Just a thought: Take a sheet of foam board, hold it by opposite edges and shake it back and forth. Flexes a lot, right? Now tie some string around it and tighten it so that the board is held in a slightly bowed shape. Shake it again. Much less flex, right? So a construction technique that results in slightly bowed panels will greatly reduce the flexing and thus the amount of bracing required. Plus it provides more possibilities for enclosure shapes that don't look like speakers, increasing the SAF.
Pre-stressed structural members. Increased effective Young's modulus. This is how they make bridges, they bend the concrete in one direction with pre-stressed rebars that are then captive once concrete sets. I agree we need more speakers with curved walls as they will inherently be more rigid.
A square "ring" that is glued (normally into dado's) in increments up and down the inside of a TL (or any tall/slim speaker). If the inside dimensions are 10" x 10", they would also be outside dimension 10" x 10" squares, with an 8.5" square hole cut out of them. Glued in perpendiculare to the baffle. Will add a lot of structural integrity to the beast. Also, the allthread and fender washers can then hold "stress" against the spans. Will make it a complete bitch to get the stuffing in right, but it should be a lot, lot stronger.
Good idea with the rings or window braces. Would they be made of plywood or out of foam? Which way would the threaded rod and nuts be placed? A sketch would be helpful. This Goldwood driver is really nice for a MLTL with its higher Qts as I am having a terrible time getting a good flat response from a low qts driver in the 881si mltl thread.
That is somewhat what Magico did with the Mini II. Round outer profile with
rods from front to back to apply some tension on those walls.
There is an interesting discussion going on in this thread http://www.diyaudio.com/forums/full-range/235230-anyone-build-rondo-inspired-speaker.html about curved plywood walls. Perfect for FC. I may try to build a Rondo but on a smaller scale.
Here is an example of a copy of one by Cervelorider at Fleawatt.
Based on plans from Troels Graveson: Greencones
These speakers look really cool and from what I have heard can sound really good for chamber music and vocals.
Here is an example of a copy of one by Cervelorider at Fleawatt.
Based on plans from Troels Graveson: Greencones
These speakers look really cool and from what I have heard can sound really good for chamber music and vocals.
Those look really cool!
For the sub braces, I would just cut them out of the same styrofoam. Being 2" material, it will be sufficient (I would think).
The allthread would be placed probably every foot (between window braces). Might be overkill, will have to look at it once it is glued together. By placing a nut and fender washer on the insides, one can tighten it to where it just starts to push outwards on the panels then tighten the outsides to hold tight (with hotglue to avoid leaks). Doing this, I can't see why the enclosure would not be able to withstand the pressures. The weak points will end up being the hotglue joints. I figure if they are completely wrapped in gaffers tape (similar to wrapping the handled of a ball bat or tennis racket), it woudl resolve the glue joint issue. Might end up being more time and money than it is actually worth, but I want to try it anyhow.
Also, on a side note. I am reconsidering the drivers for it. Not set yet, but wondering if a PE DVC12 would be a better idea? Or maybe even a 15" pro woofer with a Q of 1.5 and FS of 34? Will think about it.
For the sub braces, I would just cut them out of the same styrofoam. Being 2" material, it will be sufficient (I would think).
The allthread would be placed probably every foot (between window braces). Might be overkill, will have to look at it once it is glued together. By placing a nut and fender washer on the insides, one can tighten it to where it just starts to push outwards on the panels then tighten the outsides to hold tight (with hotglue to avoid leaks). Doing this, I can't see why the enclosure would not be able to withstand the pressures. The weak points will end up being the hotglue joints. I figure if they are completely wrapped in gaffers tape (similar to wrapping the handled of a ball bat or tennis racket), it woudl resolve the glue joint issue. Might end up being more time and money than it is actually worth, but I want to try it anyhow.
Also, on a side note. I am reconsidering the drivers for it. Not set yet, but wondering if a PE DVC12 would be a better idea? Or maybe even a 15" pro woofer with a Q of 1.5 and FS of 34? Will think about it.
I think what you describe with the bolts and washers may be achievable with wooden dowels hot melted in place at strategically selected spots at angles even? Bracing with a 4 in wide strip of foam internally can also work in compression as well as tension.
Are you sure you want to go with the 2 in thick stuff? Maybe 1 inch is enough and go for the egg carton foam or isocyanurate foam rather than the polystyrene bead board foam which may be kind of brittle.
The PE DVC12 is a bass monster for sure but a totally different purpose: lots of watts and lower efficiency of only 87 dB. Plus it costs a pretty penny and loses its "budget costs only as much as 6 fancy Starbucks lattes" appeal.
Not sure which pro 15 in woofer you are looking at but all the ones I see seem to have rather low Qts (to keep the cabinet small for travel). The 12 in pro woofer I am looking at (Dayton Audio PA380-8 15" Pro Woofer) has a very low Qts (0.28) and a 98.5 dB awesome efficiency. Surely, the cabinet dimensions will have to change. But it's Qts is so low, that it won't allow tuning anywhere near or below its fs.
Often referred to as shelf braces in speaker building. They often have multiple cut-outs for the 'window' rather than just an opening.
I would use 1.5 - 2 inch unless the box is small. Definitely use extruded not expanded bead or iso.
I thought the pink stuff was extruded foam? (it is sometimes blue, but usually pink.)
I think it would almost have to be 2" stuff, for the ridgidity and also for the extra glue surface so as to not blow out any of the glue joints. I actually had time to go pick some up today, but the prevailing 30MPH winds out of the North was not conducive to a one-man show trying to load a couple sheets of styrofoam.
I am thinking if I use window...or shelf-braces every six inches, I might get away without having anything extra after picking up a piece. So I might scratch the allthread and see what happens.....
The 15" Driver was just a thought, I was considering using four of them in an OB....so I would not have an extra driver around but not worth the extra effort. And they are only $22.....
I think it would almost have to be 2" stuff, for the ridgidity and also for the extra glue surface so as to not blow out any of the glue joints. I actually had time to go pick some up today, but the prevailing 30MPH winds out of the North was not conducive to a one-man show trying to load a couple sheets of styrofoam.
I am thinking if I use window...or shelf-braces every six inches, I might get away without having anything extra after picking up a piece. So I might scratch the allthread and see what happens.....
The 15" Driver was just a thought, I was considering using four of them in an OB....so I would not have an extra driver around but not worth the extra effort. And they are only $22.....