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Old 7th June 2004, 09:37 PM   #1
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Default dumb question on ports and volume

Does the volume of the port affect the overall volume of the enclosure?

i.e. If I have a 1 cu ft ported box and the port is 2"x10". I would have to make the box volume roughly .018 cu ft larger to make up for the volume of the port? (this is all hypothetical and I'm just trying to get a understanding of what I'm doing)
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Old 7th June 2004, 09:42 PM   #2
Guss is offline Guss  Canada
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Sure, you must substract the volume of the port from your total enclosure volume.

1 cubic. + your port volume (2x(3.1416) x 10) = total cab volume

Goss
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Old 7th June 2004, 09:44 PM   #3
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Fantastic, thank you.
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Old 7th June 2004, 10:12 PM   #4
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Default Don't forget the driver volume

The driver also takes up space that must be accounted for. A good rule of thumb with a VB is to make it 10 to 20% oversize. If flat response is absolutely critical you can always put bricks inside the box to make it smaller; you can't add a dormer to the attic if you need more room later.

Also, don't go with a rectangular ducts. Go with the requisite number of round ducts of equivalent area and use those that are flared at both ends; they have been proven far superior in both higher SPL and lessened distortion than non-flared ducts.
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Old 7th June 2004, 10:14 PM   #5
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I knew about the driver volume already. Although I didn't know about the slotted ports to be inferior to flared/rounded ports?


Hmm, more to think about. Thank you
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Old 7th June 2004, 10:48 PM   #6
Guss is offline Guss  Canada
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Smaller ports are more accurate than bigger ones because there is more interaction between the port and the air that flows through it, regardless of the amount and the speed of the air at this moment. Slotted ports are often larger and longer than any equivalent round vent to get satifiying results.

The diam to length ratio is to be considered too if you want better results. A ratio of 3/1 is a good rule of thumb to apply to moderated values and it should yeld more than acceptable results. It doesn't mean a port with a ratio of 5/1 sounds bad, many of us may ignore it, but with a too long port you may end up with an ''Helmholtz resonator''. All those informations have been discussed in earlier threads about port ratios/placement so a little search might be revealing for you.

Goss
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