Dual Sealed Mach 5 ULX-18 Subwoofers
So I have not posted here in a while. I have tried to enjoying my system as it is instead of doing endless tweaks and upgrades. Other priorities have taken a focus away from this hobby. Luckily, I am really happy with the system the way it is for what we use it for.
However, I digress, the reason for this post is I built some sub about 2 years a go, and just finally got around to finishing the raw MDF cabinets last week. I thought I would share with the community since I quietly got all the info to get these bad boys built from here.
Unfortunately I did not take any build pics other then before and after finishing. I did not do anything that can't be found in other build threads so you are not missing much.
Double baffle, recessed driver mount. Sealed, 21" in all dimensions. I don't remember what the internal dimensions worked out to be in the end. There is a a bunch of cross bracing. Front to back bracing is located at the drive mount holes so the driver could be attached without t/hurricane nuts.
I used t-nuts on my last build and they were a pain. Boxes were glued and screwed with standard dry wall screws. I don't have any clamps so went with the screws. They are filled with poly fill, again I don't remember how much I calculated to go in there. I don't have many tools. In total I only used a table saw, router and drill. I made my own circle jig for the router.
March 5 ULX-18. Beautiful beasts. Not much to say other then heavy, well made, look and sound great. Being in Canada they were and easy choice.
So for two years they sat as MDF monstrosities. I made a point to take a week off work before temps got too low to use the contact cement and got these done. There is a local wood supplier that has a huge selection of veneer. Exotic woods in Burlington. Check them out, they have great stuff. I got a 4x8 sheet of paper backed walnut veneer for $100, which was enough to do both boxes. I did not cover the bottoms or back. I figures why waste the money on the sides no one will see.
I attached the veneer with Lapage heavy duty contact cement. I know there is a lot of advise about the best method to apply veneer. I have used contact cement in my last build and it was fine so went with that method again. I am not expert but if you do use it, make sure you get excellent coverage on both parts. The MDF, especially end grain will soak up the contact cement and need several coats. Similarly the paper back seems to soak up a lot as well. Make sure there is a sheen to the glue, if it goes dull when dry add some more. Also make sure it dries well before attaching the veneer. Sides need to be not sticky to the touch. I give at least a good 15 mins before connection.
To make sure your veneer is lined up properly I use the wax paper method. Dowels work as well but wax paper is what I had on hand. The dried glue will not stick to the wax paper. Lay 2 pieces on the box. each piece overlapping in the middle of the side by a few inches. Lay the veneer which you have cut to hang over each edge by about a 1/2 inch on the side. This lets you position the piece where you want it. Once it is in place hold it steady and slide one of the wax paper pieces out gradually, from the center. Then the same for the other piece. Use a land scrap piece of wood instead of a j roller to smooth out any air bubbles and provide the force for the glue to stick fully.
I did the final trim of the veneer with a razor blade and sanded it flush. I guess a flush trim bit would work as well but I just don't trust power tool (in my hands) on the delicate veneer edge. i may just be paranoid.
Once covered I sanded down to 300 grit I think (need to double check this). Finish applied is pure tung oil. It is easy to work, non toxic, smells nice (like nuts) with and I find it brings out the grain and natural walnut color well. It does take a long time to cure fully, but they have all the time in the world to cure sitting in the theater. Application is easy. Rub on with a rag, let it sit for a bit and remove extra with another rag. Let it sit over night. Apply another coat the next day and sand with 600 grit. Remove extra and let it sit over night. Do this for 3 coats and you should have a nice smooth durable finish. At least that is what google tells me. Tung oil dries to a fairly matte finish.
Hope you like the result. Thanks for all the help everyone gave me without knowing. I will try to answer any questions as best I can.
Sound great. My previous sub was a 12" ported Adire Shiva DIY. These are night and day, which they should be. So tight and clean. I have them powered each with an bridged EP4000. The theater is in a basement with a concrete slab and these will shake the couch without braking a sweat. I am running an XMC-1 processor and using the standard Dirac room correction with a house curve to bring up the deep stuff. I had REW graphs on an old laptop that has since died other wise I would provide the frequency graphs. Unfortunately I don't see a time in the near future to be able to run any measurements. If I ever get around to upgrading Dirac or re running things I will update this post.