Box Shape?

[r_s_dhar]

All Elders,

Older books advise that the ideal box should have a golden ratio (which approximates to 4:3:2). This ratio yields a rectangular cube. However there are all sorts of tower-shaped boxes around. Are these "tower" construction, then, a compromise?

Please advice.

[roddyama]

Originally posted by r_s_dhar
All Elders,

Older books advise that the ideal box should have a golden ratio (which approximates to 4:3:2). This ratio yields a rectangular cube. However there are all sorts of tower-shaped boxes around. Are these "tower" construction, then, a compromise?

Please advice.

R-S-dhar,

Almost every speaker design decision is a compromise as is the case in the speaker box shape. The tower shape is used mostly for esthetics to sell more speakers, or vertical driver placement configurations or both. There are, of course, other reasons to use a tower shaped box, but these are the most prevalent.

Rodd Yamashita

[Dave Bullet]

Quite a few 2 way tower speakers simply use the tower as a built in stand. As such - they have a divider that completely separates the speaker enclosure from the rest of the tower (acting as the stand). the golden ratio can therefore apply "within" the tower (above the divider).

planet10 (Dave) can no doubt comment on transmission line / labyrinth speakers and tower type enclosures (a bit beyond me at this point!).

Dave.

[roddyama]

The question is whether the tower box shape was necessary to sonic performance of the speaker or used for its esthetic qualities. I think you’ll find the tower shaped box to be a compromise in most cases.

Clearly in the cases of tall ribbons, line arrays, or WMTM configurations, the driver arrangement dictates the box shape. El-Pipe-O is another situation where the tower shape is important to the sonic function of the speaker, but I can’t think of any other case where the tower is the best sonic choice.

There are ways to overcome the shortcomings of not adhering to the “Golden Ratio”. The use of stuffing, damping pads, dividers (as you mention), and curved surfaces, can all counter the problem of standing waves in lieu of the golden ratio. Using these methods to help improve the sonics of a tower shaped box doesn’t change the fact that the tower shape was most likely chosen for esthetic purposes in the first place. Folded horns and TL’s are folded into shapes (often towers) that your wife will allow you to bring into the living room, not because the folds makes the speaker sound better.

Rodd Yamashita

[Andy G]

... except it happens to look good to the eye (look how much he romans etc used it for their buildings) and the mathematical fact that there are no common multiples between the sides. There are many other irrational ratios that would work the same way.

[Andy G]

4:3:2 is probably not a good approximation to use..... see the 2 and the 4, big no-no !!!

the actual ratio no. is (sqrt(5)+1)/2 which is approx 1.618.....

Bass Box 6 uses this ratio for the sides in its "optimum" cabinet, but there actually a common ratio between the ratio of the sides, which may or maynot be good. I read somewhere that close to
1: 1.618: 2.3xx (can't remember) , was even better, but where that comes from I really don't know.

[fdegrove]

Hi,

Actually I don't think most boxed speakers are build with a golden ratio in mind.

What is often used (because it is pleasing to the eye) is a ratio of 1/3 for the front and 2/3 for the sides.

Cheers,

[pinkmouse]

What is often used (because it is pleasing to the eye) is a ratio of 1/3 for the front and 2/3 for the sides.

Nasty, you would get some real standing waves in that...

Ideally, no dimension should be a multiple of any other in an enclosure, for instance, my HT centre, ( the only rectangular box I have ), measures 584mm x 244mm x 334mm internally, and the internal dividers are set up so as not to be symetrical either.

[haldor]

One ratio I've seen used for rectangular performance spaces is 0.6 to 1 to 1.6.

This ratio gives a good distribution of modal frequencies and maps easily to standard construction practices. I expect it would work just as well in speaker enclosures.

Phil

[Equilibrium]

Originally posted by haldor
One ratio I've seen used for rectangular performance spaces is 0.6 to 1 to 1.6.

This ratio is the Golden Ratio aka Golden Mean.

approximately 0.6180339887 to 1

and 1 to 1.6180339887

and 1.6180339887 to 2.6180339887