Thanks a lot, David, for your comment and quick analysis on the CVX.
Marco Pesente
--- In wrote:
>
> Oops, my mailer sent a reply before I had written it.
>
> I found a link on the CVX rig:
>
> http://www.pamodelforest.sk.ca/pubs/PAMF2800.pdf
>
> I'm always open to new ideas but I can't see how this rig would give a cl=
ean
> sound. It is a type of horn (not a "reverse horn" as described) but there=
is
> still going to be a resonance across the device horn terminal as it is ab=
out
> a wavelength wide at 1KHz. Put another way, it is in effect a "closed
> housing" between the distributed horn mouth and the focal centre.
>
> The theory that sounds will travel bidirectionally ignores the effect of =
a
> sudden change in acoustic impedance at the distributed horn mouth.
>
> The article made no attempt at describing the frequency response or verti=
cal
> polar response and while there would be a small acoustic gain from the ho=
rn
> loading, this would only have the effect of reducing the effective mic no=
ise
> at high frequencies after a gain adjustment. The three dimensional pickup=
> solid area would be reduced at high frequencies, countering the horn gain=
.
>
> The horn mouth vertical dimension is about 30mm, roughly a wavelength at=
> 10KHz, so I would expect any vertical directional response to be near omn=
i
> at lower frequencies.
>
> What the article does not include is any indication of the vertical polar=
> response and the vertical frequency responses of the rig which I would ha=
ve
> thought would be a starting point. The least would have been a direct
> comparison with an open omni mic.
>
> If this rig is still in existence, it would be interesting to hear some
> comparative recordings against a simple omni.
>
> David Brinicombe
>
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