Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[andychamp]

In the process of checking out a newly acquired mic, I did one of my usual tests: put on some phones, touch the mic with my lips and start talking/screaming/kinda-singing into the mic, into each and every preamp currently available. These were: GR500NV, API512c, Audient Mico, Chandler Germanium, Voxbox and Amek CIB.

I noticed something strange: when flipping the polarity on the preamps, the effect wasn't always the same.
It was most obvious on the GR, followed by the CIB, then the Mico, the API, the VB and the Germ. On the last two I even had to double-check if I was on the right switch. Incidentally, the 2 "winners" seemed to extend lowest.

When used on sources in another room, the switches on all preamps usually work fine, so I guess it must have something to do with their internal polarity, in respect to "real", unamplified, direct sound: maybe some aren't 0/180 degrees, but rather 90/270 or some other values in-between?

Alternative theories anyone?

[Rick Sutton]

On the human voice a switch of the polarity shouldn't make ANY difference in the sound. Now, seeing that you had headphones on at the time you were switching I would wonder if the switch is messing with you due to the combination of headphone sound and bone conductance to your ears from your mouth. My advice is to find another way to test your mics and stop smoking that stuff that makes you want to put on headphones and yell into microphones.
Also, all the polarity switches are 0/180. They are just reversing the positive and negative wires.

[Bill_Urick]

Something is going on with phase cancellation between the sound of your voice conducted through your skull vs. the sound coming through the headphones.

Variations in response could be due to variables in the way you're doing the test.

My theory, anyway.

[Bill_Urick]

Rick Sutton wrote on Mon, 19 January 2009 19:24

On the human voice a switch of the polarity shouldn't make ANY difference in the sound. Now, seeing that you had headphones on at the time you were switching I would wonder if the switch is messing with you due to the combination of headphone sound and bone conductance to your ears from your mouth. My advice is to find another way to test your mics and stop smoking that stuff that makes you yell into microphones.

Beat me by one stinkin' second!

[Rick Sutton]

Bill_Urick wrote on Mon, 19 January 2009 16:26

Beat me by one stinkin' second!

You were just at 180 polarity. Does it every time!

[andychamp]

Rick Sutton wrote on Tue, 20 January 2009 01:24

On the human voice a switch of the polarity shouldn't make ANY difference in the sound.

IME,and that of some singers I've worked with, it DOES make a difference when you're wearing phones, one position always feels "more right" than the other to the wearer.
Probably because of the effect you describe here:

Quote:

(...) due to the combination of headphone sound and bone conductance to your ears from your mouth. My advice is to find another way to test your mics and stop smoking that stuff that makes you want to put on headphones and yell into microphones.

Actually that's quite a reliable way of tuning my ear to my own voice AND different mics AND different pres.
And it's only ONE way of testing.(and I found out quite some years ago that dope and AE don't go together well, thank you very much)

Quote:

Also, all the polarity switches are 0/180. They are just reversing the positive and negative wires.

Aggreed.
What I meant was: maybe the different preamps add a slight phase shift of their own, different for every model, and these are more or less audible, depending on their relationship to the direct/skull sound (all other factors being equal)
So, if the phone sound is perfectly in phase with the "bone" sound, the effect of the polarity switch would be much more obvious to the wearer than if it were slightly off to start with.

Maybe someone reading this thread wants to try it for themselves...

[Rick Sutton]

andychamp wrote on Mon, 19 January 2009 17:37

Rick Sutton wrote on Tue, 20 January 2009 01:24 On the human voice a switch of the polarity shouldn't make ANY difference in the sound. IME,and that of some singers I've worked with, it DOES make a difference when you're wearing phones, one position always feels "more right" than the other to the wearer. Probably because of the effect you describe here: Quote: (...) due to the combination of headphone sound and bone conductance to your ears from your mouth. My advice is to find another way to test your mics and stop smoking that stuff that makes you want to put on headphones and yell into microphones. Actually that's quite a reliable way of tuning my ear to my own voice AND different mics AND different pres. And it's only ONE way of testing.(and I found out quite some years ago that dope and AE don't go together well, thank you very much) Quote: Also, all the polarity switches are 0/180. They are just reversing the positive and negative wires. Aggreed. What I meant was: maybe the different preamps add a slight phase shift of their own, different for every model, and these are more or less audible, depending on their relationship to the direct/skull sound (all other factors being equal) So, if the phone sound is perfectly in phase with the "bone" sound, the effect of the polarity switch would be much more obvious to the wearer than if it were slightly off to start with. Maybe someone reading this thread wants to try it for themselves...

Andre, I was just kidding you, Don't ever take me too seriously as I have a tendency to see the lighter side of things.
The only serious point I was trying to make was that the polarity switch should have no effect on the sound of a voice when it is evaluated in a conventional manner or used in a recording. If it does there are other problems.....talking voice here, all bets are off on low freq. impact tones like kick.
Cheers, Rick
By the way, are you listening to a direct feed from preamps or through a DAW like PT? I would guess that once the singer is hearing the mic through a DAW's converters (like most studios have the HP feed set up) that the delay in the sound would complicate your findings on a polarity test dramatically. Just a thought.

[andychamp]

Rick Sutton wrote on Tue, 20 January 2009 03:32

Andre, I was just kidding you, Don't ever take me too seriously as I have a tendency to see the lighter side of things.

No problemo! Just trying to make sure I'm properly communicating what I hear.

Quote:

The only serious point I was trying to make was that the polarity switch should have no effect on the sound of a voice when it is evaluated in a conventional manner or used in a recording. If it does there are other problems.....talking voice here, all bets are off on low freq. impact tones like kick.

Absolutely aggree, what I heard probably only matters to someone hearing themselves on phones, if it matters at all. And then there's that switch to put them at ease.
I just expected the effect to be equally obvious with all pres. But on the way to the final mix, any signal will get phase-distorted in so many places that this bit won't really matter anyway.

I was indeed listening back through the MOTU CueMix Console, so there's my 1st possible source of error. I'll repeat the test through a completely analog path and see if the effect persists.

But you're right, it probably won't make or break a mix.

[Fletcher]

Rick Sutton wrote on Mon, 19 January 2009 19:24

On the human voice a switch of the polarity shouldn't make ANY difference in the sound.

Actually... it should.  The human voice is an asymmetrical wave form and all amplifiers, even Class A amplifiers are also asymmetrical which means that the top of the wave form is being amplified differently than the bottom of the wave form... flip the polarity [so long as that polarity switch is on the input of the unit and not the output] and you should hear a difference.

If you look at it on an oscilloscope you'll see what you're hearing and perhaps understand it better.

Peace.

[Tomas Danko]

Rick Sutton wrote on Tue, 20 January 2009 00:24

On the human voice a switch of the polarity shouldn't make ANY difference in the sound.

A plosive that pushed the speaker cone towards you would instead push away from you, and therefore (depending on the vocals of course) flipping the polarity may yield a slightly different listening experience/feel although you probably won't be able to say which one's better. They're just different, in this aspect regarding what the plosives feels like.

[Fibes]

Fletcher wrote on Tue, 20 January 2009 09:13

Rick Sutton wrote on Mon, 19 January 2009 19:24 On the human voice a switch of the polarity shouldn't make ANY difference in the sound. Actually... it should.  The human voice is an asymmetrical wave form and all amplifiers, even Class A amplifiers are also asymmetrical which means that the top of the wave form is being amplified differently than the bottom of the wave form... flip the polarity [so long as that polarity switch is on the input of the unit and not the output] and you should hear a difference. If you look at it on an oscilloscope you'll see what you're hearing and perhaps understand it better. Peace.

IME Different pres handle assymetrical waveforms differently on the front end.

I've flipped polarity before the preamp (for the sound) on voices, then flipped it back before the compressor and subsequent storage.

I also think Fletcher may be the only person not to call me crazy about this yet. Waits...

Also, that doesn't mean that's what's going on with the andy's stuff.

[Audio Craftsman]

I've been buying used mics on ebay a lot lately, many of them cheap enough that I don't care too much that I don't already know what they sound like.

So to get to know them, I do what you're describing and talk into the mic with my own voice.  But I don't evaluate the sound at the same time.  I go back into my control room and A/B the mics on speakers.  I feel this is a more objective way to listen because:
(1) Most of my listening is on speakers, not headphones
(2) Aural memory is short, so quick A/B comparisons seem more helpful
(3) I can level match the recordings by ear to help minimize the "louder is better" problem
(4) No bone induction, delay in phones against my own voice, etc.

Also, a friend of mine told me the word "precipitate" helps reveal plosive and sibilant problems because it contains both.

[Fletcher]

Fibes wrote on Tue, 20 January 2009 13:49

IME Different pres handle assymetrical waveforms differently on the front end.

It's all about how close to symmetrical the amplifier is as to how well it will handle an asymmetrical wave form.  It really is one of the deciding factors on why we do or don't like certain pre-amps in certain applications though it's probably the least talked about parameter [after phase shift and frequency response and noise floor etc., etc., etc.].

At the end of the day if you know your tools you'll be able to achieve the desired result... because at the end of the day nobody gives a shit about anything except the sound of the end result.

How we get their may be our own intellectual process... but the tools are just a means to an end... and the end result comes out of the speakers [which determines whether or not you can keep working or need to find a new vocation].

Peace.

[bruno putzeys]

There's no need to invoke asymmetries in the amplifier and the loudspeaker. Even on very low distortion replay systems (electrostatics), polarity reversal is clearly audible on some material. The ear is quite nonlinear enough.

[0dbfs]

Fletcher wrote on Tue, 20 January 2009 09:13

If you look at it on an oscilloscope you'll see what you're hearing and perhaps understand it better. Peace.

I was recently sending some square waves through a pre and comparing input to output on a scope while switching polarity among other things.

The reversed polarity signal was significantly different (in addition to being inverted) than the non-inverted signal.

I'll be checking this on my other pre's as well as comparing my findings against actual complex sources in listening tests.

I know for a fact that this particular mic-amp does more than invert polarity with the phase button. I expect others to behave in a similar fashion as well.

Good to be aware of and quantify in a sonic context.

Cheers,
J