recording 20 voices

[gehauser]

Disease8 has you on the right track, with a minimal cost option of decent quality. Upgrade the individual components in his list as you see fit within your budget. For example, you could replace the Alesis interface with RME Fireface UFX (30 inputs, 12 analog + 18 digital).

Maybe replace the lapel mics with headmics, but remember that if the kids are very young, they tend to get annoyed by stuff on their heads and may start ripping off the headset at inopportune times. But they are likely to fiddle with lapel mics too, so you and the teacher will need to give lots of guidance in this regard.

Cable management will be important (duh)

 

[moresound]

Anyway you look at it you should be considering the purchase of quality equipment (child proof).
For when your all said and done if half of your microphones (be they lapel,headsets what have you) are in need of repair that will be an extra cost.

I say this for I'm constantly being contacted by local school systems for repair work on their audio gear.

 

[Treeline]

How about something simple and old school? An Alesis 24 channel unit (HD24XR) with analog inputs would allow you to pull analog signal off a 24 channel mixer using the mixer inserts and a 1/4" - 1/4" x24 snake. (Tap into the insert and simply don't return the signal to the mixer). Your front end could be any mixer, such as a 24 ch Mackie, as long as it provides you with individual mic inputs and preamps - and inserts.

Your mics could be a series of miniature (say, Panasonic element) mics - lavaliers or similar. Try and affix the mics to the desks, not the kids. This will allow you to wire the room in advance and have the kids sit at their designated spots. It also increases the likelihood that all the mics will *keep* working.

If kids need to move around, say to the front of the room or something, use mics for that purpose to capture whomever is in that position.

Something like this:

With a mixer:

And mics:

These are available online from about $ 25 each to hundreds each - so be astute about what you are getting. However the idea is to have them small enough to manage 20 - 24 in a classroom setting... with enough gaffer tape.

 

[Disease8]

i would have to agree with this. if your computer lab is capable of doing this (each computer has garageband or something like that loaded) this seems like the easiest way to go without buying an expensive interface. it would be a lot of work to get all the computers into one room, but this would be the cheapest. that is if you don't have to buy 11 computers. also, if each kid has a powerful enough laptop, use theirs.

then (like moresound said) record 1 on the left, 2 on the right. next computer; 3 on the left, 4 on the right... etc. just remember that at the very beginning, once all of the computers are recording (AT THE SAME TIME) to get the class to be quiet and add a 'pop' or 'click' sound loud enough to register on each mic. bouce all of the recordings down to MP3, AIFF or WAV files and download them onto one computer. drop them into your mixing software and there is your 21 separate tracks.

oh... one last thing is that you will probably want another 2 channels for a L/R stereo pair to be in the room somewhere as a 'room' sound. this would basically be your reverb and you would want to use a pair of condenser mics for this. this would be what you add into the background to make things sound 'natural' (which was something you said you were trying to achieve.)

Sorry this is the most impractical and silly idea I have ever heard and should only be done in extreme circumstances where there is NO other choice!