Damping Materials

[Lindahl]

I'm building a sealed ~3.5 cuft TC-3000 subwoofer (well two.. and some speakers ). Will I need to line the subwoofer boxes with any damping materials? I've heard they're mainly for ported systems, and I should just use a little polyfill and EQ to adjust to my Q tastes?

[ThomasW]

Sealed subs are stuffed. The rate is .05-1.5 lbs/cu ft.

Fiberglass is the best choice for this task, but you can use polyfill

Establish the initial amount you want to use then fine tune it.

Use a CD/DVD you're familiar with that has well recorded bass. Play a section of the disc and listen for any nuances or cues that will be helpful. Real musical instrument transients (not synthesized) are the most revealing. So things like the attack of a kick drum, pluck of a bass guitar string, etc., note are good indicators.

Next you're going to add damping material and replay your reference cut. (those with smaller boxes add 4oz, if the box is large add 8 oz.) If the additional material results in tighter bass with better definition and detail, you're on the right track. Continue this process (adding and listening), until the last amount added has no impact other than to lower the overall output level. At this point remove the last amount of damping added and you're done.

[Lindahl]

Next you're going to add damping material and replay your reference cut.

That's the problem, I'm not sure if I can reach some of the volume after the box is built.

The box is braced with a central brace, running the height and width of the box. There are two horizontal braces behind that (in the back of the sub), running the width and depth of the box.

Here's a diagram:

+--------------+
X      |   2   |
XX     +-------+
XXX 1  |   3   |
XX     +-------+
X      |   4   |
+------+-------+

The X's are the driver. I've numbered all the volumes that are seperated by braces (but are open to one another through cutouts). I'll have no problem lining volume 1, after the box is built. But volumes 2, 3 and 4 will be difficult to reach and I'm not sure how much of it I can line. Do I want to line them now while the box is open? Or should I just not worry about it?

Great instructions, by the way. Thanks.

[ThomasW]

Line the inaccessable areas before closing up the box. Add more if needed by pushing it in with a stick