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Old 30th March 2009, 01:52 PM   #1
Dan2 is offline Dan2  South Africa
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Default filling a sub enclosure

i have a sealed sub enclosure with a slanted back, in a sedan. i got hold of some foam which i stuck inside the box. the foam covers most of the top, bottom and the entire back of the box. the sides though are not covered. the sub seems to sound the same than when the box was empty. do you think covering the sides would make a diffence??
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Old 30th March 2009, 02:00 PM   #2
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From my experience, it will make very little difference in a sub enclosure.

It's commonly used in home speakers where the low frequency woofer/driver sees signals up into the mid-range frequencies. It helps absorb/kill standing waves and can make a huge difference in sound quality (particularly in ported enclosures).
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Old 29th April 2009, 03:03 PM   #3
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When ever I build an enclosure for a competition sound system I always lay down at least two coats of paint inside the enclosure. Sometimes I lay down three or four. It depends on the size, shape, type of subwoofer being used, if there is internal bracing. These are just a few of the factors I take into account. But two coats of paint should do just fine in almost any application.
The paint I use is designed for protecting garage floors. Its very durable, easy to apply, and effective in absorbing negetive waves produced by the positive stroke of the subwoofer. The paint has a flexable rubber or laytex based ingredient that prevents it from cracking, peeling, or chiping.
This is not a common method used by professional audio shops. However, I can reasure you that it does produce positive results. One thing you should know before applying the paint is that the surface of the MDF has to be free of all dirt and any foreign matter. Sealing the enclosure with a silicone caulk (which I recommended doing) should be done after the final coat of paint has fully dried.
As for the foam you put into the enclosure, I would take it out and try a medium density cotton fill. The cotton will be alot less dense than the foam. Which will produce a tighter and more accurate bass responce than the foam filler will. Also you said the back panel was at a slant or angle, which sounds like a pre-fab design. If the box is a pre-fab that could be your problem right there.
Thats all I can tell you without knowing the specific details of your setup. If you need more assistance with this project post the details. Such as... Enclosure air space, subwoofer make and model, number of subwoofers in the enclosure(if more than one, is there a divider present?) , subwoofer size, enclosure construction material and thickness, and if internal bracing is present.
I hope the information I provided can assist you in reaching the level of performance that you desire from your sound system.
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Old 30th April 2009, 01:46 AM   #4
jol50 is offline jol50  United States
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In a nutshell, with a sub mostly what what changes it is the loose fill like the cotton or I always use poly batting. You need to nearly fill the box (don't compress it) to hear a difference and it equates to making the box maybe 20% larger...there are different answers for that. Anyway, it can make it play a little deeper and take some of the higher bass out, sort of like if it were 20% larger. Sometimes I only fill it half to 2/3 full if that does enough, and I always leave the sub VC vents open.

That works because it slows the air down inside the box as the sound waves travel through the batting, in effect tuning it lower. You can find plenty of complex explanations on the web. If you pack it in tight or use (lots of) foam the air can't travel through it, and you effectively make the box smaller and tune it higher, boom-boom is what you get not thump-thump.

When you put something on the walls of the box it tends to take out reflections of higher frequencies or dampen the box walls. Of course you should not have any of those in a sub box unless the box itself is vibrating, and that is bad (or the sub is making odd noises like tinsel slap). That should be fixed mechanically first with braces or thicker walls/etc. If you have a good box it will make little difference as the MDF will dampen it enough. For full range home speakers like Perry says, it can make a huge difference in midrange areas because they like to reflect a lot and will come back out through the cone.

I use ply for most of my sub boxes and baffles, some boxes I use MDF or layer with MDF over ply. Even ply I have little problems with any resonance/etc. It is easier to work with and mount to IMO when I can get away with it, and lighter. Some boxes/power levels you will need MDF, it is the safe way to go, I just don't like the stuff for most of my projects. It is more dense and less prone to vibrate, let sounds through, etc.
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Old 30th April 2009, 02:10 PM   #5
Dan2 is offline Dan2  South Africa
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Quote:
Originally posted by team_innovative
Also you said the back panel was at a slant or angle, which sounds like a pre-fab design. If the box is a pre-fab that could be your problem right there.
i made my own copy of a pre-fab box that my friend had - i figured it would b a good place to start, and it fits quite nice in the trunk
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Old 30th April 2009, 03:22 PM   #6
jol50 is offline jol50  United States
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Often the issue with pre-fab is thin panels that vibrate, inadequate bracing or attachment at the seems. The box needs to be solid everywhere and sealed.
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Old 30th April 2009, 11:31 PM   #7
pong is offline pong  Philippines
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what type of material do you use for dampening?
i don't use ordinary foams for sub woofers enclosure rather i use carbon fiber fill (used inside mufflers to fill it). its much more effective i guess.
you put too much of it and it will be like poof.just use right amount.very effective on sealed enclosures to reduce excess excursions to the sub.

Caution: carbon fiber fill is a carcinogenic material. be very good in handling it!have a mask and gloves
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Old 1st May 2009, 01:47 AM   #8
jol50 is offline jol50  United States
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I use walmart $2 a bag poly, about the size of a pillow and feels near the same. I mess with enough chemicals and such, don't need to add to it. I don't like fiberglass either, not just for itching but don't like the idea of it getting into the sub either. Poly tends to stay together and seems to work well enough.

lol, seal the seams of the box not seems.
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Old 9th May 2009, 07:44 AM   #9
dangus is offline dangus  Canada
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I usually just buy a pillow at Walmart, preferably one that uses some name-brand fill like Qualofil that has hollow fibers. Then I use the shell of the pillow as a pillowcase.

If you apply some coating to the inside, consider that some things like asphalt may give off fumes that will eat woofer surrounds.
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