How to split guitar signal?

[The Elf]

I’ve just discovered this with the drums that I’ve recorded. I checked for phase when setting up but later found that flipping one overhead (Glyn Johns) tightened the whole sound up.

That's often the case. Think in terms of how the skins are moving in relation to each mic.

[gingertimmins]

I’ve just discovered this with the drums that I’ve recorded. I checked for phase when setting up but later found that flipping one overhead (Glyn Johns) tightened the whole sound up.

That's often the case. Think in terms of how the skins are moving in relation to each mic.

Thanks elf, so my having to flip polarity isn’t necessarily because I messed up with the placement but rather that it’s just the nature of the beast? Or a combination of both?

[Hugh Robjohns]

...so my having to flip polarity isn’t necessarily because I messed up with the placement but rather that it’s just the nature of the beast? Or a combination of both?

Nature of the beast...

Of course, it could be down to a mic cable wired up incorrectly, or a vintage mic that is wired internally such that a positive air pressure generates a positive voltage on XLR pin 3 instead of the modern standard of pin 2.

But more likely is that it's a combination of the distances between drums and mics, and the pitches of the drums.

It's all about wavelengths... The GJ technique sets the 'overheads' at the same distance from the snare, so the sound waves radiating from the snare should reach both mics in phase. Flipping the polarity of one 'overhead' should therefore result in a significant reduction in the lower frequencies of the snare sound. If it doesn't, you have a cable problem or a funny mic (or a polarity button active in the mic preamp)!

The distances between each tom and the two mics will, however, vary greatly, and so it's quite possible that the radiating sound wave from one (or more) of the toms will arrive at one mic as a compression wave and the other as a rarefaction at different frequencies, and thus some phase cancellation could occur, changing the overall tonal character of the drum kit. Flipping the polarity of one of the mics will change that character in a way that you might prefer... (particularly if you are supplementing the snare and kick drum content with separate close mics).

The alternative would be to move the mics around a bit to alter the relative distances between drums and mics and change the combined sound that way instead of hitting the polarity button (which offers pretty crude options in comparison).

H

[The Elf]

I will often time-align overheads (and other mic's) to the snare. Doing this I will typically see the initial transient of the snare dipping into negative. Compare this with, say, bleed into the kick mic and the same transient may be going positive.

Multi-miked drum kits are always a compromise, but by starting with over-mic's flipped and under-mic's un-flipped it gives me a starting point.

[gingertimmins]

Thanks again for the detailed help! I never intended this thread turn into a drum phase thread but I appreciate your time answering my questions.
Next set of questions will no doubt be bass and guitar related!