexandrov begins. “We buy tonnes of metal, we buy wires, all the raw materials, and everything else we do in house; the metalwork is done by our many machinists working day and night. There are some gaps that we will close when the new factory arrives [in late 2018], like the coating of metal, which is currently done outside because we don't have space in the factory, and you need a different building for that, as they are chemical processes. But even that will soon be done by us.”
Sounds like it'll be a proper one stop shop, then?

“Yes, but we knew we needed to invest in people and machines, and that is a heavy investment. But it means we have the control of the quality, and ultimately, we can realise almost every idea because we don't need to speak to external suppliers,” Alexandrov says. “For example, the pins for the line array. I had three meetings in this room with pin manufacturers; people buy them, but never produce them. I tried to explain to them what I wanted, but three meetings later, I thought, 'ok, let's do it ourselves'. With every other speaker manufacturer, you take the pin out, and put it back in – it's easy to lose them. But our pins always stay in position: they can be locked in or out, but they can't be lost! This is what I wanted 10 years ago, but no one does it, even now! [smiles]”

In addition to the pins, there are various little 'touches' that Coda applies to its boxes, which will all be highly beneficial to touring teams and crews: vents that keep water out, connectors on front and back of subs to make cardioid setups easier, custom dollies easy manoeuvrability and setup, the list is long.

Smart Thinking

Unique may be an overused word in this business. Game-changing definitely is. But when you take into consideration, and really get your head around Coda Audio's many proprietary technologies, it's difficult to keep your jaw off the floor. It's easiest to let Alexandrov to do the talking.

“OK, first and foremost, we use technology that we built and designed in house, and it is very different to our competitors; for example, all high frequency transducers are with ring diaphragms instead of dome diaphragms, which I'll come to in a second,” he says. “We then have our Planar Wave technology, whereby the driver produces a Planar wavefront without transforming a spherical wavefront coming from a compression driver, like almost every other speaker manufacturer. We do this in just one driver design, which itself produces a planar wavefront.

“Then there is DDP (Dual Diaphragm Planar-wave-driver), another unique technology. Normally, if you see a big line array, you see lows, which could be double 12-inch speakers; then four small speakers for mid range, maybe 6.5-inch; and two or three compression drivers for the highs. But this never gives you a really good directivity; you're using some small mid range drivers which aren't efficient. So what we did is put mid and high range in one relatively small transducer with very high efficiency, and as a result, we get 12-15dB more headroom than the traditional technology, but with a much smaller and lighter design.”

At this point, Alexandrov uses an interesting analogy: the electronics industry in the early '50s, where you had big boards with different electronic components and transistors, and then someone managed to put it all into a small package, which caused an electronics revolution. He wants to create one in audio.

“It's the same principle, really: our package is much, much more efficient,” he insists. What this means, I am told, is that Coda is able to reduce the size and weight of its big systems by around 50%, while actually increasing performance, which sounds pretty crazy to me.

“[laughs] In the early days, a computer was a building... I was in such buildings! But now it's more powerful, and all in one box. Traditional loudspeaker technology is a building, and we tried to do that same thing with our technology: get it into a smaller, lighter format, yet more powerful and efficient. So this is what we have done using DDP.”
Then comes DDC (Dual Diaphragm Curved-wave-driver), a similar technology, but with a bit of a twist.

“With DDC, we don't produce a planar wavefront, we curve the front, and we have the technology to do so,” Alexandrov states. How so, exactly? “Well, normally you have a compression driver, and you have a horn, and the horn makes the directivity - 90- by 40-degree, for example - and it always produces some kind of distortion to reshape the wavefront. With the DDC, we can shape it in the way we want. Take our small format APS speakers as an example: the wavefront is already produced with 20 degrees, we don't need to reshape it and add distortion, and it's much more precise, so when you put more APS together, they perform as one single cabinet; there is no interference between them because of the principle of how it works. Already in the transducer we produce the wavefront we need, so we just add another piece, and another piece.”

The Driving Force

Very smart stuff. But it's Coda's compression driver technology that's probably the most mind-blowing – it's the core of everything, Alexandrov says:

“The conventional dome diaphragm design is very old; it was designed and invented in the '20s, and until today, almost all drivers are working like that. Sure, there are new materials, therefore you can increase power handling and performance, but the basic design hasn't changed in 90 years.

“The problem with a dome is, you have a voice coil, it moves, and then a mechanical wavefront starts to move and reflect back, creating distortion; the diaphragm itself is actually larger than the wavelength. So let's say a wavelength at 10kHz is 34mm, but the compression driver is a three- or four-inch voice coil: at 4-5kHz, it already starts to be incoherent and unstable, as the wavelength is smaller than the physical size of the diaphragm, which means it's very hard to transform that energy into acoustical energy. So what happens is, some pieces of the diaphragm will start to resonate at 10kHz, 11kHz, and so on. What a transducer engineer will do to fix that is essentially like putting a band aid over the fundamental problem: he'll search for materials, perhaps put some coatings on the domes, but it's all cosmetic. You still have the problem, which people have put up with for years.”

And Coda has the answer?

“We do. We put in a ring diaphragm, where all of the pieces of the diaphragm are very near to the voice coil. What that means is, when the voice coil moves, the diaphragm moves as a piston, because the wavelength is larger than the diaphragm itself, which then means we can constantly accept the wavelengths without any distortion – it results in the purest audio you can get.”

But isn't the ring diaphragm a considerably smaller diaphragm than the dome diaphragm?“Actually, no – we have two diaphragms on the ring one: one inside, and one outside of the voice coil, so we actually have a larger diaphragm than a dome,” Alexandrov reveals. “But still, all of the pieces of the diaphragm are very close to the force, which is the voice coil; and this is how we tune the diaphragms: the higher frequencies are produced only from one diaphragm, and on the lower range, both are working in phase. This has helped us to increase the frequency range of the driver, as we are actually driving two diaphragms of two different sizes with the same voice coil.”

As I try to compute this, I realise I'm almost sold without even listening to the kit, or for that point, any evidence that it can do all Coda says it can. I explain this to Alexandrov, at which point he begins to talk about sound quality, and why we as humans perceive something to sound good, and not so good. Not entirely sure where he's going with this, I decide to sit back, and listen on.

“An engineer measures frequency responses, and with modern DSP, you can tune all speakers with the same frequency response. It could be a €100 or €10,0000 speaker, but with the same frequency response – so why does one cost 100 times more? Well, frequency response is obviously not sound quality; you measure some distortion, perhaps they even have the same distortion, or even a speaker with more distortion sounds better. But why? This is the intermodulation distortion, which is very important, and difficult to measure; the coherency, which are the resonances of the diaphragm; and the time domain. What mostly measure the electrical domain, and the acoustical domain; but in the middle is the mechanical domain, which is not very well researched – and distortion and resonances happen there, also.

“Also, with a dome diaphragm, you need to use some special materials like titanium or neodymium, which are light and strong, but because it's a long distance from the voice coil, you still need to use some heavy stuff. There are two different ways of designing this: some companies will use light aluminium domes, which are better, but when you apply a bit more power, they produce distortion, and everything gets crushed; other companies take slightly thicker titanium domes, which is more stable, but heavier, so you can apply a bit more power, but you have other problems, because of the moving mass. What we do, because the distance to the voice coil is very short, is use very thin and strong polymers, which means the moving mass is less, and the efficiency is high.”

How high, exactly?

“We don't have any driver less than 35% efficiency, and we can be as high as 50%, compared to 15% from the competing manufacturers. Because of the efficiency, we have applied less power to achieve it, too.”

Feel The Music

So each part of the Coda pie, so to speak, acts like a domino to the next. I ask Alexandrov to tell me a bit more about measuring intermodulation distortion.

“Normally, engineers are measuring distortion with sweep signals, then you measure harmonic distortion, second harmonic, third harmonic, and so on. But music is not like that. The sweep is always one tone at the same time, whereas music is always many tones at the same time; and these many tones are making behaving differently in the mechanical domain, therefore we want to see what's happened in a real music application. So we apply three tones at the same time, very close to each other, on a very small one-inch high frequency driver. As the tones are very close together, and the diaphragm tries to produce this, it gets stressed, and unstable. This is a small dome, high end tweeter, which is used in very high end products, bear in mind.”

And how do the results differ compared to the ring diaphragm?

“On the dome, we can see second and third harmonics, and high order harmonics – that is the suspension. You can see the second harmonic is almost the same on both readings, so that means it's a well designed dome driver; the third harmonic is higher, though, as the dome has one suspension, and we have two suspensions, and we can tune it fine, so our third harmonic is very nice; and here in the high order, they are almost not measurable in the ring diaphragm, yet here is where the dome becomes very unstable, and produce things which are not there.”

These are real measurements, which basically show that human ear has masking effects at certain frequencies. It also shows that subharmonic distortion is much more audible to the human ear, which brings Alexandrov to another sonic example:

“If you take a subwoofer, apply 50Hz with 120dB, then apply a second tone at 100Hz with 100dB, which means it's 10% distortion, and you then switch off the 100Hz, you will not hear it. Why? Because they are close to each other, and it's inside the mask. So we are sensitive to high order distortion, yet we are not even able to hear low order distortion. This means many people think the second harmonic distortion is not a problem - even that it sounds good, as it's a second harmonic, and it's one octave. But that is not true! It's because it is a low order distortion, and normally it's inside the mask of the human ear.

“So basically, depending on the level of the SPL, if you listen to low level music, you won't hear the distortion, but you will not hear the fine details, because they are very low energy, high level harmonics: like the voice, violin, or even the sound of the room. Ultimately, you won't hear everything in a speaker without this level of resolution; or in other words, when people listen through any Coda system, they'll think, 'wow, I am hearing stuff I never heard before!' But they don't know why..!”

So in simpler terms, it's a bit like pixels in visuals – that Coda produces a higher resolution of audio than its competitors, to deliver a more immersive experience?

“Yes, and not only for sound engineers,” Alexandrov points out. “Anyone might hear a song they love, and suddenly hear new things – and these are not always good things! Mistakes in the recordings, for example, as the studio engineer was not able to hear things correctly in the monitors. And what's worse, mp3s on these speakers sound terrible, because it's shit in, shit out, basically!”

Sonic Boom

So if a live sound engineer comes in with an existing show file, for example, and plugs into a Coda system for the first time, he or she might be in for a bit of a shock?

“Well, that's part of the issue; if you are mixing from scratch, that's one thing, but if you come in with an existing multitrack on playback, the mix you were doing is masking problems you were trying to fight with, so yes, when you first put it on a Coda system, it doesn't necessarily immediately sound better, because you mixed it with that distortion, not with clear audio.

“When you push the level hard, then it's not only the resolution that's missing, it starts to sound noisy; but it's what an engineer knows, so they do push it, then they try to cut it out and mask it. Good engineers will try to cut a guitar frequency, bring the voice outside, and so on - but it is all tricky, and you have this 'noisy' sound. With Coda, you don't have this; you put the voice there, the guitar there, and it stays there. And they work together – they are not fighting. Suddenly you can hear everything, so it's a different way of mixing.”

So the big Coda challenge will be to get engineers in the driving seat, and see what they make of the systems. This is already happening, of course – in fact, an AiRAY system (Coda's flagship) was deployed to great effect on Ed Sheeran's first show back after breaking his arm last week in Singapore. A taste of things to come, perhaps? So let's have a listen.

We head to the demo room, and I am treated to a presentation, from the little APS, which in themselves pack an incredible punch and carry, to a point source setup, which blows me away – especially when I am told the subs aren't yet switched on (what?!). Then there's the very mini TiRAY, which is surely too small for a line array, isn't it? Evidently not – it'd easily fill any Apollo/Brixton type venue, and some.

Then finally, the ViRAY, which I am reminded is the 'medium sized' Coda system. First, we hear it with just the main speakers, and it's already extraordinarily clear, and rich; then we hear it with the flown lows, which to me feels like sub is filling the room already, when actually, it's not. And when the subs are finally implemented, it's almost a frightening experience: I find myself backing further away from the system, not because it hurts – far from it – but because I feel like the kick drum is literally right in my face, and could punch me between the eyes at any minute! Everything is in your face, and I notice this doesn't really change, the further I go back – for maybe 30 metres. SPL feels the same, and the sonic experience is certainly identical no matter where you walk in the room.

After the 20-minute demo, I find I have zero buzzing, zero fatigue – if anything, the experience has cured my hangover. The clarity is extraordinary, and what keeps amazing me is how small all of these systems are in terms of footprint. Alexandrov and co. really do have something special happening here – and this isn't even AiRAY, the company flagship. What can that do, I wonder? Provide more power, more coverage, and more everything, I would imagine.

It's funny. When digital consoles first came out, they were very poor, got a bit better, and are now extraordinary, with one or two firms clearly dominating the riders. That hasn't really happened in loudspeakers since the '90s. Yes, there are plenty of good new systems out there today – and Coda would be first to acknowledge that - but you could argue that no company has really grabbed the reigns since. Maybe these guys will finally rock the boat.

Words by Paul Watson.