I was recently able to just squeak in to a group buy for a pair of Mach 5 UXL 18s, and I jumped on it before I had a chance to do much research or planning. I took enough time to assure myself that the price was right, and that they were still solid performers, and the local Canadian source (no need to re-ship/drive to border/etc.) was what sealed the deal for me.
I had been planning for a long time to use a pair of sealed 18s in our theatre build, so there’s no deviation there. I was considering the SI HT18 before they disappeared, and then looking at either the new DS4-18 or possibly an Ultimax 18, both a step up with a corresponding increase in price. When I saw the chance for a pair of UXLs, I did some quick googling and determined that they seem to have more output capability than the other 2 (at least a higher Vd), were well regarded, and perform well in small sealed enclosures. That’s another plus for me, because I wanted to keep mine under 2x2x2 to hide behind a tight screen wall. Price will be reasonably comparable by the time I get them all to my door, though they are still likely a little more than the SI or Daytons would have been.
Now... what to do with them!? As I said, I had been planning for a pair of sealed 18s. Right now I’m running a large ported (original) Tempest tuned to 19Hz, and a ported SDX10 tuned around 25Hz. By my calculations, those two combined still fall well short of the Vd of a single UXL, so I think I’ll be in for a noticeable upgrade. I’ve been very interested in trying a Linkwitz Transform design for a long time, and I think that’s the route I’d like to take with these. I like the idea of a small sealed sub with a very capable driver given a good amount of power and EQ to achieve optimal results. My planned amp so far is an inuke 6000DSP based on the performance per dollar ratio. I get the impression that the UXL is a hungry beast, and I want to make sure they have enough power to really get moving. With that said, my room is less than 10x20x8 (1,600 cubic feet) so I don’t anticipate the need to drive them very hard to get enough output.
So, where do I start? It seems that the UXL likes small sealed enclosures, so let’s start with about 3.5 cubes, which seems common. A 20x20x22 enclosure made from 3/4" material with a double front baffle, less about 1/3 cu ft for the driver gives me 3.566 cubes (internal). Minimal bracing won’t hurt that too much, and stuffing will help to offset.
If I’m modeling that correctly in WinISD, that gives me an f3 of 46Hz, and an f6 of 32 Hz. Now I’ll need to improve on that. If I wanted to do it quick and simple, I could use the DSP from the inuke6000 and dial in a few bumps. Alternatively, I still have my BFD (Behringer DSP1124P) that I could use for simple EQ and not need the DSP model inuke. OR... if it actually provides a better solution, I’d be happy to skip the DSP model and pick up a MiniDSP, which I could program with the Linkwitz Transform tool and do it properly. I have a few problems here.
First, I don’t really have a specific target frequency, I just want to maximize my useable low end response. Second, I’ve been playing with the LT in WinISD and it seems to take the cone excursion beyond Xmax pretty quickly with well under the 3,000W theoretically on tap (as expected, really). Building in a 10Hz high pass seems to help, but I really don’t know how to properly model this and integrate real world amplifier power.
I guess that’s where I am right now. Maybe not as completely lost as I thought, but in need of some serious mentoring to make what will be my last (?) sub build as epic as it can be.
