Even BIGGER than Bigger, Badder BIB...

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BHD

diyAudio Member
Joined 2004
Yet more progress.

Installing wool felt with contact adhesive.
 

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BHD

diyAudio Member
Joined 2004
It's thicker than it looks because the speakers are seven and a half foot tall. I'm putting a layer of the felt on the bottom as well as acousta-stuf in the peak and a 4" thick layer of acousta-stuf on the bottom over the felt as well. I don't want to over do the damping.

These are test cabinets to check out the viability of the design. I didn't feel like spending the money on plywood until I had a reasonable idea of what they'd sound like.

At 24 bucks a square yard (I had a coupon and only paid half of that) I can only afford so much felt. If you think it will make a difference I might put another layer on the inner baffle. What do you think?
 
Actually, it's a >12 deg slope, so no damping is required for reflections back to driver, but do need damping around the horn if metal and on at least one side wall. Of course it still needs some stuffing to damp the line, so if the woofer is covered in cheesecloth or similar, then lightly stuffing the whole area 'kills' all the potential 'birds' with one stone. ;)

GM
 

BHD

diyAudio Member
Joined 2004
Actually, it's a >12 deg slope, so no damping is required for reflections back to driver, but do need damping around the horn if metal and on at least one side wall. Of course it still needs some stuffing to damp the line, so if the woofer is covered in cheesecloth or similar, then lightly stuffing the whole area 'kills' all the potential 'birds' with one stone. ;)

GM

The tweeter horn is a plastic QSC waveguide so no damping is probably needed. I might do it on the next iteration if the speakers sound good. I did put felt on the sides to the "outside" sides of the cabinet.

Do you think stuffing the peak with a good amount of acousta stuf in the peak and 4-6 inches layering the bottom is enough?
 
The tweeter horn is a plastic QSC waveguide so no damping is probably needed. I might do it on the next iteration if the speakers sound good. I did put felt on the sides to the "outside" sides of the cabinet.

Do you think stuffing the peak with a good amount of acousta stuf in the peak and 4-6 inches layering the bottom is enough?

Actually, it needs to be seriously mass loaded, not as much as this alum. horn, but as a general rule make it at least twice as heavy: High Efficiency Speaker Asylum

Don't know, I posted how I've done tapered TL/pipe horns. ;)

Re the bottom, I've put it only on the first half, then if fine tuning is needed, I recommend either suspending/dangling a 'blanket' of insulation diagonally across the mouth and shorten it as required to tone down the pipe's raw harmonics or treat the mouth as a huge vent and use the click or digital impulse test to critically damp it: Click Test | GM210 | Flickr

GM
 
Hmm, not sure that's sufficient for a prosound 15"; at the very least I'd 'X' brace the mouth, i.e. notch what you have and notch another cross brace to interlock them, tie all four sides together. Also, run a full panel vertically down the initial expansion or at least a bunch of scrap tied together to create a rigid framework.

GM
 
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