On the subject of shuffling:-
http://www.urlme.net/blog/?p=3D1277
Smaller omni capsules would be more ideal, the 10mm one used in the article=
s becomes more directional above 10khz.
I used the technique (post processing) the brass wonder mic:-
http://www.urlme.net/blog/?p=3D1254
--- In "simmosonics" <> wro=
te:
>
> --- In Paul Jacobson <pj@> wrote:
>
> > In this case my interest is in Blumlein Difference Technique (BDT) usin=
g baffled omni's rather than the better know Blumlein pair using crossed fi=
gure-8 mics. Jecklin apparently developed his disk from the BDT idea.
>
> Yes, I believe that is so. I also believe it has the potential to be an e=
xcellent stereo technique, offering the best of omnis - including no proxim=
ity effect and consistent LF response with distance - with the added benefi=
ts of directionality.
>
> It is amazing what Blumlein himself came up with, including MS, BDT and, =
of course, Blumlein. There is a saying about BDT that is quite funny. I can=
not remember the year it was invented in, but let's say it was 1938. The sa=
ying goes, "BDT... invented in 1938, forgotten in 1939"! Apparently it refe=
rs to the introduction of directional microphones a year or so after the in=
troduction of BDT...
>
>
> > The shuffler is used to convert phase difference to amplitude differenc=
e below 700hz. My understanding is that the conversion is derived from the=
physical spacing of the mic capsules, so it's not 100% clear how to transl=
ate this into something like Greg's method of shuffling based on mid and si=
de eq adjustments.
LR to MS
Apply EQ to the lows/ set levels
MS to LR
>
> The method I use is predominantly intended for coincident miking, especia=
lly with either dual diaphragm designs or lower priced capsules where the p=
olar response approaches omnidirectional at low frequencies, so all the low=
frequencies tend to pull towards the centre of the stereo image (very noti=
ceable when recording a string quartet that sets up with the cellist on the=
far right, for example). In fact, the method I described with Ozone is the=
same method shown in Figure 2 of the Gerzon article you have linked to, as=
reprinted from Studio Sound magazine from some time in the '80s.
>
> Gerzon discusses the effects of using it on a spaced pair that is relying=
on time *and* amplitude differences to create a stereo image. In the artic=
le he refers to the problems it can cause for ORTF, but a similar set of is=
sues might arise if using it with BDT because, like ORTF, BDT uses time *an=
d* amplitude differences (hence the baffle) to create a stereo image.
>
> I am sure I have read about the type of shuffler you need for BDT. It may=
be in Blumlein's original paper. If I remember correctly it uses interchan=
nel crosstalk as part of the process - feeding some of the left channel out=
of phase to the right channel, and vice versa. Or perhaps that's what the =
MS process is doing anyway? I can't think the maths through right now...
>
>
> > I've replicated Greg's setup in apQualir/apEQ as per Rob's suggestion a=
nd it looks like this will work pretty well, although I'm fairly certain ap=
Qualizr isn't linear phase.
>
> The effects of the phase errors due to non-linear phase EQ are described =
in the Gerzon article, and these can be negated if using linear phase EQ (w=
hich wasn't readily available back when Gerzon wrote that paper - it existe=
d, but was damn expensive!).
>
> I find that with the iZotope/Ozone approach, being all linear phase and s=
o on, the smallest amount of change is quite noticeable. A 1dB difference s=
hared between M and S (i.e. +0.5dB on the S, and a corresponding -0.5dB on =
the M) is sufficient to move energy below 250Hz from 12 o'clock (centre) to=
10 o'clock (over to the left).
>
> I don't remember Waves S1 being that effective, although I am in no hurry=
to find out. There is no space on my system for Waves products these days:
>
> Waves =3D over priced + stupid bundling policies + iLok key requirement =
=3D bah humbug!
>
> - Greg Simmons
>
Reaper - peanuts.
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