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Inside Views: Aphex

Article from Sound On Sound, January 1987

Paul Gilby returns with the series that takes a behind the scenes look at companies and design personnel working in the field of music and recording technology. This month: Marvin Caesar, President of Aphex Systems USA - creators of the legendary Aural Exciter.

The series that takes a behind the scenes look at companies and design personnel working in the field of music and recording technology.

The Aphex Aural Exciter has been surrounded by an air of mystery like no other product in the audio field. Paul Gilby spoke with Aphex's Marvin Caesar to uncover the truth about the effect and to learn more about the company's very individual approach to solving some age-old audio problems.


How was the first Aural Exciter invented?

"The 'invention' of the Aural Exciter was much more a 'discovery' actually, which took place back in the late Fifties. There was a Heath Kit amplifier which had been wired incorrectly, one channel was OK but the other wasn't, and so the result was a very distorted sound. However, when the two sides of the amplifier were combined, the sound actually became cleaner and more musical. On further investigation nothing could be determined - it just didn't make any sense that by adding a distorted signal to a clean signal the result would be a far better sound, and musically more pleasing to the ear!

"The man who made this discovery, Curt Knappel, met me in 1974, at which point he still didn't know what he had stumbled upon. He had left notes of his discovery lying around for over a decade!

"At first, we only had an idea of what might be going on technically and the only certainty was that it sounded good. The problem we had was that without any real technical description of the device, we couldn't market it or sell it to anyone. We certainly didn't have any Patent protection because we truly didn't know what was going on. So we sealed the circuit up to keep it from prying eyes and put it in a box, then said to people, 'OK, here's a device you might like to try out, but don't buy it.' (Mainly because they wouldn't buy it anyway!) We said, 'Don't even rent it - just pay us if you use it', and the only way for us to determine if it had been used, was if it turned up on a final mix of a record. This is where we got the novel idea for a 'charge per minute' of usage from - it was the only way of establishing the Aural Exciter.

"The initial concept was to charge ten dollars per minute of 'treated' finished mix. The first big album we did was Linda Ronstadt's Hasten Down The Wind and when we presented the bill to her record company for 390 dollars (that was for 39 minutes), they laughed at us and told us we should charge three times as much - so we did! Our marketing policy was quickly formed!

"For several years we still didn't know what the Exciter had technically that was 'special'. So we worked more and more on deciphering what parameters were musical, what were useful, and what were redundant within the effect. That pursuit resulted in the invention of the Aphex II (launched 1981) which had more facilities than the original 1975 unit - which was basically an in/out enhancer box; the Aphex II is much more parametric in its operation."


Having established the Aphex name with the Aural Exciter you moved on to other products. How did this come about?

"We work with a guy, Donn Werrbach, who is primarily a radio engineer. Donn has the ability to solve problems very quickly and also invent things on the spot. Because of his ability, he once ended up taking care of the total maintenance for six or eight radio stations in Hawaii all by himself - that's some going. He also happens to be a musician who likes good sound. So, he was able to combine all of these things and design a product called the Compellor. He then approached our company with the Compellor because he thought what we were doing was pretty interesting. We re-packaged the Compellor and launched it in 1983.

"Things were working out so well that Donn then came to work for us fulltime. On the basis of that, his next product came along in the form of the Dominator."

The success of the Exciter obviously enabled you to expand the Aphex product range and sell to a broader section of people. Could you tell us which market areas you are now looking at and what is happening in them?

"We started our product base exclusively in the recording studio market. Then we branched out into sound reinforcement and one of the first concerts we did was the Wings Over America tour for McCartney. In 1981 we moved into the broadcast area with the Compellor - indeed now, almost every major broadcast station in America has a Compellor on-line. That's quite a statement to make when you consider that we have a fair proportion of the 10,000 stations out there.

"The other market we are into is sound contracting, particularly with the Aural Exciter, Compellor, and now the Dominator. We recently did the Aztec Stadium in Mexico for the World Cup. There were these screaming Mexicans all over the mixing desk, jumping up and down on the faders, so we had the Compellor to control the average level, the Aural Exciter to project the high end out into the stadium, and the Dominator protected all the power amplifiers so that they could be run full up, right to the clip point. So, no matter what peak signal was thrown out of the mixer by these crazy Mexicans, the amplifiers just never went into clipping but they were operating at maximum level all the time!

"The final comment from the sound contractor on the job was that when he was running through his system while the stadium was empty, he played a few CDs through it and it sounded like a hi-fi. That's what all that gain control and aural excitement did for him.

"Our products are now being used everywhere: we're in train stations, broadcast, disco, recording studios and communications."


Tell us more about how the Dominator works.

"The design concept of the Dominator was to provide an absolute peak 'ceiling'. Most other limiters let you set how much limiting you want and then tweak the output with some makeup gain. You never really know what your peak output truly is, that's something which you have to measure later. All limiters have a certain amount of overshoot and if you set a very fast attack time you will still get overshoot. It will be less, but then you have a tremendous amount of modulation of the signal in terms of the distortion that's generated by that fast attack time. The most audible effect would be the washing out of all transients.

"The way the Dominator works, there's a limiter section but there is also a clipper which provides a calibrated peak output. 'Clipping' in itself sounds bad if it lasts longer than a certain duration. The trick of the Dominator is that it can analyse how long that transient will be in 'clipping', and if it is longer than a defined time it will automatically lower the threshold of the limiter so that the difference between the clip point and the threshold will be increased. The nett effect of this is that the limiter section does nothing for as long as possible. It just stays out of the way, but if it has to work, it does. In operation, the attack times are slow enough to allow the transients to pass through and maintain the punch and accuracy of the sound without any serious degradation. That is the true value of the Dominator.

"In most recording studios, having a maximum peak output is not that critical because with analogue tape recording there's what is called 'soft clipping' where the tape goes into saturation. Now you may or may not like that sound, but for those people who want absolute accuracy in their sound reproduction, they can set the Dominator to a little under the saturation point of their tape and have a more accurate signal going onto tape rather than letting the signal transient go into soft clipping. This results in a tighter sound and better use of the maximum signal-to-noise ratio the tape allows.

"You can see from that application that digital recording also benefits enormously. Most people who record with digital gear leave themselves a tremendous amount of headroom because when a digital recorder runs out of numbers it doesn't sound very good! By having the Dominator set right at the clip point, you don't have to watch recording levels any longer, so you can also use the digital recorder to its maximum benefit and utilise the full 90dB or so dynamic range that is available."


Aphex have now moved into the home studio market. Why did that come about?

"We were selling the Aphex II's for $3000 quite well, however, the market is limited in terms of those who can afford such a unit. So we introduced the Type B Exciter in 1983 because so many people were demanding the Aural Exciter on their records. People really enjoyed getting their hands on that unit, but to the small home studio or musician it was still out of reach financially, so we came out with the Type C. This was actually better than the Type B in certain parameters and it's only $300 or around £300 in the UK. That product has spread the Exciter throughout the entire end-user range, from guys with Fostex tape machines to musicians out on the road, PA companies and in-house installations."

What improvements were made on the Type C Exciter?

"We have been improving the way in which the Aural Exciter works. At one time, the harmonic generator of the Exciter was amplitude dependant only. What we have now done is to make the harmonics transient dependant. This is much more natural sounding than just the amplitude controlled approach. You see, you can have a pure sinewave at a high amplitude which doesn't have any harmonic content and, obviously, it's better if it stays that way; but you can also have a transient at a low level with lots of harmonic structure. So we have now put another circuit in the side-chain to detect transients and generate more harmonics off these transients, therefore making it less dependant on long-term amplitude."

Are you looking to have the Exciter circuit built into other manufacturer's products just like Dolby noise reduction has been?

"Yes, AKG have already developed a separate car hi-fi unit which uses our technology. The Exciter is now even being built into disco mixers and there's a company who makes telephone interfaces for broadcast applications which incorporate the Exciter to extend the high frequency end of the signal coming off the telephone line."


You have covered your present activities, but what does the future hold for Aphex Systems?

"We are very much involved in the idea of 'surround sound'. That is a growing market. Many of the movies these days are using Dolby stereo sound and people are expecting more of this quality in their own homes and from their TV. What is happening though is that certain stereo televisions lose the 'centre image' and the screen dialogue appears to come out of the left and right speakers leaving a big hole in the middle. The result of this is that you lose intelligibility.

"The idea then is to have a system which has a very strong centre image but also has very wide stereo and surround channels. We have developed a product for this system which is now selling into the consumer market.

"The philosophy behind our company is that everything must be of the highest quality because good audio quality translates into intelligibility - and not just in the short-term. A graphic equaliser, for example, could be seen as a short-term intelligibility boost, in terms of increased clarity or presence in one particular frequency range. But if you have it set statically across all inputs, in the long-term it's actually going to induce a phenomenon of listener fatigue - or at worst add a 'sound' of its own to your music. The purpose of all our equipment is to allow people to listen for long periods of time without suffering these problems."

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Publisher: Sound On Sound - SOS Publications Ltd.
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Sound On Sound - Jan 1987

Feature by Paul Gilby

Previous article in this issue:

> E-Mu Systems EMAX

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