[netring]

I have a 22"H 8"W 6"D bookshelves that i need to add damping to, 2 6.5" mids with a 1" horn. Air Suspension design, no port.

I have decided on Sonic Barrier 3 year 3/4" foam w/vinyl ( http://www.parts-express.com/pe/show...number=260-530 ) for the back wall of the speaker.

And Sonic barrier 1/2"( http://www.parts-express.com/pe/show...number=260-520 ) for sides, top and bottom.

1.Should i add polyfill to the speakers also?

2. Am i going for an acoustically dead enclosure?

 

[Bigus]

Damping the enclosure walls and damping the enclosure internal air cavity are two different things with differing goals and differing material requirements... and differing forum opinions on their relative importance.


I believe both are usually important.


You have a pretty good plan for addressing wall resonances, assuming that material is something close to what I think it is (never used that particular product, hard to navigate to that page at the moment on my phone).

 

[LTD02]

there was a guy at silcom or something that did some measurements on this...let me see if i can dig up a link...


ah here:

http://www.silcom.com/~aludwig/Louds...ration_damping

 

[netring]

how do i know how much acousta stuf to add to the speaker?

 

[Bill Fitzmaurice]



Quote:
Originally Posted by Bigus /forum/post/20859988


Damping the enclosure walls and damping the enclosure internal air cavity are two different things with differing goals and differing material requirements... and differing forum opinions on their relative importance.

+1. IME a well built cab needs no mechanical damping; products that do so should be employed in enclosures that can't be well constructed and braced, as in car doors. As for acoustical damping, at the least line the cab or fill it lightly, unless its final Q measures more than .85 or so, in which case add polyfill as required to lower the Q.

 

[LTD02]

what happened to the fiberglass?

 

[LTD02]

"IME a well built cab needs no mechanical damping..."


what about the back wave from the driver bounce that comes back through the driver and messes up things in the midrange?

 

[CZ Eddie]

I'd like to tack onto this thread if you don't mind.

I just built a pair of 1.6 cu^3 enclosures (8" main speakers) for my cousin. These are sealed and thus,, are the first sealed enclosures I've been in years. I bought two king size WalMart pillow so I could stuff one into each enclosure. Is that too much stuffing for 1.6 cu^3? It seemed like a lot.

 

[Volenti]



Quote:
Originally Posted by LTD02 /forum/post/20860215


"IME a well built cab needs no mechanical damping..."


what about the back wave from the driver bounce that comes back through the driver and messes up things in the midrange?

Yea it's part of the "damping 2 different things", thing. The well built cab won't impart any coloration to the sound from wall flex/rattles ect, but you still have standing waves that can occur inside from the physical dimensions of the interior space that need to be addressed. These you damp with polyfill/acoustic foam/fiberglass ect.

Quote:
I just built a pair of 1.6 cu^3 enclosures (8" main speakers) for my cousin. These are sealed and thus,, are the first sealed enclosures I've been in years. I bought two king size WalMart pillow so I could stuff one into each enclosure. Is that too much stuffing for 1.6 cu^3? It seemed like a lot.

I'm not familiar with how large walmart kingsize pillows are, but if you had to force a lot of it in there it may be a little much. I generally like to just "fill" the space with polyfill, as if you were pouring it in out of a bucket. But really the margin for error with packing fill in a sealed enclosure is pretty large, worse case you end up reducing the effective air volume inside, but you really have to cram a lot in there to start doing that, to the point where you have to force the driver down into the fill to get it screwed in...

 

[NicksHitachi]



Quote:
Originally Posted by netring /forum/post/0


how do i know how much acousta stuf to add to the speaker?

up to 1lb per cubic foot polyfill.....

 

[smokarz]

i recently built roughly 2.0cf boxes (sealed) and lined up the walls with poly-fill sheet. i also have cross bracing internally.


stuffing the box with poly fill is probably not necessary.


http://www.avsforum.com/avs-vb/showt...1318791&page=3

 

[Bill Fitzmaurice]



Quote:
Originally Posted by LTD02 /forum/post/20860215


"IME a well built cab needs no mechanical damping..."


what about the back wave from the driver bounce that comes back through the driver and messes up things in the midrange?

That's addressed with acoustical damping.

Quote:
what happened to the fiberglass?

That's one of a half dozen or so acoustical damping materials. Type 700 is best. But if you need to stuff a sealed cab polyfill is a better option, as type 700 doesn't compress well.

 

[A9X-308]



Quote:
Originally Posted by smokarz /forum/post/20861114


i recently built roughly 2.0cf boxes (sealed) and lined up the walls with poly-fill sheet. i also have cross bracing internally.

Putting it on the walls does nothing as you want it where the particle velocity is highest for it to be effective. On the walls particle velocity is low.

Quote:
Originally Posted by smokarz /forum/post/20861114


stuffing the box with poly fill is probably not necessary.


http://www.avsforum.com/avs-vb/showt...1318791&page=3

For a sub that size, no, for a wide range speaker, definitely yes.

 

[smokarz]

i stuffed my subs


i lined my speakers

 

[CZ Eddie]



Quote:
Originally Posted by Volenti /forum/post/0



I'm not familiar with how large walmart kingsize pillows are, but if you had to force a lot of it in there it may be a little much. I generally like to just "fill" the space with polyfill, as if you were pouring it in out of a bucket. But really the margin for error with packing fill in a sealed enclosure is pretty large, worse case you end up reducing the effective air volume inside, but you really have to cram a lot in there to start doing that, to the point where you have to force the driver down into the fill to get it screwed in...

thanks for the input!

 

[Mpray1983]

Does anyone know where to get polyfil batting?

 

[smokarz]



Quote:
Originally Posted by Mpray1983 /forum/post/20864498


Does anyone know where to get polyfil batting?

got mine from walmart. right next to the polyfill stuffing.