Mixing DIs and Condensers on stage

[DanielBarnes]

This was a small problem we ran into a while back some time ago.  We had a band on stage consisting of an acoustic guitar, electric guitar, and violin all using DIs, and then 1 cello miked using a condenser mic(a Behringer C-3 if that matters).  It was configured cardioid, without the low cut or the -10db, positioned slightly off to the side and aimed between the bridge and f holes, roughly 12-14 inches away.

In the solo on the board(Behringer x32), the instruments all sounded good, but in the room the cello was being completely buried under the other instruments.  I took the cello out of the instrument DCA and cranked the gain pretty high on the condenser.  I hestitated pushing it any higher because I was worried about feedback(it actually did feedback really bad through the monitor for some reason when they weren't playing).  But even with all that it couldn't be heard past the second row of seats.  We also had a piano on the opposite side of the stage, which I had turned down but was still being played loud enough to rival the other instruments.

So my main question is what's good practice when mixing DIs and condensers on a stage?

Assuming the answer isn't to just buy a better condenser.

Our stage setup was electric guitar, violin, cello on one side.  Center stage we had our lead guitar/singer.  Then the vocals and piano(on the floor in front of the stage) on the opposite other side.

Thanks for any advice you guys might have!

[RexBeckett]

@DanielBarnes 

Hi Daniel, large diaphragm condenser mics can be a mixed blessing on a live stage. Their high sensitivity and wide frequency response can make them susceptible to feedback from monitors and main speakers. If the feedback is at a low frequency, it could be that the mic is picking-up signal from the rear of the speakers/monitors and repositioning the mic and/or player may help.

Is the cellist against a bridge/string-mounted mic? That is normally the best way to get a good level without feedback.

You mentioned that feedback occurred when not playing. This suggests that there is a compressor somewhere in the signal path. It is not usually a good idea to have compression in a monitor feed for this reason - and because an uncompressed monitor often encourages better performance. Using a Post EQ (or Pre EQ if the compressor is before EQ) signal tap for the channel to monitor send may help.

If the feedback is being caused by pickup from a monitor, reduce the level of the mic in the monitor mix and see if you can get a better level in the main PA. I prefer to set monitor levels after getting the FOH mix right.