Serenade: the 1996 Santa Fe Chamber Music Festival CD Page 5
In post-production, the cardioids I use full-range to preserve their excellent imaging, but they do have a slightly rolled-off bass. The omnis have excellent bass but terrible stereo imaging, so I cut the treble on the omnis, then mix them into the cardioids. The cardioids are the primary microphones in the upper midrange and treble, while the omnis give you the sense of space and envelopment in the low frequencies. The result, I believe, is that I get the best of both worlds. You get an accurately defined image, where you can almost look into the soundstage to see where the musicians are. But at the same time you get some of the sense of bloom that you would have heard had you been at the concert.
A point I should make is that I couldn't have done all this before the advent of digital editing. Because it is very important when you're using spaced microphones to ensure that their outputs are in time synchronization. In other words, if you have a musician in the center of the stage, as pianist Max Levinson was in the Brahms Horn Trio, the sound from his instrument reaches all the microphones at exactly the same time. In the analog days, you couldn't do that unless you very carefully measured the distances from each microphone to the instrument and made sure they were the same. But then the microphones might not be in the right place to get the optimal sound quality from each. So what I do is to set up the cardioid pair to give me the sound picture I want, and the omni pair to give me the tonal colors I want.
Each reel of tape that I record starts with the sound of someone standing at the dead center of the stage banging a pair of wood blocks. This is exactly analogous to the "clapper board" used in movie-making, and gives me a very nice, clean impulse on each of the four tracks of the digital recorder. Before the editing and mixing starts, I upload those four channels into a computerized hard-disk editing system. Calling up the four channels on the computer screen, I can slide the tracks backward and forward independently in time until the sound of the wood blocks is synchronized on all four tracks. Now I know that anything that was in the center of the stage will produce a signal at exactly the same time in all four microphone channels, and therefore by definition be in the exact dead center of the reproduced soundstage.
Fig.2 Recording setup used for Serenade.
Phillips: That sounds fairly time-consuming.
Atkinson: Yes, it is, but you only have to do it once for each reel's worth of music. And once you've done it, it stays fixed. When you get it right, the sound clicks and you just really feel that you're there in the hall.
Phillips: Did you do anything different in terms of microphone placement this year?
Atkinson: Because the musical works we were recording are generally smaller in scale than last year, I started off with the microphones about 5' closer to the stage. However, I quickly realized that the sound was too vivid, so we moved the mikes back almost to where they were in '95 [fig.1]. One of the problems with live recording is that you can't generally use microphone stands, which are easily moved around, because they interfere with the audience's sight lines. So we hang the microphones from the ceiling of the auditorium and tie them back to the balcony with 70-80' of monofilament fishing line. We can change their distance from the musicians by pulling them backward and forward. But you basically have to get the position within a few feet or so right from the outset.
Phillips: Some audiophiles hold that suspending the mikes from above lends an unnatural perspective to the event. Yet I've never been able to get much of a sense of height perspective from recordings I know were done that way.
Atkinson: Well, I think it's not so much a matter of height perspective. When you're looking for the best position for the microphones, you have a problem in that microphones tend not to pick up sound in the same way that the ear does. The human ear---it has a computer attached to it in the form of the brain---has almost a zoom capability. You may be quite a long way away from a sound source, but you can zoom in on it and hear it as though you were closer to it. Microphones can't do that. If you have microphones at ear level, you get too much of a wide-angle perspective of the soundstage. The instruments that are at the back of the stage sound too far away and the instruments at the front of the stage sound too close.