Ported Subwoofer Build Projects

**bdrrusty** · **09-04-09, 08:06 PM**

First of all I'd like to thank Mike and all the other posters here for the help I've received. There's alot of good info here. I've spent more time researching than actually building.

Dimensions
21"x21"x42"
7.9 cuft usable internal volume
6" port 24.75" long

Hopefully this weekend I'll get a start on finishing the exterior. I can't wait to get it finished.

**ironglen** · **09-04-09, 08:39 PM**

Nice box- I like the bracing and port job. Keep us posted

**Mike P.** · **09-04-09, 09:15 PM**

Looking good!

**bdrrusty** · **09-05-09, 08:58 PM**

Edges routered and had to bondo a few inperfections at the corners. Ready for primer!

**annunaki** · **09-08-09, 07:39 AM**

Quote:

bdrrusty wrote:

Edges routered and had to bondo a few inperfections at the corners. Ready for primer!

This looks really nice so far. Great work. I would suggest playing with your internal damping material though. Vented enclosures should not usually exceed 50% damping of internal surfaces. Too much damping will lower overall output. I would start with 25% coverage of internal surfaces and then experiment from there. Be sure to take measurements with each of the fill/damping coverage amounts.

**Mike P.** · **09-08-09, 02:09 PM**

Quote:

annunaki wrote:

This looks really nice so far. Great work. I would suggest playing with your internal damping material though. Vented enclosures should not usually exceed 50% damping of internal surfaces. Too much damping will lower overall output. I would start with 25% coverage of internal surfaces and then experiment from there. Be sure to take measurements with each of the fill/damping coverage amounts.

As mentioned in another thread, I compared lined to unlined by ear and there wasn't much difference. Do you have any measurements to show "lower overall output"?

**bdrrusty** · **09-08-09, 06:16 PM**

Finished! Put on the last coat of paint Sunday and lugged it into the house yesterday. I haven't had a chance to really test drive it with any movies yet. Got it connected to my Denon 2310CI and ran through the Audessey setup. Played a couple scenes from Underworld: Rise of the Lycans. I now know where all the loose wall hangings are.

Overall, I'm very pleased with the finish of the cabinet.

**Mike P.** · **09-08-09, 09:16 PM**

The finish looks great! What kind of paint did you use?

**annunaki** · **09-08-09, 11:06 PM**

It turned out really nice! Great work!

**annunaki** · **09-09-09, 12:47 AM**

Quote:

Mike P. wrote:

As mentioned in another thread, I compared lined to unlined by ear and there wasn't much difference. Do you have any measurements to show "lower overall output"?

Nearly all of the vented designs showcased on the site tend to be Larger Low Tuned designs with Chebyshev type alignments. These are "over-damped" enclosures by design typically yielding system 'Q's in the neighborhood of .57 QTC or so with out the requirement of damping enclosure mterial. By completely lining the vented enclosure with absorptive damping material, one is choking off some of the air movement to a degree that the enclosure is designed to take advantage of.

Now, I am not against using well placed damping or reflection absorption materials (8lb ft^3 density mineral wool/rockwool), but lining an entire vented enclosure with it is simply not necessary and begins to be counter productive (increasing impedance peak frequency, further reduction of system 'Q', along with slightly lowering output).

As for specific measurements, output differences will be smallish sometimes more sometimes less. It will be dependent upon the frequency and the system 'Q' in which the driver is aligned with. I have not had a chance to measure this specifically but I will see what I can dig up for you.

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