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The GSMS Holophone Surround Mic System


by Bobby Owsinski

While the last few years have witnessed an explosion of surround sound, most program material (except for Classical, which has been more adventurous than most) has been recorded either in mono or stereo only to be mixed to surround at a later time. Even those pioneers who wish to record in surround find a frustrating lack of tools to do so, since there's just no surround sound mics available yet.

Until now that is. Recently I witnessed the unveiling of the GSMS (Global Sound Microphone System) Holophone; a 6.1 microphone system that may be the only mic specifically designed for surround sound recording at the moment. Although the prototype on display was focused toward the sound-for-picture side of things, it was obvious that this device could have many far-reaching applications. And the fact that the unit is a 7-channel unit, with separate elements for both LFE and height, raises the bar significantly from those mics in development that are only 5-channel.

The Holophone was designed and patented by musician/sound designer Mike Godfrey and was developed by Rising Sun Productions of Toronto and Canada's National Research Council (NRC). As with many ground-breaking

The age of recording in surround - not just mixing - has arrived.

developments, the unit was inspired by chance. The story goes that Godfrey, listening to Pink Floyd's The Final Cut on his Walkman via headphones, was fooled by the recording into thinking that someone was walking up behind him. Some time later, Godfrey discovered that what he had experienced had in fact been a binaural recording, so he set out to re-create the effect. After a series of dummy head binaural experiments, the inventor found that, by applying some of the techniques used in surround sound, he could re-create that same three-dimensional space that he'd experienced before, but now without the use of headphones. After he made his first prototype and it became apparent that the patent would issue, Canada's NRC joined in a collaborative research agreement to fine-tune the system and take the prototype to the next level.

The Holophone is actually an entire system rather than just a microphone. The focal part of the system features a 7.5- x 5.7-inch fiberglass epoxy ellipsoid that looks something like a giant teardrop. This ellipsoid holds seven Sennheiser MKE2-5 omnidirectional microphone elements; five in the now standard multichannel fashion with the front center element at the tip of the teardrop, plus one on top for height and an element internally mounted in the ellipsoid for the LFE. The mic elements from the ellipsoid are connected to seven Sennheiser UHF wireless transmitters that can be worn around a belt by a person holding the ellipsoid. The multichannel signals are then sent to four dual UHF receivers and then to a custom designed preamplifier control module. This setup makes it relatively easy for the sound designer collecting samples in the field; just point the mic and the Holophone does the rest.

Having a mic preamp supplied with a microphone is a bit unusual, but the 2 U, 19-inch rackmount PCM-7 control module does provide several functions unique to surround sound. There is the prerequisite front-panel gain trimming for all seven channels, a built-in headphone amplifier with channel selection for monitoring each channel individually, and a 10-turn precision pot that enables the height channel to be precisely mixed into the remaining channels. Then there's the seven LED status indicators that are arranged in a cluster that represent the physical location of the microphones, with the brightness of the LEDs correlating to the sound pressure level of its respective microphone. Despite the all-encompassing nature of the PCM-7, I can't help but wonder what the Holophone would sound like through a stack of high-quality mic amps like Neves or Hardys or Avalons.

In the demos I heard, the Holophone certainly created a most realistic soundscape, although the most effective examples were oriented toward sound effects. I was most impressed with the sound generated by the LFE channel, as it was quite natural and not at all forced, as a manually generated LFE can sometimes be. Another impressive feature was the height channel, which really added a tremendous sense of presence even when mixed into the other channels. In fact, I found that it added so much added dimension that I couldn't live without at least some of the height mixed in as I played with the supplied DA-88 demo. Height is an element that's been overlooked for too long, but hopefully people will begin to see its usefulness as a byproduct of using the Holophone.

So the good news is that a surround mic has finally been developed, but the bad news is that it's not really available yet. I guess you'd have to say that the Holophone is in the advanced prototype stage at the moment. Godfrey is currently in negotiations with several microphone manufacturers with the hopes of bringing this innovation to market, and only a couple of units (one wired and one wireless) actually exist.

Having not actually played with this unit yet (but I will have by next issue though), there are a few questions that come to mind about how the Holophone will perform. As stated before, I am most curious about how the unit fares when used with mic amps other than the supplied PCM-7 unit. Is this unit necessary for normal operation? How about the performance with elements other than the Sennheisers used in the prototype? I'm also dying to get my hands on this unit in front of a drum kit. How does placement differ from traditional mono or stereo units? These questions and more will be answered in the next issue.

This article written by Bobby Owsinski appears in issue six, page 24, of Surround Professional magazine.