Getting phase right on a drum kit

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Phobos
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Getting phase right on a drum kit

Post by Phobos » Sat Oct 31, 2020 8:01 am

I have struggled with this for years. I now understand the concepts pretty well, but am still unsure of the proper process. Here is what I do. Any advice would be appreciated.

1. Set up overhead mics. If not using X/Y, make sure both mics are equidistant from the middle of the snare drum.

2. Set up close mics on kick, snare, and toms

3. Test each mic's polarity by viewing waveforms in Pro Tools. Flip if necessary.

4. Play the kit and then look and listen.

I can hear phase cancellation when it's bad, but not when it's subtle. Maybe this just takes time. But it's this last step that I need the most help with, unless I'm missing something basic earlier on. Once the polarity is positive on all the mics, how do you improve the phase relationships further? Just by moving the mics around and listening? Are there any visual cues in the waveforms that can help? How much does phase matter on close mics? And considering the toms are going to be "gated" with Pro Tools editing, does it even matter on those (as long as polarity is correct) since they will be out of the mix most of the time?

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Re: Getting phase right on a drum kit

Post by MoreSpaceEcho » Sat Oct 31, 2020 9:10 am

You just gotta listen to it, with practice your ears start to hear the finer points of phase. Don't rely on your eyes too much, what looks right on the waveforms often doesn't sound right.

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Re: Getting phase right on a drum kit

Post by vernier » Sat Oct 31, 2020 9:41 am

Yep, check position and polarities to reduce the effects of multiple mic'ing.

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Re: Getting phase right on a drum kit

Post by digitaldrummer » Sat Oct 31, 2020 12:36 pm

I always just listen, invert phase, listen again. make a choice on what sounds better.

I don't think this is what you are doing.. but don't try to line up waveforms for microphones that are different distances from the source (for example, and overhead and a close snare mic). that would certainly mess it up. inverting is ok, but it doesn't always guarantee its going to sound better just because the waveforms look like they line up.

I don't always do this but some (famous kinda people) say they zoom in and making sure that the initial transient is "positive" (which if you think about a waveform going into a mic... and then coming out of a speaker). You could do that for kick, snare, maybe other close mics, bass guitars, guitar, etc. but gets tricky on a drum kit with lots of mics.
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Re: Getting phase right on a drum kit

Post by losthighway » Sat Oct 31, 2020 12:58 pm

I'm pretty sure that once you get to 4+ microphones, and definitely when you get to the 8-9 that are common on a lot of modern setups you're inevitably getting some destructive phase interaction. You can tame it by getting the overheads coherent with the snare like you mentioned, but to some degree it's inevitable. Most of the time it doesn't matter. Some of the time it actually has positive side effects. The rest of the time you change things.

Phase relationships are more of an ecosystem in a drum setup to me. It's not like putting two mics on a guitar amp and going "Wrong...... move this...and now right. Good. Ready."

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Re: Getting phase right on a drum kit

Post by Scodiddly » Sat Oct 31, 2020 4:04 pm

I've been wondering for a while - wouldn't it make sense to get the phase/distance correct on the instruments with the highest pitches? Like the hat instead of the snare?

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Re: Getting phase right on a drum kit

Post by MoreSpaceEcho » Sat Oct 31, 2020 4:30 pm

I think it's actually the other way around, more important for the low freqs.

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Re: Getting phase right on a drum kit

Post by The Scum » Sat Oct 31, 2020 4:32 pm

I usually work the opposite way - try to get the lower pitched pieces to reinforce the close mic with the overheads.

The longer wavelengths can pretty noticeably cancel/reinforce with just a polarity flip, especially if they've got a strong fundamental with some sustain (like a wide-open floor tom.).

Hats are such a weird sound (no strong, low fundamental, more of a bunch of stacked up impulses), and are often short. The wave they produce might be so decorrelated between mics that there's not much obvious difference.

And, yeah, sometimes there's no real difference with either setting...if things are "in between", they stay in between.

Someone wrote a pretty good guide to how to approach it long ago...Slipperman or Fletcher maybe? It was a very quick, almost "gut-feel" thing, flipping polarity, listening for a moment, and deciding which was better. The first step was to pick what the "absolute reference" was going to be, usually the overheads.
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Re: Getting phase right on a drum kit

Post by drumsound » Sun Nov 01, 2020 11:34 am

You're method of looking at the waveform is a bit misguided. What we're trying to do is make a cohesive sound where big parts of the frequency spectrum aren't canceling and making the sound thin or hollow. Most of what has already been said in the thread is true. The more mics, the more possibilities of issues. The other really important thing is that when using multiple mics, and especially with the various distances for the different, close together sounds with different pitches, there WILL be phase anomalies. That isn't a bad thing, because those are the things that help us perceive distance and space.

We must also remember that phase coherency is is most critical and perceptible in MONO. To that end, its best to check for phase coherency in MONO.
Someone mentioned Fletcher, and one thing I picked up from him many years ago was to check of mono compatibility using ONE SPEAKER. I believe the reason being that, even using the mono button on a console, hearing mono from two speakers would interact differently with the room, and also, if you weren't in the perfect triangular sweet spot, the signal from each speaker would hit your ears at different times. AND...phase issues are 100% time related.

So, when you are checking for mono compatibility and phase coherency it is simpler and more accurate to listen to just one speaker. When I had Mackie monitors I'd hit the mono button on the console and just power one off. Now that I have moved on to passive Truth Audio monitors, I hard pan the mics to one side with doing my drum record ritual. (oddly enough, when I'm working with a drummer in the room playing I use the left speaker, because its in front of the drum input channels, but if I'm recording myself, I use the right, because the computer in on the right in my control room)

So, here is how I go about it. With all mics panned to one side, I start with both overheads. I reverse the polarity* on one mic. Hopefully the sound gets really thin and shitty. That tells me they are right. This is of course generally the case with a coincident pair, but it will tell you if there's possible a cable issue in the sound gets bigger with a coincident pair. Spaced pairs are more prone to coherency issues, even if you've carefully measured, it's just their nature. Next added will be the bass drum. [if using 2 or more bass drum mics I will mute the overheads and compare the mics to one another before comparing to the overheads] I'll reverse the polarity of the bass drum mic in relation to the overheads. Often the low end gets bigger, clearer and more defined. If that's the case I leave it reversed, if it get thinner, I go back to the original polarity. I add the snare next then each tom individually, using the same process. Each mic that I add to the mix remains ON as the next is added. If there are stunt mics (knee, cheapo, super high overhead etc..) those are added after the close mics. There are ALWAYS stunt mic(s).

Now comes the room mics. Usually its a stereo pair, and often spaced. I'll actually check those alone first. I want to make sure their relationship to one another is good before comparing to the rest of the drumset. So, just like the overheads, I listen to the pair and reverse the polarity on one mic to see if the low end gets bigger or smaller. There are times when that is the case, so I end up with one room mic's polarity reversed from the other. Then I open the overheads back up and listen to rooms in relation to the overs. I switch BOTH room mics in relation to the overs, so if the left room is reversed and the right isn't I change to the opposite to see how it works with the overheads. Again if the bass gets bigger, that's how they stay, if it gets thinner, it goes back to where it was.

Then I add all the other mics back in and spend a little time on balance, so that the general drum mix sounds right with the playback faders at 0, as a good place to start tracking and mixing.

* Polarity refers to the positive and negative of a balanced signal. It is a binary situation. Reversing the polarity switches positive and negative. Phase, however is more intense than + or - and is time based. There are times when reversing the polarity isn't enough of a fix and that's when its time to move microphones.

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Re: Getting phase right on a drum kit

Post by Phobos » Wed Nov 04, 2020 7:10 am

drumsound wrote:
Sun Nov 01, 2020 11:34 am
* Polarity refers to the positive and negative of a balanced signal. It is a binary situation. Reversing the polarity switches positive and negative. Phase, however is more intense than + or - and is time based. There are times when reversing the polarity isn't enough of a fix and that's when its time to move microphones.
Drumsound, your method was helpful beyond description. As I followed it, the light bulb went on in my head! I do have a question, however. When flipping polarity on the drum mics one at a time to avoid phase cancellation, are there certain drums (such as the kick) that you definitely want to make sure have a positive polarity, so they are pushing and not pulling the speakers? In my case, in order to get the snare in phase with the overheads, I had to make its polarity negative (waveform begins facing down). Is this a cause for concern? Would it be with the kick?

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Re: Getting phase right on a drum kit

Post by Recycled_Brains » Wed Nov 04, 2020 11:05 am

Drumsound's mono/one speaker method is legit. I'm sure that I must have read that here many years ago and have been doing it ever since. I think it's a lot faster for making sure the low end sounds right than keeping stuff panned and I think it gives a better assessment of how the bass drum, toms and snare drum are interacting with each other, and with the overheads. I do tend to like checking room mics once I pan the kit how I want it more, would be the only caveat.
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Re: Getting phase right on a drum kit

Post by Recycled_Brains » Wed Nov 04, 2020 11:11 am

Phobos wrote:
Wed Nov 04, 2020 7:10 am
Drumsound, your method was helpful beyond description. As I followed it, the light bulb went on in my head! I do have a question, however. When flipping polarity on the drum mics one at a time to avoid phase cancellation, are there certain drums (such as the kick) that you definitely want to make sure have a positive polarity, so they are pushing and not pulling the speakers? In my case, in order to get the snare in phase with the overheads, I had to make its polarity negative (waveform begins facing down). Is this a cause for concern? Would it be with the kick?
I'm interested in that too actually. that's a good question.

I always use the overhead mics as the thing that dictates the polarity of everything else. Meaning, if I have the OH's solo'd and then when I introduce the bass drum it sounds fucked up... I flip the bass drum, not the OH's, and on down the line. Sometimes once I start putting the other drums in, it'll sound better if I un-reverse something that I had previously reversed. Maybe when the bass drum sounds fucked up, it's the snare that needs to be flipped... that sort of thing. I still use the OH's as the benchmark either way.
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Re: Getting phase right on a drum kit

Post by MoreSpaceEcho » Wed Nov 04, 2020 2:21 pm

I do the opposite....I figure the kick mic is picking up a positive wave motion so I leave that one and flip the oh's to match if necessary (almost always is). Then check the snare/toms with the overhead(s) and then the room mics.

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Re: Getting phase right on a drum kit

Post by drumsound » Wed Nov 04, 2020 5:51 pm

MoreSpaceEcho wrote:
Wed Nov 04, 2020 2:21 pm
I do the opposite....I figure the kick mic is picking up a positive wave motion so I leave that one and flip the oh's to match if necessary (almost always is). Then check the snare/toms with the overhead(s) and then the room mics.
Yeah, that makes sense, I suppose I should consider seeing if it's "better." You've done a bunch of my records, did you ever notice anything weird?

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Re: Getting phase right on a drum kit

Post by MoreSpaceEcho » Wed Nov 04, 2020 7:35 pm

Naw.

I don't really think absolute polarity is that big a deal, honestly. Some people say they can hear a difference, and logically it makes sense that one way should really be right/better but ehhhh.....compared to tuning the drums well and hitting them correctly I'd say it's low on the list of priorities.

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