The dynamic range of real world audio events is actually quite difficult to properly capture in a recording as is illustrated by this frustrated inSync reader.
“I’ve been using an AKG C3000 mic in our studio with outstanding reliable results. Just a couple of weeks ago we recorded a real ‘screamer’ of a blues singer and it handled it without any distortion and without applying the 10 dB pad on the mic. But as luck would have it, the very next week I had to mic a really fine ladies choral ensemble. They had a dynamic range of a whisper to an atomic bomb blast. The microphone was preamped with a dbx286a that I had at the church where we recorded, and was set to ‘middle of the road’ signal manipulation on every setting. All settings I had used many times before and never once had any trouble with distortion. Should I have added the pad on the mic and beefed up the input at the preamp? Since it’s over now, I’ve had a 100 ideas of other things to try, but I’d like to know what one of you pros would have done in the same situation.”
As hinted above, the problem most likely is a result of the vast dynamic range of a choir. Most good singers (like your blues guys) know how to “work” a microphone and rarely need as much dynamic range as something like an orchestra. An orchestra can spend 10 minutes down in the noise floor of your equipment and then in an instant be clipping it. You just really need equipment with a very wide dynamic range to properly capture this sort of thing. Short of being able to go out and buy this equipment there are a few things that can help.
My first suggestion would be to figure out where you were clipping. This is critical. It could have been the mic, the preamp, or something else further down the signal path. Try turning the offending piece down until it never clips even at the highest level. If the source material is really distorting the microphone then your only option is to turn on its pad. Once you get rid of all the clipping you then have to ascertain whether or not you can make a usable recording at these lower levels. You may not be able to because of noise problems. Try different gain structures. It may be quieter to use the pad in the microphone and turn up the preamp, but it may not. You have to experiment. Putting a compressor after the preamp to bring the dynamic range of the material into a more workable range will make it easier to get a good recording, but if the problem is in the mic or the preamp (which I doubt) then your options are limited. This is one reason why people doing this type of recording carefully look at the self-noise specification of microphones and preamps. It requires tons of headroom, which means you have to have low noise since the noise floor of the system pretty much determines the lowest levels you can record.