Diving in - a pair of DR250s

[billkatz]

The finishing line is a mirage... it's still a long way off. Slow, steady & methodical will do you grand.

Yes, that's the way I have been going. I was working with the dremel last night, and almost have my melded array fitting into the module. Just a little more sanding... The good part is at this point it is starting to look like a speaker rather than a pile off odd shaped wood bits! And as others have noted - once the PVC reflectors are glued on the back the DR takes on a certain rigidity and realness.

[billkatz]

After too much work with the Dremel, I finally got it so that I could slip the module in and out, at least temporarily. Today I added the little bits that allow for mounting the top and bottom of the module. You can see them being glued in with a fresh set of wax paper here:

Once the glue dried, I discovered that the places I'd Dremeled out were just a bit low, and now the module won't go in again. More sanding in the morning.

I also got one side brace installed. The second side brace was my first time in this project I cut on the wrong side of a line. It is now having a 1/8" think bit of BB PL'd onto its side to make it fit out to the sides.

[billkatz]

A little vacation slowed me down - two weeks in Prague adn Budapest to visit my daughter who is studying abroad. But now back to the speakers. Just before I left I got one sheath glued on the module, and then the second when I returned. Next I turned to fabricating the nacelles. I picked up a trick in hifibob's latest thread about tilting the blade against a piece of wood against the fence, and was able to cut the correct angle. Then sliced into half inch pieces, we have nacelles!

Then I drew the markup lines adn glued them on - I spread a very thin layer of PL with a putty knife and then used some hot melt at the tapered end. Once the glue dried, I was ready for the next step.

I wanted the inital holes to be perpendicular, so I borrowed a drill press, and that worked great. Then I clamped the module back on the rest of the cab, and used the holes in the module as a guide to drill through the front of the flanges. I then enlarged the flange holes and seated hurricane nuts. Here's the module bolted up using 2" long hex-head cap screws (actually torx head). Everything lined up nicely. I still need to put the gasket tape on, but I might put on some Duratex first.

Just for grins, here's the tweeter module sitting in the front of the cab. I have my butt-cheeks being pre-bent, and they go on next.

Random DR question of the day: what do you need to do to seal around the top hat that goes in the bottom of the cab? Just gasket tape on the mating surface? Some silicone caulk on the inside?

[Tom Smit]

Random DR question of the day: what do you need to do to seal around the top hat that goes in the bottom of the cab? Just gasket tape on the mating surface?

I don't, but you do.
Gasket tape.

[billkatz]

Tonight I installed the butt cheeks.

The first one didn't go very well - after the PL was on and I had many staples in, I realized that the center support was a tiny bit bigger, and there was a gap at the bottom. I squirted in some extra PL - I hope it holds.

Before I put the next cheek on, I checked everything with a straight-edge, and sanded down the high points on the center support.

The strap clamps and boards at the ends as shown in the plans were crucial to getting this put together correctly. The poplar wants to pull through the staples.

[billkatz]

Just some little bits of progress... DR #1 had the back halves trimmed to size and a little black spray paint on the inside. The sides are trimmed to their proper trapezoidal shape and ready to go. The sliding table really saved me here, as I could adjust 1/4 degree or so to get the top and bottom cuts on the sides just right.

I built the second melded array last night, and tonight assembled the speakon jack plates and cut the hole in the first back. Still contemplating the 77 degree cut on the back to make it match the slope of the curved back halves. More pictures soon.

[Grant Bunter]

Still contemplating the 77 degree cut on the back to make it match the slope of the curved back halves.

Even using a complementary cut (look that up if you don't know what it means) to end up with a 77 degree cut is difficult.

Have you got a sanding table? Or a belt sander? Or any sander?
Do 45 degree cut(s) to de bulk the ply and finish it off with a sander...

[billkatz]

Still contemplating the 77 degree cut on the back to make it match the slope of the curved back halves.

Even using a complementary cut (look that up if you don't know what it means) to end up with a 77 degree cut is difficult.

Have you got a sanding table? Or a belt sander? Or any sander?
Do 45 degree cut(s) to de bulk the ply and finish it off with a sander...

I only have a handheld belt sander, which is less than a precision instrument...
I built a jig to cut complementary angles on my table saw when I had to make the ~57 degree cut for the horn throat of the DR, and that piece came out fitting just right. Gee - that seems like so long ago. DRs really are a marathon build. I'll try making some cuts on scrap pieces and see how they come out...

[billkatz]

Well, the 13/77 degree cut went easier than expected, but my calculations must be off, as it hits a tangent farther in than I planned:

This would make the back panel about 1.5" narrower than spec, but it still might look OK. I'm having second thoughts about the 3/4 length sides, but really don't feel like turning back now.

[billkatz]

I made a little progress tonight. On the first DR I spent an hour or more with the dremel making the melded array fit into the module. Now that I have a drill press, I decided to do something that would look a lot neater. I got the appropriate hole saw blade, clamped everything up, and drilled litle arcs from the module fronts.

It worked very well, and the module fits nicely. It does look much better, even if only I will see it.

Next I put the first side panel on cabinet #1. Lots of PL. Not much clamping needed, just a bunch of brads. I rounded off the rear part where it comes down to the back butt cheeks.

It really is starting to look like a DR! Once I figure out how to finish off the back, the woodwork on cabinet one will be done! (save for some rounding off and such)

Then there's the acoustic foam I need to glue in, the wiring, etc.

My Metcal soldering iron is coming back from storage tomorrow, so the wiring will be straightforward. (For those that don't know, Metcal is a special temperature controller soldering iron that cost more than my table saw... It is usually used for surface mount electronic components.)

[howiez]

Metcal is the bomb! My brother used to work in a surface mount shop as a repair tech. They upgraded their repair line and he was able to get a Metcal they were throwing out. its a stripper model, but boy oh boy can that baby solder. Makes me sick when i have to use a $30 gun or $15 iron that i own. I borrow it for months at a time : )

[billkatz]

The wood pieces are all in place on DR #1. And the module sheaths are on DR #2.

I think that means that every bit of wood is now installed on DR #1!

I rounded the outside edges with the round-over bit tonight so that the chevron corners will at least fit on the front 4 corners. (They don't have the back 4 corners - one of the tradeoffs of the 3/4 width sides.)

I used my complementary angle jig and cut the 77 degree angles on the back, and then worked it with the belt sander. This is probably the worst looking part of my DR build, but it's done and PL'd together.

I also bough the terminal strips that I'll use to build the crossovers. Drivers are broken in, and my amp is arriving on Thursday.

[billkatz]

My son chose a blue enamel for the tweeters, so I removed the piezo elements (60 screws) and painted the horn parts. Then I re-attached the driver elements (60 screws, by hand) and added the wires (80 solder joints) I made sure each little driver made noise (using my waveform gen at 2.5k) I trusted the phase markings on the tweets. We'll see later if that trust is misguided. Tonight I finished the wiring:

That's some 22 gauge teflon insulated wire I had in my junk box from some long-ago electronic project.
Then I added a terminal block and glued up the wire hole. I drilled out the holes that had mostly disappeared when the piezos were trimmed, and attached the tweeter assembly to the module. It still needs the diffuser dowel. But it looks pretty good on the front of the cabinet:

A little more paint, some foam, and crossovers.
The mid-bass driver is mounted and ready.

[billkatz]

Just a little progress tonight - I built the crossovers for one cabinet:

I used single sided PCB, but didn't etch anything. I did use the plane as the negative conductor on both sides.

I also painted the dowel I will used as the diffuser in the melded array.

[billkatz]

My ears are ringing - and that's a good thing!

Tonight I finished the first DR250 - wired up the crossovers, glued in the egg-crate foam, added the gasket tape, and screwed on the front. Then I got out my electronics - powered up the Driverack and set some useful settings - HP 45 Hz 24dB LR, set the crossovers at about 100 Hz, put in some GEQ that was a mirror of the DR250 chart from the sales page, set the limiters to about 35V just to be safe. Here's the test setup:

Then I cued up Boston's first album - and - I was only getting subwoofer output. After checking some cables and moving things around, I removed the jack plate from the DR and found one of the crimp connectors had come apart. D'oh. I re-crimped that, put it back together and - Yes! Music!

Being in the garage I could see the bass had good spots and bad spots, and the highs sounded like they need better equalization, but even at modest volume I could feel that bass drum in the gut. Now to finish the paint, and try some RTA in the den, with proper sub placement.

Here's the speakers together:

Now to finish my second DR and then my second sub.