" egg crate " foam or polyfils for sub ??

eyesofra · Post by **eyesofra** » Tue Mar 20, 2007 7:17 am

hi guys,
i need some help with the choice of dampening material in my sub enclosure.

I was all set to stuff some polyfils into my new enclosure when i come across this ( figure 1 ) egg crate type foam in the Hi-Fi store that i bought the sub speaker cable from.

The guy there suggested this foam works a little better than polyfils in breaking down standing waves and all.

I know a lot of ppl use this type of dampening material but are they really better than polyfils ? Or is it that each is suited for different need ??

The sub box is a sealed 1.3cuft.

Pls advice frens.
Any input is much appreciated.
Thanks

Post by **Francious70** » Tue Mar 20, 2007 7:32 am

Never lined the inside of my enclosures. I'm not to sure what it'll do for you wither.

vin78 · Post by **vin78** » Tue Mar 20, 2007 7:54 am

I think they are supposed to eliminate standing waves, I may be wrong though.

I usually use poly-fill b/c its cheaper.

Post by **VW337** » Tue Mar 20, 2007 8:56 am

The foam will eliminate standing waves which is good however the poly-fil will do that and also move around slightly which makes the enclosure size seem a bit larger to the speaker allowing a smoother response.

Both materials serve a slightly different function.

eyesofra · Post by **eyesofra** » Tue Mar 20, 2007 9:29 am

thanks guys and thanks errin ,
think i'll just go with the polyfils ....

how much would be enough ?

These polyfils that i have are like 1 inch thick uncompressed , should I go with 1 layer on all the walls .

Are these(polyfils) the same material that my brother uses in his aquarium as filter material....gosh it looks and feels exactly the same with some that i pulled out of my old speakers.

The only difference i can see is this aquarium filter material looks a a little less dense than the "real thing.

Errin i hope you can help me out a little here....thanks
The subs goin to house the 12"RSD in a 1.25cuft sealed.

Thanks guys...u ppl the greatest...

Post by **VW337** » Tue Mar 20, 2007 3:38 pm

2 bags like this should be more than enough.

http://cgi.ebay.com/Poly-Fil-BIG-BAG-Fi ... dZViewItem

Post by **bdubs767** » Tue Mar 20, 2007 6:05 pm

go to walmart its cheaper too

eyesofra · Post by **eyesofra** » Tue Mar 20, 2007 7:03 pm

two bags of those ?
it has to be more than enough....

ok i'll try that out.
Thanks a lot guys

Post by **VW337** » Tue Mar 20, 2007 8:35 pm

Yes 2 bags would likely be a bit overkill but stuff it so it is not hard packed but loosely-full. Most likely you will have some left over.

eyesofra · Post by **eyesofra** » Wed Mar 21, 2007 5:49 am

thanks errin,

lastly can you pls explain on how exacly should i fill up the enclosure.

I've got two types of polyfils with me now, one is poly wool type (fig1 )and the other one comes in a a little firm rectangular shaped form (fig 2)).

1) Should i use the fig.2 type and just line and attach it to the sidewalls and floor in the enclosure ??
If its better to use the wool type , how should i go bout it ??
Do i need to use glue to paste it within the enclosure or just stuff it to the rear wall and floor ??

2)Is there any specific weight guideline I've got to follow or how many grams must i use for my enclosure ( an approximate ).

Pls suggest , ur help is much needed and appreciated.
Friends pls suggest too.

Thanks

Wink · Post by **Wink** » Wed Mar 21, 2007 7:16 am

dont you have to worry about that stuff getting into ur coils....thats just what ive heard....

Post by **VW337** » Wed Mar 21, 2007 7:33 am

Just loosely fill the enclosure with either, you'll be fine. The flat version is great in a ported enclosure because you can line the walls and it has a cleaner look when viewed through a port hole, however the effect of the two is the same.

You should not worry about it getting into the coil as most drivers have a grill of some form in the pole piece vent, however it would take intent to get it into the speaker assembly in most cases and is not going to get in the works accidentally that I have ever seen.

Wink · Post by **Wink** » Wed Mar 21, 2007 9:28 am

aaahhh ic

eyesofra · Post by **eyesofra** » Wed Mar 21, 2007 10:03 am

thanks again errin ,
just wandering , if we loosely fill in with those wools ,
dont we have to worry of them flying around within the enclosure when the sub is working?

Or does it creates some sort of vacuum when completely sealed??

Just brushing up some physics...hope u wont mind answering this..

thanks a lot for all the guide.

Post by **VW337** » Thu Mar 22, 2007 7:25 am

It'll move around but nothing to worry about.

If a vacuum was formed then the speaker would be sucked inward. You only get a sealed airspace no vacuum. If a vacuum were to be formed there would be no back wave from the sub as sound doesn't really convey through a true vacuum so the need for poly-fil would then be negligible, and the fact of no sound moving off the back of the sub means the energy being created would not be leaving the source and the driver would quickly fail due to heat build up...............wow where did that come from, it's way to early to be thinking like that.

eyesofra · Post by **eyesofra** » Thu Mar 22, 2007 10:41 am

that is truly a " wow " errin

man, what did u major in , acoustical engineering ??

yes of course, it cant be a vacuum now can it...like you said it'll be sucked inwards by the difference of air pressure
........mind me with that question

errin, one last question, are there any difference between normal rectangular enclosure and the sloped( triangle) type?
In terms of resonance, sound quality, standing waves ??

Also i came across a complete enclosure building guide for the RSD12 but into a 0.8cuft enclosure. I think i got it from the PG ftp.

I've attached it down here and I was just curious if there any other guide available for fitting the RSD into a 1.2 cuft ??

Regards,
Amuthan

dedlyjedly · Post by **dedlyjedly** » Thu Mar 22, 2007 11:57 am

Not that it has any bearing on the polyfill question, but a sealed enclosure does act like a vacuum 50% of the time if the enclosure is completely sealed after the sub is mounted. A vacuum has to occur when the sub is exerting itself outward. Then as the sub moves back to its resting position pressure becomes equal on both sides of the cone.

Post by **VW337** » Thu Mar 22, 2007 4:38 pm

You can take that diagram and make the side to side length a bit more and be golden. The angled side help to reduce standing waves.

dragonplayboy · Post by **dragonplayboy** » Fri Mar 23, 2007 7:34 am

would it make sense to polyfill the .6 cube enclosure I'm building for my RSD10? if so will do. also, I only have about half an inch to an inch clearance behind the woofer, should I try to squeeze some behind it anyway?

Post by **VW337** » Fri Mar 23, 2007 9:29 am

Poly-fil will help to flatten/smooth the response so go for it, you may like it better that way, you may not. I however would not say to squeeze it behind the motor if you have such minimal clearance.

dragonplayboy · Post by **dragonplayboy** » Fri Mar 23, 2007 10:40 am

would it be wise to go to a half cube and then polyfill it? Errin, as I recall, you reccommended .6 cubes = perfect for musicality (not going for loud AT ALL) on the rsd10, would polyfilling change that or just smooth it out at the same (enclosure) volume?

thx!

Post by **VW337** » Fri Mar 23, 2007 11:22 am

It'll smooth it out.

eyesofra · Post by **eyesofra** » Fri Mar 23, 2007 12:21 pm

if the polyfils make the enclosure appear larger to the sub , wouldn't that affect the volume , thus the Qtc of the enclosure

My enclosure of around 1.2 cuft gives a Qtc of 1.07.
So Errin, does this get changed after i stuff in whatever amount of polyfils ?

A little confused here

Do explain pls

Post by **VW337** » Fri Mar 23, 2007 1:20 pm

Poly-fil allows for a 10% variation in enclosure size (+/- 5%) but ultimately it allows a flat response without internal reflections. The variation of the "seen" volume will change a bit under typical driver movement so at certain notes the enclosure may act smaller and others may cause it to act larger, again this variant allows the driver to act more linear in a typical enclosure and this linear fashion tends to smooth out peaks and roll off a little less steeply.

eyesofra · Post by **eyesofra** » Wed May 16, 2007 8:56 am

errin , is this enough or should i add more polyfils....still got a bag full of them....

(and thats a 1.22cuft box for the ultimate rsd 12")