Scott:
> > The results that Paul obtained, showing significant cancellation in
> > the high end, is indicative of the fact that placing a mic body on the
>> boundary with the capsule perpendicular to the boundary doesn't locate
>> the diaphragm sufficiently within the pressure zone for those
>> frequencies. Obviously part of the diaphragm is in & part of the
>> diaphragm is out of the zone.
Dan:
>Yes
Scott:
>
>> The Schoeps boundary mic places the
>> diaphragm flush with the boundary, & thus is truly reflection free at
> > all frequencies.
Dan:
>Yes. The SASS does that, too, with the advantage that the diaphragms
>also face forward. The SASS "nose" is padded to reduce reflection
>coloration, same as with the Jecklin disk.
The cumulative advantages of a MKH-20/AT3032 modded SASS rig
including flush-mounted capsules definitely out-weigh the
disadvantage in my opinion. Crown, interestingly, was convinced,
that the SASS-P array using PZM mounted capsules performed better.
Its a challenge to effectively compare the performance of these two
rigs with the noisy pzm capsules they use. A larger scaled Partially
Baffled Boundary rig with down-firing AT4022's (like Dan pictured)
might make a good approximation.
In terms of surface absorption, the SASS's foam baffle does act like
the padded surface of a Jeckln disc but the baffle could allow
off-side transmission. The mics are located very close to leading
edges of the small boundaries.
Trying to purely abide in one acoustic principle in array design can
create more downside than up. Outside of the Partially Baffled
Boundary rig, I haven't come across another boundary array where the
capsule residing fully within the pressure zone is better. That
includes the Schopes KFM 6 for outdoor work. Also, if fewer or no
reflections was inherently superior, we'd have to rule out the human
ear as a good design. :-) Rob D.
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