Help needed, Port lengths

Can you help please.
I have built Eminence Bandpass enclosure with 2 x 15 inch Beta-15A speakers inside.

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Low frequency designs:
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I can only find plastic port tubes with an internal diameter 70mm (not as stated 75mm). What would be the port tube lengths at this smaller diameter? What difference (db or hz) would it make if cut to recommended lengths with 5mm smaller ports?
Thanks for you help.
Dub57m

Smaller diameter reguires shorter port, so if you keep the length same you will be tuning it tad lower than designed. If it doesn't sound right, you can cut of 5-10mm and try again. Most likely difference isn't more than few hertz.

I don't think that there will be any problems with wind noise in port because of that missing 5mm.

IF you want to play safe, use 100mm tube and make it longer. How much, can't say directly. Perhaps you can use Winisd to check that?

Hi Pasi
Thank you very much for your advice, a great help!
As you can gather I am new to speaker designing, but construction is never a problem.
Cheers again.
Dub57m