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Discussion Starter #1 (Edited)
I just finished a ported sub, 3cu. @ 21hz and lined the walls with 2in fiberglass. I am used to using poly-fill. Do I need to also place poly-fill (lightly) in the enclosure?

I have read in an older speaker design book that one can stretch a piece of carpet pad across the back of your driver and staple it to the backside of your front baffle to reduce any back EMF?

I am just trying to get this thing as perfect as possible, I've spent a lot of time so far so why not go the extra mile, probably doesn't help that I'm a perfectionist!

Thanks in advance for all feedback on this subject, I'm interested in everyones input.

P.S. I would like to post pictures of the build but unsure of where I should do that. I'm using a jl audio 13w1v2-4 driver and a pretty decent amp, thought maybe someone would like to see it. :help:
 

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You can post your photos on this forum here and then simply link your photo to this thread using the "insert image
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I just finished a ported sub, 3cu. @ 21hz and lined the walls with 2in fiberglass. I am used to using poly-fill. Do I need to also place poly-fill (lightly) in the enclosure?
No reason why.
I have read in an older speaker design book that one can stretch a piece of carpet pad across the back of your driver and staple it to the backside of your front baffle to reduce any back EMF?
Maybe but this is not needed for a sub driver.
 

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Fiberglass is shown to be ineffective in frequencies below 100hz in testing.

You should use 6 or 8lb rock wool to line the sub walls. For ported subs 2inch should be plenty we don't want to over dampen a ported sub. I've seen people have great success with simply put 4inch rock wool only on a brace.

http://forums.audioholics.com/forums/attachment.php?attachmentid=6883&d=1234388792

Is an example of a well executed sub box interior. The insulation is rock wool wrapped in cloth.
 

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Discussion Starter #6
Thanks for the all the input guys, I appreciate it! I'll get my pics up as soon as the stain/finish is done drying.
 

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Stuffing of various kinds can help in ported subs. As Michale Hurd discovered in one of his previous posts it can help smooth out frequency reponse quite a bit.

http://www.hometheatershack.com/forums/diy-subwoofers-sealed-ported/18349-tc-1000-sonosubs.html

I belive it probably also helps absorb harmonic distortions and other noise that would normally escape through the port. I have a pair of 4 cu ft subs that I have crossed over at 80hz using a 4th order filter and they had nothing in them at all. Just for the fun of it I bought a 10lb box of pillow stuffing at the local walmart and stuffed about 3-4lbs into each one and they seemed to go from being boom boxes to having a bit more natural tone. I would post measurements but at the moment I don't have anything to do so with but, unless you just want to listen to club music all day they sound alot better now. I modeled them in Unibox with and without the stuffing and it indicates that it smoothed a hump they had at 60hz and ever so slightly raised the output in the 25-40 hz range.
 

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Discussion Starter #8
I ended up putting about 1-1/2lbs of polyfill in the enclosure, and it seems to do just as the last poster said it did for him. It's more of a warm smooth sound, explosions sound thicker if that makes sense!
 

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I would be careful stuffing a ported sub with any sort of fiberglass product. Don't forget as the sub is working it will be pumping fiberglass particles all over the room... so small you won't be able to see but your lungs will know it.I would use pillow stuffing instead.
 

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Discussion Starter #11
I with ya on the fiberglass floating around. I lightly sprayed the entire inside of the cab, glass and all, with clear acrylic, it stiffened the loose fibers pretty well. However, I am still a little cautious and will be ordering some rock wool to line the cab instead, that is if I can find it!
 

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Fiberglass is routinely used by companies that make ported subs. The coefficient of absorption of fiberglass at frequency like any other damping material depends on the thickness used. This is but one reason why it's used by companies manufacturing bass traps.

Ported subs lined with fiberglass are not cannons shooting particles into the room. Where that the case it wouldn't be used by manufactures offering subs at retail since they'd be subject to law suit.

If you'd paranoid about this take a piece of grill cloth, put a single layer of it over the port end inside the enclosure.
 

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Manufactures install cloth grills on their subs... I am not sure if the practice of fiberglass installation in commercial subs is still going on. I think they line the insides of the subs with something less toxic nowadays.
 

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Discussion Starter #16
So far I haven't noticed any fiberglass coming from the ports. I did lightly spray the interior with clear acrylic sealer to help keep the fibers all stuck together, yet not too much to affect any thing volume wise (ie. I didn't make it stiff as a board) I took a piece of paper coated with wet sealer, played some 30hz tones and held it in front of the ports for about 30 seconds and saw no pieces of fiberglass stuck to it.

Furthermore, I will say however that when I added poly-fill (only about 1-1/2 lbs) it did change the overall tone of the sub. It made low freq's sound a lil' warmer/thicker, yet not muddy. Overall I'm super satisfied with the build....my fiance' on the other hand thinks it's nutso loud so I can only really let it hum when she's not home! :(
 

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