Need help picking insulation type for ported speaker - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 17 Old 04-03-2019, 01:15 PM - Thread Starter
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Need help picking insulation type for ported speaker

I have my speaker cabinet built and now need to use insulation or some form of damping material and the verdicts seem to be all over the place. Could somebody help me pick which is best for a ported titan 615? I see my stores carry in stock rockwool (multiple types including safe and sound) multiple types of fiberglass and I could order and wait for foam or denim insulation. This is for the woofer which plays 350hz down to about 30hz. Any input would be greatly appreciated.
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post #2 of 17 Old 04-03-2019, 05:09 PM
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I personally went with denim insulation for less of the 'itch' factor. It performed admirably in the tests I looked at, but still, fiberglass is the standard. Partially because it is super cheap, but it performs nicely too. I just didn't want any to eventually come out the ports (not extremely likely, but you never know), and end up being a nuisance. Rockwool is a decent option too, and definitely less itchy than fiberglass.


As far as performance, I can't say as of yet, since I'm about 70% done with my speakers. The only concern now is cutting the stuff since apparently it is difficult to trim down. We'll see how that goes after I get my panels glued together and bracing done. I tend to over complicate my builds, so it takes longer to get them done than most, but hey, I'm used to myself by now... :-p



I'm off to work on them now in fact. :-)
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post #3 of 17 Old 04-04-2019, 06:59 AM
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I've never used fiberglass insulation... I've always use either Dacron, or egg crate foam or both. Some also use wool or I guess denim, and maybe there is some advantage to one of those, but I would stay WAY clear of fiberglass.

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post #4 of 17 Old 04-04-2019, 08:46 AM
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I've never used fiberglass insulation... I've always use either Dacron, or egg crate foam or both. Some also use wool or I guess denim, and maybe there is some advantage to one of those, but I would stay WAY clear of fiberglass.

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For a ported box, I would steer clear of loose fiberglass. I've used paper-backed pink fiberglass in sealed sonotubes. I just stuck the paper side to the walls of the cardboard tube. It made it pretty easy. In my passive radiator build I used two ~1" layers of moderately compressed fiberglass duct liner (that comes on big rolls). I glued the looser side of the fiberglass to the enclosure and left the more treated sided (that doesn't have loose fibers) exposed in the box. I wouldn't have any issues using the duct liner type of fiberglass in a ported box.

I'm just going to use loose polyfill for the Volt-10 speakers (sealed) I'm building now because they're too small to be cutting up and trying to fit pieces of any more rigid insulation product in them.
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post #5 of 17 Old 04-04-2019, 08:53 AM
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"rigid insulation" wood just make the volume smaller. Lose fill poly or Dacron or open cell egg create , or other lose fill, as I understand it, make the box volume appear to be both a little larger, and absorbs the higher frequency standing waves within the box.

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post #6 of 17 Old 04-04-2019, 09:16 AM
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Originally Posted by kennyandersen View Post
"rigid insulation" wood just make the volume smaller. Lose fill poly or Dacron or open cell egg create , or other lose fill, as I understand it, make the box volume appear to be both a little larger, and absorbs the higher frequency standing waves within the box.
*sigh* No, it wouln't unless is was closed cell. Compressed fiberglass product that are used in on wall sound treatments are not "closed cell", but are quite rigid. Lots of the foam products I see people using in boxes are rigid to some degree in comparison to loose polyfill or loose fiberglass.
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post #7 of 17 Old 04-04-2019, 09:22 AM
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Originally Posted by Stereodude View Post
*sigh* No, it wouln't unless is was closed cell. Compressed fiberglass product that are used in on wall sound treatments are not "closed cell", but are quite rigid. Lots of the foam products I see people using in boxes are rigid to some degree in comparison to loose polyfill or loose fiberglass.
Sigh... Over that? Sigh. In any case. I, personally, would recommend egg-create foam for a sub. I wouldn't use fiberglass anything. Fiberglass is obnoxious., And yes, closed cell foam is out. Your sub, do what you want.

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post #8 of 17 Old 04-04-2019, 11:13 AM
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There was some extensive testing done on acoustical absorption properties of various insulation types several years ago, and fiberglass actually outperformed the 'specialty' speaker insulation. From what I recall, denim performed quite well too, though I think they were separate tests posted on different websites.


Some recommend simply lining the walls with open cell egg crate foam, simply for standing waves, with perhaps a little loose fill behind the woofer to damp the backwave.


Looks like eng-399 used denim behind the woofer in his Titan build:


https://www.avsforum.com/forum/155-d...l#post51024313
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post #9 of 17 Old 04-04-2019, 11:28 AM
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Originally Posted by drewp29 View Post
There was some extensive testing done on acoustical absorption properties of various insulation types several years ago, and fiberglass actually outperformed the 'specialty' speaker insulation. From what I recall, denim performed quite well too, though I think they were separate tests posted on different websites.


Some recommend simply lining the walls with open cell egg crate foam, simply for standing waves, with perhaps a little loose fill behind the woofer to damp the backwave.


Looks like eng-399 used denim behind the woofer in his Titan build:


https://www.avsforum.com/forum/155-d...l#post51024313
Most anything will work, but I hate fiberglass insulation. It makes such an itchy mess, Imo, it's simply not worth messing with.

Having said that there is probably no industry that has more shake oil in it than audio video. There has been some really expensive stuffings sold and I've always thought many of them were overrated. Now I'm either egg crate and poly for subs or poly for small speakers. Cheap pillows from Walmart are about the cheapest way to get it. No need a getting crazy!

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post #10 of 17 Old 04-04-2019, 12:04 PM
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Originally Posted by kennyandersen View Post
Most anything will work, but I hate fiberglass insulation. It makes such an itchy mess, Imo, it's simply not worth messing with.

Having said that there is probably no industry that has more shake oil in it than audio video. There has been some really expensive stuffings sold and I've always thought many of them were overrated. Now I'm either egg crate and poly for subs or poly for small speakers. Cheap pillows from Walmart are about the cheapest way to get it. No need a getting crazy!

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I 100% agree. In a sealed application, where you stuff it, measure, stuff it some more, and then forget it, maybe fiberglass. Even the more rigid stuff is pretty nasty, at least in my opinion, though I agree with Sterodude that it likely wouldn't be an issue in ported vs loose fill.

After wiring my surrounds through the ceiling in the attic, no matter how good of coverage your clothes have, you will get itching everywhere. Reminds me of the bleacher seats they had at our local city park tennis courts. I learned quickly that you never sit on them without a towel or blanket underneath. Plenty of itchy red skin to attest to that.

Considering the elegance of the Titan design, I don't think the OP will need to tame much, so egg crate foam is probably plenty good enough.
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post #11 of 17 Old 04-04-2019, 12:24 PM
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I expect the difference between closed- and open-cell foam is that the latter would give lower Qa because of the airflow and subsequent frictional losses through the cells.

I expect the volume-increasing effect would be the same for the same cell size and density, because it's a function of how much and how quickly heat can transfer from the air to the material.

That all said, foam is what I use because it's non-itching but more so because if you cut it slightly oversize it will stay put on its own.


Quote:
Originally Posted by kennyandersen View Post
Sigh... Over that? Sigh. In any case. I, personally, would recommend egg-create foam for a sub. I wouldn't use fiberglass anything. Fiberglass is obnoxious., And yes, closed cell foam is out. Your sub, do what you want.

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Originally Posted by Stereodude View Post
*sigh* No, it wouln't unless is was closed cell. Compressed fiberglass product that are used in on wall sound treatments are not "closed cell", but are quite rigid. Lots of the foam products I see people using in boxes are rigid to some degree in comparison to loose polyfill or loose fiberglass.

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post #12 of 17 Old 04-04-2019, 08:51 PM
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I use fiberglass in my sealed UM18's, but I would never use it in a ported application. I'm not sure how much of a big deal it would be, but I'm really not keen on fiberglass fibers blowing around my living room.

Since those UM18's I just use standard pillow stuffing. 10lbs for like $30 at Walmart, often on sale for significantly less.
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post #13 of 17 Old 04-05-2019, 11:03 AM
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When I was doing research for my ported martys, I found some information on measurements that were done.

With ported subs, there was no discernible difference between insulated vs non-insulated. Unless you have a box longer than 8' I believe, then you may get standing waves inside the chamber.

The person in the forum who did build a long box, found he could use a pillow half way down the inside to mitigate the wave.

I had already bought a cheap foam mattress topper for box wall liner when I was building mine, so I just put it in anyway.

Last edited by Shadowed; 04-05-2019 at 11:06 AM.
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post #14 of 17 Old 04-05-2019, 11:15 AM
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Originally Posted by [email protected] View Post
I have my speaker cabinet built and now need to use insulation or some form of damping material and the verdicts seem to be all over the place. Could somebody help me pick which is best for a ported titan 615? I see my stores carry in stock rockwool (multiple types including safe and sound) multiple types of fiberglass and I could order and wait for foam or denim insulation. This is for the woofer which plays 350hz down to about 30hz. Any input would be greatly appreciated.
Loose denim fill, or guy buy a could cheap pillows at walmart cut them open and use that.
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post #15 of 17 Old 04-05-2019, 11:53 AM
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Originally Posted by Shadowed View Post
When I was doing research for my ported martys, I found some information on measurements that were done.

With ported subs, there was no discernible difference between insulated vs non-insulated. Unless you have a box longer than 8' I believe, then you may get standing waves inside the chamber.

The person in the forum who did build a long box, found he could use a pillow half way down the inside to mitigate the wave.

I had already bought a cheap foam mattress topper for box wall liner when I was building mine, so I just put it in anyway.

For subwoofers there is the law of diminishing returns due to the frequency range in which they operate, so you are correct that it may not make much difference, if this was a subwoofer.


It is, however, the woofer in a Titan 615, which covers 30-350Hz. 350Hz half wavelength is about 19". There is definitely a need for insulation to combat standing waves.
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Last edited by drewp29; 04-05-2019 at 12:07 PM.
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post #16 of 17 Old 04-05-2019, 01:50 PM
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Originally Posted by drewp29 View Post
For subwoofers there is the law of diminishing returns due to the frequency range in which they operate, so you are correct that it may not make much difference, if this was a subwoofer.


It is, however, the woofer in a Titan 615, which covers 30-350Hz. 350Hz half wavelength is about 19". There is definitely a need for insulation to combat standing waves.
Ooops, yup, sorry, I thought this was a sub thread ...
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post #17 of 17 Old 04-05-2019, 02:01 PM
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Ooops, yup, sorry, I thought this was a sub thread ...

No worries! Since 9/10 posts in the DIY forum are subs, it's easy to confuse the ones that aren't!
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