Help building cheap sub

[World Leader Pretend 0]

Hey, my friend recently inherited two 12" Sony Xplod subs for free, and we want to design a subwoofer for his dorm using these. He needs the line-level inputs on his amp so he can hook up via speaker wire (no LFE channel), and it needs to be fairly reasonably sized.

I am thinking about this amp: Parts Express 70 watt plate amp

Sound quality? obviously not key, but it would be nice to have smooth and fairly deep bass.

I have lots of tools and saws, and some left over OSB to laminate to MDF if that works...

I was thinking ported, but sealed may be easier to build.

Here is the front view of what I was thinking in ghetto type:

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-+++---+++--

---------++++- <-drivers

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[...................] <-port

Something like that with a big built-in port in the front that goes almost to the back, but is open into the large main space. A lot like that Axiom EP500 subwoofer.

Or,

We could go one front firing and one down firing in a sealed box...

Please help!

[topgun 262]

I sold my Behringer EP2500 to a guy in the dorms for a pair of Xplods... Made me laugh, but hey, he is happy with it.

Theres not much room to work with in the dorms especially the KSU ones. I've had the best luck with my sealed 10" one firing into the back corner up against the wall. Using it as a coffee table dosen't work worth a damn (downward firing), under the desk dosen't work (downward firing), but into the corner works alright. This is considering its only getting like 80 watts to it...

I'd say do a sealed box and try to fire into the corner, it dosen't take much to get loud in the dorms and have people complaining. I got complaints with my last setup 2 floors away and I didn't even have a sub with that rig.

*edit* What dorm is he in, and does he have a false ceiling. If he does we should get him to but a bunch of PA woofers and do an IB intall... :D

[World Leader Pretend 0]

He is in Marlatt hall, with the cinder blocks and all. They have a solid ceiling so no IB

Right now we have his room absolutely full of stuff, for instance he sleep on a futon that is stacked about 3 feet high on those dumb drawers they make you keep in your room. I'm sure that we could find a place for a sub though

Should we use both drivers or would it be better to use one and sell the other? I'm not sure that we would need two if we are going the sealed route.

BTW I am building an IB woofer in my loft (attic), using two 18" Mach 5s and a Crest amp. Hopefully it performs well, but not well enough to get me kicked out!

Edited March 23, 2007 by World Leader Pretend

[Aaron Clinton 2,372]

I believe Mach4 is selling plate amps also.

[World Leader Pretend 0]

Yeah, we are trying to keep the amp under 50 dollars.

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[topgun 262]

Yeah, we are trying to keep the amp under 50 dollars.

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Cheapass....

If you want to hear what a 10" sealed woofer and under 100 watts sounds like in a dorm, shoot me a PM sometime next week and you can come over and hear it.

[World Leader Pretend 0]

Yeah, we are trying to keep the amp under 50 dollars.

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Cheapass....

If you want to hear what a 10" sealed woofer and under 100 watts sounds like in a dorm, shoot me a PM sometime next week and you can come over and hear it.

Hey, I'm not the one who is setting these limits here! I would spend more, but whatever.

As for listening, I might have to stop by sometime, but I'm going to be busy for the next few weeks...

____

Tonight I am going to take a look at the drivers and hopefully find a model number, then design a box. I'll probably suggest a sealed enclosure since I don't want to mess with ports and tuning.

[World Leader Pretend 0]

Alright, we tore the woofers out of the fiberglass enclosure tonight and they turned out to be 10" 4 ohm drivers. That kinda ruled out a two driver set-up.

I'm still thinking about going with the amp in my original post since it has line-level inputs and outputs. This is essential since his system uses speaker wire and has no pre-outs.

The box we decided should be a 16x16x16 inch sealed cube, with either a down-firing woofer or a front-firing one. The cone looks pretty gaudy and we aren't sure which config will work the best.

My friend wants to somehow test the drivers before buying an amp, so is there any way that we can use a standard receiver to do this? I have a 55watt by 7 channel harman kardon receiver, so could we just hook up the driver and see if it does anything?

[topgun 262]

Alright, we tore the woofers out of the fiberglass enclosure tonight and they turned out to be 10" 4 ohm drivers. That kinda ruled out a two driver set-up.

I'm still thinking about going with the amp in my original post since it has line-level inputs and outputs. This is essential since his system uses speaker wire and has no pre-outs.

The box we decided should be a 16x16x16 inch sealed cube, with either a down-firing woofer or a front-firing one. The cone looks pretty gaudy and we aren't sure which config will work the best.

My friend wants to somehow test the drivers before buying an amp, so is there any way that we can use a standard receiver to do this? I have a 55watt by 7 channel harman kardon receiver, so could we just hook up the driver and see if it does anything?

I've got a 1kw and a 3kw rack amp in the dorm, how much testing do you want?

[World Leader Pretend 0]

Thanks, we just ended up using my harman kardon to make sure that the woofers still worked. Both seemed fine.

Ok, here is what has gone down so far. We have built a beast! A 24"x24"x24" box is cut out, now we have to brace it and fill it. We are going with both woofers, one on each side. The box will be sealed, and we will utilize a 70 watt plate amps to power each driver, so 2 amps total. This will allow us to run a separate channel of audio to each driver.

Obviously, this thing has a huge footprint, but we think that it can work as a TV stand or table. I must stress, this thing is huge!! Also, how should we go about bracing this? I have some 2x4s and some 2x2s, and some leftover MDF...

We are going to cheap out as well and use generic insulation I had laying around as the stuffing.

I do need a circle jig to cut holes for the woofers, does anyone know if Sears would have them?

[topgun 262]

Just make one out of a piece of plywood, its what I did.

If your going to have "stereo" bass you are going to need to sepearate the chambers for each sub. I also would not put a TV on a woofer box, I think the vibration would kill the TV over time (prob wouldn't take that long either ona cheap TV.

One more question... Why on earth did you make an 8cube sealed box?

For bracing if you put 2x4's across the center of the panels to make them 2.25" thick total (or 4.25" depending on what way you lay the 2x4) that should help out with any panel flex, although I doubt you will have a problem with that.

[gmilitano 0]

I am thinking about this amp: Parts Express 70 watt plate amp

We could go one front firing and one down firing in a sealed box...

Hi, I used that same plate amp for my MAW-10 DIY Subwoofer Project.

It will do the trick.

If you do go with two woofers, I would suggest you go push-pull with them, not at 90 degrees as you mentioned.

Edited March 25, 2007 by gmilitano

[World Leader Pretend 0]

Just make one out of a piece of plywood, its what I did.

If your going to have "stereo" bass you are going to need to sepearate the chambers for each sub. I also would not put a TV on a woofer box, I think the vibration would kill the TV over time (prob wouldn't take that long either ona cheap TV.

One more question... Why on earth did you make an 8cube sealed box?

For bracing if you put 2x4's across the center of the panels to make them 2.25" thick total (or 4.25" depending on what way you lay the 2x4) that should help out with any panel flex, although I doubt you will have a problem with that.

Alright, basically we just had a 4x8 sheet of MDF, then we cut it in 2x2 squares. Officially nothing has been glued yet so we might be able to modify it a bit if we feel that it too big.

Is an 8 cubic foot box going to be good? Or should we chop it back to 20" per side?

I am thinking about this amp: Parts Express 70 watt plate amp

We could go one front firing and one down firing in a sealed box...

Hi, I used that same plate amp for my MAW-10 DIY Subwoofer Project.

It will do the trick.

If you do go with two woofers, I would suggest you go push-pull with them, not at 90 degrees as you mentioned.

Cool, can you wire two 4 ohm woofers up to one of these amps? We were planning on buying two of these, one for each driver since we would create a 2ohm load on the amp with only one.

Also, we have since modified our plans and have push-pull woofer action going on in our current plans.

[gmilitano 0]

The amp probably will not like 2 ohms. Go for 4 ohms or 8 ohms total.

[juddspaintballs 0]

a 24" cube box is more like 6.5 cubic feet cuz the MDF takes up space

i also would not suggest setting a TV on the box...the magnets can mess with the TV's color. That's why they make shielded woofers that you can use near TV's.

[CustomAudioTechnology 0]

www.apexjr.com has som insane cheap plate amps, go and look around on there

They have all kinds of electronic/audio stuff for pretty cheap.

CT