On 05/01/2011 04:32 AM, Stefan Schreiber wrote:

> P.S.: Speaking of B format recordings, there are the well-known issues
> of sound quality. SNR? High frequencies?

b-format != soundfield microphone

the soundfield does have a more pronounced hf roll-off and gerneral
oddity coefficient than, say, a pair of schoeps omnis.

but nothing prevents you from encoding very high frequencies in
b-format. it will be more or less impossible to record that flying bat
with a soundfield, but if you have a very keen boom operator and a
recording chain that goes way up to 50k or so, you could resynthesize
the bat's flight with panning.

SNR is certainly an issue with HOA mics (to the point where i'd consider
them unsuitable for general-purpose music application), and to a lesser
degree with the tetramic, but soundfields deliver very good SNR.

> A typical B format mic is good for ambience recordings, but maybe not
> for orchestral recordings, or in fact any musical recoding with a group
> of people playing.

that depends on the material, and your target system. spaced omnis sound
more "WOW" on stereo than any coincident technique, so if that's the
target, no point in using a soundfield, unless you want to cater to
those few localisation nutheads who'd also use (gasp!) a blumlein pair
(like yours truly :).

> (I have participated in quite some surround recordings. Not any
> tonemaster I know would do an orchestral recording with just one B
> format microphone. This is not the case because tonemasters supposedly
> don't know Ambisonics. There are probably too many disadvantages and
> limitations?
> Just speaking from a practical point of view...)

sadly, it seems there is very little knowledge about ambisonics among
professional classical recording engineers.
most have, at some point in their career, stuck a soundfield somewhere
they'd also stick a main A/B, rendered it either to stereo or to 5.1,
very possibly using incorrect or at least sub-optimal techniques, been
disappointed and haven't looked back since. not that there aren't many
perfectly valid reasons to reject ambisonics in many situations, but
this level of understanding is reached by few people - it just doesn't
sound like spaced omnis, and that's what the producer wants.

vice versa, there are some really weird spaced omni methods being
proposed for 3D sound, by professionals who like to argue that since A/B
is the bee's knees for left/right, so it has to be for front/rear and
up/down. when you ask them what kind of hearing mechanism they are
aiming at in using time difference between up and down, they'll reply:
but the sense of space and envelopment. well, yeah. if the aim is to get
the sound all over the place, that's certainly the way to go.




-- 
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487

Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister (VDT)

http://stackingdwarves.net
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