-JL audio 10'' 10 0 series 8 ohm ea.
do i need polyfill./foam for these subs in this box?
http://www.cardomain.com/item/RTE21210
Replies (11)
MrBrownstone on 01/19/2006 13:27:08
Polyfill can provide a miniscule amount of benefit to a woofer by converting heat energy and consequently, making the box 'appear' larger to the woofer. The effect is like a maximum of making your box 0.05 cuft bigger...which isn't a whole lot.
I seriously doubt you'd be able to hear the difference between a filled and unfilled enclosure. In fact, I'd bet you $1000 you couldn't. fill is just old audio lore. Unlike a capacitor, it's cheap, so there really isn't any detriment to adding it. At a pillow store, it costs like $3.50 for a trashbag sized amount.
swez on 01/19/2006 13:59:07
Frankly, on every low frequency driver enclosure I have ever made, have used fill.
Have also installed many Pro & Commercial audio enclosures and ALL used fill as well.
What fill does, is absorbs some rear cone bass waves, slows the return waves within the box and helps dampen the reflections. As B said, only a well fitted audio test lab can detect the audio differences. A very slight bump in the lower octave of a subs' output performance is noted on these tests. (less then 1.5dB)
Fill is optional, but I have seen many high end woofer sites that specify using it and in what amounts as well.
Swez
MrBrownstone on 01/19/2006 16:22:05
Swez
The ONLY meaningful purpose of polyfill is that it absorbs heat, changing the thermal properties of the air in side the box. You aren't damping (not dampening as that is making it wet) the waves providing a bump...the bump is due to the heat principle....and the perfomance isn't necessarily a bump up either.
lilschtive on 01/19/2006 17:25:24
i will have to agree with swez. i think i do get a MINIMUL 'bump' when i added fill to mine. i used a bed foam. its the yellow egg carton foam about 1-2 inches thick around the whole inside. i was just not sure because i was wondering if it can lower the bass?
lilschtive on 01/19/2006 17:26:47
by the way swez, ill send you a picture of the completed subs and amp :). i finally got my act together. you were right, boxes do make a huge difference ....my home made one sucked compared to factory built...
MrBrownstone on 01/19/2006 21:35:35
Concerning the standing waves...unless the box is enormous or the wavelength very short, it won't have an impact. Bass frequencies have wavelengths longer than the dimensions of the box...poly won't make a difference if the distance the wave travels through is far shorter than the wavelength. (80Hz = 14.0625ft)
A lot of that might be psychological. I really doubt that you could even find sensitive equipment to measure the difference. Even a lb/ft wouldn't yield enough of a difference to actually hear a difference. an inch on the outside of the box is less than 4 oz...and if you look here....:
http://web.archive.org/web/20020808224043/integra.cyberglobe.net/caraudio/resources/fiberfill/
the actual box size differential is 0%
You might be imagining things.
PS Polyfill actually LOWERS the SPL....period.
PSPS Here's a better link:
http://www.carsound.com/cgi-bin/UBB_CGI/ultimatebb.cgi?ubb=get_topic;f=2;t=003741
PSPSPS Possibly the best link:
http://www.carsound.com/UBB/ultimatebb.php?ubb=get_topic;f=1;t=022663#000000
lilschtive on 01/19/2006 22:17:33
alright, case made. But should i still use the egg carton foam inside?i just dont want to lower the performance of the subs
ps its a sealed enclosure
swez on 01/20/2006 05:17:08
Thanks B... that last link had some very interesting insights. RC and others go into the topic much deeper than most guys care to even consider.
The short form version I got from all these threads, is that Polyfill does trap heat, does drop the sub F3 performance a few Hz., and it is measurable, if not audible. Is it absolutely needed? Nope! Do people use it anyway? Yep. Does it matter if one chooses to use it or not? Debatable???
" The idea is that adding stuffing to a box partially changes the state of the system from adiabatic to isothermal...........RC"
Does anyone really care about such isoteric debates? Interesting read, but not enough to sway me in a new direction.
What I do know, is that pretty much every sub enclosure I have worked with, (Pro, Commercial and Homebrews) all use some fill. If JBL uses it in ALL their designs, that's good enough for me.
Swez COFFEE
PS Ohhh Mr. B.... Just put some 1/2" thick foam padding in my house slippers. Why? A nice cushioning spring, holds some heat and feels much softer as I stomp around the house. I have extra padding if you'd like some for your slippers. Just send me a tracing of your shoe soles and I'll make a pair for ya. Maybe it would give you a kinder disposition
too.... ya old CRANK !!! HAPPY
Ash on 01/20/2006 10:58:34
I agree with both of you guys. Yet, it should be noted one less used option that gives better results in smaller enclosures is a combo of 50/50 mixed fill. This can be in the way of high density fill (fiberglass) along the walls with a low density fill (fiber-fill, Dacron or whatever) between the sub and fiberglass. Long fiber wool shouldn't be ruled out either. The single fills 100% (without combinations) used will result in the lesser changes of course.
Although all is questionable, it is sure that compliance and efficiency can be increased, change in moving mass and impedance peak reductions occur.
The average listener may not detect or even care, but I myself still can't help to apply use of the above techniques when building my own enclosures. To me, the results are definitely there and audible enough to use.
lilschtive on 01/20/2006 19:04:41
wow this really turned into a debatable post :)
i feel better when i put fill in for some reason. maybe its just all in my head.
i like the feel when its all nice and stuffed inside :P
Ash on 01/21/2006 20:06:18
That's the thing to realize about audio period, wether car or home. It's just as much as an art as it is a science. Knowledge and creativity go a long way in this game.
do i need polyfill./foam for these subs in this box?
http://www.cardomain.com/item/RTE21210
Replies (11)
MrBrownstone on 01/19/2006 13:27:08
Polyfill can provide a miniscule amount of benefit to a woofer by converting heat energy and consequently, making the box 'appear' larger to the woofer. The effect is like a maximum of making your box 0.05 cuft bigger...which isn't a whole lot.
I seriously doubt you'd be able to hear the difference between a filled and unfilled enclosure. In fact, I'd bet you $1000 you couldn't. fill is just old audio lore. Unlike a capacitor, it's cheap, so there really isn't any detriment to adding it. At a pillow store, it costs like $3.50 for a trashbag sized amount.
swez on 01/19/2006 13:59:07
Frankly, on every low frequency driver enclosure I have ever made, have used fill.
Have also installed many Pro & Commercial audio enclosures and ALL used fill as well.
What fill does, is absorbs some rear cone bass waves, slows the return waves within the box and helps dampen the reflections. As B said, only a well fitted audio test lab can detect the audio differences. A very slight bump in the lower octave of a subs' output performance is noted on these tests. (less then 1.5dB)
Fill is optional, but I have seen many high end woofer sites that specify using it and in what amounts as well.
Swez
MrBrownstone on 01/19/2006 16:22:05
Swez
The ONLY meaningful purpose of polyfill is that it absorbs heat, changing the thermal properties of the air in side the box. You aren't damping (not dampening as that is making it wet) the waves providing a bump...the bump is due to the heat principle....and the perfomance isn't necessarily a bump up either.
lilschtive on 01/19/2006 17:25:24
i will have to agree with swez. i think i do get a MINIMUL 'bump' when i added fill to mine. i used a bed foam. its the yellow egg carton foam about 1-2 inches thick around the whole inside. i was just not sure because i was wondering if it can lower the bass?
lilschtive on 01/19/2006 17:26:47
by the way swez, ill send you a picture of the completed subs and amp :). i finally got my act together. you were right, boxes do make a huge difference ....my home made one sucked compared to factory built...
MrBrownstone on 01/19/2006 21:35:35
Concerning the standing waves...unless the box is enormous or the wavelength very short, it won't have an impact. Bass frequencies have wavelengths longer than the dimensions of the box...poly won't make a difference if the distance the wave travels through is far shorter than the wavelength. (80Hz = 14.0625ft)
A lot of that might be psychological. I really doubt that you could even find sensitive equipment to measure the difference. Even a lb/ft wouldn't yield enough of a difference to actually hear a difference. an inch on the outside of the box is less than 4 oz...and if you look here....:
http://web.archive.org/web/20020808224043/integra.cyberglobe.net/caraudio/resources/fiberfill/
the actual box size differential is 0%
You might be imagining things.
PS Polyfill actually LOWERS the SPL....period.
PSPS Here's a better link:
http://www.carsound.com/cgi-bin/UBB_CGI/ultimatebb.cgi?ubb=get_topic;f=2;t=003741
PSPSPS Possibly the best link:
http://www.carsound.com/UBB/ultimatebb.php?ubb=get_topic;f=1;t=022663#000000
lilschtive on 01/19/2006 22:17:33
alright, case made. But should i still use the egg carton foam inside?i just dont want to lower the performance of the subs
ps its a sealed enclosure
swez on 01/20/2006 05:17:08
Thanks B... that last link had some very interesting insights. RC and others go into the topic much deeper than most guys care to even consider.
The short form version I got from all these threads, is that Polyfill does trap heat, does drop the sub F3 performance a few Hz., and it is measurable, if not audible. Is it absolutely needed? Nope! Do people use it anyway? Yep. Does it matter if one chooses to use it or not? Debatable???
" The idea is that adding stuffing to a box partially changes the state of the system from adiabatic to isothermal...........RC"
Does anyone really care about such isoteric debates? Interesting read, but not enough to sway me in a new direction.
What I do know, is that pretty much every sub enclosure I have worked with, (Pro, Commercial and Homebrews) all use some fill. If JBL uses it in ALL their designs, that's good enough for me.
Swez COFFEE
PS Ohhh Mr. B.... Just put some 1/2" thick foam padding in my house slippers. Why? A nice cushioning spring, holds some heat and feels much softer as I stomp around the house. I have extra padding if you'd like some for your slippers. Just send me a tracing of your shoe soles and I'll make a pair for ya. Maybe it would give you a kinder disposition
too.... ya old CRANK !!! HAPPY
Ash on 01/20/2006 10:58:34
I agree with both of you guys. Yet, it should be noted one less used option that gives better results in smaller enclosures is a combo of 50/50 mixed fill. This can be in the way of high density fill (fiberglass) along the walls with a low density fill (fiber-fill, Dacron or whatever) between the sub and fiberglass. Long fiber wool shouldn't be ruled out either. The single fills 100% (without combinations) used will result in the lesser changes of course.
Although all is questionable, it is sure that compliance and efficiency can be increased, change in moving mass and impedance peak reductions occur.
The average listener may not detect or even care, but I myself still can't help to apply use of the above techniques when building my own enclosures. To me, the results are definitely there and audible enough to use.
lilschtive on 01/20/2006 19:04:41
wow this really turned into a debatable post :)
i feel better when i put fill in for some reason. maybe its just all in my head.
i like the feel when its all nice and stuffed inside :P
Ash on 01/21/2006 20:06:18
That's the thing to realize about audio period, wether car or home. It's just as much as an art as it is a science. Knowledge and creativity go a long way in this game.
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