Convert old chest into subwoofer? (1 Viewer)

[Terry Wysocki]

I have a Denon 4802 amp with Sonance speaker system but no subwoofer. I have an old wooden chest 38"x16"x16" that I want to place under my projection screen and think I could use this as a subwoofer cabinet. It's 3/4" oak construction and is very solid. I'm thinking about putting one or two 12" speakers in it firing toward the rear, a few inches from the wall. Any suggestions on how to port this (if at all) or what speakers to get for it? Or is this a really stupid idea?

 

[Dave Poehlman]

Actually, a 12" Shiva would fit nicely in that box with a 3" diameter port at about 6.66" long. You'd wind up with a box tuned to about 22 Hz. (I figured the box is about 126 liters internally)

The fact that it's a chest means you would need to make sure it's airtight and free of rattles.

You may need to look into "deadening" the box a bit since it's only 3/4" wood. Some cross bracing might be in order (but that would change your box volume, remember) and possibly some sort of treatment to the inside walls. I've seen some people put a layer of oil based modelling clay on the inside walls (sometimes with lead shot mixed in... that seems a little much to me.. not to mention hazardous). Also, I've heard that spray on sound proofing stuff from auto part stores... or spray on truck bed liner material (although I've been told it's pretty smelly stuff).

So, if you are really attached to the chest, it sounds like with a little treatment you could make a decent box out of it.

Good luck.

 

[David-S]

Just a thought... If you don't want the chest back, at the end: use fiberglass to reinforce it. I don't know how solid it is, but you could lay a couple of layers of fiberglass over the insides, to reinforce it, and make sure it's airtight (you could probably do the seam through the sub hole or something)... that would kill some vibrations, make it airtight, and not take up too much volume either...

 

[Terry Wysocki]

Thanks Dave(s) for both the suggestions. I was thinking of sealing the box with wood strips glued/screwed to the lid and box from the inside once I cut the hole for the speaker. The box inside is very rough and probably quiet acoustically already but I was thinking of lining it with carpet (is the deadness necessary at those low frequencies?). Maybe a few 1"x1" oak braces wouldn't take out much volume of the box? I'm impressed with however you calculate the port size but does it matter where it's placed? I picture putting the speaker on the right third of the back panel and the port about a third in from the left. Is this placement thing critical? How is this better than just sealing the box airtight? Last question: where's a good place to get the 12" Shiva and will it handle the power? Whew!

Thanx!

 

[Dave Poehlman]

Last question: where's a good place to get the 12" Shiva and will it handle the power?

The SHIVA is available from Adire Audio and it probably wont break a sweat with 250 Watts. I'm a little biased because I love my Shiva sub, I'm sure other members could recommend other drivers.
One question... how are you powering your sub?