Recording ambience/surround channel for concert
 

I'm leaving Wednesday to record a concert. I'm planning on recording all the performer and instrument mics separately using a laptop with a MOTU 896 FireWire interface for mixing in post. I was also planning on recording room ambiance using my Audio-Technica AT835ST stereo/M-S shotgun mic to have to mix with the vocals/instruments if needed, and for back channels for a possible surround mix. Being as this is the first time I've done a concert recording, I'm looking for tips on what might be the best position and orientation for the AT835ST (and any other tips you might care to throw my way to get the best audio recording).

I've done this technique for stereo mixes, using variously an ORTF array of two small diaphram cardoids or an M/S mic.

In my experience it's been a little hit-and-miss on mic placement, due to lots of variables outside my control and the difficulty of monitoring.

If the hall sounds good, and the P.A. folks are doing a good job, then a stereo mic in the right place can be fantastic. Do you have your choice of where to put the mic? Can you place it in the middle of audience seating? "The right place" for primary use in the mix will usually be about 1/3 back in the house, center. If you can wipe out 2 to 4 prime seats, great. For providing room sound reverb efx perhaps 1/3 to 2/3rds back in the house - gotta' listen to know.

Finding the right spot is a problem - you really need to be there for a sound check. It's hard to judge placement listening on headphones, but you can do it. Ideally, you'd be in an isolated room listeing on monitors and on walkie-talkie to an assistant moving the mic. If your mic is in the middle of the audience you'll not be able to move it during the performance.

If your mic is back at a camera position at the back of the house it's still worth laying down the tracks, but you may find it more useful for an applause mic than for adding as room reverb during the music. I recently mixed a recording that was about 12 instrument tracks and a very high quality m/s mic at the mix position (3/4 back or so). After a lot of hair-tearing I junked the m/s tracks and used a software reverb/echo instead, and I'm quite happy with the final mix. OTOH, I've most often found this technique very useful when there are good choices on mic placement.

I don't know what you'd do for surround channels, but unless you are in an exceptional hall with good mic placement you may find more success with surround generated with post efx.

Thanks much for the advice, Seth. I'll probably be able to place the mic wherever I need. Unfortunately, no isolated sound room with monitors as far as I know.

I really appreciate the tips.

stereo mic facing rear for a 5.1 mix sounds good. however, have you cleared with the PA company that they will give you split feeds ? if not, never ever assume you will get it. in fact assume you won't if you haven't gotten it in writing from whom ever is handling the PA. been there done that on some really big gigs way too many times. if you should up without prior arangements, the best you'll get is a mono board feed.

if you record instruments, it means you have to record the room from the scene.
because placing a mic far from the scene (middle of the room) will induce a phase (delay) with sound recorded on the scene and in the room.
ideally you would record the room ambiance in the room while no instrument is playing, and use this to "fake" the room ambiance over instruments.

Thanks for the pointers. The group (actually a family) who is performing has their own sound system. I've already talked with them and it won't be a problem to put the MOTU 896 in line for recording.

Thanks for the help!