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DIY SI HT18D2 sealed dual opposed sonosubs.

34K views 223 replies 35 participants last post by  Nalleh 
#1 · (Edited)
My turn to DIY.

So, exept from some DIY car subs in earlier years, i have used SVS (and lately PSA) as subs in my HT.
Been thinking about going DIY for HT subs too, and when i found this thread about coolrda and his most exellent sealed dual opposed 18 SI sonosubs, i got really temted:

http://www.avsforum.com/forum/155-diy-speakers-subs/2052482-fat-man-little-boy-build.html

The reason this got me exited was partly because i heard how deep my PSA S3000i dual opposed sealed 15"s worked, and partly because we use sonoco tubes at my workplace, so i have free acess to tubes.
That suddenly makes sonosubs easy attainable.

So the tubes have these maximum measurements:

ID x thickness x length
597 x 10 x 1500 mm = 420 liter
23.5 x 0.39 x 59 inch = 14.93 ft3

Also there is pre-cut lengths of 1230mm/48 inch.

According to coolrda's recept, they are 9.2 ft3 in net volume, but since his tubes were 30"D x 24", and mine are 23.5"D, i need to make them longer, like 0.99meter /39 inch to get 9.2 ft3 net volume.

I plan on having them in the front corners, where the subs i have today is, so i have room for more tube length, if needed.

And of course i plan to use the same drivers, the Stereo Integrity HT18D2 v2, 2 per cab.
http://stereointegrity.com/product/ht18-v2-subwoofer/



Basically a copy of coolrda's Fatmans, just adjusted for length.

Couple of questions:

1. Would a push-pull design be any better?
2. Would a ported design be better?
3. Is there a better driver in that pricerange?
4. Is there a better cab volume?


PS: already ordered the drivers, but will take a while to Norway.

Edit: as the drivers is ordered, forget question 3 ;)
 
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#3 ·
My turn to DIY.

So, exept from some DIY car subs in earlier years, i have used SVS (and lately PSA) as subs in my HT.
Been thinking about going DIY for HT subs too, and when i found this thread about coolrda and his most exellent sealed dual opposed 18 SI sonosubs, i got really temted:

http://www.avsforum.com/forum/155-diy-speakers-subs/2052482-fat-man-little-boy-build.html

The reason this got me exited was partly because i heard how deep my PSA S3000i dual opposed sealed 15"s worked, and partly because we use sonoco tubes at my workplace, so i have free acess to tubes.
That suddenly makes sonosubs easy attainable.

So the tubes have these maximum measurements:

ID x thickness x length
597 x 10 x 1500 mm = 420 liter
23.5 x 0.39 x 59 inch = 14.93 ft3

Also there is pre-cut lengths of 1230mm/48 inch.

According to coolrda's recept, they are 9.2 ft3 in volume, but since his tubes were 30", and mine are 23.5", i need to make them longer, like 0.95 meter /37.5 inch to get 9.2 ft3.

I plan on having them in the front corners, where the subs i have today is, so i have room for more tube length, if needed.

And of course i plan to use the same drivers, the Stereo Integrity HT18D2 v2, 2 per cab. Basically a copy of coolrda's Fatmans, just adjusted for length.

Couple of questions:

1. Would a push-pull design be any better?
2. Would a ported design be better?
3. Is there a better driver in that pricerange?
4. Is there a better cab volume?


PS: already ordered the drivers, but will take a while to Norway.

From what I have looked into reduced distortion from using push pull didn't seem like it was that significant. Slot loading them like PSA can give you increased output but you need someone to model it in hornresp to see what happens. That would be interesting actually, from the little I know it helps more in the upper end of the FR. Maybe @LTD02 or someone good with hornresp could do that, slot loaded like the PSA 7201 but only using 2 18". https://www.powersoundaudio.com/products/S7201

Also, you could get a little more low end if you want by going slightly larger than 4.5cf per driver. Around 7cf each will get the most out of the new V2s it would only add around 2dB down low but every little bit adds up. How much power are you giving them?

Ported will give you a good 6-10db more on the low end but then you are looking at 9-11cf+ for each sub.

I hope someone does a slot loaded push pull sim in hornresp for you to see how it looks. If you don't get a reply maybe start a thread with that title help with slot loaded sub. I am curious to see the difference in output vs plain sealed.

Here is a couple thread on PPSL. http://data-bass.ipbhost.com/topic/179-push-pull-slot-loaded-quad-si-ht18s/ http://www.diyaudio.com/forums/subwoofers/177905-thread-ppsl-enclosures.html
 
#4 · (Edited)
Thanks, bscool. Yes, i was hoping for some help from the experts in here. As i said , the blueprint is basically ready: follow coolrda's work. And since his build was two years ago, i wondered if any improvements have happened since then.
I was actually taking some ideas from here and there(7201, MKSound), and dual opposed is already acepted, one driver on the top of the tube and one on the bottom. But what if i turn the bottom one around, with the magnet facing down? Ie both dual opposed and push and pull?

To get slot loading as coolrda did, i would have to stack both cabs on top of each other, wich was not my original plan. Or build one driver pr cab, and then turn them on top of each other, driver to driver.
But hey, nothing is set in stone so far, that's why i started this thread.
If another design will get better performance with the same drivers, it's all good.

However: i WAS planning on having end plates on both ends(as coolrda did), so maybe slot loading will still happen?

Amd as i said i can go up in volume, to get better performance, but coolrda already says his design gives 120dB @ 6Hz, and that sounds plenty, lol.
I was thinking about using a Inuke 6000(DSP?), but running 4 SI18's would give 8 ohms pr channel, so maybe that's not optimal. Maybe a EP4000?
 
#5 ·
the manifold won't do a whole ton in this one when crossed at 80hz or so. there will be a rise toward a peak up in the 180hz ballpark (guesstimate based on form factor), with a little increase spilling down toward 80hz or so, so some increase in the upper bass output. my guess is the primary purpose with this one is simply to get all four drivers loading the same air in as small of an area as possible.


most folks aren't going to get a pair of these and generally most folks would be better off with a pair of lesser subs than a single super sub. now, if you want to run a pair of these, well... :)
 
#7 ·
Any recommendations, based on drivers and sonotubes?

The EP400 looks like it would work, run them at 2ohm 2 18" on each channel or the Inuke 4u 6000 1 on each channel around 600 watts each.

Option 2 (series/parallel) = 2 ohm load
Voice coils wired in series, speakers wired in parallel

https://www.the12volt.com/caraudio/woofer_configurations.asp?Q=2&I=22
Yes, that's the problem, the Inuke 6000 can't take 2 ohm's, but the EP4000 can. Although the nu4 might work.
 
#10 ·
@bossobass is the source that I copied. Everything you'd ever want to know about this design is available there. There really isn't a tune by slot loading the stack this way as its open all the way around, though you do get a FR change. But theres so many advantages to this design. If I had a big room I'd put one of these in each front corner. The aesthetics alone are desirable.

I've built several push/pulls and isobaric with this design with excellent results. I prefer sealed over ported. Ported isn't better, its louder. Pretty much anything you would do with a single sub you can do with this. I don't know of a driver that has a better displacement/dollar ratio. Don't be to concerned with cab volume. I had them heavily stuffed so the drivers were probably seeing a 5cuft cab. My new under screen cabs are probably 3.5cf per 18 and yet FR and extension to 5hz is the same. You trade cab volume for power and likewise. This particular driver's limitation is excursion which runs out way before the coils will. This has a huge motor by standards used five years ago but is dwarfed today. So the best efficiency with this driver will be an IB. Having said that, you will have a great sub.

As far as ULF goes its all about size and quantity of drivers and room volume. Once below half wavelength, it doesn't matter what you do or where you place the subs, your room is pressurized.

Heres a couple things to remember as pertaining to the 120db's. The video of my 123.5db@6hz is a continuous 20 second sine wave. This was using 8 subs, this 4x18 stack and 4x15's up front. I had exactly a 6db drop with just the rear stack on, 117.5db. This measurement was taken at the MLP. The sub was power limited using a EP4K. Do not compare this measurement to Databass numbers. Used the numbers their then add 12db to sim what you will have. Whats important to remember is Volume of Room, not Room Gain which I've measured as being the same in all four sealed rooms I've had. Each sealed room from 1400-2800cf, measured 10-11db of RG. The 4x15's in the 2800cf room maxed out at 103db vs 117db in the 1400cf room I have now. While distance to speaker is very important and measures consistently and can be calculated in ground plane measurement(Its how subs are tested and can be compared to each other fairly), its not below the point where RG starts. In room distance doesn't matter, SPL remains the same Fairfield or near, only TR changes.
 
#11 ·
@dtsdig : yes i believe he meant the NU4.

@coolrda : yes, i discovered @bossobass several years ago and was fascinated by his work. Flat to 3hz ! That is insane, and his products is first class, and he has shared tips and tricks all over the net.

Your Fatmans reminded me of his Raptors, and made me realise how easy this could be done. NOT to bassobass's level, but nevertheless.

Ok, so you had some more subs at that level, but that's still impressive.

I have a bigger room than you, 3000 ft3, and that room has a open left wall to another almost as big room, maybe 2500 ft, and then a open doorway to the kitchen, so alot more air to pressurise.

Remember the video i posted earlier showing off the Crowsons? If you look at the REW on the PC screen running RTA in that video, you will see i have 96 dB @6 Hz, and that is all PSA S3000i. I was impressed it managed that much. That was at MV -20 with the subs "a bit" hotter than Audyssey, but still not at reference.

Pic from work :)
 

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#15 ·
You probably shouldn't have shown that pic here:D. 96@6hz with a vented sub is a very good number. You already have a potent system. I have a feeling adding this sub will lead to three more. You have the room and they are one of the prettiest subs around. Any things better than square or rectangular cabs. I'm looking forward to seeing this build:cool:.
 
#12 ·
BTW @coolrda, do you think the wallthickness of 0.39 inch is enough on my sonotubes? We have thicker tubes too.
 
#13 ·
A couple of pics from MLP. Showing the PSA in the right corner, and SVS in the left. Also showing opening to room on the left side.


 

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#18 ·
having one driver magnet facing out will help reduce even order distortions, but most folks don't find that to be a big benefit.

since you have all the "tube" that you could possibly need, if you have the space, you may want to consider a concentric ported sonosub.

just another option to put in the mix...


 

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#19 ·
Funny you should mention that ! I was actually thinking about a tube within a tube to get the port at the same end as the driver.

Ok so like i said i have acess to several diameter tubes:
597 ID x 10 x 1500 mm/ 23.5 ID x 0.39 x 59 inch(outer tube)
497 ID x 9 x 1520 mm/ 19.5 ID x 0.35 x 59 inch (inner tube)
If i put the small tube in the big one, that would leave a 41mm/1.6 inch opening around the circle.

Would this measure up to any good solutions?
 
#20 ·
1.6" would be the port height and the width would of course be the circumference around the port about half way in between the tubes, which in this case would be about 73" or so around. that is actually a pretty big port. with some vertical boards in between the tubes, the port could be sectioned off into multiple ports, which would allow for stuffing a port or two in order to adjust the tune up or down.


if it is practical largely depends on how big you want to go. with a net internal up around 16 cubic feet or so, a port that is 48" long would tune the cab to around 18hz. stuffing half of the port area would drop the tune to about 13hz and the port area would still be large enough not to have severe compression or chuffing problems.


one "missile silo" in each corner would be pretty ridiculous as far as bass output with the 13hz tuning option.


not sure what to make of this concept. :) 6 foot tubes with approximately 4 feet overlap (in order to create a 48" long port.


 

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#24 ·
not sure what to make of this concept. :) 6 foot tubes with approximately 4 feet overlap (in order to create a 48" long port.
I think i found a way to get 16+ ft3 within a 7 ft height:



What do you think?
 

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#21 ·
@LTD02: WOW! That is pretty much the idea i had in mind. As you can see in the pics earlier, i have 7.8ft ceiling, and plenty of space in the front corners, so 6ft should be doable.

Just to be clear: this is still dual drivers, one on top, and one in the bottom, right?

And i was thinking about vertical boards to mount the outer and inner tubes, thanks for confirming.

This would complicate the build, but it would be a upgrade to the Fatmans, yes?
 
#22 ·
Hmm, i might have been a little hasty there. With two 6ft tubes and the inner telscoped out 2 ft(4ft overlap), that would make the total height 8 ft, right?

I don't have ceiling height for that.

And i only have 5ft tubes at work. So that would make the tune higher, right?

Bummer, as it would look awsome with two missile silos....heck, if i put the bigger tube in the bottom, then the smaller tube, and the top driver with magnet up, it would look like a rocket :)
 
#25 ·
^ I hereby name said design the "Heavy bag" because it reminds me of one lol..

 
#26 ·
#27 ·
After some consideration, i have desided to go for the original design, the sealed coolrda's design. Much simpler to build, and my guess is it will be plenty for my use. Got the tubes today, and had the pre-cut at correct length. I know they are smaller(23.5 ID inch) vs coolrda's design(30 ID inch), but man these are big:



Today the SVS is in this corner:



And this is one tube in that corner:



And if i deside to stack them:



Do not think stacking would be needed :)
 

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#28 ·
And a mandatory pic with bluray cover to show size :)

 

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#32 ·
My turn to DIY.

1. Would a push-pull design be any better?
@bossobass is the source that I copied. Everything you'd ever want to know about this design is available there. There really isn't a tune by slot loading the stack this way as its open all the way around, though you do get a FR change. But theres so many advantages to this design. If I had a big room I'd put one of these in each front corner. The aesthetics alone are desirable.

I've built several push/pulls and isobaric with this design with excellent results.
having one driver magnet facing out will help reduce even order distortions, but most folks don't find that to be a big benefit.
Mark Seaton explained to me that push-pull only mitigates distortions attributed to asymmetries in movement (motor/cone moving in vs out) and will only reduce even-order distortion. Some drivers may benefit more than others in this alignment. I am planning to test push-pull vs standard DO between a pair of Funk 12" DOs. The amp is in a separate, vented compartment which allows it to be external without breaking the cabinet seal.

You will have to evaluate if PP is worth the added wiring complexity. Some driver motors can emit noise (air turbulence?) from the rear. Lastly, driver distortion may already be low enough to make any marginal reduction in distortion inaudible. I would ask Nick (Stereodynamic) and/or David Gage (dgage) for their opinion before attempting PP.

Knowing the complexity of your Atmos setup, I'm sure you could pull off the PP with ease. If the motor is quiet, I don't think it can hurt. I defer to the experts of course.
 
#33 · (Edited)
Mark Seaton explained to me that push-pull only mitigates distortions attributed to asymmetries in movement (motor/cone moving in vs out) and will only reduce even-order distortion. Some drivers may benefit more than others in this alignment. I am planning to test push-pull vs standard DO between a pair of Funk 12" DOs. The amp is in a separate, vented compartment which allows it to be external without breaking the cabinet seal.

You will have to evaluate if PP is worth the added wiring complexity. Some driver motors can emit noise (air turbulence?) from the rear. Lastly, driver distortion may already be low enough to make any marginal reduction in distortion inaudible. I would ask Nick (Stereodynamic) and/or David Gage (dgage) for their opinion before attempting PP.


Knowing the complexity of your Atmos setup, I'm sure you could pull off the PP with ease. If the motor is quiet, I don't think it can hurt. I defer to the experts of course.
Yes, that sums up what i have heard too. Some say that it sounds 'thinner' with PP, but it is actually than the sound is more 'pure'.
If it is noticable for all to hear, is another matter.
I will go the easiest route first, and then if i am not satisfied, i can experiment :)

EDIT: Another clue here is the endplates. As we know, a driver in a sealed box has different resistance when it moves in vs moving out, and by mounting endplates(or what it's called), the out movement of the cone is also given a resistance. And this can be 'tuned' by the height/free opening between cone and endplate.

I think ....

I have read Bossobass talked about this somewhere, but i can't find it again. Coolrda also mentions this.
 
#34 ·
Some thoughts about the look of the cabs. Normal look is black/fabric like SVS:



I find it boring...

I have some movie posters left from when i made acoustic panels, so with a little work, something like this:



Or:



I have also ordered some 3D wood-wallpaper:



Kind of like the Blackbirds:



What do you think?
 
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#41 ·
Finally got a start today on the many circles needed, with two sheets of 3/4 inch MDF.
I made a REALLY simple circle jig, and it was not perfect, but i made it work :)
I broke a bit for the router after 4 inches, LOOL, so had to do a trip to the store and get a couple new ones. After that it went pretty easy.



So i got more than half of them cut today, will do the rest tomorrow.



After that there is more work, cutout for drivers, holes for the feets, connectors, sanding painting, etc, but the big circles is the most work, so i am happy i am well on the way with that.
 
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#42 ·
More progress.

Here is a pic of my super simple adjustable circle jig, mad from some part included with the router, and som aluminium piece.



Ok, so i am done with the circles, and started on the radiuses, around the egdes.



Nice stack.



Just some sanding left, and i can start painting and gluing.




Still waiting for the drivers, will hopefully be here in two weeks.
 
#43 · (Edited)
After some sanding, it was time to glue it all together, first the two endplates.



I use expanding PU-glue, so i have to cut away the overrrun when it is dried.



And after it dried a little, gluing the endplates to the tubes. I taped some plastic over the tubes, so that hopefully the overrrun of glue doesn't get stuck on the tubes.



Got a good start on the bottom/top plates too.



Rest of the feets to the right.



Some more sanding, and then paint :)
 
#44 ·
The cabs are pretty much done, wood wise. Glad i put the plastic over the tubes, as there was some work cleaning up after the glue dried. But all good now, and ready for som black paint.



All in all, the cabs themselves has been a easy job, compared to a normal square box. A bit timeconsuming with the router job, but still easy.

Top tip: use a vacuumcleaner for all the dust from the MDF sheets. It was so much cleaner to work, as the dust is almost nonexistent this way. And believe me MDF work is dusty !
 
#45 ·
Here we go.




Found a ultra matte black paint. Still wet on pics.




 
#46 ·
Almost forgot, i had to paint the feet to, so screwed them onto a board, wich made it easier to work with.




Some small things to button up, but running out of materials to finish them, like drivers, t-nuts, speakon connectors, wall paper, etc (all of it ordered though), so it's the waiting game a while forward now ;)
 
#47 ·
Amp choise !

I am considering a Behringer NU4-6000 or a EP4000.

The load will be 4 subs with 4ohms, so can be either 1x4ohm pr ch(NU4-6000) or 2x2ohm (EP4000).

Any recommendations? Wich one is best?


@coolrda @Scott Simonian
 
#52 ·
Got some more parts today: a Inuke6K, some speakon plugs, XLR cables and the wallpaper. Wallpaper looks very nice with a real strucutre to it and a matte finish. Will be cool to see it on the «barrels» :)

 

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