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Old 6th July 2004, 09:33 PM   #1
dveous is offline dveous  United States
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Default Question about port volume

I noticed the Wilson MAXX speakers have a port that is 5X12.2 inches. I cannot find any 5" ID pipe anywhere. Using these calculations the port volume comes to about 240 cubic inches. If I use two 4" ID ports about 9 1/2 inches long this will give me the same volume (each port having a volume of about 120 cubic inches).

So my question is will the results be the same if I use two ports who's volume totals the same as a single port? I guess I'm asking if in port calculations only the port volume matters.

Thanks

Dveo
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Old 6th July 2004, 10:50 PM   #2
Svante is offline Svante  Sweden
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We were through this just some weeks ago:

Converting port dimensions.

Roughly, the ratio between area and length should be kept constant, but have a look in the thread above for details!
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Old 7th July 2004, 05:41 PM   #3
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Yes, only the port volume matters if the cross section is identical, but in this case it isn't. A five inch port is about 20 square inches, two fours about 25 square inches, so the two fours would have to be longer to maintain the same tuning.

You can model your box in WinISD and put in any vent area and number of vents and shape you wish and the program will tell you the required length(s).
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Old 7th July 2004, 07:24 PM   #4
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Default Re: Question about port volume

Quote:
Originally posted by dveous

So my question is will the results be the same if I use two ports who's volume totals the same as a single port? I guess I'm asking if in port calculations only the port volume matters.

Thanks

Dveo
Nope,

Also the port cross sectional area matters. That is part of the tuning frequency setting together with box volume and air mass in the port (port volume). Only if you keep total port area the same you can do so. Otherwise you need to recalculate or use a LS simulation program for the new port size(s).

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