Polarity invert toms ?

[andrew gissing]

I'm sure this realisation isn't new to most of you but..

Most mics on stage receive postiive air pressure producing positive voltage - guitars miced in front, vocals - lots of inputs.

But Toms, snare and cymbal's don't. The skin/cymbal moves aware from the mic causing negative air pressure (unless miced from underneath).

How many of you polarity invert to fix this ?


Andrew

 

[Brandon G Romanowski]

Re: Polarity invert toms ?

Was it actually broken ?

 

[Mike McNany]

Re: Polarity invert toms ?

Too many mics to invert polarity on. IF it's a big deal (or you could experiement with it), try inverting the kick mic ONLY, then ALL the drum mics would be in matching polarity to the drum hit signal. It also can affect a full drum monitor setup. Dave Rat wrote an article on that a couple years ago for when the drummer loses the kick in his drum fill.

Boomerweps

 

[John Roberts]

Re: Polarity invert toms ?

Drums, like all other instruments generate AC sound waveforms, while there is a polarity associated with the initial transient hit. Your question is based on the assumption that we actually want a positive pressure attack from toms. BTW the kick drum, if mic'd from the resonant side does generate a positive pressure attack. Tom's are generally neither pointed at or away from the audience, so the natural way we experience these waveforms un-amplified, is actually at a right angle to the drum heads.

I believe absolute polarity "could" be audible when reproducing drum hits, while subtle. When close micing a drum kit with multiple mics there are far more sound altering consequences from exactly where the mics are pointed at a given drumhead, and how multiple mics interfere if they pick up the same sound field.

Most polarity tweaks around drum kits are to get the mics to play nice together. If concerned about polarity, make the kick drum front mic your "in polarity" reference sound, and then get the others to play nice with that.

JR

 

[Dale Christenson]

Re: Polarity invert toms ?

Drums, like all other instruments generate AC sound waveforms, while there is a polarity associated with the initial transient hit. Your question is based on the assumption that we actually want a positive pressure attack from toms. BTW the kick drum, if mic'd from the resonant side does generate a positive pressure attack. Tom's are generally neither pointed at or away from the audience, so the natural way we experience these waveforms un-amplified, is actually at a right angle to the drum heads.

I believe absolute polarity "could" be audible when reproducing drum hits, while subtle. When close micing a drum kit with multiple mics there are far more sound altering consequences from exactly where the mics are pointed at a given drumhead, and how multiple mics interfere if they pick up the same sound field.

Most polarity tweaks around drum kits are to get the mics to play nice together. If concerned about polarity, make the kick drum front mic your "in polarity" reference sound, and then get the others to play nice with that.

JR

I don't think it's the audience that you're trying to "put into polarity". It's the microphone and how it interacts with the system. Specifically the speaker(s).

I would agree that if the mic is on top of the drum, you may consider reversing the polarity. Try an A-B test to see the difference. I am going to try this out later in sound check today. I will report what I find. Last night, I had the mixer behind the speaker stack for a number of reasons not related to this thread, but I reversed the kick polarity. In doing so, I heard an immediate increase in kick sub output. I went out front to see what difference it made and was surprised to find the kick had more attack as well. I am going to do some more experimenting on this to gain some more data.

 

[John Roberts]

Re: Polarity invert toms ?

There are two different kinds of polarity. The OP is asking about "absolute polarity" which is about the integrity of even a single audio stream. You are talking about interference caused by relative polarity between multiple different paths of the same audio stream.

The OP wasn't asking about this, but I agree it is the more likely problem in sound reinforcement, whether is it interference between multiple mics, or acoustic and reinforced paths, or whatever.

One simple rule is for interference to make a significant difference the two sources need to be similar in level. The difference between acoustic and reinforced drum levels, depends very much on the scale of the system. If you are small enough that you don't reinforce the entire drum kit it's not much of an issue, if large enough that you easily overpower the drums, once again a non-issue. If at playback levels where they compete, relative polarity matters.

 

[Dale Christenson]

Re: Polarity invert toms ?

There are two different kinds of polarity. The OP is asking about "absolute polarity" which is about the integrity of even a single audio stream. You are talking about interference caused by relative polarity between multiple different paths of the same audio stream.

The OP wasn't asking about this, but I agree it is the more likely problem in sound reinforcement, whether is it interference between multiple mics, or acoustic and reinforced paths, or whatever.

One simple rule is for interference to make a significant difference the two sources need to be similar in level. The difference between acoustic and reinforced drum levels, depends very much on the scale of the system. If you are small enough that you don't reinforce the entire drum kit it's not much of an issue, if large enough that you easily overpower the drums, once again a non-issue. If at playback levels where they compete, relative polarity matters.

Hmmm. Interesting, John.

My sub chain is 2 PLX3402 in parallel feeding 4 18" drivers. I'm pretty sure that the reinforced path is louder than the acoustic path. What I don't know, however, is if the drummer owned kick mic is wired correctly. Is there a way, aside from using an oscilloscope, in determining if this is the case? He has a D6.

My signal path(s) are in correct polarity throughout my system. I have spent numerous hours checking for this. So, if the polarity reverse made that much difference, doesn't that point to the mic being miswired?

You said that if the system is easily overpowering the acoustic that it is a non issue. What do you mean by that? Why wouldn't it? Or, am I thinking relative polarity again?

Sorry if I took this thread out of context.

 

[Evan Kirkendall]

Re: Polarity invert toms ?

I flip the polarity on my kick mics, snare top, hat, ride and overheads. Reversed kick mics works for the drum fill, and gets me better separation from the bass guitar. Snare top seems to pick up less hi hat. I mic the cymbals from below, so that's the reason there.

The key is to play with it until it sounds best. And then just when you figure it out, you get a new kit and start all over again.


Evan

 

[John Roberts]

Re: Polarity invert toms ?

Hmmm. Interesting, John.

My sub chain is 2 PLX3402 in parallel feeding 4 18" drivers. I'm pretty sure that the reinforced path is louder than the acoustic path. What I don't know, however, is if the drummer owned kick mic is wired correctly. Is there a way, aside from using an oscilloscope, in determining if this is the case? He has a D6.

A quick easy test for relative polarity between two mics is to patch them both into console inputs, turn them up to roughly the same gain when speaking into one or the other alone, then hold them both together and speak into both of them at the same time. If your vocal gets roughly twice as loud, they are in the same polarity, if your vocal gets thin with most of the bass dropping out, one is opposite polarity from the other.

My signal path(s) are in correct polarity throughout my system. I have spent numerous hours checking for this. So, if the polarity reverse made that much difference, doesn't that point to the mic being miswired?

it depends on what difference you are talking about?

You said that if the system is easily overpowering the acoustic that it is a non issue. What do you mean by that? Why wouldn't it? Or, am I thinking relative polarity again?

Sorry if I took this thread out of context.

I can't tell what you are thinking about.

The OP seems to be talking about "absolute" polarity, at a best a subtle phenomenon, only audible on some types of waveforms, and not a huge concern for live sound reinforcement.

I suspect you would be talking about relative polarity but I can't be completely sure.

JR

 

[Douglas R. Allen]

Re: Polarity invert toms ?

Another thing to consider is polarity between the tom mics together in regards to bass cancelation. If no gates are used or even if gates with long release times are patched in the distance the microphones on the kit are apart can effect bass output of the drums.
If the mic on Tom 1 is the wrong distance from the Floor tom as an example when the 2 microphones are mixed you could get some cancelation in the low freq range. Sometimes flipping the polarity on tom 1 will give you better bass response for the floor tom. ( AT the expense of low freq response for tom 2..)
Depending on the number of toms, their freq. range,distance apart, and mic placement flipping the polarity on just one of the toms can improve overall response of the whole kit. Again this depends on allot of factors. I record live gig drum tracks then try different polarity settings of the toms - whole kit. Its quite amazing the different tones that can be found on a kit with just a few polarity swaps.
As Evan stated. Just swapping the Snare polarity can do wonders to the bass drum and snare sound.
Should you happen to do a choppy 20ms noise gate release time on your drums then YMWV but fast rolls around the kit with 150ms and longer release times polarity does seem to come into play.

Try the polarity switch. If it does nothing or makes things worse then put it back where it was. There sometimes is no "Right" or "Wrong". Something that should not matter or should not work turns into just the thing you needed to get your mix right.

Douglas R. Allen

 

[Royce Covington]

Re: Polarity invert toms ?

Is there a way, aside from using an oscilloscope, in determining if this is the case? He has a D6.

you could probably check the mic with a cricket.

You said that if the system is easily overpowering the acoustic that it is a non issue. What do you mean by that? Why wouldn't it?

I think that reference is with regards to the size of the system in play.
meaning, a small S.O.S. system would likely be more problematic than an arena-sized system.

R~

 

[andrew gissing]

Re: Polarity invert toms ?

Thanks all for your responses.

I was originally thinking of just absolute polarity but Douglas you've really got me thinking now. I usually don't gate for most of my work 'cause I don't need to.

Now youi've got me thinking. I'll try what you've suggested and see how it sounds on a recording.


Andrew

 

[John Roberts]

Re: Polarity invert toms ?

you could probably check the mic with a cricket.



I think that reference is with regards to the size of the system in play.
meaning, a small S.O.S. system would likely be more problematic than an arena-sized system.

R~

Simple math... for two similar signals to interfere noticeably they need to be similar in level. If the PA is much louder, or much quieter, than the acoustic sound source, the interference will not be significant.

JR

 

[Robert Burns]

Re: Polarity invert toms ?

Practically speaking in a live context most that I know don't go beyond observing the 3:1 or 5:1 distance rule.
Not to say that having the capability to flipping polarity might help; buy often there simply isn't enough time to try and hear.
In a studio I can understand the meticulous tweak.

 

[Tim Weaver]

Re: Polarity invert toms ?

Practically speaking in a live context most that I know don't go beyond observing the 3:1 or 5:1 distance rule.
Not to say that having the capability to flipping polarity might help; buy often there simply isn't enough time to try and hear.
In a studio I can understand the meticulous tweak.

I play with polarity all the time. I will cue up the snare + another drum mic (like an OH) and flip the polarity in and out until I see which one sounds better. Continue on down the line comparing the other mics on the kit with the snare. Use your EARS and not your brain when you do this and you just might be surprised at the results.

I will listen to the bass with the PA on and flip the polarity in/out and see if one way sounds better or not. Often times you'll hear a big suckout somewhere and a big addition somewhere else. This is usually the bass cab to PA interaction. Adjusting the polarity here won't solve all the problems, but often one way is more pleasing than the other.

When using area mics on a theatre stage it helps to have one or two mics out of polarity with the others to prevent feedback. If you have 5 PCC's across the front of the stage, then throw at least one of them out of polarity. If you get a little ring in the PA, it'll prevent the whole line of mics from picking that up and taking off. I actually flip the polarity switch on floor and hanging mics as my first step in ringing them out. Usually one way will offer more GBF than the other way. That's where I start EQ'ing from.

 

[Robert Burns]

Re: Polarity invert toms ?

Tim: The OP was asking for a consensus (which I added to ). You chose to quote me ( unsure why ), but failed to consider the gist and context of my statement.
Your response comes across not as feedback to the OP, but as a lecture to me:

Use your EARS and not your brain when you do this and you just might be surprised at the results.

( IMO: That statement is presumptive and somewhat condescending. )

 

[John Roberts]

Re: Polarity invert toms ?

We're all preaching here, just not from the same sermon....

the point I take is that he feels polarity is worth experimenting with, but isn't preordained one way or the other.

-----
I will not take the bait to veer into polarity wrt feedback concerns, other than to say that isn't very simple either.

JR

 

[Tim McCulloch]

Re: Polarity invert toms ?

Tim: The OP was asking for a consensus (which I added to ). You chose to quote me ( unsure why ), but failed to consider the gist and context of my statement.
Your response comes across not as feedback to the OP, but as a lecture to me:
( IMO: That statement is presumptive and somewhat condescending. )

You are a victim of a "flat-view poster."

 

[Curtis H List (Too Tall)]

Re: Polarity invert toms ?

Drums, like all other instruments generate AC sound waveforms, while there is a polarity associated with the initial transient hit. Your question is based on the assumption that we actually want a positive pressure attack from toms. BTW the kick drum, if mic'd from the resonant side does generate a positive pressure attack. Tom's are generally neither pointed at or away from the audience, so the natural way we experience these waveforms un-amplified, is actually at a right angle to the drum heads.

I believe absolute polarity "could" be audible when reproducing drum hits, while subtle. When close micing a drum kit with multiple mics there are far more sound altering consequences from exactly where the mics are pointed at a given drumhead, and how multiple mics interfere if they pick up the same sound field.

Most polarity tweaks around drum kits are to get the mics to play nice together. If concerned about polarity, make the kick drum front mic your "in polarity" reference sound, and then get the others to play nice with that.

JR

Well it seems everyone agrees, except me. LOL

In the end whatever makes the mics play well together, that said here is what I often do.

For rack toms if the mics are under the head to let the shell isolate them I flip polarity.
I prefer micing rack toms from the top often using half as many mics
Typically I do not allow big floor toms to be miced under the head.
For the kick I rarely mic from the front.
Almost always put the mic (mics) inside the shell but I do not FLIP POLARITY.

This is my starting place.

PS-If I use two mics on the snare the bottom is flipped. I rarely use two mics. Instead use a very nice wideband condenser if I can find one.
Same with micing the rack toms and the lead guitar amp if I have enough mics. I avoid SM57 where I can.
Beside the obvious that they sound better than a SM57 having the same type of mic everywhere helps with the bleed. The bleed seems to be less of a problem.
For instance using a great vical mic means when it picks up the piano bleed it sounds better.

 

[Tim Weaver]

Re: Polarity invert toms ?

Tim: The OP was asking for a consensus (which I added to ). You chose to quote me ( unsure why ), but failed to consider the gist and context of my statement.
Your response comes across not as feedback to the OP, but as a lecture to me:
( IMO: That statement is presumptive and somewhat condescending. )

Possibly I didn't explain my position well enough. My opinion is that there is always time to hear, in the headphones during the show.

Not to say that having the capability to flipping polarity might help; buy often there simply isn't enough time to try and hear.

I typically won't do this step during soundcheck, but will go back and do it during the first few songs of the night. This is just another reason to carry good cans with you. (It amazes me how many touring guys show up to my consoles and ask to borrow MY cans! {beside the point, I know, but just ranting})

You are correct in saying that most people don't bother, but I say, Why don't you? It's and easy thing to do that can improve your drum sounds considerably in a way that no amount of EQ will fix. You can't EQ away phase cancellation. You can improve it sometimes by flipping polarity though.

Sorry if my first statement hurt anyones feelings. Sometimes I start typing a response to a post and my train of thought gets totally derailed. I replied to your post and then started talking to the OP when I said "use your ears" since he was looking for a "rules of using the polarity switch" type response. I've never been accused of being "nice" anyway. That's what my wife keeps telling me anyways.... lol