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LTD-M18 Sub Build

43K views 639 replies 48 participants last post by  jbrown15 
#1 ·
Okay, so here goes. So for a few months now I have been considering getting into a DIY project with my first sub build. As of right now I have dual XS30's that I've been really happy with but have always wanted a little more. I always wished to myself that I had the budget to be able to buy dual JTR Captivator S2's but knew the wife would kill me if I spent that kind of money on some subs for our theatre room.


So in October I finally decided to redo the front of my room, so I ripped the carpet up, build a front stage, packed 2500lbs of sand down into the basement, filled the front stage and now have build a false wall. And will be ordering a Falcon AT screen this week. So now I've decided its time to start a sub build. I plan to start building them at the beginning of the New Year. So after having the PSA XS30's I was thinking that I would do a sealed sub build and use them along with the XS30's. So I was thinking of a couple deferent options, at first I thought I would build two sealed subs using some FTW-21 drivers, then I thought I'd build my own version of a Cap S2 build two enclosures each using two UXL-18's. And of course then I started to come up with some other ideas, building two sealed subs with SI 24's and the very last idea I had was building two tower subs, each consisting of three SI 18's


So at the point I had some my different ideas running around in my head that it was starting to spin, so after talking with steve nn I decided to send off a PM to a pretty popular forum member after reading lots of his great posts. So of you have probably heard of him LTD02?...lol aka John.


So after some back and forth with him on pretty much every idea I had running around in my head, from different drivers, sub designs and amps. (sorry for the never ending PM's John) I have finally decided on a design, driver and amps that I feel will really deliver the performance that I'm looking for.


So John has helped come up with a design, that's similar to another sub that he's helped with. So I'm going to build two enclosures with rough dimensions of 32-34" wide, 21-22" deep and 72-76" high, they will be ported subs with a slotted port on the very top of the enclosures, and each one will use two UXL-18's and a inuke 6000DSP powering it and be tuned to 15hz.


They will look something like this




This build will probably take a few months and will probably start off a little slow, but I wanted to start a thread on the build and I'm open to suggestions for a name on the build...lol



****Update****


So the build ended up taking a different direction due to the fact it would of been a total pain in the A$$ to get two of those monsters down into my theater room. So I decided to go with four single driver cabinets, each one being 32"wide, 22"deep and 40"high with a ported tune of 15-16hz.


Here's a graph for one cabinet




And here's some build pics.








 
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#2 ·
congrats on getting the thread going...you're halfway there. :)


one thing that has been on my mind with respect to your build is how deep the cabs need to be so that they don't rock forward and back once the woofers get moving to high excursion. 'not pointed this out as a possible risk point with 316's build in his thread. ported benefit by reducing cone motion over a good range of frequencies, but from around 17-34hz, there could be a good bit of cone motion going on. and even though the weight of the cabs is something like 100:1 relative to the mms, there could still be some vibration.


i'm not quite sure how to calculate it though and i'm not sure if it will be a problem or not. there are some relatively easy fixes for this (should it vibrate too much) since both of you have ceilings directly above the subs and both builds are behind screens and that could be used to brace the cabs with some sort of compression brace between the sub and the ceiling.


this is why i have been holding off commenting on the cabs with less depth than what we had discussed previously. the shallower the cab depth, the more that it will be inclined to rock. since this build is a bit of a ways off, let's see how these tower type cabs perform in this respect for 316 and then adjust plans if necessary...
 
#5 ·
"LTD...any downside to laying cab on side besides the above?"


with the vertical cabs, you can get the drivers at 1/4 distances from the walls and ceiling/floor. this eliminates most room modes. huge benefit to doing it this way.
 
#6 ·

Quote:
Originally Posted by LTD02  /t/1506201/unnamed-sub-build#post_24086531


congrats on getting the thread going...you're halfway there. :)


one thing that has been on my mind with respect to your build is how deep the cabs need to be so that they don't rock forward and back once the woofers get moving to high excursion. 'not pointed this out as a possible risk point with 316's build in his thread. ported benefit by reducing cone motion over a good range of frequencies, but from around 17-34hz, there could be a good bit of cone motion going on. and even though the weight of the cabs is something like 100:1 relative to the mms, there could still be some vibration.


i'm not quite sure how to calculate it though and i'm not sure if it will be a problem or not. there are some relatively easy fixes for this (should it vibrate too much) since both of you have ceilings directly above the subs and both builds are behind screens and that could be used to brace the cabs with some sort of compression brace between the sub and the ceiling.


this is why i have been holding off commenting on the cabs with less depth than what we had discussed previously. the shallower the cab depth, the more that it will be inclined to rock. since this build is a bit of a ways off, let's see how these tower type cabs perform in this respect for 316 and then adjust plans if necessary...

Thanks again for your very much appreciated input John!
 
#8 ·

Quote:
Originally Posted by blah450  /t/1506201/unnamed-sub-build#post_24086661


jbrown...are you constrained by space for the footprint? Is it possible to run the above design on its side in your theater? Will ports be blocked?

If lateral placement, high excursion rocking is no longer a factor?


LTD...any downside to laying cab on side besides the above?

Well the front of my room is 14ft and from the top of the stage to the ceiling is about 80". I need to take into account that I'm going to have corner bass traps and my three JTR 228HT's vertically.





Here's a few pics without the screen in place to give a little bit of a better idea of how much space I have to work with.






I'd really prefer to have the subs vertical too rather then laying on their sides.
 
#9 ·
Hey jb welcome to DIY. These are going to be two serious subs and I look forward to your project! I’m heading out now to pay my subscription ahead as not to miss anything.



A quick idea though.. what about dropping both drivers down? I know it wouldn’t look as aesthetically pleasing but it would alleviate the possible problem, floor issue though. I’m sure if we keep thinking about it we can come up couple different ideas.


EDIT> Platforms??
 
#12 ·

Quote:
Don't worry about the vertical tower. We can cut braces to attach to back of sub and the back wall.

Auhhh! I thought about that, but that’s no challenge.
 
#13 ·

Quote:
Originally Posted by steve nn  /t/1506201/unnamed-sub-build#post_24086932


A quick idea though.. what about dropping both drivers down? I know it wouldn’t look as aesthetically pleasing but it would alleviate the possible problem, floor issue though. I’m sure if we keep thinking about it we can come up couple different ideas.

That's not a bad idea, I'm sure LTD can weigh in when he gets a chance. So maybe something like, bottom of the sub, and then have the driver 8" from the bottom, then another 8" in between the second driver. So the top of the second driver would be at a height of about 52".


I'm being honest here, I really don't know much about designing a sub. I mean I can build one, but coming up with the overall design and bracing; I'm really hoping LTD can help me out with that.
 
#14 ·

Quote:
Originally Posted by chalugadp  /t/1506201/unnamed-sub-build#post_24086993


Don't worry about the vertical tower. We can cut braces to attach to back of sub and the back wall.


What you need to worry about is bribing the guy who is opening his shop up for you to build that beast



I kind of like the ring of chaluga sub
:p

I'm sure we can work something out
 
#15 ·
"A quick idea though.. what about dropping both drivers down?"


one thing that we were shooting for is to have each woofer 1/4 distance from the floor/ceiling and from the walls.


this thread is on two separate, but related, ideas and shows some of the benefits.

http://www.avsforum.com/t/837744/double-bass-array-dba-the-modern-bass-concept


here is an example to show what I mean by "1/4 distances" from the walls and ceiling/floor. the picture is for an infinite baffle concept, but the location of the drivers is what is the takeaway.

 
#17 ·

Quote:
Originally Posted by LTD02  /t/1506201/unnamed-sub-build#post_24088326


so translating that into the build at hand, we would want to shoot for something like this:




as that would help eliminate a lot of problems before they get started.


picture not to scale.

Perfect, that's pretty much what I'd like to accomplish. The only issue is that my front wall is offset to the right a little. What I mean by that is the front wall is 14ft wide but the back wall is just over 11ft wide. So the extra three 3ft on the left side of the room is where I have my AV rack and mini bar. So the screen is a little more to the right side of the room.


So the screen and speakers are all setup as if the room was 12ft wide. So there's more room on the left hand side of the room then there is to the right side. Does that make sense?


I could post more pictures that show this a little better. I have 81.5" from the top of the stage to the ceiling. The actually floor to ceiling is about 91".
 
#18 ·

Quote:
one thing that we were shooting for is to have each woofer 1/4 distance from the floor/ceiling and from the walls. this thread is on two separate, but related, ideas and shows some of the benefits.

Gotcha! That reminds me of a earlier conversation with jb regarding IB (how where to place drivers) but have never thought of designing a SW to address. Design your subs to give you the best shot at room response, this is good.

Quote:
34" wide, 21-22" deep and 72-76" high

Just to be clear.. as things stand this is what we're looking at so far. Is there any more room at the base of your subs depth wise? just the base. If not can room be made? if so, how high?
Quote:
I could post more pictures that show this a little better. I have 81.5" from the top of the stage to the ceiling. The actually floor to ceiling is about 91".

That would be very welcomed, please do. EDIT> Pictures of placement location.
 
#19 ·
Why not the FTW over the UXL for these builds?


Don't get me wrong, the UXL will still be insane, but those 21's just add to the awesomeness factor!
 
#21 ·

Quote:
Originally Posted by lukeamdman  /t/1506201/unnamed-sub-build#post_24099206


Why not the FTW over the UXL for these builds?


Don't get me wrong, the UXL will still be insane, but those 21's just add to the awesomeness factor!

Ah well one thing is that four UXL-18's would have more output then two FTW-21's from what I'm told and I just don't think I 'd really have the room for four FTW-21's in a ported enclosure. Those would be two massive enclosures wouldn't they?
 
#24 ·
#26 ·
an infinite baffle works just like a sealed sub, but...the drivers are designed to give decent performance in VERY large enclosures, so what you do is use an attic or adjacent room as the "enclosure".* because the cabinet is so large, there is very little air spring resistance and so it takes only a little bit of power to get a ton of bass.


BUT as with sealed subs, all the spl must come from the driver displacement, so spl is still limited to what the driver can do with its xmax.


because i.b. subs don't need as much motor on the driver, they can be cheaper, so folks tend to just keep buying more drivers until the target spl level can be hit.


a uxl driver in an infinite baffle, for example, would still be limited to the max spl that we talked about in the sealed enclosure, so the ported would have a significant advantage in the neighborhood of the tuning frequency.








* that's not quite right, but that's the idea. technically, the room becomes the enclosure and you are inside the subwoofer, but that is a little less intuitive for most folks.
 
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