Mic Phase

[blackfoot]

Ala Ricks article I've been checking through my mics to sort the lefty's from the righty's. Most are clearly defined as to their leaning. But a few seem to dip negative before swinging positive at a much greater level for a much greater duration. What's the call on this?

[rick]

probably a reflection from the internal shape of the mic , it happens a bit
hit the mic harder as well

the next test is to pair it with a known positive mic and see if it cancels to some large degree or if not

[rob]

I must admit I was puzzled by the complexity of Rick's polarity test and the potential for error.

I usually just talk into the mic whilst wearing headphones and make some suitably low tones, you can "hear" mics that are out of phase, they sound "hollow" or lacking in bass. Having a pre with with phase rev switch allows to compare which phase sounds right and note the position of the phase rev switch.
Of course this assumes that the cables, preamp, headphone amp and headphones are all in phase. But Rick's technique also assumes that all the gear used is also in phase. If you start finding mic after mic is out of phase then assume that there is something else in the setup that is phase reversed and correct before retesting the mics again.
If you can't get a clear picture if mics sound in phase in the headphones, set up two mics, call one the reference, mix both mics to mono and talk into them with the mics side by side. An out of phase mic will then stand right out , with all the low tones being diminished. Once again if mic after mic seems to be out of phase then assume that the "reference" mic you have chosen is out of phase. Replace with another and start the testing again.

You could test a slew of mics in no time flat like this and no need to interpret waveforms...use your ears.

btw I rarely find a mic that is out of phase, unless it has been "worked on"

[Chris H]

I think Rick's point is when the mic creates a + signal that pushes rather than pulls the speaker driver when reproducing the first transient of for example a kick drum, then the mic is as it should be, positive polarity......not if the mic is "in phase" with rerference to another mic. Of course when one mic is established to have a + polarity then comparing other mics to this one to see if they are in phase will let you know which mics in your collection suck when they should push :)

[jasound]

There's a new Iphone app called Audio Tool Kit which has a phase check section as well as a number of other handy tools for sound engineers. Designed locally by Tony David Cray. Yes he's a friend of mine. [/img]

[Chris H]

There's a new Iphone app called Audio Tool Kit which has a phase check section as well as a number of other handy tools for sound engineers. Designed locally by Tony David Cray. Yes he's a friend of mine. [/img]

Great but does it test for polarity :(

[Kurt]

Doesn't come up in an appstore search...

There's a new Iphone app called Audio Tool Kit which has a phase check section as well as a number of other handy tools for sound engineers. Designed locally by Tony David Cray. Yes he's a friend of mine. [/img]

[jasound]

Hi here is the link
http://itunes.apple.com/au/app/audiotoo ... 37751?mt=8

[rick]

I must admit I was puzzled by the complexity of Rick's polarity test and the potential for error.

I usually just talk into the mic whilst wearing headphones and make some suitably low tones, you can "hear" mics that are out of phase, they sound "hollow" or lacking in bass. Having a pre with with phase rev switch allows to compare which phase sounds right and note the position of the phase rev switch.

You could test a slew of mics in no time flat like this and no need to interpret waveforms...use your ears.

btw I rarely find a mic that is out of phase, unless it has been "worked on"

the point of my test is any monkey can SEE whats going on , and then if they have some kind of methodical brain they can label all of their mics with either a positive or negative, then they will know forever more that it is NOT the mic combination that is out of phase its something else .
Rob the reason i wrote that thing is many people have never experienced the out of phase sound in such a way they knew what it was .with the screen shot method you can see it , talk about it and think about it .

i am getting lots of reports about brand new " backwards firing" mics , like the audio technicas .. that was a suprise to me .
so rob you will find that amonst new and old mic and the kinds of mic lots of people have the split i am getting reports on is about 70 positive 30 negative - with NEW mics - so i think you might be taking a techs eye view on this !

it would be great if we can all listen , i just think those days are gone for a large group of engineers
this method is designed to make them listen, but with a confirmation of WHAT they are listening for.

also it works on just one mic , which no listening test does !
and also nearly nothing you buy on the cheap actually has a phase switch , ( including protools)
i thought i was pretty clear about the instructions , but you should see some of the emails i get .
you can never dumb it down enough me thinks

if everybody that has never tested their mics for polarity stepped of a cliff , it would be a ghost town out there in studioland
yet once the phase check it was a normal thing to do ...

so was using you ears :)