Owen's Dual UXL-18 Sealed Build

After a lot of calculation, speculation, and general sitting around doing not much, I've finally made some progress with real tangible results.

My drivers came in (boy, are they heavy!) and arrived in good condition. My junior inspector seemed excited to get them... but it turned out he just wanted to play with the packing material. They sat around in their packing for quite a while, because I didn't have an amp for them, MDF for them, or time to actually DO anything with them. Eventually I picked up an iNuke 6000 (non-DSP), and hauled out the MDF sheets I had buried in the garage, and got to work.

Where to start? First impressions I suppose. Until now I have owned an original 15" Tempest (which was a monster, especially to me, back in 2006 or so). These things are straight up beasts in comparison. The carbon fiber cones and caps are beautiful, and the big fat surround is impressive, to say the least. The magnets are huge, and did I mention they're HEAVY? I know there are bigger drivers out there now, but these are still right up there. Build quality seems very good, and I found no issues with a visual inspection on arrival. Mark does great work, and I am very excited to have 2 of his exceptional drivers in my theatre.

I will be using Speakon connectors, so to get any kind of a signal to the subs, I had to put together the enclosure connection terminals. A little bit of soldering, and some quick and dirty heat shrink, and they were ready. My senior inspector enquired about modifying some settings before going off to bed, and had his request denied. Lol. When I did have the opportunity to set up a quick test with the iNuke, everything worked the first time out, which is always nice. In free air, sitting on the floor, with limited power after the kids were in bed, my wife could still hear "Bass I Love You" from upstairs. I had a bit of hum at higher gain, but I'm not worried about that for now since the setup for the theatre will be completely different.

Now that I knew I had working subs and amp, it was time to start the hard part and do some work. That didn't happen for another month or so until I had a morning off work with the kids at daycare. A week or so prior, I pulled out the MDF sheets I had and did a quick thickness test, and a rough cut with the circular saw to make the rest of the cuts more manageable on the table saw. Conditions hadn't improved much by the time I got to the rest of the cutting. I had less snow, but a lot of fog and periodic misty periods. I rigged up a little support system for the first cut on the larger panels, and got to making dust.

Setting up the saw and running all the same length cuts one after another makes things SO much easier. Then even if I make a mistake, at least I'm consistent and things will match up. By the end of the morning I had 2 nice piles of panels ready to go. I decided to make the inner baffle out of 3/4" plywood, to give the T-nuts something a little tougher to bite into with this heavy driver. The final subs should be about 20 x 22, which seems tiny when I look at them now, but I have no doubts they'll get the job done.

The driver is bigger than your helper! :clap:

Excellent build thread.

theJman said:

The driver is bigger than your helper! :clap:

Excellent build thread.

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Tonto said:

Coming along nicely! Looks like you could use an outflow table. You have some nice tools. It would make life a lot easier. Looking forward to the build!

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fusseli said:

Wowzers that's going to be one monster sub setup! Looks great :grin2:

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Thanks everyone! I'm REALLY looking forward to getting these up and running.

Prof. said:

That is very small for that size sub woofer!..Is that the recommended size cabinet?

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It's on the small side, but this driver does well in small sealed enclosures. 3.5 - 4 cubes is great, but in all my sims it was barely noticeable to go down to 3.3, and that fit the size I was hoping for. They'll be tucked behind a screen wall eventually, so I wanted to keep the depth under 2', with enough wiggle room to move them around. Also, the smaller airspace will give me a bit more protection from accidental overexcursion.

Oh, and yeah Tonto, I really could use a nice outfeed table setup. This was the best I could cobble together on short notice, but it actually worked really well. There are so many tools and accessories that I would LIKE to have, but I just can't justify for practical reasons. My tools aren't super fancy or anything, but they do the job.

That table saw was rescued from the dump by my dad and rehabilitated for me. I like the old SOLID saws vs the newer contractor ones, because having a big rigid surface is a big help sometimes. He put it on wheels for me, and I built my garage bench with a little parking spot for it underneath, so I can still fit the car in when it's put away. A table saw was one tool I wasn't willing to go without, even with my limited space.

Tonto said:

Wear a respirator as well when cutting that MDF. That stuff is so toxic.

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Yeah Tonto, that's good advice. I always cut this stuff outside, and make sure my helpers are in the house when the dust is flying.

Still making progress when I get some time. I got to work on the baffles this weekend, and feel pretty good about the outcome. Maybe not 100% good... but at least 90%.

The first thing I did was clamp the 2 baffles together, use scrap MDF to make sure they were centered and wouldn't leave me with overhang, and then mark the centre on the smaller inner baffle. Then I drilled out a pinhole to use as a pivot for my router jig.



My jig is just a simple piece of smoked 1/4" plexiglass that I used way back on my original Tempest build, and have somehow managed not to lose, despite moving since then. We drilled and countersunk for the 3 mounting points on the router, and cut a hole in the middle. Then I just measure and drill the pivot holes as needed. In this case I think I went with 8 3/8" for the inner baffle, and 9 1/4" for the outer baffle. I set up a piece of 1/2" foam board to test with, since I haven't done this in about a decade.



I did notice some wobble, since the foam can't really hold the pin nail perfectly still, but I figured this was as much a conceptual effort as it was practical, and I just tried not to wiggle it too much. The inner baffle test piece seemed to go well.





The wobbles are evident, but the process went fairly smoothly, so I used that hole to continue on to the plywood inner baffle. That cut well, and was a pretty good fit. I probably could have gone about 1/64" smaller, but I'd say that's about as good as I can ask for without CNC help.



I cut out both baffles, and somehow had some variance, but they're both good to go.



Next I set up for the outer baffle, and again did a test on some foam board. Actually I wasn't 100% happy with the first cutout, so I did a second foam test, to try to keep the cutout a little tighter. I figured "I can always take more off, but I can't put it back on". So the foam baffle was just about perfect, and I moved on to cut the MDF.



Here's where the wobble came back to bite me. The cut looks good, but it's basically snug to the thick rubber gasket, and I can press fit the baffle holding itself up in place without any support. In this case I could have taken an extra 1/64" off, which would have been about perfect. Somehow I didn't take a pic of it in place, but here's my helper holding up the baffle.



Now I have to figure out how to shave sown the inside of the cutout a little bit. I already went at it by hand with some 80 grit, which took care of any little imperfections, but didn't make much difference in the overall fit. Is there an easy way to take a bit of material off? I don't want to buy any of those fancy sanding drum barrels, but I might be able to rig something up to chuck into the drill. I don't think either of my palm sanders will make much contact with the surface on this arc.

The other option is taking off that massive rubber gasket and just using some foam weather stripping tape or something around the inner baffle. Any thoughts on these gaskets? Are they recommended to use, or will something more generic work just as well?

The next thing I was blissfully unaware of is how tight my overall fit is, regarding the actual dimensions of the sub. I had planned for 20" width and 22" height. The width got reduced by about 1/8" during my panel cutting thanks to a sloppy cut (so I shaved down all the panels to match). When I fit the 2 baffles together, it's clear there's a gap at the sides.



The gap is small, actually a bit smaller than in the pic above, and it will be covered by where the side panels fit in, I just have to make sure there's room for T-nuts. I'll probably offset the mounting to account for that and hope it will be enough.

And that's about as far as I got over the weekend. Now I just need to decide if it would be better to trim down the inside of the outer baffles a bit or to remove the rubber gaskets from the drivers. Then I can figure out an assembly order and start gluing panels.

NOTE: I tried using the gallery and directly inserting images into this post, instead of attaching them at the bottom. I always feel that it's better to see pics in order as the "story" unfolds, but it is definitely a bit slower this way. The gallery is better than other forums, but still a bit clunky. I don't want to come back to this thread in 5 years and have all the images missing, which is the case with a lot of my old threads, so I'm avoiding external hosting. I might just go back to attaching next time, we'll see.

Owen Bartley said:

After a lot of calculation, speculation, and general sitting around doing not much, I've finally made some progress with real tangible results.

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From the looks of it right now, I'd say your calculations and speculations are paying off nicely! I mostly do the sitting around part (lol). Anyway, I'm loving the updates and pics! Please keep 'em coming.

Owen Bartley said:

Where to start? First impressions I suppose. Until now I have owned an original 15" Tempest (which was a monster, especially to me, back in 2006 or so). These things are straight up beasts in comparison. The carbon fiber cones and caps are beautiful, and the big fat surround is impressive, to say the least. The magnets are huge, and did I mention they're HEAVY? I know there are bigger drivers out there now, but these are still right up there. Build quality seems very good, and I found no issues with a visual inspection on arrival. Mark does great work, and I am very excited to have 2 of his exceptional drivers in my theatre.

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I'm excited, too, and they're not even mine. Please forgive this noob as I don't want to derail your thread. And I'm not looking for a lesson in Designing Subwoofers 101 - just curious about some basics. Do you subwoofer DIY'ers have a secret decoder ring for estimating your lowest usable output? Is that known as the f3? I'm thinking the light blue trace in the graph up top is what you're after.

Owen Bartley said:

My junior inspector seemed excited to get them... but it turned out he just wanted to play with the packing material.

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:jump:

Owen Bartley said:

I will be using Speakon connectors, so to get any kind of a signal to the subs, I had to put together the enclosure connection terminals. A little bit of soldering, and some quick and dirty heat shrink, and they were ready. In free air, sitting on the floor, with limited power after the kids were in bed, my wife could still hear "Bass I Love You" from upstairs.

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Now who's playing?! :jiggy:

theJman said:

The driver is bigger than your helper! :clap:
Excellent build thread.

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Owen Bartley said:

....here's my helper holding up the baffle.

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Come to think of it, car rims come in 18" diameters, too :rubeyes:!

Lumen said:

From the looks of it right now, I'd say your calculations and speculations are paying off nicely! I mostly do the sitting around part (lol). Anyway, I'm loving the updates and pics! Please keep 'em coming.

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Thank you Lumen! The calculations can become a little obsessive, and at some point you have to stop fiddling and start building.

Lumen said:

I'm excited, too, and they're not even mine. Please forgive this noob as I don't want to derail your thread. And I'm not looking for a lesson in Designing Subwoofers 101 - just curious about some basics. Do you subwoofer DIY'ers have a secret decoder ring for estimating your lowest usable output? Is that known as the f3? I'm thinking the light blue trace in the graph up top is what you're after.

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Usable output will depend greatly on the room and the sub's location in it. But as far as the initial calculations, F3 is the point where the response is 3db down, and continues to roll off from there. For example, if this sub had an F3 of 25Hz, it doesn't mean that there still won't be usable output below that. For one, sealed subs roll off more slowly than ported subs do, so a sealed sub with an F3 of 25Hz would have more usable output below that point than a ported sub with the same F3. For another thing, room gain will usually contribute to the low end of your response when it is actually set up in place in your room. There can also be negative impacts from the room, like nulls (dips in response) which are somehow usually right at the main seating location, but these can be managed to a degree by either moving the sub around, or sometimes with EQ.

Lumen said:

Come to think of it, car rims come in 18" diameters, too :rubeyes:!

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Hey, now there's an idea... my car DOES have 18" summer wheels, and they're just sitting waiting to be swapped back on... lol.