AIRSOUND

Since the ’60s, Ted Fletcher has earned an enviable reputation as a pro audio innovator. Originally an assistant engineer for the legendary record producer Joe Meek at his fabled Holloway Road studio in London, Fletcher went on to form the Alice sound mixer company in 1969, where he developed and manufactured large sound consoles for a number of recording studios and the BBC.

    Later, after developing voice communications systems for the spot banking market, he invented the first ‘hands-free’ in-car telephones for Motorola and Vodafone and in 1993 paid homage to his one-time boss by launching the Joemeek line of classic sound processing equipment.

    Ever restless, Fletcher is now focusing on his latest and potentially most revolutionary concept of all, airSOUND.

    Would it disturb you to discover that you may never have experienced true stereo sound? I have to admit, before I discussed the subject with Fletcher, I’d taken an awful lot for granted.

    Before I go further, let’s engage in a history lesson. In 1931, scientist Alan Blumlein patented a method of recording and reproducing ‘stereophonic’ sound. His belief was that as we have two ears, the ability to recognise where a sound is coming from is connected with how the sound reaches our ears — if one side is louder than the other, then the sound is obviously located on the loud side.

    Blumlein, however, recognised that there was a lot more to stereo listening than the positioning of the sound. He described in theory how it might be possible to record and reproduce ‘spatial’ sound, using a principle called ‘sum and difference’ or ‘middle and side’ (M/S). This involved using an omni-directional microphone to record the main signal information, and a figure-of-eight response (or ‘dipole’) microphone set across the field of sound to record the spatial information. By adding and subtracting the ‘omni’ or ‘sum’ signal with the figure-of-eight or ‘difference’ signal, it is possible to arrive at a conventional left and right audio signal.

    There are, however, significant flaws in the argument that creates a left/right stereo signal from an M/S signal. In spite of the inaccuracies, the M/S system can be used as the basis of reproducing sounds with space; the M signal represents the majority of the signal content, while the S contains all the spatial information.

    It’s Blumlein’s theories that, by complete coincidence, are related to Ted Fletcher’s current, ongoing project and one that could make a serious dent in our perceptions of how live sound or the playback of recorded sound should reach our ears.

    It was in the early hours of August 5 2005 that Fletcher had his “Eureka” moment. “I’d been recording a choir using the sum and difference microphone technique which gives you a beautiful stereo image without a ‘hole’ in the middle,” said Fletcher. “I woke up in the middle of the night thinking that it would be wonderful if I could monitor the recording with that same technique to enable me to listen back more accurately to what was going down, but it had never been used. I wondered why.”

    After thinking this through and losing a night’s sleep, a weary Fletcher arrived at his office the next morning and set about designing an electronic system that would reproduce the effect of sum and difference playback. “Lo and behold, it worked, although it seemed so obvious to me that I assumed it must have been done before, and so I did a little research. That’s when I discovered Alan Blumlein’s comments about how reproduction of stereo can be done with two speakers, but it’s not the correct method.

    “Suddenly I realised that we’ve all been duped — what we‘ve been listening to for the last 50 years has not been true stereo! And the right way to do it was by sum and difference.

    “I did further experiments over the next few days and found that if you do it the obvious way, which is to use a frontal mono signal and a left-minus-right signal on one speaker, transverse across the other loudspeaker, you do achieve a stereo effect but it’s not a perfect image; it sounds better on conventional L-R speakers when you’re sitting centrally. And if you run the spatial sound — as I now call it — along a surface, you can get a wider stereo image.”

    Armed with prototypes, Fletcher began seeking advice. “I was informed that my idea was patentable so I took my demos to some financiers I knew in the City of London. Their positive reactions made me realise I’d been too close to the project to appreciate the financial implications. There was instant interest from a variety of sources.

    “Now we have a very firm financial base upon which to launch Airsound LLP, which I founded with two City investor partners.”

MAKING AN IMPACT
Airsound LLP is now looking for licensees from any area in which loudspeakers are used. This, of course, covers a very wide range of applications, from MP3 playback to large permanent installations and any form of live event, particularly those with small to medium PA systems.

    “The more people we talk to, the more we realise just how far this could spread. In a theatre venue, for example, each flown loudspeaker array would individually become a stereo source and anywhere you are within that auditorium you will hear a true spatial stereo image with width and depth that you just can’t get with a mono signal. With this effect of unmuddled high frequencies, the result is a cleaner sound with less perceived phasing.”

    For the pro live sound world, much of this remains theory at present, said Alan Johnson, formerly of Yamaha, Sony and Sennheiser, who recently joined Fletcher as director of business development to help propel airSOUND’s sales and marketing. He’s hoping that the technology’s forthcoming exposure within the industry will result in a classic example of who dares wins.

    “We’re looking for someone within live sound who is brave enough to work with us in developing a new sound experience for the audience,” Johnson explained. “We see the use of existing rigs with airSOUND ‘fills’, these would be new speakers with licenced airSOUND technology, to provide the airSOUND solution. The existing FOH cabs would run in mono — providing the ‘main’ signal and fills would provide the ‘spatial’ signals.

    “It’s potentially a very exciting prospect for many people in the live business who want to be part of a new approach.”

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