Encore: the 1997 Santa Fe Chamber Music Festival CD Notes on the Engineering

Notes on the Engineering
As with our previous two Santa Fe Chamber Music Festival recordings, we used four microphones: two outrigger B&K omnis were hung by their leads from the ceiling, 8' from the stage and 13' from the floor. A central pair of B&K cardioid microphones was mounted on a stereo bar, and hung by their leads from the center of the ceiling 11' above the level of the stage and the same 8' back as the omnis. The two cardioids were used in what's called an ORTF configuration: the mikes angled at 115 degrees, their tips spaced about 7" apart. The ORTF microphone technique was developed in France and gives a nicely defined soundstage, but the tonal balance lacks low-frequency bloom. The spaced omnis, on the other hand, give a wonderful sense of bloom and very accurate tonal color, but have mediocre stereo imaging.

In post-production, the cardioids were used full-range to preserve their excellent imaging. The treble was cut on the omnis, then the two pairs of mike signals, time-aligned on the digital audio workstation to preserve transient information, were mixed together. The cardioids are the primary microphones in the upper midrange and treble, while the omnis give the sense of space and envelopment in the low frequencies. The result is that 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 live event. By using the minimum of miking, we tried to achieve a very natural, realistic soundstage, with a good sense of depth. Fig.1 shows what you should hear in the Brahms Piano Quartet: the piano keyboard is center stage behind the cello, with the body of the Steinway extending almost all the way to the right-hand loudspeaker. The violin and viola are to the left and right of the cello, respectively, each about halfway to the speaker position.

Figure 1 The microphones' view of the Brahms Quartet, relative to the listener's loudspeaker positions

All the editing of the performance tapes was done with 24-bit resolution to preserve as much of the original quality as possible. But once the master edit list for the CD had been assembled, the problem remained of how to reduce those 24-bit data to the 16 bits mandated by the "Red Book" CD standard. Simply dumping the output of the computer hard disks to DAT or CD-R, thereby truncating each digital word from 24 to 16 bits, both reduced the sense of recorded space and added a feeling of "digititis." During the preparation of the master, therefore, the digital data were "redithered" using a Meridian 518 Mastering Converter. This applies a choice of noise-shaping curves to the music data. By shifting quantizing noise up to the inaudible 20kHz region as it reduces the master's 24-bit word length to the CD's 16, the 518 preserves as much as possible of the original's resolution in the midrange.

No compression was used in the production of Encore. The maximum level on this CD was adjusted in the mastering to reach the maximum possible on a CD. For those listeners with sound-pressure-level meters, 0dBFS on this recording corresponds to a peak spl at the microphone position of 100dB. If you set your volume control so that the applause at the end of the Mendelssohn generates a peak level of 100dB at your listening position—which is loud—the playback level will be pretty much the same as that in St. Francis Auditorium.

Encore costs $15.95 plus $3.50 S&H. See the "Recordings" page on this website for details of how to order it. Enjoy!—John Atkinson

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