polarity and gain relationships between mics

O.k. I'm trying to wrap my head around this. I have 2 side address cardioid tube condenser mics(pin 2 hot on both) I am using to cut vocals on a project. I am tracking both mics at the same time onto 2 seperate tracks in the slow tools. One mic is pointed straight up and the other is pointed straight down and sits on top of the mic pointed straight up. The idea is to capture the vocal via 2 different mics and blend getting the prefect tone without using an eq. If I pan the tracks in the center and have equal gain on both mics I get a sound of mono and out of phase. To fix the problem I hit the polarity button on the mic pre and the vocals sound normal. I
What I am trying to get my head around is why I am getting cancellation? Is it because both capsules are on the same plane and equal distant from the source or is there something more a foot? In other words is it similar to that of 2 mics on a snare drum and having to flip polarity on one of them?

I'm not understanding how you have the mics placed, you mention straight up and straight down.. in relationship to the ground?

:shock:

A picture is worth a thousand words they say..

:green:

picture would help, and i think yes to the snair analogy ....

[quote author="Svart"]I'm not understanding how you have the mics placed, you mention straight up and straight down.. in relationship to the ground?

:shock:

A picture is worth a thousand words they say..

:green:[/quote]

o.k. here goes...



the mic pictured is what I am referring to straight up. Now imagine a similar moc upside down and the tops of the grills resting on one another.

because the sound hitting the bottom mic is going left to right, but the top mic is right to left, so they are already out of phase?

For close-micing, it's very easy to get phase problems if you don't have the source placed fairly precisely equidistant from each capsule. This is made more difficult by singers if they move.

[quote author="pucho812"][quote author="Svart"]I'm not understanding how you have the mics placed, you mention straight up and straight down.. in relationship to the ground?

:shock:

A picture is worth a thousand words they say..

:green:[/quote]

o.k. here goes...



the mic pictured is what I am referring to straight up. Now imagine a similar moc upside down and the tops of the grills resting on one another.[/quote]

Allign membranes paralleled and if they face the same direction, but give opposite polarities, one of your mics is wider a wrong way (inside!).

(When Wavebourn writes "Wider" he means "Wired".)

Pucho, one of your mics is pin-2/pin-3 swapped in terms of polarity.

It's more common than you think. I've checked ALL of my mics, and my 2500 was in opposing polarity to ALL my others. -I swapped pins 2 & 3 and now they all play nice together.

If I pan the tracks in the center and have equal gain on both mics I get a sound of mono and out of phase.

Click to expand...

No matter WHAT you do with polarity, when both are panned to the center, you will ALWAYS get mono...

The idea is to capture the vocal via 2 different mics and blend getting the prefect tone without using an eq.

Click to expand...

Uually a bad idea unless your singer is paralysed. Any variation in the exact angle of arrival means that the phase-related notches/peaks are moving in frequency... Put him in a head clamp, otherwise there are more pitfalls to this approach than benefits. -Ever heard of the "rule of three"?

Keith

wow keith didn't bust me on that one too badly. My first impression was the mics have a different hot pin one with pin 2 and one with pin 3 but unfortunately that is not the case. I have crossed checked them with other mics that were wired pin 2 and they both by themselves and the other mics work fine, It's just when they are together that there is polarity issues.

I know of rule of 3. :thumb:

So maybe this is not the best approach but with it's been working well aside from hitting the polarity button. The end result will be a mono vocal as both tracks will be in the center. I will get to use the different mics and their eq curves that they produce.

Cool. -As you wish.

To make this more of a learning experience, -specifically so that you can "see" how the physics of the "problem" work, you should increase the distance between the two mics to say six inches.

-Then bet the talent to make a continuous and constant "shhhhhhhhhhhhhhhh...." sound while he (or she) bends at the knees (to shorten themself by about 3-4") and then stands on tiptoe (to do the reverse).

Have them do that 3 or 4 times, then listen to what it does to the signal... -pretty bad, huh?

Then put it halfway back to where you were originally and repeat the test. -A little better, right?

-Then try it with the mics as they originally were. -Now see what I mean. -Better, but still rather susceptible to movement. -It's why mics like the Soundfield and other native B-format mics like the Josephen C700 are a little susceptible to near-field motion. (the problem is with comparative time differneces, which are related to PATH LENGTH differences. -The nearer, the worse. -At ten feet, you won't hear the effect. -At six inches, it'll make you squirm. -You may not notice it while you do the vocal, but if you don't LISTEN for it, you could be letting something past which will bite you in the ass later.

If you have two mics almost the exact same distance away, you're breaking the "rule of three"... and that's why you're batting on a bit of a treacherous wicket.

SEPARATE TRACKS. -If you permanently combine them, you'll never be able to "undo", and that's suicide for this treatment.

Keith

[quote author="SSLtech"](When Wavebourn writes "Wider" he means "Wired".)

[/quote]

Not always;
sometimes it means "Weird". Like a vertical directivity pattern in such case. :green:

here is a thought because they are 2 different mics could it be as simple as the diaphrams are far enough or not far enough apart to cause polarity issues :?

[quote author="pucho812"]here is a thought because they are 2 different mics could it be as simple as the diaphrams are far enough or not far enough apart to cause polarity issues :?[/quote]

What frequencies do you speak about?
For "out of phase" distances between mics and the singer should be 1/2 of the wavelength in difference.

loss in the low end mainly

[quote author="pucho812"]here is a thought because they are 2 different mics could it be as simple as the diaphrams are far enough or not far enough apart to cause polarity issues :?[/quote]
Pucho,

You're using polarity now in a situation where "phase" would typically be used... Quite the reverse from the mistake that most people commonly make...

...but...

It seems to me that you're not getting it. If the capsules are effectively coincident, (i.e. as close together as is reasonably practicable) then PHASE becomes as small a problem as it can possibly be.

If reversing the POLARITY improves things under coincident conditions, then you have a POLARITY problem. NOT a phase problem.

The test outlined earlier begins by increasint the distance between the capsules to reduce the effective coincidence, it's then trying to illustrate how things improve with increasing coincidence. -After that, you have POLARITY problems. -Just like with my own experience, the only irritation was caused by an old Russian interloper...

Keith

only irritation I got, they have cream... um never mind.

Time to rewire one of these...

[quote author="pucho812"]loss in the low end mainly[/quote]
Resolder then.

[quote author="SSLtech"]-Ever heard of the "rule of three"?[/quote]
Three... hmmm, how about The Rule of Six ? :grin:


But kidding aside, this is obviously a shoutout, not for blending (although the source is more or less static...)

What I actually am wondering with all these mics on each others lap, how honest can shootouts like this be... certain degree of compromise... still better than separate performances, OK, but can imagine every mic would like to have some more room to do its thing...

Here's some more madness

I am working now on a "rule of 4" currently: bi-gradient stereo using electret capsules.

[quote author="clintrubber"]



[/quote]

I'd call this "target practice" for the D112's...

I use close mics together on a fairly regular basis, but the first thing I do is flip the "polarity" on one of the preamps and do very small distance adjustments until they sound as bad as they possibly can. Then I put the polarity switch back to normall on the one preamp. The two mics generally sound phase coherent after this proceedure...