# DIY SUBWOOFER



## rf5000

Hey All,

I'm in the process of building my own subwoofer and I wanted to get some input. I'm building a curved box design. The front and rear faces will be flat but the sides will be curved. The box will have roughly 4.0 cubic feet inside. I'm using a SDX15 that will be mounted on the front face. I originally bought (2) 15" passive radiators that I was going to mount on the sides. I knew that this would happen, but on a curved box those passive radiators mounted on the side becomes a bit of a problem. I would have to cut into the side of the box to make a falt surface to mount each PR and then make some sort of curved grill to cover it all. This was my plan all along but now it is looking a bit difficult and in the end it might not look right anyways.

So now, I am thinking of just using this box as a sealed enclosure and wanted to get some feedback on this. I will be using a Behringer EP1500 bridged, so about 1400 watts. Will I be sacrificing anything going with the sealed vs. ported with PRs? The sub will be used only for home theater. Will I be giving up some things but gaining other things? Will I get that deep low rumbling bass that is need for home theater that will shake the whole room?

I notice that most of the high end $$$$$$ subs are all sealed, but then they usually have more wattage then 1400. I don't know. Please help.

Thanks.


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## Mike P.

Going sealed you'll give up 3 - 4 db in the 20 - 50 hz range compared to using the PR's. With sealed you won't need a Hi-Pass filter, with PR's you would need one at about 16 hz.


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## rf5000

But do you think it will still be very loud and give me the deep "feel it in my chest" bass that I'm looking for? Also, I will be running a cable from subwoofer out to the EP1500 and then speaker wire to the sub. Will I need any sort of EQ? If so, what do you reccommend that would do the job that is low priced. What should I have the settings on the EQ set at? Thats if you think I need one.

I would ideally like this thing to produce frequencies and output levels of say a JL Fathom, Velodyne DD-15 or Paradigm SUB15. Am I setting my sights to high?


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## rf5000

CORRECTION : I meant to say I will be running a cable from the receiver out to the EP1500. Sorry


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## dougc

The 60-80hz range is the "hit you in the chest" range, and the 20-30 range is the jiggle your guts range. Port it with a large enclosure and your neighbors will feel it in their chest and it will also give you the low end that sealed doesn't get as well as ported.


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## rf5000

The enclosure is already made. It has roughly 4.0 cubic feet of space. So that is the largest box will be. Right now it just has the hole cut out to mount the 15 inch sub in the front. I have decided not to go with the PRs and had decided on going with a sealed design, but I guess I could make some port outlets in the rear. I'm confused now. With this size box, the sdx15 sub, 1400 watts of power, what would be a better choice? Sealed or port tubes?


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## Mike P.

This is the difference between sealed and ported in your cabinet size. The ported box is smaller because of the volume the ports will take up. Two 4" ports would need to be 45" long each plus you'll need a Hi-Pass filter at 15 hz.


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## rf5000

I like the output from the vented box better, but I still think I'm going to go with the sealed design. Just much easier to do and its pretty much already done.

I have a dilema though. Sometimes I wonder if these DIY subwoofers are really worth it. I have close to $750 into mine already and it isnt even done. I guess if I sell my two PRs for like 80 then I will have $670-$700 into it. A guy right now will sell me a barley used Earthquake Supernova V 15" for $700. That sub reach 117 DB at 20hz. By the looks of those graphs, mine wont even come close to that Earthquake. Plus, down the road the Earthquake sub will be worth something if I want to sell whereas I never will be able to get really anything for a homemade sub. These deals are out there all the time on Ebay and other sites. So it makes me wonder. What do you guys think?

All of that aside, I have already spent the money so I'm going to finish this sub. If I go with ther sealed design, am I still going to get decent performance or will it be about the same as a retail sub in that price range? Also, will I still need an EQ or filter?


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## Mike P.

> That sub reach 117 DB at 20hz.


It does 117 DB at 40 hz and 102 DB at 20 hz. Your sealed SDX15 will do 116 DB at 40 hz and 107.5 at 20 hz.

http://www.earthquakesound.com/supernova15.htm

Whether or not you'll need EQ and how much will depend on how the sub interacts with your room. REW will show you how your sub in performing and if it needs anything.


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## rf5000

Sorry, what is REW?


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## rf5000

Also, if it were you Mike, would you do the ported or sealed?


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## Mike P.

REW = Room EQ Wizard. There's a link to it at the top of the page.


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## rf5000

If I use this Mike, am I going to understand the results it gives me?


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## Mike P.

In 4 cu.ft. I'd stay with sealed. Depending on the size of the room the sub is in you could also get some room gain that will also boost the low end output.


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## rf5000

Sorry for all the dumb questions, but I assume I will need this program and some sort of microphone or something?


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## Mike P.

Everything you need to know about REW is here:

http://www.hometheatershack.com/forums/rew-forum/


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## rf5000

Thanks Mike, I will go sealed. I'm going to finish it in piano black so it should be a real nice sub when its done. I will send you some pics when I finish it. Thanks


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## rf5000

Got another question

So originally I was building this box with the intention of putting a 15" passive radiator on each side with the subwoofer mounted up front. By the way, I'm doing this box in glued stacked layers so I can get my curve. So from the start I made the box almost 2+ inches wide on the sides to account for mounting the PRs to a flat surface. Now, all that has changed in that I'm going yo use this same box and go sealed, but now the sides of the box are extremely thick. I could cut more out of the inside on each side that would give me added volume but its way to much work now and would probably look like . So here is my question:

With the sides being that thick, do I really need to do any internal bracing from side to side? Could I just do bracing from front to back and be fine? Or do I really need to do any bracing at all because a box made of glued stacked layers is ALOT stronger then a normal box build. And the bracing really wouldnt do much and just take up valuable interior volume? Or maybe I'm wrong. What do you think?


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## rf5000

Here is a quick drawing of what I mean by the thick sides


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## rf5000

Or if I do bracing I was thinking of maybe one of the following


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## 1Michael

I like the cross best. The diagonal braces do nothing, the corners are already a brace in themselves. 
It is the walls that need bracing.


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## rf5000

Maybe just one brace in the middle like this?


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## rf5000

Or maybe this sicne I really dont think those thick sides are doing to flex?


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## Mike P.

What are the box dimensions?


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## rf5000

All I know is the inside dimensions off hand. Interior Width is 17.25", Length is 21.25" and height is 20.75"


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## rf5000

The sides are at minimum 1" at the very corners and at the middle opf the sides probably 2.5" to 3" thick. The front where I'm mounting the sub is 2 " thick and the rear of the sub box is 1" thick.


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## rf5000

So the interior cubic space actualy comes in at about 4.4 cubic feet without adding the bracing, sub, and foam. So I was guessing around 4.0 cubic feet, maybe a bit less


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## Mike P.

A cross brace, like a +, side to side and top to bottom should be enough.


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## rf5000

So it would be a + brace in the middle touching the two thick sides and then the top and bottom plates in the middle. Nothing then touching the subwoofer wall (front) or the back wall (rear)?


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## Mike P.

I wouldn't think so, the front and back panels are fairly small and thick.


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## rf5000

Sorry to ask, but the side panels are almost 3 inches thick. You still think they need the bracing? Or are you saying that because they are longer? Maybe I'm looking into this too much. I will just do the bracing the way you suggested. That should be enough, right? One more thing, how thick should the bracing itself be? I'm using 3/4" board so will one layer be enough at 3/4" or should a double stack the bracing for 1.5" thick?


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## Mike P.

3/4 x 3" x the length you need should do.


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## rf5000

Thanks


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## rf5000

rf5000 said:


> Thanks


Mike, do u think if I used a bridged ep2500 instead of the ep1500, it would be too 
much power or would it be better in every way?


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## Mike P.

A Bridged EP1500 is lots.


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## rf5000

Mike P. said:


> A Bridged EP1500 is lots.


So would an ep2500 be too much for that sealed sdx15?


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## Mike P.

Not if you only use one channel. If you bridge it then yes, it'll be too much.


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## Theresa

REW=Room equalization wizard, a free program for acoustic testing, ie. room equalization. You would need to supply a mic though.


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