what happens when you put polyfill in a ported enclosure?

[goku87]

as in what effects does it end up having on the tuning?

[supmet]

From http://www.klausaudio.com/subwoofer-...woofer-box.php

In general, a subwoofer box that would require polyfill would be a subwoofer box that is close to, or smaller than the manufacturer's minimum recommendations for internal volume. Polyfill will make a subwoofer perform as if it were in a larger enclosure by slowing sound waves as they pass through the polyfill. The physical internal volume of the subwoofer box remains the same, yet the effective internal volume changes when polyfill is added.

Sealed subwoofer boxes are the best candidates for polyfill. It is possible to use polyfill in a ported enclosure, but this is not recommended, as it would then change the tuning of the box. Sealed subwoofer boxes generally yield a better, flatter frequency response curve when the enclosure is larger (to a certain point). If you need a subwoofer box of a given size, and your available trunk dimensions do not allow you to customize a subwoofer box with enough internal volume, it is possible to get the subwoofer enclosure built a little smaller than desired and have polyfill added. This will make the subwoofer box "appear" larger to the subwoofer.

-----------------------------

Interesting. I just cut my box down a little because it was taking up too much room, but it definitely lost some of its punch. I'm gonna go to a craft store and try this out :D

[The Architect]

so what would happen if you filled a 6 cubic foot sealed box with poly fill and dropped an s15l7 in there, would it make it better or worse or no difference really since the box is already big enough

[goku87]

Originally Posted by supmet

Interesting. I just cut my box down a little because it was taking up too much room, but it definitely lost some of its punch. I'm gonna go to a craft store and try this out :D

Originally Posted by The Architect

so what would happen if you filled a 6 cubic foot sealed box with poly fill and dropped an s15l7 in there, would it make it better or worse or no difference really since the box is already big enough

Maybe give it a "looser" sound?

[goku87]

So is there some sort of equation or chart that would say "if your box is X ft^3, add Y amount of polyfill to get an effective size of Z ft^3?"

[talnlnky]

Ok... here's the deal.

Polyfil works by slowing down the soundwave in the box and transfering some of the acoustic energy into heat. In doing so the sub will react as if it is in a slighly larger box. Depending on how much you put in your box your box can effective gain up to 40% more airspace. If you put too much in, you won't get 40%, it'll actually start to go down after a certain amount. And of course, too little and it won't reach 40%. Realistically, without a lot of testing, 20-25% is about what you can expect to gain. Means in a 4cuft box, you can load it up, and expect it to play like a 5cuft box.

Sealed is easy, box size is really the only variable you deal with.
Ported is different, you got box size, and port tuning. The port tuning is dependent on the box size. A 4" round port 5 inches long in a box with X cubic ft (cuft) could have a tuning of 40hz, but put that same port in a box that is 2X cuft and it will be tuned to 20hz giving a MUCH MUCH different sound.


People put polyfil or fiberglass insulation (does the same thing) in ported boxes all the time... cept, those people are making home theater boxes usually. You only need to make sure that the polyfil is somehow glued down or held in place so it doesn't get into the port.

As for a ported box, the second you put polyfil in your tuning will drop, which depending on the original box config may make for a better or worse sound... I'm an SQ guy, so I tend to think that a lower tuning will always be better, EXCEPT for in terms of volume(loudness). Low tunings will really start to limit how loud the sub can play, so be careful.

[goku87]

Originally Posted by talnlnky

Ok... here's the deal.

Polyfil works by slowing down the soundwave in the box and transfering some of the acoustic energy into heat. In doing so the sub will react as if it is in a slighly larger box. Depending on how much you put in your box your box can effective gain up to 40% more airspace. If you put too much in, you won't get 40%, it'll actually start to go down after a certain amount. And of course, too little and it won't reach 40%. Realistically, without a lot of testing, 20-25% is about what you can expect to gain. Means in a 4cuft box, you can load it up, and expect it to play like a 5cuft box.

Sealed is easy, box size is really the only variable you deal with.
Ported is different, you got box size, and port tuning. The port tuning is dependent on the box size. A 4" round port 5 inches long in a box with X cubic ft (cuft) could have a tuning of 40hz, but put that same port in a box that is 2X cuft and it will be tuned to 20hz giving a MUCH MUCH different sound.


People put polyfil or fiberglass insulation (does the same thing) in ported boxes all the time... cept, those people are making home theater boxes usually. You only need to make sure that the polyfil is somehow glued down or held in place so it doesn't get into the port.

As for a ported box, the second you put polyfil in your tuning will drop, which depending on the original box config may make for a better or worse sound... I'm an SQ guy, so I tend to think that a lower tuning will always be better, EXCEPT for in terms of volume(loudness). Low tunings will really start to limit how loud the sub can play, so be careful.

Yeah, thats what I'm understanding, I just wanted to make sure ported vs sealed had the same concept going on. The problem I'm dealing with now is figuring out how much I might need. I found this site but i'm not sure how much i should really trust it:

http://www.moodym.com/audio/fiber.html

But since it's cheap and easily removable/addable, no biggie. I'll just go with the good ol' guess-n-check method.

[bzinn 1]

When I put poly in my sealed boxes they actually got crisper in the low sounds,I like SQ setups over SPL,but my .68 boxes sound much bigger and the lows are a lot better,I tried putting more in them and it got weird sounding and i lost too much of my 60-80 range in my subs volume wise,so i took some back out and left it with my first try.....

[talnlnky]

Originally Posted by goku87

Yeah, thats what I'm understanding, I just wanted to make sure ported vs sealed had the same concept going on. The problem I'm dealing with now is figuring out how much I might need. I found this site but i'm not sure how much i should really trust it:

http://www.moodym.com/audio/fiber.html

But since it's cheap and easily removable/addable, no biggie. I'll just go with the good ol' guess-n-check method.

i'd say that site is probably good enough to base your install off of. the cool thing about ported boxes is that you can always just throw more in, if you don't like it without taking the sub out!

[goku87]

Originally Posted by talnlnky

i'd say that site is probably good enough to base your install off of. the cool thing about ported boxes is that you can always just throw more in, if you don't like it without taking the sub out!

very very true!

[supmet]

I went down to michael's (craft store) and got 20 oz for 5 bucks. I only used about 1/4 of the stuff in my box, but it sounds like it did before I cut it down :D. Now I have enough left over to stuff the dual 12" sub enclosure I'm gonna get.

Not a bad investment for 5 bucks in my opinion..

[talnlnky]

Originally Posted by supmet

I went down to michael's (craft store) and got 20 oz for 5 bucks. I only used about 1/4 of the stuff in my box, but it sounds like it did before I cut it down :D. Now I have enough left over to stuff the dual 12" sub enclosure I'm gonna get.

Not a bad investment for 5 bucks in my opinion..

yeah... when you first hear about it... it totally sounds like snake oil... but the shit actually works... physics is weird.

[sqcomp]

Making speakers "Breathe" differently in enclosures is always fun.

I love aperiodic membranes!

[talnlnky]

Originally Posted by sqcomp

Making speakers "Breathe" differently in enclosures is always fun.

I love aperiodic membranes!

I came soo close to doing an AP in door design once.... would be fun to play with.... you going to do that with the 10's?

[sqcomp]

Remember? I've been "consulted" by an unnamed manufacturer...

I'm keeping the Illusions in the closet until someone wants them or I find a project that better suits those speakers.

I'm going to be using two 12" slim woofers, one on each side of the Yaris' trunk. We're keeping the floor of the trunk clear to demonstrate that you can absolutely have ground pounding bass and a clear trunk. It's going to be similar to the Audi enclosure...but using different angles on the baffle and the variovents to get the woofer to think it's got a bigger enclosure. I'm estimating .75 cube actual on each side, maybe more, then the vent will prolly push that up to maybe 1.25 cube. We'll see how that sounds later this summer. The three ways, deadening, and alarm go in first. I'm looking for a good price on an Audison Bit One...If I don't get that, it'll be an Audio Control piece as the processor. All of this before the low end (two DVC 12"s and a nice little 1 Ohm D class 2200 Watt amplifier...I need some headroom, I'll never use that much power though. It's not my style).

When I worked at The Sound Choice, we did two 15" Illusion Audio ND-15 woofers in the FRONT FOOTWELLS of the owner's Mercedes. We made the enclosures directly under the front quarter panels placing the AP membrane out into the wheel well (it was protected adequately). That was ABSOLUTE in terms of up front bass, I'm telling you. It was a fun project. We got the enclosure glassed flat enough as to not interfere with the driving functions of the pedals.

...that was eight years ago now...

[talnlnky]

Originally Posted by sqcomp

Remember? I've been "consulted" by an unnamed manufacturer...

I'm keeping the Illusions in the closet until someone wants them or I find a project that better suits those speakers.

I'm going to be using two 12" slim woofers, one on each side of the Yaris' trunk. We're keeping the floor of the trunk clear to demonstrate that you can absolutely have ground pounding bass and a clear trunk. It's going to be similar to the Audi enclosure...but using different angles on the baffle and the variovents to get the woofer to think it's got a bigger enclosure. I'm estimating .75 cube actual on each side, maybe more, then the vent will prolly push that up to maybe 1.25 cube. We'll see how that sounds later this summer. The three ways, deadening, and alarm go in first. I'm looking for a good price on an Audison Bit One...If I don't get that, it'll be an Audio Control piece as the processor. All of this before the low end (two DVC 12"s and a nice little 1 Ohm D class 2200 Watt amplifier...I need some headroom, I'll never use that much power though. It's not my style).

When I worked at The Sound Choice, we did two 15" Illusion Audio ND-15 woofers in the FRONT FOOTWELLS of the owner's Mercedes. We made the enclosures directly under the front quarter panels placing the AP membrane out into the wheel well (it was protected adequately). That was ABSOLUTE in terms of up front bass, I'm telling you. It was a fun project. We got the enclosure glassed flat enough as to not interfere with the driving functions of the pedals.

...that was eight years ago now...

dumb me... i forget soo easily.

[sqcomp]

LOL! Sheesh!