Topic: B&K 4021 modified hypers ??

[JasonSobel]

hey folks, I recently downloaded Phish 8/14/97, and this is the source for the show:

B&K4021 (modified hypers)> Beyer MV-100> SBM-1> D8 DFC Tapers Section

so someone modified their 4021's to be hypers?  is that the deal?  or does DPA now modify them?  I don't think so, but I could be wrong.

anyone know the story behind this?  just curious really.

thanks.
Jason

[nickgregory]

If i remember right, someone in NY had theirs modified...cant remember if it was JK Labs or someone else...but it was not DPA...paging Scott Brown...I believe he knows the full story

[cbd]

how is that even possible Nick. DPA doesn't make a hyper card

[jeromejello]

could it be they were using reflector rings like the violet black fingers?

i know nothing.

[Shawn]

could it be they were using reflector rings like the violet black fingers?

i know nothing.

I was thinking something along the same lines. I 'm fairly certain that the schoeps switchable small diaphragm caps (i.e the mk5, mk6, etc) use some sort of physical shielding around the cap/vents to transform the polar pattern between card/omn/fig. 8. I was wondering if that was possibly what was done here.

[scb]

"suicide todd" (todd hinden) told me a few years back that his 4021s were modified to be hypers.  he told me something about "rings" but I never got any more details than that

[DSatz]

Shawn, you're completely right that the Schoeps multi-pattern capsules (MK 5 and MK 6) use mechanical pattern switching. When you change from one pattern to another, the mechanism alters the acoustic environment in which the (single) membrane operates within the capsule.

However, that works because the capsule was designed from the start to provide this capability, and its design includes all the necessary internal elements to do this. (The patents for this, which have since expired, are all available on line.) There's no practical way to modify an existing capsule to provide anything like the needed capability, working "from the outside in"--you'd have to redesign and replace nearly every part of the capsule. It would be like converting a rabbit to a squirrel.

About the same thing is true even if you only want to take a single-pattern capsule (e.g. a cardioid) and make it into a hypercardioid. You could put a phase ring on the front of the capsule, and that would narrow the response at high frequencies somewhat--but the midrange and low-frequency response of the capsule wouldn't be affected at all. You'd really have to change the capsule's fundamental acoustical design if you wanted it to deliver a pattern that's consistent across the audio band; it can't be "Band-Aid"ed onto some other design. The membrane tension, the air friction coefficient of the holes in the backplate, the dimensions of the capsule's internal Chamber of Secrets, and everything about the rear sound inlets all need to be optimized specifically for the intended directional pattern.

--best regards

[Shawn]

thanks for the info dsatz. I had a feeling this topic, and my comment specifically might get a resposne from you. your wealth of knowledge is much appreciated.

+T

[DSatz]

Shawn, I went on a lot longer than I thought I was going to do, but thanks for the kind words.

(This message will lower my average words/message, making my previous message easier to read, I hope.)

--best regards

Edited later: Actually, on reflection I decided to remove the mile and a half of verbiage about why the term "hypercardioid" is often misused. I've saved it off, though, and I hereby threaten to post it again if the occasion arises.

[DSatz]

Moke, this idea comes up from time to time but in practice the answer is no. If that trick worked, every cylindrically-shaped cardioid would automatically be a highly useful two-pattern microphone, and no one would make single-pattern omni capsules any more; all it would take would be a 20-cent plastic collar of appropriate size to seal the back vents and change the pattern over.

Part of the idea is right--a pressure transducer (= a "pure" omni) doesn't use separate front and rear sound inlets. Mechanically switchable microphones such as the Schoeps CMC 55, CMC 65 or CCM 5 and the Shure KSM 141 effectively close off the side (= back, from the membrane's point of view) vents in the omni setting. But this is done internally, at a point right behind the backplate. (This is all made somewhat clearer in the patent drawings.) If you closed off the vents at the outside of a cardioid capsule, you'd have a more or less omnidirectional microphone, but it would sound very muffled.

--best regards