I'm not a dish user so I can't verify the veracity of this in
practice, but I was reading John Fisher's "Wildlife Sound Recording"
the other night and came across an interesting tidbit relating to
cardioid and omni's in parabolic dishes.
In Chapter 5 - Reflectors - Fisher discusses at length tests carried
out by Professor G. N. Patchett of various 24" reflectors which
showed a -7dB dip in gain between 600-700Hz. This was attributed to
"... partial cancelation of the reflected wave by the direct sound
waves." Several pages later Fisher states "As the cardioid has very
little response from sound waves approaching from the rear, there is
no cancellation of the reflected wave by the direct wave."
The graphs accompanying the text show the cardioid+reflector does not
suffer from the dip in gain displayed by the omni+reflector.
The text is somewhat dated, but hopeful this information is still
relevant.
cheers
Paul
On 18/07/2007, at 7:07 PM, D Secomb wrote:
> Hi all
> I know this subject as been mentioned recently. It has been mentioned
> that omni are in theory the mic to use in a reflector but several
> members state a cardioid is the better type to use. Why?
> What is the reason behind the preference? Is it gain, tone qualities,
> low gain of sound outside the focus area or is there something else?
> David
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