Impact of box shape?

[oilstain]

So, I originally put this question in the Subwoofer section. Sorry, it belongs here:

Suppose woofer x requires 1 cu ft (because it makes for easier math) for a ported box, not including port volume. Assume the ports will be run externally, and the woofer will be inverted, so mounting depth is not a factor.

What would be the difference of a 'normal' shaped box roughly 10x14x18 (3/4 material) versus a long box like a 40x14x5 (same 3/4 material).

Now finally, what if the long box was wedge shaped so that it was 40x14, but one side is 3" and the other 7" (keeping the internal volume the same, just significantly changing the angle of the surface the woofer is facing)

I'd guess with box 2, the reflection off a surface so close to the woofer may cause out of phase waves trying to drive back through the cone (all boxes have this, but I'm guessing the proximity would make a difference) or, is the fact that the low fq waves are soooo big, that it doesn't matter (the wavelength of 60 hz is 5.5 feet, so logically a wall a foot away is still REALLY close in terms of size).

I'd also guess that box 3, with the sloped opposite wall may help keep any direct reflections, but may introduce weird reflections that could be better or worse.

I'd think either 2 or 3 would need more internal bracing against flex, but that could be easily added with slight outer dimensional changes, so please ignore that for the sake of this discussion.

PS, I know the answer would be easy to find out by building all three said boxes, but ain't nobody got time for that!

Please discuss!

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[DARKHART 10+ year member]

As was stated in the other trend, unless you are chasing numbers, in a real world application you would never even notice the difference.

 

[Boominburban 10+ year member]

PS, I know the answer would be easy to find out by building all three said boxes, but ain't nobody got time for that!

Please discuss!

Yea, we've done just that, back in like 89-90,. I left you an answer in the other thread ....

Wayne Harris had this figured out probably two yrs before that ..... he was always ahead of the curve back then ....

 

[Boominburban 10+ year member]

Here it is ...

" Yes, There is a "golden box" for every custom built enclosure for every sub. That has the best H to L to W ratio. And when you start to deviate from that set of dimensions, you lose a tiny bit of sq and efficiency. I do not remember all the math and audio theory behind it,(it's been like 25+yrs since I studied it). But it does make a difference. But unless you are chasing 10ths on the meter, or are going to the extreme out of the normal range,(like trying to mount a sub playing into like 2" of airspace in front of it) it prob wouldn't ever matter for a normal build. "

 

[oilstain]

Cool, I did see your response, and I want to thank you for that! Sorry, I should have before posting it over here. I just realized that I had posted it in the wrong area.

I actually am thinking of firing a sub into a wedge that will be 2 or 3 inches on one side, 5 or 6 on the other and 40" wide.

 

[Boominburban 10+ year member]

If you fire a sub into 2-3" you are going to have some sound degradation. And odd air movement, depending on power/sub, ect, it could possibly damage your cone/surround as well., idk. But it will deff not be efficient.