Mic for Stereo Techniques - SE2200a

S

stereoid

New member
Hi,
I own a SE 2200a and i was thinking about buying a new mic for some stereo techniques, like XY, etc... And here's the question - does every 2200a mic has the same phase or it depends on a model? also - does different mics have only two phase levels (in-phase and out-of-phase) or it can have various phases (f.e. 39 degrees or 144degrees)? also is there any specific mic that is known for it's use in stereo techniques in similar (or a bit more) price range?
thanks in advance
 
A mic can be of one polarity - i.e. where zero degrees/ + pressure = + voltage, or the other 180 degrees/ + pressure = negative voltage. And polarity' phase (either way) means viewed at one point in time.
All that in between stuff is the object's sounds arriving at various times vs. your placement of one or more mics and how those time differences effect different frequencies when they're combined.
 
It's optional whether you get a second mic that is of a different flavor. It sort of divides as to where the importance lands where a 'matched pair is wanted where you want a fairly accurate match for a 'true stereo picture.
As a second mic in many other stereo or dual mic uses a second flavor is no harm. Dual stereo micing an acoustic guitar for example; maybe one grabs the '12th fret, another body. Both get moved to play each's best tone, there each mic base tone is less of a concern.
 
I think you are a little confused about phase. mixsit explained it, but here's a poor mans version. When a mic picks up sound, the diaphram vibrates, so think of it moving in or out. With one mic, it doesn't matter. With 2 mics, you can have the same sound while the diaphram of one is moving in and the other is moving out. This is when they are out of phase. Played back, the 2 sounds somewhat cancel each other. You can flip the phase of one mic through your DAW or also as mentioned, change the placement of the mics.
 
We need a phase / polarity sticky if there isn't one already.

Feel free to correct me, but this is how I've always though of it.

Picture a mic on top and a mic on the bottom of a snare, then picture the skin moving in slow motion.

As it moves up, the top mic's diaphgram responds by moving up; It moves towards the back of the headbasket.
This creates a positive signal.

At the same time, the bottom mic's diaphragm responds by moving up; It moves towards the front of the headbasket.
This creates a negative signal.

These will cancel to a great degree, and in a world with no variables, they would completely cancel.
They are at opposite polarity.


Now picture you record a sine wav with two mics at the same distance, side by side.
If the wave goes from -1 to +1, you've recorded it twice so max peak and trough is -2 and +2.

If you re record with one mic at a greater distance, the wave arrives late to one of the mics.

Say as mic one is picking up the wave at it's peak, while mic two is just picking up the start of the cycle, then the max peak can never be +2 since the peaks no longer co incide.

This is a phase discrepancy.

I think the two get confused a lot because people use sine waves diagrams to explain and mathematically there's no difference between two sines out of polarity, and two sines out of phase by half a cycle.
With any non uniform waveform though, there's a big difference.
 
Re: the original question, my personal preference would be to have at least two mics of the same model which opens the door to stereo techniques like a coincident pair/X-Y placement. Using two different sounding mics can sound good on certain instruments (the example of an acoustic guitar is a good one) but that's not truly stereo in the pedantic sense.

I now own several 2200a mics (all bought at different times) and the quality control is good enough that I can get away with using them as a stereo pair even though none of mine were bought as a matched set.

As for the polarity vs. phase discussion, I find the easiest way to think of this is that POLARITY is changing the positive/negative relationship by 180 degrees without any change to the time relationship. PHASE is a difference between the movement of the waveform caused by a difference in the time relationship. When using two mics, if one is slightly closer to the sound source than the other, the electrical waveforms are created at slightly different times and don't line up exactly. This can cause some frequencies to be slightly exaggerated (when two waves line up closely and add together) or attenuated (when a peak lines up with a trough).

In X-Y miking, you place the two microphones (or at least their capsules) as physically close together as you can so any phase differences are caused by the placement of the sound source(s) and this is what gives you a stereo image!
 
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