Instruments / Drums

Out-of-Phase Overheads

Originally posted by Cliff-at-Bose: in Out of Phase Overheads

These are not "overheads" but 57's placed below the cymbals and above the top heads of a small kit. The mics are wired out of phase, basically 2 and 3 reversed on an XLR. There's lots written about this on our forum. But the basic idea is that the pair will cancel onstage bass but pick up local instruments on the kit, in an effort to reduce rebroadcasting onstage bass from the drum mics. This way we get a stronger signal than typical overheads and cleaner bass onstage. To "mix" these, just move the mics closer to the instrument you want to emphasize. Typical setup is on either side of the snare facing the snare. Snare is everywhere and there is no need to put a mic directly on it. It's actually pretty easy to set up and adjust, moving the mics around for a good kit mix. With 3 mics and only 2 inputs on the PS1, we get a really nice amplified sound for our shows. I listened to the output of the pair recently (multitrack recordings of a recent show) and the cancelling thing really works great. Give it a try.

Hilmar-at-Bose talks about Wiring Two SM57s with a Y cord

Here's the nerds view.

Wiring the the two mics out of phase creates essentially a "dipole". Everything that is in the middle (i.e. equal distance) between the two microphones will get equally but out-of-phase so it cancels when the two microphone signals are summed together. In essence it creates a "blind spot" for the microphones for whatever is right in the middle plane. For the drums, that's mainly the kick (as Larry pointed out) and also the drummer (when he/she is hemming and hawing, squeaking with the chair, yelling about or in general having a grand old time).

Another nice trick is to place the L1 that gets the mic signal somewhere the middle plane of the microphones. This drastically reduces potential for feedback and unwanted regeneration. Sound sources that are significantly closer to any one of the microphones are not much affected by the whole procedure.

the original discussion ← is highly recommended.

Sources for the Cables

Hilmar-at-Bose talks about buying an out-of-phase adapter.

The Y-adapters are pretty rare, I don't think you can buy them on line. You can buy an ordinary 2-female/1-male XLR Y adapter like YMFF type

and put an XLR phase inverter on one of the female ends.

Out of Phase Condenser Microphones - Not Recommended

Hilmar-at-Bose talks about Wiring Two Condenser microphones with a Y cord

I would NOT recommend the out-of-phase Y adapter (or any kind of Y-adapter for that matter) with condenser mics. These mics have build in preamplifiers and connecting the outputs directly will present the mics with the wrong input impedance.

Again, I would only recommend the adapter for dynamic microphones (like for example a Shure SM57). If you want to use KSM109s (which are nice microphones), you may have to use a little mini-mixer to combine the microphone signals. You can still use the XLR phase inverter on one channel to get the cancellation effect. The 109s should work for bear field as well as for overhead. For near-field you might have to engage the -15 dB pad on the microphones.

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