Making a figure-8 with an omni and a cardioid capsule.

[RCAguy]

Here's my plot summing out of polarity cardioid at +6dB and omni microphones...

 

[RCAguy]

Keep in mind the pickup regions of all common mics are 3D - envision the plots rotated about the 0\180deg axis. The omni is a ball, the cardioid an apple, the fig8 a balloon squeezed in its middle.

 

[k brown]

A nice 3D summary:

- The parenthetical "noise-cancelling" is rather nonsensical, though. Hypercardioid has a considerably greater distance factor, if that's what they are referring to.

 

[RCAguy]

A nice 3D summary:

BTW, my 2-mic sum plot is NOT merely an illustration, it’s an actual plot summing omni & cardioid mathematically, a screenshot from a spreadsheet. (I would refine it for use with any two mic polar patterns if anyone is interested?)

 

[RCAguy]

- The parenthetical "noise-cancelling" is rather nonsensical, though. Hypercardioid has a considerably greater distance factor, if that's what they are referring to.

K Brown - I’m not sure what you meant, but if by “parenthetical noise cancelling“ are you referring to my post “Mixing coincident mics equally reduces noise, as the correlated signal gain is 6dB while the uncorrelated noise gains 3dB, for an improved SNR of 3dB.”?

Only if so, this is well-known re noise gain for mixing equal levels of correlated and uncorrelated signals, both electronically and physically, such as the width of mag tape tracks. However I did err in applying it in the present case, as the cardioid is mixed at +6dB. - Robin

 

[k brown]

K Brown - I’m not sure what you meant, but if by “parenthetical noise cancelling“ are you referring to my post “Mixing coincident mics equally reduces noise, as the correlated signal gain is 6dB while the uncorrelated noise gains 3dB, for an improved SNR of 3dB.”?

Only if so, this is well-known re noise gain for mixing equal levels of correlated and uncorrelated signals, both electronically and physically, such as the width of mag tape tracks. However I did err in applying it in the present case, as the cardioid is mixed at +6dB. - Robin

No, I was referring to the text on the pattern graphic in post #24.

 

[RCAguy]

No, I was referring to the text on the pattern graphic in post #24.

Got it - thanks.

 

[MicMan]

"As was done with the AKG CK6, combining an omni and a cardioid out of phase, one gets a figure-8 pattern.."

This brings to mind the exact(?) opposite: the old Western Electric / Altec 'Birdcage' 639 which combined a figure-of-eight ribbon + an omni capsule, giving - in combination - a front cardioid pickup pattern. (See https://coutant.org/altec639/ )

(Sound from behind took - or takes - longer to reach the front of the omni capsule than its rear ..as it's close to the front of the assembly, directly beneath the front of the ribbon, so is out of phase with the REAR of the ribbon - cancelling that - and reinforces the audio at the FRONT of the ribbon, giving enhanced pickup from the front and not much from the rear. Mine had a fault with the omni, so I just stuck in an omni capsule from a - similar vintage? - Grampian DP4 dynamic omni. Now works a treat!)

 

[k brown]

"As was done with the AKG CK6, combining an omni and a cardioid out of phase, one gets a figure-8 pattern.."

This brings to mind the exact(?) opposite: the old Western Electric / Altec 'Birdcage' 639 which combined a figure-of-eight ribbon + an omni capsule, giving - in combination - a front cardioid pickup pattern. (See https://coutant.org/altec639/ )

(Sound took - or takes - longer to reach the front of the omni capsule than its rear ..as it's close to the front of the assembly, directly beneath the front of the ribbon, so is out of phase with the REAR of the ribbon - cancelling that - and reinforces the audio at the FRONT of the ribbon, giving enhanced pickup from the front and not much from the rear. Mine had a fault with the omni, so I just stuck in an omni capsule from a - similar vintage? - Grampian DP4 dynamic omni. Now works a treat!)

And after that, the Schoeps M 201 https://schoeps.de/en/about-schoeps/product-history-1/detail/m-200201-1.html
and currently, the Josephson C700A https://www.josephson.com/c700a.html

 

[RCAguy]

And after that, the Schoeps M 201 https://schoeps.de/en/about-schoeps/product-history-1/detail/m-200201-1.html
and currently, the Josephson C700A https://www.josephson.com/c700a.html

Like its om\cr MK5, Schoeps’ MK6 mechanically switched its rear port for selecting om\cr\bi. It didn’t perform to their standards, so they’ve dropped it.

 

[Barry Hufker]

I wonder if it was that or if the capsule was too "fiddly." I know the gaskets wore out over time and were hard to replace. I had a pair of capsules re-done before Schoeps stopped repairs.

 

[RCAguy]

I wonder if it was that or if the capsule was too "fiddly." I know the gaskets wore out over time and were hard to replace. I had a pair of capsules re-done before Schoeps stopped repairs.

Possibly so. I had a 1985 MK5 back to Deutschland in about 2000, but only to change the case from nickel to umber. Nevertheless, Schoeps cleaned the diapragm & retensioned it, but reported no change in a gasket. Below are the Mk6’s polars FYI…

 

[RCAguy]

I refined the spreadsheet to sum up to 4 mics, and below is a polish on the mix discussed.

 

[RCAguy]

Anyone know of an Excel-compatible chart for polar plotting? Its "Radar" chart must be worked-around to get it to work in this application.

 

[k brown]

Perfect board for a dual-capsule mic:
https://www.jlielectronics.com/diy-accessories/opa-alice-dual-channel/

 

[Khron]

Perfect board for a dual-capsule mic:
https://www.jlielectronics.com/diy-accessories/opa-alice-dual-channel/

... If you ignore the lack of attention given to the high-impedance areas, and otherwise haphazard routing and so forth...

 

[k brown]

... If you ignore the lack of attention given to the high-impedance areas, and otherwise haphazard routing and so forth...

. . . so, less-than-perfect

- Other options?

 

[Khron]

Other options?

Not just yet, but... Maybe in the near-ish future..?

 

[k brown]

Further tests:

Since the B-5 cardioid and omni capsules have such different responses (and the card doesn't sound very good any way) got much better results from an MK-012 cardioid and an EM23 omni.

Great combo because the Oktava is actually closer to subcardiod, so this goes subcard > card > supercard > hypercard > figure-8, without having to change phase (keeping the omni flipped). The Primo's response matches that of the Okatava better than the B-5 does.

______

If @kingkorg 's omni mod of the "KK12 V2" works as well as his mod of the V1, could be a great way to make a vari-pattern mic with the un-modded "KK12 V2".
@kingkorg : does the omni mod require disassembly of the capsule, or can the back holes just be plugged up? I haven't had good luck getting these back together and sounding right afterward.

 

[Khron]

- Other options?

Would independent front/rear pads make any sense? Or just an overall one...