Richard Campbell shares his thoughts on Surround Sound recordings.
For a number of years I have been experimenting with 5.1 surround mastering. I made a recording in “genuine” 5.1 of a string duet concert by using an X-Y mic in the audience row three, plus two mics on the surface of very large round pillars toward the rear of the audience.
First, I calibrated my tiny studio monitor system with pink noise + Smaart to get a desired level and spectrum from all loudspeakers. During the mastering process I put an equal level of pink noise on each track which I called “calibration” tracks that were also recorded on the CD, and appeared one-by-one on playback.
I chose DTS encoding because I like the less compression and the full range of the dot-one channel. Ray Dolby is an old acquaintance, as I was AES Technical Committee Chair when Ray was President, however, I could not afford the pricing scheme that Dolby was charging at the time for surround encoders. Minnetonka was offering DTS at a reasonable price so I got it (with a hardware dongle). When I got Sound Forge 10 it came with an Dolby Digital AC3 encoder.
Back to the recording. At the first calibrated playback I was aware of a spatial quality but dismissed it as, “huh”? Then some dude on the left side of the audience coughed, and I almost came out of my chair. Whoa! Let’s hear that again. It is wonderfully subtle.
Many experiments later, in different listening environments, I came to a conclusion. But wait – back up – I took my DTS CD to one popular purveyor of home theater systems. I “borrowed” his auditioning room and proceeded to play my calibration tracks. Front left, front right, rear left rear right LFE front center, each one second, full bandwidth pink noise. Not bad, except that the rear channels were reversed. I heard him say, “Geeze – we just got that rewired!”.
My conclusions follow:
1) Let the recording environment dominate the listening environment. This means that listening room T60 should be less that 0.3 seconds at all frequencies.
2) All channels should be tested with full bandwidth pink noise, including LFE that has is own internal electronic filter. Doesn’t really matter because the owner has an LFE level knob that gets adjusted to rock, regardless of the “accurate” setting (with apologies to Tom Holman).
3) The surround focus should be in the audience, not in the middle of the musicians. The Roy Orbison “Black and White Night” is a superb piece of work from Gateway Studios if you like the backing chorus behind you along with some instruments. What you see on the screen is not what you hear.
4) If your surround effort is leading to a release, then try it in a few different home theaters and be sure and bring the calibration tracks to run first.
My thanks to Brenda for all the work she put into this great blog setup – Dick Campbell