> ?? not sure what you want to say here.
> But for info, a Fig8 is the narrowest (or most directional) 1st
> order mic
> possible.
John,
Sorry if I'm unclear. I was originally trying to clear up the
confusion between stereo object/image angles and noise rejection
angles. With any stereo double mic or array, there is virtually an
omnidirectional pickup in total solid angle of background sounds
unless an interference tube or reflector is used.
Take a fig-8 mic polar diagram and extend that into two dimensions ie.
the vertical, and much of the solid angle of 4pi steradians (the
inside surface of an imaginary sphere) is substantially sensitive to
sounds. Any sounds from any sensitive angle add to the background
noise.
As you say, the fig-8 is as directional as you can get with a
single element mic, back end included, and adding a mono response to
this will increase the pickup solid angle. For instance, a cardioid
response will fill in most of the fig-8 "dead doughnut" leaving only a
narrow rear cone of rejection. (Draw out the less than -12 dB area on
a ball) Add a second mic for stereo and one mic will pick up most of
what the other mic is rejecting.
The least stereo pickup solid angle is with the crossed fig-8 Blumlein
pair, when there are two "insensitive" cones top and bottom. The snag
is that you have a rear image superimposed on the front image whether
you like ot or not.
If you don't believe me, try my canister of peanuts shaking test all
around and above and below a stereo rig (tip it sideways). Look for
directions where the response is more than 12dB down which is quarter
volume.
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
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