Mic phase invertion

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PowerCouple

PowerCouple

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Hi there!
I´ve just learned what phase inversion can do to say a pair of Shure SM57 recording a guitar amp (one front, one rear) but I don´t seem to get any results when recording onto my Roland VS880EX.
Is this due to the digital enviroment?
I use the mics trough a Presonus Bluetube Preamp (one mic´s phase is changed) and then I record on separate tracks on the VS880.
Should I record on one track only?
I discovered that inverting phase for one mic made the sound thicker with more bass response...

Thanks in advance and apologize me if I couldn´t translate and explain my problem well...

PC
 
Dont just flip phase cause you can, it may sound better if you dont flip phase. Try it.

Adding and combination of 2 or more signals together (digital or analogue) will create phase cancellation. Move you mics around, half an inch can make all the difference!

Mic placement is where it all begins, listen to the mics phase relationship, and move you mics to get a better bass response. Phase will help you do this. Do some research on sine waves, and how sound waves (sine wavs) are added together, you'll be much wiser!!
 
ok...I´ll try

Hey dmuzz, thanks for your advice...
So what I´ve learned is useless?
What good can phase invertion make?

Hope you can de-jackass me.

Other thing: How do you add that cute snake to your posts?
I´d like to add something to mines... but I don´t know how.

Thanks
PC
 
Your original tracks were recorded (one mike at the speaker front and one mike at the rear) out of phase.The front mike got the sound waves produced by the speaker pushing air forward.The rear mike recorded sound waves produced by the speaker moving back.Exactly 180 degrees out of phase.When you put either one one those signals through a phase reversal,you put both signals back in phase with each other.
You noticed how the bass came back.That is what the signal is supposed to sound like to start with.Loss of bass is a telltale sign of a pair of out of phase tracks.
See the user profile edit function for adding thoses little icons.New guys get to choose from a certain group.Then after so many posts you can get a custom icon.

Tom
 
Re: ok...I´ll try

PowerCouple said:


Hope you can de-jackass me.

PC
Click to expand...

What did you mean by this?

And Tom Hicks
"The rear mike recorded sound waves produced by the speaker moving back.Exactly 180 degrees out of phase". Depends on whether the two mics are identicle distance from the speaker cone. Its all about what sounds the best anyway :)
 
De-jackass

I live in Argentina, and here we got an expression (desasnar) that means the following: When someone does not know something (me in this case) needs to be converted from a Jackass to someone that knows. Just as simple as that. I just translated the expression because right now I´m a Jackass cause I have a lot to learn...

PC
 
Dmuz
The original post didn't specify the distance of the front mike from the speaker relative to the rear mike.Making phase judgements on that kind of lack of info is just plain guessing.Based on the info the poster actually gave about miking front and rear,as well as the aural result of phase-cancellation bass loss,its pretty clear that was due to the two signals being out of phase.
Your point is well taken about various distances from the mikes which cause the signal to arrive at differing times will indeed cause phase bugaboos.However,these are rarely 180 out of phase,which the front/rear miking scheme is a classic example of.

Tom
 
Thanks for joinin´Tom

You´re right. I´ve not specified the distance.
The mics are placed at the same distance and angle from the speaker, one front one rear.
The question is: Can digital enviroment automatically correct the phase difference? Because I don´t seem to get any difference.

PC
 
pc editing makes all this so simple

Hey PC
Line up the tracks in your multitrack editor and zoom in untill the waveforms are clearly visible.Pick a point (peaks are easy to spot) and offset the trailing (by time) wave untill it lines back up. Presto chango,back in phase!
Lots of hardware has phase switches;direct boxes,mixing consoles etc. so outboard processing is an alternative as well.
Best of luck.

Tom
 
Thanks Tom...

That´s a good idea...
What I´ve been doing here seems to do nothing.
I own a Presonus Bluetube preamp with 2 channels and a phase inverter per channel. I use my Shure SM57 one inverted one not, and I record to a Roland VS880EX in two tracks (one mic per channel). If I invert one mic´s phase I get no difference. If I don´t I don´t get any kind of "cancellation" as it probably should be (that´s basic physics). Can that be due to the digital recording?

Thanks in advance!

PC
 
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