Is it impossible to amplify and record a choir at the same time?
A question recently received from a Audio Masterclass visitor...
hola: tengo un mic condensador XML990, tengo un coro de 60 personas de mi iglesia. me gustaria saber posicion correcta para grabar y amplificar un coro de estas proporciones muchas gracias.
Sender: Guillermo memo Marvin
David Mellor replies...
It's not often that someone asks the impossible, but this time someone has! Basically what Guillermo seeks is to amplify and record a 60 voice church choir.
It is impossible to amplify and record a choir at the same time!!!
Did I say impossible? OK, nothing's impossible and in fact you can do both. But if the set up is optimized for recording, it won't be very good for amplification. If the set up is good for amplification, it won't be good for recording.
"Aha", says the smartarse at the back, "What about having two separate systems, one for recording and one for amplification?"
Nope. That won't work either. Let me explain...
For recording, you need the mics at a distance from the choir. Get the choir bunched up so that it is no more than 1.5 times wider than it is deep. (i.e. don't let them splay out in a huge semicircle - you're the recording engineer and you even get to tell the choirmaster what to do!).
Now position the microphones about 3 to 4 meters high, about one choir's depth in front of the choir. You can choose any of the classic coincident crossed pair, near-coincident crossed pair or spaced omni techniques.
You don't need more than three mics.
YOU DON'T NEED MORE THAN THREE MICS!
Unless there are soloists, but that's for another day.
With a bit of experimentation to find the best position for the mics, this will get you a recording as lovely as it possibly can be - hopefully you're working in good acoustics.
The trouble is that to use the same mics and mic positions to amplify the choir will a) result in a poor sound quality due to too much reverberation being picked up and amplified, and b) risk feedback because too much gain has to be used to hear the choir through the speakers.
So let's look at the ideal set up for amplification. Here you would bring the mics much closer so that each mic is no more than about 1.5 meters from the singers. You can use several mics spaced out, each mic covering maybe ten singers or so. You have to be there to judge it.
But if you try to record this, the sound will be dry and lacking in reverberation. Also it will be a confused, unclear sound because you have used more mics than necessary. (Never use more mics when fewer will do the job better, as is very often true).
OK, back to Mr. Smartarse at the back. What about using two systems?
Yes, but... what about the sound coming from the speakers? The sound of loudspeakers may be acceptable for amplified music. No moving coil loudspeaker produces a sound that is anything like the original, but we accept them because they are practical in other ways, and we have become used to them.
But if you record the sound from the speakers, as you will with an ideally situated mic set up, even if just the reverberation from the amplified sound, the end result will be pretty awful.
So the best advice is to do recordings separately from performances, so that amplification is not needed. If you really do need to record a performance, put the mics in the best position for the PA, and record the sound from those. You will have to work on what you get later and almost certainly add artificial reverberation.