At 9:06 AM -0700 4/18/06, Eric Benjamin wrote:
>Rob,
>
>The measured polar patterns of real-world microphones
>are (almost) always narrower than the theoretical
>pattern at high frequencies. This is less so for
>figure-of-eight polar patterns than for other types,
>but the problem is still there.
Hi Eric--
I wish all manufs produced polar pattern charts
like AKG. Wow! I've tried 414's in the field and
they did reveal pronounced off-axis warmth as
those charts suggest.
I understand that actual performance can vary
from what manufacturers' claim, and maybe Rode is
telling larger lies, but the NT2000 seems to hang
in with small diaphragm mics pretty well:
http://www.uwm.edu/~type/Mic%20Preamps/Fig8_CardioidPolarPatterns.doc
As you point out, the fig 8 Hz responses are more
uniform than the cardioid patterns. For the small
and large diaphragm fig 8's, there's about a
5-8dB drop in sensitivity around 4K Hz at 60
degrees off axis. Off-axis warmth drops off
faster with cardioids-- particularly starting
around 4K Hz and up.
In terms of our discussion about maximizing
spatial rendering, for me, capturing the subtle
amplitude differences in the softer reflections
is key and this content primarily resides in
125-1300Hz range. All of the mics seem to be
performing fairly similarly in this range except
the mkh 40 has about 5dB more rejection to low
Hz's from the rear which should help with
localizing a bit.
> As a result, sounds that are centrally located will have a response tha=
t
>is rolled off at high frequencies.
Some of us have been assuming that our large
diaphragm NT1A's (cardioids') cover about 60
degree maximum with good tonal uniformity. The
NT2000 could prove to add another 30 degrees to
place it in the performance of the MKH-40. Only
field testing will tell. Walt Knapp also has a
pair of Nt2000's he's rigging up.
>
>For large-diaphragm types, the roll-off may start as
>low as 2 kHz. See the specifications for the AKG414:
>http://www.akg.com/products/powerslave,mynodeid,186,pid,781,id,781,_langua=
ge,ENUS,_view,specs.html
>
>For small diaphragm types the roll-off starts at about
>8 kHz. See the specs for the Schoeps Mk8
>http://www.schoeps.de/E-2004/specs-mk-ccm8.html
>
>This is, of course, not a fault of the microphone
>design but rather an unavoidable side-effect of their
>size.
>
>So one thing that could be done is to use the
>'Blumlein' array rotated by 45 degrees, so that one of
>the microphones is facing front, and then to use M-S
>matrixing to recover left and right. What this will
>do is to put the frequency response errors out to the
Based on the charts, it does make sense that the
fig 8's effectively used in M-S would cover the
field more uniformly above ~4K than cardioids.
Capturing full treble "in surround" is probably
beyond the abilities of any two mics, even
omnis.(Personally, I'd like to see a dual capsule
figure 8 where the angle could be adjusted from
110-180 degrees. The more four mic recording I
do, the less of the full horizon I attempt to
capture. I 've even tried covering the holes in
my mkh40/80 MS with my two NT1A's cardioids and
spread "Left" to "Left Rear" in post.
As for the hole in center of Greg's Blumlein
tests, assuming the fours sides of the mk8's
cover 4 X 60 degrees (within ~5dB at 4K Hz)--
this leaves 120 or 4- 30 degree holes. I'm also
hearing less signal below 200Hz in the middle too
for some reason. Seems like one would still get
frequency coverage holes using the traditional 90
degree rotation even with M-S matrixing-- though
the volume in the middle can be controlled
separately to help compensate. This is one reason
I'd try an omni as the mid in the set-ups using a
pair of NT2000's. Rob D.
>side.
>
>eric
>
>--- Rob Danielson <> wrote:
>
>> At 10:34 AM +0100 4/18/06, Antti Sakari Saario
>> wrote:
>> ,<snip>
>> >
>> >Blumlein array functions like any other coincident
>> XY pair and hence
>> >does not require any matrixing for deriving the L
> > and R elements of a
>> >stereo signal. The capsule pointing 45=FBto the left
>> of the axis of
>> >symmetry will provide your L signal and vice versa
>> for the R channel.
>>
>> Hi Antti--
>> If you agree that the middle is under-represented
>> in Greg's recording, do you have an explanation
> > why? Rob D.
> >
>
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