That was the plan to have one flipped with magnet out but I miscalculated the clearance required to slip the driver in with the bezel of the other one sticking out. Off by maybe 5mm.
The bolts to hold them mechanically rigid is a great idea - it would really make it quieter as the opposed motion is already vibration cancelling.
What's the benefits of having one driver mounted "magnet out" over just running the driver in reverse phase?
Don't they amount to roughly the same thing?
You also reverse the phase of 1 driver so that when 1 driver is moving out, the other is moving in while they are both pushing on the air in the slot. This cancels even order harmonics due to suspension non-linearities. Also it breaks up resonances in the slot due to the motor structure of 1 driver being in there.
You can read more about it here:
http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html
You can read more about it here:
http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html
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Geez! Thanks for all the replies. Sonotube: been there, done that. Works great, but I don't need a 12 foot long subwoofer in my living room. 
Toilet: never would have thought of that. Hmmm..Neighbor is throwing one out here today.... nope, I think that idea craps out, so to speak. :-D
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Toilet: never would have thought of that. Hmmm..Neighbor is throwing one out here today.... nope, I think that idea craps out, so to speak. :-D
Sent from my SPH-L300 using Tapatalk
Ed Schilling's Redneck Engineer's special?
Subwoofer
I've not built or heard these, but I believe several DIY Audio regulars have, and in typical Horn Shoppe design discipline, you probably don't wanna futz with anything but the final aesthetics - I think Ed is now a qualified drone pilot.
You could paint the damned thing in camo if you like
Subwoofer
I've not built or heard these, but I believe several DIY Audio regulars have, and in typical Horn Shoppe design discipline, you probably don't wanna futz with anything but the final aesthetics - I think Ed is now a qualified drone pilot.
You could paint the damned thing in camo if you like
Report from the field...
I wish I had a field. Then I could take better (outdoor) measurements. But I live walking distance to a major highway and a minor airport. Noise!
The coroplast-foam-coroplast sandwich sub, I dub thee "son of Frankenclosure" (the "original" 2 foot cubed box previously with 2x 15" drivers, having donated one driver to his son now...), of course has its bugs but in fact works ok in normal listening. I haven't really pushed them hard ... yet. "Son" will get some more internal bracing and better sealing. Conveniently, the 15" circle cut out of the baffle for Son plugs the "donor" hole left in Dad
More thoughts on the money angle: while it's fun to try alternative materials, it really doesn't save much cash. Worst (?) case, a 4x8' sheet of "suitable" normal board (birch ply, or MDF) is maybe $50 tops (I just priced yesterday). One sheet is plenty for my 2 ft ^ 3 box. With some left over for scrap, bracing, etc. My foam sheet was around $11, even if it were free, making the composite takes time and adhesive. Worth it? Increasingly doubtful.
The current box is strong enough that it would -- briefly -- bear my weight (about 210 Lb.), I sat on the wooden baffle when it was up-facing. So that speaks well of even basic plastic-and-foamcore walls.
I wish I had a field. Then I could take better (outdoor) measurements. But I live walking distance to a major highway and a minor airport. Noise!
The coroplast-foam-coroplast sandwich sub, I dub thee "son of Frankenclosure" (the "original" 2 foot cubed box previously with 2x 15" drivers, having donated one driver to his son now...), of course has its bugs but in fact works ok in normal listening. I haven't really pushed them hard ... yet. "Son" will get some more internal bracing and better sealing. Conveniently, the 15" circle cut out of the baffle for Son plugs the "donor" hole left in Dad
More thoughts on the money angle: while it's fun to try alternative materials, it really doesn't save much cash. Worst (?) case, a 4x8' sheet of "suitable" normal board (birch ply, or MDF) is maybe $50 tops (I just priced yesterday). One sheet is plenty for my 2 ft ^ 3 box. With some left over for scrap, bracing, etc. My foam sheet was around $11, even if it were free, making the composite takes time and adhesive. Worth it? Increasingly doubtful.
The current box is strong enough that it would -- briefly -- bear my weight (about 210 Lb.), I sat on the wooden baffle when it was up-facing. So that speaks well of even basic plastic-and-foamcore walls.
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