This question is based on my findings in WinISD:

I am currently trying to figure out how to build and port a small box. I'm working with 0.8 cubic feet tuned to 31 hz with 200wrms and this is what I roughly worked out for my options:

3 1" ports x 7.25 = 0.08 vent mach
1 2.5" port x 15" = 0.12 vent mach
1 3" port x 24" = 0.08 vent mach

The easiest option would be 3 1" ports. I don't need a super deep box, or have ports sticking out of the box, and somehow it manages to acheive the same vent mach as a single 3" port. Are there any draw backs to doing this?

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Nostalgia just isn't what it used to be.

[img]graemlins/bump.gif[/img]
DUKK, as the resident "ported" spokesperson, what do you say?

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Nostalgia just isn't what it used to be.

you arre going to get a lot of wind noise if they are to small even if the box is in your trunk you will here the noise through the ports.the ideal size is 1/3 of the speaker's size but you can cheat a little.

3 1" vents have a total open area of ~2.36sqin.

1 2.5" vent has an open area of ~4.91sqin

1 3" vent has an open area of ~7.07sqin.


I suspect the program is being fooled by the 3 vents. Try modelling a single 1.73" diameter vent.
I would use the 2.5" diameter vent.

Thanks Dukk, it seemed screwy to me that something with less air capacity could perform just as well.

I've been thinkg about doing a square port - easier to build around corner. How do I acount for the bend in square port? Do I measure the two inside lengths, or the two outside lenghts, or the inside of one and the outside of another ( I think this is what I need because that would get the overall volume of the port.

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Nostalgia just isn't what it used to be.

Tou can measure the inside and the outside and average them. Then it is the same as measuring down the middle.

[img]graemlins/thumb.gif[/img] So final volume of the port is matters when curving a port. As long as the curved port has the same volume as the straight port would its all good?

Thanks Dukk

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Nostalgia just isn't what it used to be.

I'll agree to that - as long as the cross sectional area is consistent.