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Re: Figure 8 mics

Subject: Re: Figure 8 mics
From: "Walter Knapp" waltknapp
Date: Tue Jul 25, 2006 12:24 pm (PDT)
Posted by: "Rob Danielson"

> Hi Lou--
> This is a question the micbuilders list is surely capable of
> addressing. There's Dave Latchaw DIY fig 8 circuit made with ECM's:
>  The lower noise Primo
> EM-23's or EM-158's might be similarly configured into a DIY fig 8.

Some commercial M/S mics use dual side capsules so it's certainly
possible to go that way. I'd assume some differences in the sound
characteristics might turn up compared to the true figure 8's,
particularly one like the MKH30 with it's single diaphragm.

> As Walt pointed out, the MKH30 circuit uses a fairly elaborate
> push-pull capsule design and many, if not all fig 8 mic circuits seem
> to require some low Hz boosting to more closely match the low-end
> response of gradient cardioids.

There appears to be no difference in the low end response of the MKH-30
vs the MKH-40. This may be because both use the same capsule design.
Here is Sennheiser's description from their 2002 mic brochure:

> Sennheiser=92s Revolutionary Symmetrical Microphone Capsule
> The MKH 20 to 800 microphones have Sennheiser=92s unique and revolutionar=
> symmetrical push-pull capsule. Besides the normal back plate, this capsul=
e is fitted
> with an additional front plate, with the diaphragm being positioned betwe=
en them.
> Both plates are acoustically transparent. Any impedance changes in the ai=
r gaps
> between the diaphragm and the respective plate are opposite and therefore=
> each other out, which leads to an unchanging acoustic impedance. This bal=
> design produces extremely low distortion figures and a higher capsule out=
put that
> gives a much lower noise figure. The result is a microphone series unmatc=
hed in
> clarity and neutrality.

Note that this is a single diaphragm for a figure 8. Note that all
current MKH have this capsule except the MKH-416 (and I guess the M/S
stereo shotgun derived from it)

On top of that the MKH are RF capsules adding more differences from
ordinary mics.

  For a less complicated solution, the
> multi-pattern Rode NT2000 could be workable for some applications
> (though very heavy and not yet humidity-tested as best as I know). It
> has better bottom end response over the lower cost NT2-A  and
> NT1-A's. Rob D.

The NT2000 is a dual diaphragm single backplate design I think.

Yep it's heavy, two of them even heavier. I'm not expecting to use them
handheld much. Their size and design makes them a more complex problem
when suspension and wind protection are taken into account. To my mind
the best approach with them for M/S is either a pair or combine one with
a NT1A.

I'm primarily interested in them due to the large diaphragms. Do some
large diaphragm recording.


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