"Eberhard Sengpiel" wrote in message
...
Ray Thomas wrote:
I believe the 'pressure build-up' rubber rings that are supplied with the
Sennheiser MKH20 act as a sort of small-scale HF lift when the mic is used
in the diffuse field, and perhaps they also serve to increase
directionality (or modify the off axis response) slightly also ? Could
the same principle be applied usefully to any flat response omni mic used
in the diffuse field, or is it specifically applicable to the MKH RF
mics....and how much lift?
This pressure treble lift can also used in the direct field, when ever
you need more high frequencies. It's an acoustic equalizer.
You can use it without problems on "not flat" response omni mics,
(diffuse field equalized) if you need more treble.
Sennheiser MKH 20 omnidirectional condenser microphone:
A pressure build-up ring is included and is used to accentuate
high-frequency response.
A HF lift is used on other omni microphones in form of a sphere.
The pressure lift has nothing to do with the RF principle.
DPA sells for his 4006 omnidirectional condenser microphone
the "Acoustic Pressure Equaliser" APE L50B
http://www.dv247.com/invt/45557/
Schoeps sells for his MK2S omnidirectional condenser microphone
the "Slip-on sphere" KA 40 or KA 50.
http://www.musicians-gear.com/lin/da...oeps/ka_40.htm
Cheers Jens
Thanks Jens,
I'd seen pics of them before and wondered about their size and
construction....pretty hefty price on the DPA spheres of 57 UK pounds ! I
imagine the Schoeps items are similar in price. I was wondering if toy
balls (eg tennis balls or smoother items), or even rubber squash balls with
appropriate holes cut might function ok. I wonder if they'd need to be hard
.....like billiard/pool-table balls...or whether a softer foam or plastic or
rubber might work just fine, as I imagine it's the reflective surface
property which is decisive, rather than mass per se ? Certainly leaves a lot
of scope for experimentation.
Ray