[78-L] Blumlein

[Don Cox]

Hello DAVID

On 21/04/2011, DAVID BURNHAM wrote:
> ....... Blumlein and others didn't always use a pair of bi-directional
> with one facing forward and the other facing sidewards. Sometimes a
> cardioid is used facing forward and the bi-directional pattern is
> facing sidewards. I think this is what is meant in this description.
> Using a cardioid as the forward facing mic instead of a bi-directional
> reduces pickup from the rear, such as audience noise and hall
> reverberation. Stereo mics like the AKG C-24allowed for the changing
> of the patterns -- in the case of the C-24 even from the control room
> while listening to the results live!
> 
> Mike Biel  mbiel at mbiel.com
> 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> What you're describing here is M-S, (Mid-Side), or Sum and Difference
> miking. I was discussing only XY sets-up.
> 
> But in fact, for over 30 years, I have recorded using the Sum and
> Difference system almost exclusively, employing either an AKG C24 or
> its solid state replacement, the C422.
> 
> As far as I know, Blumlein never had cardioid mikes for his
> experiments, however I think he did introduce the concept of using a
> single ribbon which was divided in half with one half exposed at the
> rear to produce a bi-directional characteristic and the other half
> sealed at the rear, acting like an omni mike, and combining the
> outputs of the two halves to produce a cardioid characteristic.
> 
> But once again, neither the XY nor the MS coincident systems produce
> the inter-aural time differences necessary for binaural recording and,
> in fact, the Styrofoam head used to mount the mikes for binaural
> recording also has artificial pinnas since this is what the ear uses
> to locate sounds up and down or front and back. Surprisingly to some,
> the hearing mechanism uses inter-aural time differences almost
> exclusively to locate sound sources; inter-aural level differences are
> almost irrelevant.
> 
They can't be totally irrelevant, or pan-potted stereo would not work at
all. All the instruments would seem to be in the centre.

But they are certainly a poor cue compared to time differences, to which
we are very sensitive.

Which is why I think audio systems should be tested with clicks (impulse
signals) rather than with sine waves of various frequencies.


Regards
-- 
Don Cox
doncox at enterprise.net