Miata Mailing List: November 1998, Message #88

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We were going to use a fill foam pack to tune the tubes since the length
required isn't really a variable.  The three cutouts were to provide maximum air
flow without making any large holes in one particular part of the firewall.  We
also didn't want to make the only reflex high in the cabin.  We wanted a more
uniform wave pattern through the car.

John

BBirdwell@swri.edu wrote:

>   I forgot to ask: Why three cutouts? One should be sufficient and bass is
> non-directional anyway. Are you going to tune the length of the PVC tube to
> emphasize particular frequencies? Or will you use three different length PVC
> tubes to emphasize three different frequencies?  Assuming pipe open at both
> ends and frequency = velocity/(2 x length).
>   Having fun with physics, audio, and a Dremel tool.
>
> Regards,
> Barry