What causes this phase phenom?

amishsixstringer · Post by **amishsixstringer** » Sun Apr 09, 2006 1:19 pm

I have noticed this at times, and use a rotary phase plug to fix it, but I have played around with some things and I can't figure out what causes it. Anyhow, it usually happens on kick or snare drum that one pole is much hotter than the other. If you look at the wave form the + is about 5-10dB higher in amplitude. I found that you get that track to sit better in a mix if the phase is rotated to even these out. I'm sure it has something to do with the source/microphone working together, but I was just curious about it today. Thanks!

Neil

philbo · Post by **philbo** » Sun Apr 09, 2006 7:26 pm

What do you mean by 'pole'?

Are you referring the snare as heard in the overheads?
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amishsixstringer · Post by **amishsixstringer** » Sun Apr 09, 2006 8:43 pm

Hmmm, I'm trying to describe this, but it's not easy. I am referring to the close mics by the way. If you were to look at the wave form you would see that the top of the wave is 0dBFS and the bottom is also 0dBFS with the the center line being the null of the wave (the speaker cone would be in it's rest position here). What I'm seeing often with kick and snare tracks is that the + or - (push/pull) of the form is stronger toward one pole. If this doesn't make sense I'll get a screen shot and put it on here.

JONMD · Post by **JONMD** » Sun Apr 09, 2006 8:48 pm

What Mics are you using? Are you compressing going in?

soundguy · Post by **soundguy** » Sun Apr 09, 2006 10:30 pm

It is most likely from your mic placement.

when people made honest rock records back in the day, they didnt tweak on that level, they just adjusted the mics until it souded cool.

dont make the process more ridiculous than it needs to be, making records is easy.

dave

river · Post by **river** » Mon Apr 10, 2006 1:08 am

What soundguy said. I've seen this multiple times on snare tracks.....but they sit just fine in the mix. That's all that really matters.

phalex · Post by **phalex** » Mon Apr 10, 2006 4:36 am

It is caused by a slight magnetic field that is created when the snare drums snare moves at certain frequencies. This magnetic field pulls the mic at the diaphragm, and it keeps it from reaching the full negative amplitude.

bobbydj · Post by **bobbydj** » Mon Apr 10, 2006 5:26 am

Hence why I use aluminium snare wires. And have done since 1992. And before any of you read any further, that's ALUMINIUM. *Not* aluminum.

It's pronounced ALLEY MIN YUM.

So please - don't give me any of this AL OOOH min UM crap.

Mark Alan Miller · Post by **Mark Alan Miller** » Mon Apr 10, 2006 7:19 am

While that magnetic field theory is interesting, I don't see it making sense, really. Among other issues, if microphones were somehow that suceptible to tiny stray magnetic fields like that (and what about non-metallic drums?) then I think we'd have a lot harder of a time getting anything recorded 'accurately'.

Many, many sounds are aysymmetrical in regards to positive vs negative going portions of the waveform.

In the case of a snare hit, the first peak transient will have slightly more energy then even it's immediately following opposite going component, as the energy added to the system (by the stick hitting the head) immediately starts to dissipate.

I would actually be surprised to see perfectly symmetrical waveforms from acoustic instruments in most cases.

And in any case, yeah, if it sounds good, what's the worry?

phalex · Post by **phalex** » Mon Apr 10, 2006 10:16 am

bobbydj wrote:Hence why I use aluminium snare wires. And have done since 1992. And before any of you read any further, that's ALUMINIUM. *Not* aluminum.

It's pronounced ALLEY MIN YUM.

So please - don't give me any of this AL OOOH min UM crap.

The american way is more fun to say.

*Magnetizes bobbydj's walker*

philbo · Post by **philbo** » Mon Apr 10, 2006 10:17 am

Here's my humble opinion:
1) One side of the wave SHOULD be louder than the other. A drum hit starts decaying almost immediately, so the first peak will be the strongest.

2) There is no way you should be recording any drum so that a hit gets you to 0 dBFS. Maybe -6 maximum, if you are still in 16-bit world. Preferrably -12 to -18 if you record at 24 bits. You are leaving yourself absolutely no room for dynamics.

3) If EVERY wave you record is skewed up or down relative to the zero line, look for an option on your DAW or audio interface to "Remove DC while Recording" and turn it on.
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Aerophone · Post by **Aerophone** » Mon Apr 10, 2006 10:31 am

phalex wrote:It is caused by a slight magnetic field that is created when the snare drums snare moves at certain frequencies. This magnetic field pulls the mic at the diaphragm, and it keeps it from reaching the full negative amplitude.

ouch! Are you saying that i can't put a mic in front of my (huge magnet) peavey speaker?

JGriffin · Post by **JGriffin** » Mon Apr 10, 2006 11:01 am

bobbydj wrote:Hence why I use aluminium snare wires. And have done since 1992. And before any of you read any further, that's ALUMINIUM. *Not* aluminum.

It's pronounced ALLEY MIN YUM.

So please - don't give me any of this AL OOOH min UM crap.

Too bad for us Aluminium products aren't available in the U.S. We only have Aluminum. Ah well, you tried to help.

Mark Alan Miller · Post by **Mark Alan Miller** » Mon Apr 10, 2006 4:43 pm

Oh, I misread the bit about the metal strainer creating a small magnetic field. Possible, I suppose. Never had it cause any issue for me that I could notice... Not being a coil of wire, but simply paralell wires, the induced magnetic field would not only be weak, but very axis-oriented. That is, it would be quite polarized in nature, and for any effect to be felt by the microphone, I would suspect the alignment or the strainer would have to be quite precise with that of the coil in the mic.

phalex · Post by **phalex** » Mon Apr 10, 2006 5:22 pm

Mark Alan Miller wrote:Oh, I misread the bit about the metal strainer creating a small magnetic field. Possible, I suppose. Never had it cause any issue for me that I could notice... Not being a coil of wire, but simply paralell wires, the induced magnetic field would not only be weak, but very axis-oriented. That is, it would be quite polarized in nature, and for any effect to be felt by the microphone, I would suspect the alignment or the strainer would have to be quite precise with that of the coil in the mic.

Parallel springs.

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What causes this phase phenom?

What causes this phase phenom?

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