Hi Tim,
Indeed, SNR is poor at low frequencies for this sort of technique as
it relies on the phase difference between the two capsules as produced
by their separation. The separation can't be too large as once it gets
over half a wavelength the phase starts wrapping around but this means
that at low frequencies the difference is tiny and requires a lot of
amplification (cf. the 6dB rise in response with frequency that
someone else mentioned). This results in poor SNR and worsening
susceptibility to capsule variances as the frequency goes down. If you
can cope with the extra complexity, using more than one set of
capsules with different spacings to cover different frequency ranges
is a good idea...
Dave
On 9 January 2013 00:15, David Pickett <d...@fugato.com> wrote:
> At 11:54 08-01-13, Tim Collins wrote:
>
>>You can make a velocity microphone by subtracting two closely spaced omnis.
>
> I seem to recall that Blumlein did this and also found that the s-n ratio
> was poor.
>
> David
>
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--
As of 1st October 2012, I have retired from the University, so this
disclaimer is redundant....
These are my own views and may or may not be shared by my employer
Dave Malham
Ex-Music Research Centre
Department of Music
The University of York
Heslington
York YO10 5DD
UK
'Ambisonics - Component Imaging for Audio'
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