# HT sub - sonotube enclosure LLT - first try



## 94VG30DE (Nov 28, 2007)

Hi guys, looking to design and build a Large Low Tune box for home theater use over the Christmas break. Looking to use Sonotube concrete form tube for most of it, and MDF for rest of enclosure. 

Here's the sub I'm using: Infinity 1252w Reference Series 12" subwoofer with dual 4-ohm voice coils - Features & Specs at Crutchfield.com 
Specs on PDF: http://manuals.harman.com/INF/CAR/Boxes and Parameters/1252W.pdf


What do you guys think of this design? 










Looking at roughly 6.3 ft^3 net internal volume, tuned to 20Hz. I will install feet at the bottom to bring it up off the carpet. Sub down firing, port up-firing. It will be placed in the corner of my basement home theater. I have a crap-ton of power to throw at it, but obviously main focus ability to hit LFE as well as mate with my beautiful surround speakers that only go down to about 100Hz...


----------



## brownmoses (Jul 23, 2008)

i'd love to see how it turns out. i have a pair of 6" Adire subs i want to build mini sono tubes to accompany some pinnacle bookshelf speakers i run.


----------



## ItalynStylion (May 3, 2008)

Design looks solid. No idea what the woofer models like in that enclosure though; didn't run the specs.

Seems very similar to one I did last year for a Shiva X. Maybe if you end up wanting a little more BOOM out of it you can swap out the driver later.

I made a base for the one I did. The tube section dropped into it so it held it up. Not sure how much work you want to do but thought I'd throw the idea out there.


----------



## 94VG30DE (Nov 28, 2007)

I'm actually leaning towards covering the whole thing in the corner with a flat panel, so that essentially the wall would be chamfered, and therefor a little less obtrusive. It would be behind some other decorations, so if it is just a flat panel with a hole in the top and a hole in the bottom it would blend in a little better. So I right now I am leaning towards less work, but the stand actually looks like it would be a great idea. It looks good, and it would mean I don't have to put the tube all the way to the wall or mess with covering it. 

Modeled in WinISD shows it should be flat to about 20Hz, f3 @ ~18Hz, with (hopefully) a little room gain helping below that. Room is roughly 14' x 22'. The only thing that bothers me a little bit is that the group delay is crazy high, like >35ms @ ~15hz, and the phase shift down there is crazy too. But I figure since it's just LFE down there anyway (this system won't be used for music) I'm not going to lose too much sleep over it.


----------



## 94VG30DE (Nov 28, 2007)

Oh, the other thing I am hoping to do over the break is play with taking measurements a little bit. I've got a mic, a mixer, and a laptop, so I would just need to figure out a rough calibration or something. But that's a whole different topic...


----------



## AndyInOC (Jul 22, 2008)

Maybe think about going up to a 6" port depending on how much power you are going to put to it? Maybe its not as critical in an HT application but in a car I've had better luck with a 6" port not "chuffing" with low frequencies and higher power.


----------



## 94VG30DE (Nov 28, 2007)

I'm going to put enough power to it that it won't take any more. I have way more on tap than it will need. Might be a good idea about the 6" ID port. The 4" port was shorter, that's why I was looking at it. But in all honesty I can probably get away with a larger and longer port, since I have room in the box to spare. I could probably go 0.25 smaller without negative effects. So preventing chuffing might be something to think about.


----------



## AndyInOC (Jul 22, 2008)

Just clicked on the link to the sub, says rms is 300 max is 1200, i assume you are going 300? if so then your 4" port should be fine. Guess i should have asked first


----------



## 94VG30DE (Nov 28, 2007)

Yeah I will be running about 300W would be my guess. Past that it is probably going to start outrunning the other speakers. We'll see where the gain knob ends up, but I probably won't even need that much.


----------



## Ray21 (Oct 19, 2009)

Sounds good to me... should perform well. In that large of an enclosure it won't take much power for that driver to reach its limit. 

I agree with using a 6" port as you'll probably get upgraditis and want to swap out for a more powerful driver later.


----------



## 94VG30DE (Nov 28, 2007)

Ray21 said:


> Sounds good to me... should perform well. In that large of an enclosure it won't take much power for that driver to reach its limit.
> 
> I agree with using a 6" port as you'll probably get upgraditis and want to swap out for a more powerful driver later.


Good call, I wasn't really thinking about further plans. I wouldn't plan on upgrading that sub in the near future (it's a Christmas present for my mom) but if that enclosure ever ends up in my place I might look at swapping subs. Right now I am prepping a 15" for my place, but that is a different post


----------



## AndyInOC (Jul 22, 2008)

94VG30DE said:


> Good call, I wasn't really thinking about further plans. I wouldn't plan on upgrading that sub in the near future (it's a Christmas present for my mom) but if that enclosure ever ends up in my place I might look at swapping subs. Right now I am prepping a 15" for my place, but that is a different post


Very good call on the upgradability of it! Prepping an old Strike AV15 for my own home theater as well. Your post actually planted the seed on a sonotube for it as well.


----------



## 94VG30DE (Nov 28, 2007)

Well, finally got settled into the new garage setup, with enough heaters to keep everything nice. Got most of my tools out of storage, assembled the parts, and started going to work. 

First item is the tube itself. I had to call an audible b/c no local places sold the 14" like I originally intended. They did have 18" ID, and I want this project done this week, so I said let's do it. Turned out to be a good decision later. Here's the tube: 









The tube had a wax lining (presumably sprayed in) when I got it, even though the outside was unfinished. This is probably to release the concrete that this particular tube will never see anyway, and I was worried about it preventing adhesion of the Liquid Nail used to fasten the end baffles in place. So, I lightly sanded the inside where I would be caulking until I saw fairly bare cardboard. It had the dual benefit of roughing up the surface a little bit too. I tried to get a pic here: 









Not all of us have fancy Jasper jigs and plunge routers. Being one of those poor folks that is still using their dead grandfather's jigsaw for most cutting tasks, I had to get creative with marking my circles for the baffles. This is what I came up with based on what I had lying around. It ended up working quite well: 









Top and bottom baffle cut. Top one will have a 4"ID x 11" long port in the center, the other will have the Infinity 1252W and posts for speaker terminals. I used 10-32 hurricane nuts from PartsExpress for speaker mounting holes and speaker terminals. Since the sub is DVC and I haven't yet decided how I intend to wire it, I wanted the flexibility to be able to change wiring without pulling the sub out. So all sub terminals will be plumbed to the outside, where the series/parallel decision can be made at my leisure. You can see the backs of the baffles (and my God-awful jigsaw cuts) here: 









I also planned on a little bit of corner bracing, to make sure the tube stays fairly rigid and coupled to the top and bottom baffles, since that (and the shape) is where all the rigidity of the enclosure is coming from. I made triangles that were 2" wide x 6" tall and placed 3 on the inside of each baffle. They were then covered in caulk, brad nailed in place, then covered in more caulk. This is the same procedure I used to attach the top and bottom baffles. The braces on the top face are deliberately not inline with the braces on the bottom face, to prevent any resonance modes that might occur. The whole result is a little sloppier (visually) than I normally work, but should definitely be solid. Pic of one of the braces here: 









As it turns out, it was a good thing that I went with a shorter 18" ID tube instead of a much longer 14" ID tube. I had to reach inside to do a lot of the caulking like I wanted to, and that would have been a _much_ more difficult procedure had I not been able to fit and arm and half a shoulder into that tube to run the sealant around. Here you can see the mostly-assembled enclosure, waiting for caulk to dry:









---------------------------------------

Next I have to make feet, cut and attach the port, and paint the enclosure. For feet I am leaning towards three legs made from 4" long 1.5"OD wooden dowel rod, with a bolt all the way through it (and the lower baffle) and washers on either end. The bolt will be facing down to give a little "tower spike" effect. Anyone see any problems with this approach?


----------



## 94VG30DE (Nov 28, 2007)

FINALLY had a chance to do more work on this. Yes these updates are spaced quite a bit apart. I can't find most of the pics I had of the painted enclosure, but rest assured, it looks like a painted cardboard tube. Everything is painted in a few coats of what the walls were painted, so that it blends in with the scenery around it. If it wasn't going to be buried behind a fake tree, I would put a little more into the cosmetics. Right now it is just a proof of concept I think. 

Pic of the binding posts (AKA SS 1.5" 10-32 screws through hurricane nuts) with leads attached. Each terminal from the DVC sub got its own doubled run of 16ga knuconceptz wire run to an individual terminal. This means that if I ever want to switch wiring configs, I can do it without removing anything. 









Pic of the doubled wiring termination:









Underside of enclosure showing terminals marked. 









Wired to run series for 8ohm bridged load to the amp: 









I am waiting on one RCA - XLR cable to get signal from the receiver to the amp, and then I can test this thing over Thanksgiving. Will post listening results then. If it works, I'm building myself one for my Kicker C15D


----------



## tonesmith (Sep 8, 2011)

Wow, anxious to see the results, but not if it takes 1 year!


----------



## EdSawyer (Jan 6, 2012)

Ive made several home subs with this approach. I usually do 4 layers of sonotube, laminated together, and a double thick set of baffles fro 3/4 MDF. they end up sounding great and relatively light and fast to build. I usually do my car subs the same way.


----------



## 94VG30DE (Nov 28, 2007)

tonesmith said:


> Wow, anxious to see the results, but not if it takes 1 year!


In keeping with delayed updates, here we go  

Finally got cabling and a crossover over Christmas break and had some time to adjust and listen a little bit. It definitely gets low, and has TONS of output. Had to turn it way down from testing, as it would shake the entire entertainment center. Pretty even output though, although I do wish I had some EQ to cut some around 40-60. Probably a room mode, I didn't do the math. 

The thing does ring like crazy though. I had to keep the LP crossover a lot lower than I wanted to, due to the enclosure ringing. I think it needs to be a LOT stiffer, but for someone that doesn't like high output at all, it is usually subtle enough that it's not a deal-breaker. 



EdSawyer said:


> Ive made several home subs with this approach. I usually do 4 layers of sonotube, laminated together, and a double thick set of baffles fro 3/4 MDF. they end up sounding great and relatively light and fast to build. I usually do my car subs the same way.


How do you get that many layers of sonotube? I didn't think they were close enough in size that you could sleeve them like that. What do you do to laminate them? 

Light and fast to build, I agree, but part of the push for me to use sonotube was cost as well. If I had to use 3 tubes, the cost gets way higher than MDF in a hurry.


----------



## EdSawyer (Jan 6, 2012)

Mine were/are all in the < 3cuft size. Usually what I do is buy one (or more) tubes, cut off the length of the outer tube that I need (say 2-3ft), then cut the rest of the tube into the same lengths as that. Then I slit the extra pieces lengthwise with a razor knife. Then I take out anywhere from .75" to 2" of the width of the tube (lengthwise) with another cut to effectively reduce the diameter of the tube. It doesnt' have to be perfect. That allows them to nest within the single uncut tube. Stagger the cuts inside the tube to minimize weakness in any one place. The deeper layers need more of the tube cut out to reduce the diameter. I laminate with Lots of LiquidNails. 

For bracing, I usually do a double-layer of MDF (3/4") for end caps, and screw and glue those in place with radial screws and liquid nails. For length-wise bracing, glue/screw long 1" or greater diameter wooden dowels the full length of the tube between the endcaps. This can hold the endcaps in tension. Another option would be use threaded T-nuts and long threaded rod(s) with a turnbuckle to tension them. 

I also usually fashion one or more rings of MDF to put in as a brace half-way down the tube, and screw/glue that in place as if it were another endcap (just in the middle of the tube.) 

once that is done, usually I'll add a dyna-mat type material to the inside of the tube, particularly the endcaps. Home Despot makes a nice aluminum/bitumen material for roof patching that works great and is basically identical to dynamat, though much cheaper. Comes in rolls about 8" wide. 

Then, stuff it with polyfill (easily sourced as pillow stuffing at Walmart). For the outside, I usually cover them with black carpet, which matches a car trunk well visually, and also cuts down on the noise of the enclosure itself (if any). 

Done this way, they are VERY dead, much deader than any MDF box I've ever built. Far less heavy and more portable too. 

I've done ones with large 1" thick PVC (16" diameter or so) and large fiberglass tubes too, but Sonotube is better for many reasons I think - cheaper, easier to source, easier to work with, and more inert sonically. 

I've never priced sonotube vs. MDF, as generally the cost of either is pretty reasonable vs. buying a commercial home sub. I dislike the dust that MDF creates from cutting (plus it's crazy heavy), so sonotube holds an advantage for me there too. 

Hope that helps
-Ed


----------

