Denham build

After having good luck with the OS MTM build from Erich, but wanting just a bit more bottom end, I was on the hunt for another build. My first direction was to build a pair of Swopes, but that didn't seem like a big enough improvement to justify the work. After looking through the DIY Sound Group "catalog", I settled on the Denhams. My retired dad agreed to CNC me up some Denham cabinet parts in return for the OS MTMs to use in his shop. It turns out he still had some nice 3/4" cherry ply that I had bought about 13 years ago, and we could make the sides out of that. 3/4" MDF was used for the internal brace, which was based upon the Dayton MTM-1.0MA specs.

The following are some of my build pics.

The first pieces we cut on a table saw back in November:

 

Then we milled a few key parts. The internal braces and rabbets for the brace were done on his CNC mill.

 

Here's the first dry fitting of the cabinet, and the glue-up that ended up happening in early February. The sides are held together with biscuits:

 

I was finally able to order the Denham kit from Erich in March, and mock up how his baffles fit to my cabinet - perfect. "Boy these things are gonna be a beast!" You can already see the nice grain from the cherry ply here, even on the unfinished boxes.

 

My next step was to work up a crossover PCB for the Denham circuit. From my experience with the OS MTM crossovers, this was a fairly quick process and I had nice gold-plated boards within a couple of weeks of starting the design. I have improvements I'll make for Rev 2, if anyone gets interested in them, but they work just great.

 

While I waited for my PCBs to be manufactured, I finished the cabinets. I used the same basic finish I used 13 years ago on my previous project that used this cherry wood - Minwax Polycrylic satin

 

After the main cabinets were done, I sorted out the backs. I also had some downtime while I waited for a new router to round the front baffles. Figuring out how I was going to cut holes for the unique ports that come in the kit, was a good challenge.

 

Continuing back work. Figuring out the positioning for the crossover board, relative to the port and binding posts, this is a good photo of the end hole(s) I ended up with for the port. Also, the holes for the binding post can be seen, and the edge painting I did.

 

With a snug fit, I just used liquid nails on a little bit of the inside lip of the port, and more on the inside to hold it in place. Here is the crossover PCB mounted up, with all of the spade terminals wired up. I also used 3/8" foam window seal tape to seal the back on the cabinet. This stuff is great - I also used some under the PCBs to pad and brace it off of the back.

 

The router arrived and I got to work finishing the baffles. I strongly suggest to anyone doing the same thing to route MDF before it gets any finish. The small amount of primer I had on mine was enough to cause it to catch up occasionally. Here's the first while layer in my "spray booth".

The first layer of the color I chose for the baffles, Rust-Oleum Painter's Touch 2X - Satin Lagoon. Upon hindsight, I see that it almost perfectly matches the color of one of my favorite albums - Transformation, by the Alex Skolnick Trio. Their cover of 'Electric Eye' is a great test track.



Here it is after a few more layers, and some sanding letting the white through. It's an interesting "blue-jean" kind of effect, and I might use it on a future finish.

 

Here's one finished baffle, after getting glued on, and another finish coat. The other baffle is setting in the clamp-up behind it. I used Titebond II for all the gluing and it worked great. Taping the edge of the glue, where the baffle meets the cabinet on the outside, and taking the time to clean up drips as you clamp up is a good way to save finishing time in the end.

 

Here's one cabinet, after center-punching the spots for the driver screws. You can also see my bag of poly-fill, waiting to spring into action.



Here is the back, countersunk and ready for the dipped T-15 cabinet screws that add another pop of color to the back.



The finished back all mounted up. Well, there was still a tiny bit of sanding to be done, but you get the idea.

 

That brings us up to last week, when I finally finished both of these. The resulting black and "Lagoon" front has a nice "'90s Tannoy monitor" look to it that I really like. The back edge adds a nice pop of color, and the screw heads give even more if you go around to the port side.



Here one is, getting some initial impressions alongside my normal HT L/R - PSB Image T6. The Denhams are being used only for music in my garage office, and so far have been an incredible step up. Very happy to have spent the time to build them, and that DIY Sound Group had kits available.

 

For anyone who is curious, these came out to 35 lbs. each.

If anyone has any questions about these, feel free to ask.

 

Thanks. Yeah, I also had the idea for a slim set of Denham towers with the same volume, but not as much depth. That may be one of my next builds for a friend. Are you doing a slimmer tower version, or just the "normal" dimensions with a pedestal built in underneath, Thucker?

I still have more Denham crossover PCBs if anyone would be interested, to help make finishing these easier. I know one can just use a piece of cardboard, globs of solder, and some hot glue to make a crossover, but that just doesn't work for me. Plus, having the layout clearly labeled makes putting in the components correctly a no-brainer. I'd also be open to suggestions for other crossover PCBs.

 

In a quantity of 10, PCBs of this size can be manufactured and shipped to the U.S. for around $5-$10 per board. What it costs in man hours and the experience required to create them is another discussion It could cost even less if you're willing to wait for shipping via a literal slow boat from China (2 months), and make them only to the minimum of electrical requirements. I'll admit that I overbuilt these with thicker board material, and gold plating, but I wanted them to be more physically robust, and to be able to pick up a pair of these boards in 5 years and have the pads and connections all still be fresh.

 

I'm also curious about your MLTL calculations, Thucker, and what that ends up sounding like. Are you going to adjust the port length?

I've been pretty happy with the bass extension in these so far, but I'm always open to more. I haven't combed through every page of the original Bagby Denham thread in a while, but there's some interesting ideas in there, too.

 

Very nice job on those, Thucker. How big is your listening space, and what kind of distance are you sitting at from these?
My experience so far with these is that they have a couple of very distinctive sweet spots.

 

After doing a lot of measuring, and some un-scientific listening, I've determined that these are great speakers, but need a fuller room to really shine. For those folks thinking that they're "normal" desktop monitors, that sit in a small room, with an 24"-48" listening distance, they are not.

 

Also, to those looking for a guide on stuffing for the Denhams, I suggest starting with one 12oz bag of Polyfil per enclosure. This is exactly what I used.
16oz was too much, stepping on the responsiveness, but making great bass at the wave nodes. "A few handfulls" was too little.