Topic: Oktava figure-8 capsule for mk012

[Petrus]

Has anybody tested this yet? Thinking about getting one for MS recording with Oktava 012 hyper and cardioid, also Sanken CS-3e.

http://www.oktava-online.com/mk012-8.htm

[ghellquist]

Interesting concept. Seems like it is not on the market yet, but I might be behind there.

I would be a bit suspicious about sound, the capsules end up a little far away from each other. Might create sound artifacts -- only way to know is to test I guess.

Gunnar

[Petrus]

I was thinking the same, if the caps are 3 cm apart, there would be out of phase cancelation at around 6000 Hz for sounds coming from the side, yes?

[DSatz]

Actually for sounds arriving from one side or the other (90 degrees off axis), the path length from the sound source to the two capsules will be identical, so the cancellation (null) should be very good. The real problem will be at angles between 0 and 90 degrees, where the path lengths are unequal and some partial cancellation will very likely occur (comb filtering effect).

The technique of using two separate cardioid capsule back-to-back to form a figure-8 isn't all that unusual. That's how most multi-pattern microphones get a figure-8 pattern; the only real difference is that the two capsules can then be very close together, sometimes even sharing a common backplate. Plus the two "half-capsules" can be selected and tested together as a unit at the factory, so the manufacturer can be responsible for how well they match, if it's a responsible manufacturer in the first place.

Neumann used to sell an interesting microphone with two physically separate, matched back-to-back cardioid capsules in it, called the KM 86. It was switchable among cardioid, pseudo-omni and figure-8, and Neumann recommended that it be used only for miking distances greater than 1 meter. But that didn't affect the cardioid setting, and Motown actually used that microphone as their standard for all kinds of recording.

Unfortunately the KM 86 in its figure-8 setting was quite harsh sounding off axis. (On the attached diagram you have to look at the 315-degree or 225-degree response to see this, because of the way the chart is divided into left and right halves. Notice that the 8 kHz response is way more than the 1 kHz response over most of the arc between 0 and 270 degrees; that's the problem.) When you're recording in Blumlein stereo, the 45-degree point is what faces directly forward for both microphones, so this is a fairly serious defect.

The good side of this approach to generating a figure-8 pattern is that it can significantly improve the low-frequency pickup, because the distance between the two capsules encompasses a larger fraction of a sound wavelength at low frequencies than the front-to-back distance of a small-diaphragm, single-diaphragm figure-8 capsule. Thus the pressure gradient at low frequencies is greater, and the sensitivity of the capsule at those frequencies is correspondingly greater.

--best regards