Dual SDX 7, Repurposed cabinet, used as computer subwoofer - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 4 Old 10-29-11, 09:26 PM Thread Starter
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Dual SDX 7, Repurposed cabinet, used as computer subwoofer

So i happen to have a couple of cabinets laying around from an old pair of yamaha NS series towers, They used to be my rear channels, but i never really built a proper crossover for them. I noticed my SDX 7 speakers pretty much drop into the slots where the previous woofers were.

Long story short, I decided that my little logitech subwoofer wasn't doing any justice to my computer music, I had a nice set of repurposed energy bookshelves replacing the logitech satellites that came with the system, but the standard 3" subwoofer that came with this tiny 2.1 system. This wouldn't do. So with these cabinets laying around i went to winisd to model what they would do with the two SDX 7 drivers.

I came up with an internal volume of 1.2 cubic feet, and then stuffed them heavily with some polyfill i had laying around. I guesstimate the effective volume to 1.35-1.4 cubes.

Using the existing port locations i went ahead and added longer ports, Worked out to be a 2.25" port, so i had to extend it to 5" from the original 3, replaced the port, and tuned the cabinet to ~36hz. Ran the wires straight from the outside of the cabinet to the woofers in parallel, for a 4 ohm load. The port speed is fairly high if i want to max out the woofers. but in reality the amp isnt very powerful so it won't ever be an issue.

unhooked my old speaker from the logitech amp, and ran a set of wires over to the new cabinet. So the old sub is basically an outboard amplifier box, Its nice that the crossover is built directly into the amp at about 125hz. The SDX's are perfectly linear up till after 800, so i figured it wouldn't be too much of an issue.
The amp puts out a modest 30w when clipping, but with two of the SDX 7 drivers, i can hit about 103db. Not a bad deal for a computer sub. The drivers dont exceed xmax with 30w with an 18hz high pass. So just in case, i have a high pass filter engaged via software at 18hz.

I left the old tweeter in the cabinet to keep it sealed. Figured it could do no harm, as its not leaking.

This wasn't the original purpose for the SDX drivers, and i happen to have two more, and another spare cabinet, i'm thinking i could wire the drivers into series and use the "subwoofers" in a stereo pair with the bookshelves on top to help with imaging.

Does anyone think im crazy for wanting to use a second one? or for using the first one?

Last edited by Binary; 10-29-11 at 09:41 PM. Reason: Added picture
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post #2 of 4 Old 10-29-11, 11:51 PM Thread Starter
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Re: Dual SDX 7, Repurposed cabinet, used as computer subwoofer

So, i did it anyways. Remembered that the little amp isn't made for 4 ohm, its an 8 ohm stable amp, and i noticed it getting quite warm, and a small amount of distortion. Grabbed my other tower. Slapped the other SDX's i have in it. Stuffed it, fixed the port length. and now im running two of em to get 8 ohm

I moved the speakers out to on top of the towers as it gets the tweeters closer to ear heights, and it stops the localization of the upper bass, (100-150hz). Put the grills on too. looks better that way.

I'm very happy with a quad of SDX 7's, its clean, and very much more bass that i need in an apartment bedroom. I had to turn the subwoofer section on the amp down, but it has a built in volume control for the sub anyways, so that was easy to do for matching purposes. I'm tempted to seal the boxes and try to EQ for lower freqs, but in all honesty, an f3 of ~33hz isn't bad for a music only system.

Another picture you say? Okay!

Before anyone decides to point it out, Yes, my computer is in my closet. As you can see, most of my clothes don't go in there, so its a great way to save space.
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post #3 of 4 Old 10-31-11, 08:25 AM
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Re: Dual SDX 7, Repurposed cabinet, used as computer subwoofer

Looks like a great computer system, and I'm sure the bass you're getting out of those 4 SDX woofers is plenty. Seeing projects like this kind of makes me want to design a nice little 5.1 system for me computer.

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post #4 of 4 Old 10-31-11, 08:48 AM Thread Starter
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Re: Dual SDX 7, Repurposed cabinet, used as computer subwoofer

The SDX Drivers are exceptional. Period. Worth every penny. In comparison, They are just as clean as the bass from a set of RBR's, with a pair of $300 Revelator drivers. The single cabinet was easily on par with the pair of RBR's for bass output, the tweeter in the RBR's is definitely nicer than my energy bookshelves. Using 4x SDX drivers is more bass than my apartment should be subjected to. (i don't want to get evicted, but these beg to get turned up over and over again)

Link to the RBR - http://www.clearwaveloudspeaker.com/RBR/infoRBR.html

I don't think i would ever do 5.1 for a computer system again. Rear speakers are hell to mount, center channels get in the way on the desk, and quite frankly, its not much better for gaming or movies. 2.1 is the way to go for a computer system, IMO.
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cabinet , computer , dual , repurposed , sdx , subwoofer

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