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Discussion Starter · #1 ·
I need to upgrade my Infinity PS-12 and want to do a DIY build to fit behind my sectional couch with the added benefit that no one will see it. Can someone help me with the design? Is there something wrong with triangular designs other than difficulty of construction? Why aren't more subs triangular since best placement is often in a corner? It will be placed left/rear, and I'll still be using the PS-12 front/right.


To get the most volume, it will need to be triangular. I have enough room for 30.5" sides which would make it about 42" across the front, and 35" tall. That should make it a little more than 1ft³ bigger than the marty cube. If it matters, I have a cathedral ceiling that's 14.9ft tall in the middle and slopes down to 8ft where the sub will be placed. I would like to get at least 100db at 15hz. I plan to buy the iNuke 3000 to power it.
Thanks.
 

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What drivers do you plan on using? I cant see the Inuke 3000 being enough. But there is nothing wrong with a triangular design. I think the biggest reason there aren't more is the reason you stated, difficulty of construction. Lots of people order flatpacks or go to home depot and build a marty design.
 

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Discussion Starter · #5 ·
What drivers do you plan on using? I cant see the Inuke 3000 being enough.
I think I've seen a graph with the Martysub hitting 111db at 15hz using the iNuke 3000. I would think the Martycube could do 100db at 15hz with room gain. Maybe? I hope to get performance similar to the Martycube since it would be about the same volume.
My triangle sub:


Construction wasn't too difficult. The 45 degree edges cut easier than I had anticipated.
That's exactly what I want to build, except shorter and fatter. I think I should go with the SI18 too. My floor plan is pretty open too, except there's only an open doorway leading to the kitchen, and the hall is more to the left.
I would say the other negative against it is you have a large footprint for a much smaller cabinet volume then if you built a square box. Of course if it is built into a corner that could work well.
In this case, the Martycube is too big to fit behind the sectional, so I will actually get around 1.1ft³ more volume with the triangular sub and it will actually fit.
 

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I need to upgrade my Infinity PS-12 and want to do a DIY build to fit behind my sectional couch with the added benefit that no one will see it.
Good idea.

Can someone help me with the design?
Put Marty figures into a simulator. Adjust port length for slightly larger box. Start sketching to see how it all fits together. At first guess, I'd place the driver on the angled panel behind the seat, facing it (make sure the is enough clearance at Xmax/Xmech so the cone won't hit anything). Put the port running along the bottom, up the side and even folded back over to make a J shape if you need the length.
I've never done a Marty, but all ported boxes are worked out the same way, just different numbers. If you can't use a simulator yet, someone here will have all the models and do it and/or show you. In the meantime, just rough up some sketches based upon your dimensions and the Marty port to at least get an idea that fits from there. Post them and others will critique and assist from there. Doesn't need to be to scale or more than 'back of a napkin ideas at this stage.

Is there something wrong with triangular designs other than difficulty of construction?
No. My 'in the design stage' large bedroom speakers are a wide design like the SF Stradivari with a three driver triangular x-section sub to more efficiently use the space behind them.

Why aren't more subs triangular since best placement is often in a corner?
My guess is aesthetics and rectangular cuboid is most space efficient and subs tend to be largish boxes.


To get the most volume, it will need to be triangular. I have enough room for 30.5" sides which would make it about 42" across the front, and 35" tall. That should make it a little more than 1ft³ bigger than the marty cube. If it matters, I have a cathedral ceiling that's 14.9ft tall in the middle and slopes down to 8ft where the sub will be placed. I would like to get at least 100db at 15hz.
Run the sims and see how that works out. Close to the couch is good and nearfield placement helps with SPL and tactile feel. I'm rebuilding my 4 subs to be two end tables, an ottoman (with futon pillow) and a box for behind the seat so they'll all be nearfield.
Cathedral ceiling will help in spreading the height modes in the room.
 

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I think I've seen a graph with the Martysub hitting 111db at 15hz using the iNuke 3000. I would think the Martycube could do 100db at 15hz with room gain. Maybe? I hope to get performance similar to the Martycube since it would be about the same volume
Ported subs are not my area of expertise, but I don't think it is as simple as building a box the same ft3 as a marty then throwing 3 drivers in it and calling it good. How do you plan on porting that box?
 

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Ported subs are not my area of expertise, but I don't think it is as simple as building a box the same ft3 as a marty then throwing 3 drivers in it and calling it good.
Where did he say his intention was to use 3 drivers?
 

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Discussion Starter · #13 · (Edited)
My mistake. When I read triangular I assumed it would be like the Paradigm Sub1 or Klipsch RT 12.
If I were going with multiple drivers it would probably be the Infinity 1260w to keep the cost down. It looks like I would be able to fit 4 across the front.
Good idea.

If you can't use a simulator yet, someone here will have all the models and do it and/or show you. In the meantime, just rough up some sketches based upon your dimensions and the Marty port to at least get an idea that fits from there. Post them and others will critique and assist from there. Doesn't need to be to scale or more than 'back of a napkin ideas at this stage.
I'm new to DIY speakers, so I don't know how to use simulators. That's why I need help with the design. I wouldn't know how the slot port should be done in the triangular enclosure. Is this simple sketch enough? That's the max dimensions I have to work with. It would be a little less than 9.1709ft³ depending on the thickness of the wood, not counting any port volume.


The iNuke 3000 and EPX2800 are the same price. Is one better than the other? The specs look very similar.
 

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I'm new to DIY speakers, so I don't know how to use simulators. That's why I need help with the design. I wouldn't know how the slot port should be done in the triangular enclosure. Is this simple sketch enough? That's the max dimensions I have to work with. It would be a little less than 9.1709ft³ depending on the thickness of the wood, not counting any port volume.
In the OP you said about 1cf more than the Marty, which would make it 12cf net. I calc'd 9.42cf external from which you'd need to subtract wall thicknesses, bracing, driver volume and port volume making it smaller. I can't work out a way to insert a slot port and make it work, at least to my standards. I can with 5 4" (internal) diameter tubes but am working out how to fit them in. They come out just under 49" long each.

From your original description I thought it was laid down behind the couch, not in the corner.
 

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Discussion Starter · #15 ·
In the OP you said about 1cf more than the Marty, which would make it 12cf net
I said 1ft³ more than the Martycube gross. It could be more than 1ft³ net if a triangle doesn't need as much bracing. The faq says the Martycube is only 4.75ft³ net. The first graph in the faq shows the Martycube able to do over 100db with the si ht18 at 15hz, but that's with 1,100w and the si ht18 only does 600wrms. I don't know if you're supposed to model with the max or rms.
 

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I misread. I thought you meant full Marty with a UXL18. Still a challenge to accommodate a relatively long port in that enclosure.

I'm on call this week, so I'll give it another look as workload and time permits.
 

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Discussion Starter · #17 ·
I'm still trying to figure out how to use Sketchup. I can't get faces to show up where I want them to, but this example should be good enough to get an idea of what I'm talking about.


What about angling the top and bottom parts of a "slot" port to compensate for the decreasing area of the sides? The angle should be able to be calculated to keep it the same volume throughout the port.
 

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I have no idea if that type of port will work properly but building it sure will be hard. Getting the cuts on the top and bottom port panels to match up well with the sides ain't gonna be easy. Those angles are complex and assembly is rarely perfect so even your best model might be off. I guess a lot of PL premium could cover some errors. Why not use round plastic ports? It will cost more but way easier to model and build.

Or if you have enough height in this box you could do a triangle shaped port up the back corner shooting out the top. But you'll need enough depth to mount the driver and kids could toss toys in there.
 

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I'd recommend running the port as shown here.

3d modeling


All the angles are simple 45 degree cuts.

The bottom length is simply the center line of the port, as the front panel is at a 45 degree angle, and the long side of the angled port adds length exactly equal to what you lose in length on the short side. It comes out to about 12" for the bottom length, with about 30" more available up the back side.
 

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Discussion Starter · #20 ·
I can't work out a way to insert a slot port and make it work, at least to my standards. I can with 5 4" (internal) diameter tubes but am working out how to fit them in. They come out just under 49" long each.
Is there a reason there should be 5? What determines the number of ports needed?
I have no idea if that type of port will work properly but building it sure will be hard. Getting the cuts on the top and bottom port panels to match up well with the sides ain't gonna be easy.
Yeah, I don't know what I was thinking. Even if cross sectional area would stay the same, the surface area would change too much throughout the port with that design. What about running it from the side along the wall?(It's a top view)
I'd recommend running the port as shown here.


All the angles are simple 45 degree cuts.
That's a pretty good design too.


Would it be better to go with 3 Infinity 1260w's or 1 SI HT18? They come out to around the same price.
 

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