Zaph SR71 port length

[BobanNN]

Hi,

I plan to make ZAF SR71 with my cabinets. Can someone tell me, what length should be this Visaton port :

http://www.visaton.com/en/chassis_zu...r/br19_24.html

http://www.visaton.com/bilder/zeichn...br19_24_tz.gif

Only this port i could find in local store.

Thanks in advance,
Boban

[BobanNN]

Anyone, please... Thx.

[jkrutke]

That port, like most one piece plastic molded ports is tapered to allow release from the mold. Average diameter appears to be about 55mm. That's a bit larger than the recommended port and the length will be longer. As such you will no longer be able to meet tuning goal of 44 Hz. If you use that port as is without cutting, you will get about a 47 Hz tuning. That may be acceptable, but only if the cabinet is deep enough for the port to work without flow interference.

If the cabinet is built with a depth as per the design on the web site, I don't recommend that port and instead use maybe a 40mm port, preferably flared to reduce the airflow turbulence. This design has a relatively low tuning for a smallish box, and port selection will be critical. If you can get one, I'd recommend the 2 inch "Precision Sound Products" flared port specified in the design.

[BobanNN]

Thanks John.

BR,
Boban