Festival! The Best of the 1995 Santa Fe Chamber Music Festival Microphones & Techniques

Microphones & Techniques: John Atkinson

Once the venue has been chosen---in the case of this disc, that was preordained---there is no quality-changing decision in all of recording that is more fundamental than that of what microphones to use. Not only does every microphone have its own sonic signature, but the combination of its pickup pattern and how the engineer chooses to exploit that pattern drastically affects the stereo image and the perceived quality of the hall reverberation.

For Stereophile's previous live recording project---Concert, featuring Canadian pianist Robert Silverman---I had used a pair of Brüel & Kjaer Model 4006 microphones. This 1/2"-diameter solid-state microphone features an omnidirectional pickup pattern (ie, it captures sound equally from all directions), and is deliciously true to the tonal qualities of whatever it's pointed at. It also has a superbly extended low-frequency response. But when you use a pair of omnidirectional microphones to record in stereo, you're forced to use them separated quite far apart if the soundstage is not to resemble a monophonic blob hovering between the loudspeakers. However, the danger then is that the stereo image might well acquire too much of an unstable "hole in the middle."

For Concert, we had not had a choice, as explained in the accompanying article (footnote 3). Though I'd wanted to stick with the spaced B&K omnis for Festival, I felt we needed to reinforce them with a centrally placed pair of directional microphones. By doing so, I hoped to be able to have my cake and eat it too: combine the true tone colors, extended low frequencies, and sense of ambient spaciousness captured by the pair of omnis with the more precisely defined sense of instrumental direction that the central array would produce.

We therefore hung four microphones for the week of recording in Santa Fe's St. Francis Auditorium: the outrigger B&K omnis were hung by their leads from the ceiling, 8' from the stage and 13' from the floor (see fig.1). As the mikes pointed straight down at the floor, each was fitted with B&K's accessory nose cone, which results in a flat response for sounds arriving from the sides. The distance from the stage had to be an inspired guess because we would only have access to the cherry picker for one afternoon before the final sound-check for the first work to be recorded, the Copland. I did a lot of listening to rehearsals from various places in the auditorium, and a lot more worrying, before picking the positions to hang the mikes. And even then, as Wes Phillips describes above, I allowed myself some leeway by tying back each mike to the balcony rail some 60' away with fishing line (the non-luminous kind). In this manner I could fine-tune the ambient pickup by moving the mikes backward and forward by up to about 18" in an arc centered on my original position.

Because I was not sure how the presence of the audience would modify the balance between the direct sounds of the instruments and the hall's reverberation, I decided to err on the spacious side of things and placed the omni mikes quite far apart---each was 7' from the hall's center line. Though this alone would produce far too diffuse and unstable a soundstage, it would not be too limiting a factor when the omnis' outputs were combined with the main pair...I hoped! An aspect of this placement that I (a bass player myself) thought particularly advantageous was that the essential sound of Marji Danilow's powerful-sounding double bass underpinning the musical development would be well-captured.

Because experience has taught me that the "art" of recording involves sticking as much as possible with what has worked in the past, I decided to stay with Brüel & Kjaer for the main microphone array and acquired a pair of B&K Model 4011s. The 4011 has what is called a "cardioid" pickup pattern, so-called because, to the imaginative, it resembles a heart. It picks up sounds most very strongly to the front, a little less to the sides, and not at all to the rear (fig.2). The big advantage of using cardioids, therefore, is that the reverberant sound arriving from behind the mikes is suppressed, making it less critical exactly how far away the mikes should be placed from the musicians. To record in stereo with a pair of cardioid microphones involves a little bit of "handwaving," however; used by themselves as a purist "crossed, coincident pair," cardioids produce far too narrow a soundstage (footnote 4).

Cardioid microphone pickup pattern.

Footnote 3: See Stereophile, November 1994 (Vol.17 No.11). Concert is available as a 2-CD set for $15.95 plus S&H. See the secure "Recordings page" to order it.

Footnote 4: Stereophile's Test CD 3 ($9.95 plus S&H) has complete demonstrations of the soundstage differences introduced by different miking techniques, as well as useful tracks to help you set up your Home Theater and stereo systems and audiophile-quality music recordings. Again see the "Recordings page" to order it.

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