inverting phase

[tamakid1292]

okay so lets say im recording a drums set and i have
2 over heads
kick mic
snare top
snare bottom
hi hat
and toms top
witch of these mics would i invert the phase on and wicth would i leave alone.

[mdoelger]

Originally Posted by tamakid1292

okay so lets say im recording a drums set and i have
2 over heads
kick mic
snare top
snare bottom
hi hat
and toms top
witch of these mics would i invert the phase on and wicth would i leave alone.

Kick and snare bottom

[bgrotto]

Depends on mic placement. You may not have to flip the polarity on any thing. You just gotta listen.

[tamakid1292]

alright

[mdoelger]

Originally Posted by bgrotto

Depends on mic placement. You may not have to flip the polarity on any thing. You just gotta listen.

But isn't snare bottom and kick common to invert cause they are facing kind of up against the other mics?

[dbbubba]

Any time you are mic'ing a double headed drum where there is a mic on each and opposite head one mic or the other will have to have it's phase inverted 180 degree in almost all cases.

Kick drums?
I have never had to do it.
A front or out of the drum mic, maybe.

[BlueSprocket]

Originally Posted by lunale

But isn't snare bottom and kick common to invert cause they are facing kind of up against the other mics?

Um...uhhhh....errrr.....ehhhhh.....

<struggles hard to make a definite remark>

Technically EVERY mic on a drumkit is out of phase with the other mics, in relation to one drum. In fact, this is kind of what ultimately gives you the sound of the drumkit with all the mics on it.

I commonly flip the phase of the bottom snare mic (if I use one), in relation to the top snare mic. But I agree with listening. I personally put my monitors in mono, with the drumkit solo'd and flip each and ever mic at the beginning of the mix. This is good practice, because you would be surprised how many tracking sessions I've mixed where a mic was wired out of phase, or an out of phase cable had been used.

If NOT inverting the phase gives you the sound you want...then that isn't completely wrong. There is always the element of "if it sounds good, it is good." Sometimes I flip the kick, sometimes I don't...tomorrow I may where a blue T-Shirt, maybe red. That'll likely depend on how I feel at that instant.

[peat]

Originally Posted by dbbubba

Any time you are mic'ing a double headed drum where there is a mic on each and opposite head one mic or the other will have to have it's phase inverted 180 degree in almost all cases.

Kick drums?
I have never had to do it.
A front or out of the drum mic, maybe.

i think we just need to clear up a few fundamental terms here

phase can not be inverted, let alone inverted by 180 degrees
it can be shifted 180 degrees which will theorectically place it in opposing polarty given that we are talking about a continuous sound source
basically phase is time based
its delaying a signal by a certain amount of time

polarity can be 'flipped' or inverted
this will not move the signal along the time axis
but it will invert it on the amplitude axis (polarity)
if two non continuous signals are taken and one has its polarity inverted
they will completely cancel, given they are the same signal

so consoles and mic pre's and other things that say phase and have a button for it are theoretically incorrect
its polarity

[Jack Ruston]

Yes...So When you have two mics which are an identical distance from the source, sound will arrive at the mics at exactly the same time. They will need to have the same polarity in order to be in phase. If you move one mic further away you will lose that relationship but you will have positive or negative reinforcement as the initial peaks and troughs of the first mic line up with the decaying peaks and troughs of the second. Or not. When these waveforms line up, even if displaced time wise they are in phase.

In the case of the snare bottom mic or top and bottom toms you would almost always have one mic flipped in polarity against the other because they are both equal distance to the source and pointing in opposing directions.

So looking at it from a practical point of view, lets consider kick snare and an overhead for simplicity. You mic the kick and the snare according to positions that you've chosen as sounding subjectively 'best'. You cant move those, they're close mics. So then we put up an overhead and look at it's relationship with the kick. The easiest way to do this is to ask the drummer to play some kicks and print them to the DAW. Zoom in and have a look. You'll see the kick in the close mic and then the kick in the overhead a few ms later. How do the waveforms relate to each other? Is the kick in the overhead aligned with the decaying close mic? Do you need to move the overhead up or down to change this relationship? How does it sound? The situation you want to avoid is one where you flip polarity on one mic and the sound doesn't really change. Provided they're similar in level, this would mean that they're half in, half out.

So now we look at the snare. We might find that the snare needs to be reversed in poloarity to reinforce with the overhead because that's the position for the overhead which worked best for the kick. We might find that with that kick position the snare is half in half out and that we would prefer to favour the snare and move the overhead due to the fact that the overheads have more snare information than kick low end anyway, which would mean that we have more to lose with a dodgy phase relationship. But whatever, there's no reason why you might not have a flipped polarity on snare top, and a positive polarity on kick inside, etc etc. It can be any way around. The thing to avoid is recording all the drums half in half out, because then you cant just flip polarity and correct it.

J

[Jaymz]

Mixing wise, solo all your drums and go through each track hitting the phase button on and off (AS Invert in PT). If you ever notice low-end changing it means that something is out of phase. To me anyway, the most obvious thing to listen for, in terms of phase, is the low-end.

Ex:

SN Top

SN Bottom

If you hear some low-end reappear when you hit the phase button on one, then you know to leave it in

[mdoelger]

Strange I always invert phase of kick and bottom snare BEFORE mic placement. Thought that would be technicaly correct because when you hit the top head of a drum with the drum stick the very first thng happen in the top mic is the diaphragm is sucked outwards. The same hit causes the bottom mic's diaphragm to be pushed inwards. So you get 2 waveforms with one starting downwards and one starting up.
by flipping phase you get the 2 waveforms starting in the same direction.

This was told to me some while ago. Maybe the one who told me that was an idiot

However I'm with you. In the mix do whatever sounds right.

Sorry for the bad english! Hope you got my point!

[Jack Ruston]

It's not an idiotic suggestion but it's slightly the mark of someone who spends more time reading than doing....There is a school of thought that says that it's best for the initial kick transient to push the speaker forward in which case you'd want to make sure that it was going 'that way'. But of course you can never assume anything because there could be a mic, cable, pre, or bit of outboard wired backwards somewhere along the line which will reverse it! So just print a bit and make sure. If you decide to leave the kick positive, you just need to ensure that everything else is going the appropriate way for it's position. The moment you get too stuck in thinking which way things 'should' be, you go wrong.

J

[sawhorse]

Originally Posted by Jack Ruston

It's not an idiotic suggestion but it's slightly the mark of someone who spends more time reading than doing....There is a school of thought that says that it's best for the initial kick transient to push the speaker forward in which case you'd want to make sure that it was going 'that way'. But of course you can never assume anything because there could be a mic, cable, pre, or bit of outboard wired backwards somewhere along the line which will reverse it! So just print a bit and make sure. If you decide to leave the kick positive, you just need to ensure that everything else is going the appropriate way for it's position. The moment you get too stuck in thinking which way things 'should' be, you go wrong.

J

Well... there is a way that things "should be." Cables, mics, outboard, etc. should be wired correctly. But I think you point was made... just listen.

IMO. I believe that, all things being as they should, or "normal" (nothing is wired incorrectly), the top snare, the top toms, and the overheads all should have they're polarity reversed. The bottom snare, bottom toms and the kick drum (being mic'd from inside or the front) have the correct polarity already, as they are receiving the signal. The "top" drum mics are not directly receiving the signal. Flipping the polarity puts the top mic in phase with the respective bottom mic.

This seems to prove true to me as when I record just a kick drum, normal polarity, the signal is positive (judging by viewing the waveform in protools). The same with the bottom mics. This is how a start nearly every session and it seems to sound best. Of course, I always check phase between the relation of mics, as well, and adjust accordingly.

Does anyone think differently of this idea? I'm curious. I'd like to read some other opinions.

[dbbubba]

Well, I've been engineering and mixing kick drums since about '75 and I have never had to INVERT THE POLARITY of a kick drum except in a few cases with a mic like a U47FET that was outside the head and a D112 inside.

In those thirty-four years I have met a lot of engineers and some are guys that have gone on to do big, high profile projects.
I have never seen any of them INVERT THE POLARITY of a single kick mic.

Yes, you DO want the speaker to move out.
With a properly wired mic cable the signal WILL be positive and the speaker will move out just like the head does on the drum.

With a multiple mic'd drum kit there is no in phase or out of phase except for the OHs (maybe) and the mics on bottom heads when there is a top head mic'd.
The other mics are all relative.

[betamatt]

I think it's all been said, but for those folks still trying to get an understanding of this, I thought I'd offer my method cause I tend to be the methodical type, so I build from the ground up:

I choose my reference mic. Usually the kick in mic.

Solo kick in and kick out if I have two mics on kick. Flip phase in and out on kick out to check which sounds better.

Now solo OH with both kick mics. Flip phase in and out on OH to see what makes drums sound fatter.

Now add in snare top mic. Flip back and forth and see what's right.

Now snare bttm in as well.

For toms close mics, compare them with OH.

Compare rooms with kick and snare.

I do this when tracking, and usually will do it again when mixing, even if mixing tracks I recorded, in case I hear things differently, or the way I'm shaping tones changes what's most beneficial, or, the most important reason, if I'm patching inserts onto the channels just in case a piece of gear or tie-line has been wired incorrectly (happens too often not to check).

How do things usually end up in this process? Kick in and out usually don't get flipped. OH often do, not always. Snare top and bttm, whichever way they are, are usually opposite each other. Some toms will get flipped and some don't, really varies. I often find room mics can be a compromise, where one way favors the snare and one favors the kick, and I'll make a decision based on what sounds better in context. Also, if when comparing any of the things I compare solo'd I'm not sure which I like better, I un-solo and then compare in the context of the drum mix.

[sawhorse]

yes, I often find that my OH's need to have the polarity reversed... as with the top snare and top toms (so as to sound best combined with the OH's)... then I add the bottom drum mics, usually normal polarity... opposite the top mics. The kick "in" is usually normal polarity... but the "out" polarity depends where it's located... as is the case with the height of the OH. The OH placement is a balance between what sounds best with kick, snare, which tom?, and the cymbals, themselves.

My main reason for asking was to get thoughts on if it actually is "better" or more "efficient" for the power amps & speakers that the kick is normal (or positive) polarity... pushing out. Especially on large PA rigs and concert arrays, etc.

just curious.

jm

[Tha Wiizard]

Damn it people. Stop worrying about what the next guy is doing. If inverting the phase on a track sounds better then do it, LOL. Don't let what other people do and the techinicalities go against your ears.thumbsup

[mdoelger]

+1 Very true.

Forget my posts above!

Cheers!