Kick drum phase reversal questions

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Tim Brown

Tim Brown

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Okay guys, here's my question:

My mixingboard doesno't have a phase reverse switch.

Can I delay my drumtacks and fix the phasing problems of the Kick vs. the rest of the kit?

i.e., can I delay the entire kit ...say 5 to 10 ms...and will it cause the drums to be in phase with the rest of the kit?

My DA-38's have a track delay function.... but too bad there's no phase reverse function!


Thanks,

Tim
 
:cool: Good question, I don't believe delay is the same as phase reversal.


da MUTT
 
isn't phase a direct result of the delay of the sound waves hitting the mic? So if you delay the signal to tape exactly right wouldn't it be in phase? hmmm, I hope I'm thinking this correctly. Phase confuses me....
 
:cool: The delay on the da38 is to delay the time of playback.......
Don't think its a way to correct or to invert an out of phase signal on the track its self.
What we really need is for Larry Robinson from the Tascam forum to give us a 10 page lesson on this. Tim trot your question over there....


da MUTT
 
if you were dealing with a pure sine wave, then yes, you could delay the track and it would be the same as flipping the POLARITY (which is what the "phase" button does. also known as "invert").

but as it is, the signal is changing greatly with time, so delaying a track will probably create more phase problems than it solves.

that said, it is possible that delaying the kick will subdue some of the phase cancellations. just don't expect it to be an equivalent to the "phase" button on many boards.

yes, phase results from the time difference in when the sound hits the mics, but you don't have just one source here. you have many sound sources, and each mic is a different distance from each. add the influence of the room, and you can see that there are more delays contributing to the sound at a given position than you could feasibly correct for.
 
jrosenstein said:
if you were dealing with a pure sine wave, then yes, you could delay the track and it would be the same as flipping the POLARITY (which is what the "phase" button does. also known as "invert").

but as it is, the signal is changing greatly with time, so delaying a track will probably create more phase problems than it solves.

that said, it is possible that delaying the kick will subdue some of the phase cancellations. just don't expect it to be an equivalent to the "phase" button on many boards.

yes, phase results from the time difference in when the sound hits the mics, but you don't have just one source here. you have many sound sources, and each mic is a different distance from each. add the influence of the room, and you can see that there are more delays contributing to the sound at a given position than you could feasibly correct for.
Click to expand...

It was like that dish soap commercial with the grease! The waters are starting to demuddify themselves.
 
a little more about the connection between delay and phase reverting.

A reversed phase signal is like a negatief signal opposed to a positive one.
If you would draw a sin. and a second one 180 degr. you will have 100% phase cancelation. (just add those 2 sin. and you will end up with nothing! 4 + -4 = 0 etc..)

The length of the wave is important to decide what delay must be use. But audio is more than one wave length... there are thousands of waves together which create music!

Phase reversion in this case is at VERY LOW delay
tyical 1 ms.
The best way is using a wave editor (Cool Edit, Wave Lab etc.) and reverse the whole sample.

by the way; Does this kick sound give phase problems? or is it something you just want to do? if you're drumkit has no troubles with the kick ... don't change it (you won't probably hear the difference anyway)
BASS is very low sin.wave so lesser phase troubles.
just use a gate to get rid of the other sounds... and you'll be fine
 
I think you might be chasing your tail on this one. If you have many mics on the kit you could move from one problem to another. and as far as I know a kick drum is the last thing you would ever want to reverse the phase on. you wouldn't want to make all of your fans speakers suck in when you hit the kick drum would you:D

Gates work well for me on the snare & the kick. I would love to not have to use them but I am in such a small room that I am better off with than without. I really need them on heavy songs.



Good Luck.

F.S.
 
I thought it depends how you point your mics. If you have 2 mics on a snare, 1 top and 1 bottom you flip the phase of the bottom mic. Wouldn't this then all depend on where your kick mic is pointed. If it is facing upwards enough, then reversing phase would be necessary.



I think.:D


oh, and polarity and phase are 2 different things. Changing the phase of a mic will not make your speakers suck in.
 
HangDawg said:
I thought it depends how you point your mics. If you have 2 mics on a snare, 1 top and 1 bottom you flip the phase of the bottom mic. Wouldn't this then all depend on where your kick mic is pointed. If it is facing upwards enough, then reversing phase would be necessary.



I think.:D


oh, and polarity and phase are 2 different things. Changing the phase of a mic will not make your speakers suck in.
Click to expand...

As I understand it in phase would mean having all of your mic's in the same polarity. Others say that one mic by it's self creating a posotive pulse initialy when it is subjected to a input with a sharp attack is in phase (thus the phase switch for a single mic). Most of the time I think of phase as a relationship between more than on mic or speaker. But I also make sure I have absolute polarity from mic to speaker so I don't really think about it too much.

The term called absolute polarity that describes pos. polarity from the mic to the speaker (requiring the the phase not to be switched)

quote from the link below:
"Microphone Electrical Phase Testing.
To test if a mic is in phase, simply plug a mic into the mixing desk, pan it to centre and slowly bring up the volume. Take off the pop-screen (or 'windsock') and while looking at the low frequency drivers, G-E-N-T-L-Y tap the mike with your finger. When a mic is correctly wired in-phase, the speakers will jump forwards, telling us that 'positive air pressure is resulting in positive voltage. ' If the mic is wired out of phase the speakers will jump backwards. Once the phase of the 'control' mic is confirmed, check the phase of all the other mics by :"

http://www.roadogz.com/stories/downunder/speakerstostage3.htm


F.S.

PS I'm not against reversing phase on a mic if needed, It's just I would never do it on a kick drum.:D
 
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all that "tapping" does is check for consistent polarity from mic to mic. you could just as easily make them all "suck in" and you'd be fine. that is not phase.

sound signals are sinusoidal .... no matter the phase or polarity, it will always be negative some of the time.

phase is all about time, and that means it depends on their positions. two mics wired with the same polarity will be out of phase at certain frequencies if they are placed at different distances from the sound source.
 
I was only saying I would not reverse phase on a kick mic, because you had mentioned reversing polarity (as in a phase switch). I should have never brought it up.

And then someone said it could not cause your speaker to suck in. Wrong! it can. Most noticable on low frequencies (I.E. Kick Drum)

And hey if you want all your drum mics to suck in your speakers go for it, I disagree that you would be fine, but what the hell.

The problem with "phase" is it has too many definitions:D

I will never speak of phase again. unless in the context of timing correction:D not phase switches & polarity. I should have added that definition of phase "being in phase" in my last post but I was at work and only disputing the fact that a single mic with reversed phase (a legit term) could not make a speaker suck in.

F.S.

PS my vote would be to move tracks individualy or move mic positions.
 
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And I was pointing out that whether the first movement of the speaker cone is forwards or backwards, it will go both in and out at any frequency.
 
very true, no argument there. But the first movement on drums is not trivial.


Anyway, no biggy either way.

Like I said there are too many definitions to phase, and they tend to get intermingled when you start to talk about switching the phase (polarity) on a pre-amp to correct a phase (out of align soundwave) problem with a drum recording. Somebody needs to rename all phase switches on preamps to - & + polarity and stop calling a microphone in phase when it generates a posotive signal on attack.

But the terminoligy for all of the definitions have been around a long time. Bad planning on someones part:D

So phase and polarity are the same thing, and phase and polarity are not the same thing depending on the context, yet they both tend to come up in the same conversation often (thanks to the phase switch I think).


Later

F.S.
 
very true about the terminology. one word can only mean so many things before it gets confusing.

Are speaker cones more resilient to moving forward than backward? (don't know here .... i'm asking) Could a negative transient bust the speaker where it would handle an identical but positive burst just fine? Just thinking about it, it would seem silly to me to make a driver that could take more in one direction than the other ...
 
I don't think that you are going to blow a speaker any quicker sucking it in than pushing it forward (not an expert here) as long as the voice coil doesn't bottom. I would guess the cone could flex more pulling it back hard just because of the design and basic physics of a speaker but I don't know if it amounts to anything. The big deal is what kind of spl you can generate and how much definition it will have pushing forward in the intended direction with a bowl shape or projecting it back into the cabnit with a dome shape. If you go to the tannoy sight and download a owners manual they really harp on it because of loss of defenition. Or as they put it Vague imaging.

You know the guy to ask would be Barefoot, but he hasn't been around much. He is the speaker man. He is moderating a forum over at John Sayers sight.

Here is a link. or you could P.M. him. Let me know.

http://johnlsayers.com/phpBB2/index.php


F.S.
 
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