vent by the speaker wall, or in a corner

[jmiyake]

Let's say you want to make a subwoofer 40" long.
To tune it correctly you need a 4" tube 36" long.
So the 4" tube end is 3" from the inside wall. Does this constrain the sound?

What if the tube is by a corner so 2 sides are close to or against it, and the inside wall is 3" away?

How would this affect the sound?

[mpmarino]

I think the general rule of thumb is that the end of the port should be no closer than its own diameter from any other surface. I think.

[nunayafb]

That is how I've heard it as well.

I know you did not ask or might not care but I'm curious why you cant use a shorter 3" port? Also, 40" is the quarter wave resonance of 83hz is there a reason the box is so long?
Since I know nothing about the design these q's sort of popped into my head. Is this a theoretical question, or is this an actual design, if so we all enjoy details.

[jmiyake]

Project: Two 15" subwoofers, prefer ported.

Drivers: Dayton 15" reference series High Fidelity drivers. (Ordered expecting in a couple of days. )
Dayton 15" High Fidelity

Space available: Area under Front projection screen to left and right of center channel. Approximately 40" by 29" and 15" deep (need to be a bit shallow).

Materials: 1" think mdf. Well braced. 4" pvc pipe. Walls lined with convoluted foam. Bracing is routed out, details not shown in drawing.

Volume: 185L (approx, accounting for bracing, damping, speaker displacement... etc.)
Vents: Two 4"x 36" pvc tubes, tuning around 16-17hz.



Room is 13' wide by 20' long. Dedicated theater with 108" front projection screen.
Subwoofers will be powered by a pro-amp QSC USA 370 with 185 watts per speaker. I could upgrade to a QSC RMX 1450 or 2450 in the future, if I feel I need it.