Originally Posted by bob_m10
It seems strange to me that you would use the efficiency of bracing to determine or increase DB output of the sub. I would imagine you would determine an appropriate enclosure volume during design phase of the sub and then look to efficient bracing schemes to shrink the size/weight or lower cost of building the box like Bill has been recommending.
Sometimes the sheet material decides what is efficient. Like my white speakers:
The depth is exactly the max you can get from using half the width of the sheet material I used. And the height is exactly the max you can get from the height of the sheet material, if you want two sections in the height of the sheet. And the baffle is exactly the smallest size you can have, and still fit the woofer dimension by width. And just a few inches taller than it needs to be to fit the woofer, horn and two vents on the baffle face (so that the vents don't have to be elsewhere). The vent is precisely as long as is possible without having bends (which wouldn't fit because of the massive woofer basket). And the vent is precisely as big area as to avoid port noise (there's danger of port noise at 50-60hz at extreme output though, still haven't gotten the opportunity to test if the vents need to be slightly bigger for max output).
I built these two speakers from three 600x2400x22mm sheets of HDP and still had strips left for strengthening (but didn't use any strengthening, its so stiff material and wanted to know how exactly they would behave alone, these aren't the "production-run" versions after all).
Therefore, the response leaves something to be desired.
If I can make the next version of this enclosure stiffer than this one, yet have more internal room, even by a couple liters, then the output can be significantly better at low frequencies. Well, "significantly" by my use of the word. And just touching the faces, even the top and bottom faces that are reinforced with steel handles and speakon terminals, there's significant movement. Well, "significant" as I use it, I want zero detectable movement if I can get it. Then I can remove almost all the filler (there's about 2cm layer of fiber on all six surfaces).
I'm even trying to find out how much benefit there would be in changing from the 40kg/m^3 pillow-filler to 800kg/m^3 of coconut coir matting for erosion control.
You could of course use the more volume-efficient bracing to double or triple the amount of bracing you have. Perhaps not a benefit on certain subwoofers, but at least for LCR's its almost never enough stiffening (the way high end speakers get around this is simply to fill it with several layers of different density of stuffing material. Completely 100% stuffed speakers aren't uncommon). If I didn't want to lose bass output from my standalone LR setup I might just have filled them completely with stuffing as well.
Originally Posted by Augerhandle
I call bull*****. Stick bracing for a typical Marty Sub takes up less than 2.25% of the net volume. reducing that percentage will not make any appreciable difference to how the subwoofer works or sounds. One might as well install mini I-beams, it would still be as pointless.
If you have a certain external size limit, like me as explained above, then the more volume your bracing uses the less efficiency you get. For people who are so far along the line so as to have 4+ big subwoofers and whatnot, then 1db here or there is a lot of money. Doubling the amount of woofers and amps would add only 6db, so you want every bit of efficiency you can reasonably expect to get from what is very very very cheap comparatively (bracing the enclosure, even if complex bracing, its still cheap, it practically only costs time).
Btw, a typical marty isn't braced a lot. It doesn't really need to be. But in any case you could get a lot more output if you didn't need any filler in a marty because of having a very rigid enclosure. Well, "a lot more" being comparative to its cost. 1db more output from a double subwoofer setup by bracing and removing filler isn't difficult. If it costs you 2 grand to double your wooferage to 4 with twice the amps, then 1db for 10 bucks or something in glue in addition to some cut-off material, is a quite rational expenditure of calories.
If you get the material to reach farther, getting more stiffness for the same volume of material, its even better. And once we figure out a very very efficient bracing scheme, it will be as easy for everyone to copy as a marty design for UM18-22 or something.