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DIY Subwoofer: Would like some feedback!

10984 Views 30 Replies 12 Participants Last post by  hddummy
Hey guys. I've been around here before, but I've never really been an active member. I recently built myself a sub and I wanted to get some feedback from you folks. This project is done, but I could apply suggestions and advice to the next DIY I am planning to build for my brother-in-law.

Anyway...I love the way this thing turned out...it has a tremendous amount of bass and it makes me grin ear to ear every time I crank it up.

The stats:
TC 12db-500
115 Liter enclosure
Two 3" x 17" ports
Tuned 21.8 Hz
Walls lined with fiberglass batting
Butt Kicker Amp with 25Hz HP

One of my concerns was whether or not I should have used more internal bracing. Questions/Comments? Thanks for checking it out!!

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Thanks for the good woods guys!!! I appreciate you advice. I was thinking one more frame brace similar to the one at the bottom of the ports would have been helpful. I ran out of MDF and I thought...aaahhh go for it.

Germain: That is Rustoleum Flat Black Latex Paint. I didn't bother getting fancy since it is hidden from view anyway. I just wanted something to protect the MDF from humidity and such. As for sounding great....I like it, though you can see what I upgraded from in the first picture. Anything would sound good by comparison. I bought the db-500 because I thought it was a great value. I just bought TC's last one in stock because I now know it is a great value. I'll keep that one tucked away for a year or so until I start building a dedicated theater room.

WillyD: A few weeks ago, I posted pics over at AVSForum. You probably saw it there.

Others...thanks for the replies.
I was thinking dual LLTs actually. My initial calculations show very promising response curves and that ButtKicker amp can definately handle both drivers at once. Though, that is another project for another day. I'll be sure to post all about it when the time comes.
Sorry...can't respond right now.....I'll be busy for a week or so. I just didn't want to leave everyone hanging. I'll get back to you when I can.
Ok...I'm back....let's see what we've got.

Enclosure is made from 3/4 MDF. I cranked it up the other day and put my hand on the outside to feel for vibration. I didn't feel too much vibration compared to the rattling in my head from being that close, so I guess I'd say it is built well enough.

Black levels on the plasma look awful because the camera flash reflected off of the screen and those pics are artificially brightened so you can see all the goods. It is actually calibrated quite well using both Avia and DVE.

When I designed this enclosure, I was looking for the volume that would give me the flatest anechoic response. I don't think I get much room gain since my living room is part of a large open floor plan common to the dining room, kitchen, foyer and stairs. I also didn't want a super large enlcosure because that would increase my risk of pushing the driver past it's excusion limits with the amount of power my amp has. Although I could have made it as much as 1.5 cuft larger because I wasn't limited by height, I am please with the final result.

Thanks for comments on the TV stand...That was another of my projects. I didn't trust the base that comes with the TV and there are no wall mounting options when the TV is in a corner. I also like it because you can't easily see the stand from the front, so it looks like the screen is just floating there. Not to mention it would take at least 30 min for a thief with the right tools to try and make off with my plasma because that sucker is bolted down.

Base coupling to the walls....uhm..yeah. the windows to the right rattle like you wouldn't believe if I crank it up high enough....which is almost any movie that I watch when no body else is home.

No worries about discussing other projects here. That's the idea..to help everyone accomplish their subwoofer dreams.
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Sure. The stand is build mostly out of 3/4 plywood. The lower half is painted black to blend in with the frontside rack and the upper half is paintd the same color as the walls. I don't have any additional pictures right now, but I sketched this up really quick to give you a cartoony idea of the overall shape.

Again, the idea was to have a really solid stand for the screen that holds in from behind rather than relying on the stand that comes with the screen. I have two very rambunctious dogs, and i was just not liking that stock stand. I'll see if I can take some more detailed pics soon.

The sreen is attached to the two aluminum angles you can see in the picture in my first post. Those hang on a steel rod (painted black), which is attached to two aluminum arms. The whole thing has a threaded rod and some bushings to hold it all together. There are also some threaded adjustment rods to adjust the angle of the screen. you can see the threaded end of those sticking up through that flat board.

The whole thing turned out really solid. I tested it out by doing pull-ups on the black steel bar before trying it out with the plasma screen.
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I had some time and decided to measure the response curve for my sub and mains. I'm using a 100Hz crossover frequency. The yellow curve is the predicted response for my sub and shifted up to best fit the SPL level I was testing at.

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I can measure all three together. I tried REW, but the sound card on my laptop is so horrible that I can't get any output of frequencies lower than about 60Hz...even with the calibration set to cancel out sound card response.

I use a frequency generator that outputs uncompressed wave files an whatever frequency I choose. I made 50 files between 10 and 200 Hz and burned them to a CD. I just record readings manually with my RS SPL meter and input them into EXCEL. I realize that this takes about 100 times longer than the sweep method with REW, but I just don't have the hardware to do it. I really should go out and buy myself a sound blaster Audigy USB sound card, but oh well.....shrug:huh:
I got my new sound card for christmas and I finally had some time to do some sweeps. Readings are in order from top to bottom on the list:
Sub only, semi near field.
Sub only, seating position
Mains only, seating position
Sub+Mains, seating Position

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