Tuba 24 Subwoofer    Back to Lou's Home Page   Jan 7, 2006

The DR250 turned out to be quite a hit with my young bass player. He used the heck out of it for his high school band, carting it to home games for half-time shows. When he decided to upgrade to a 5 string bass, he naturally wanted the same thing most bass players want -- more bass. After conspiring with his parents, we decided to do a Tuba 24 (from Bill Fitzmaurice Designs) as a Christmas gift. We used passive crossover to match the DR-250 and pick up that last octave with a bit more authority.

The project took us about 15 hours over three afternoons.


Here is the speaker baffle. We used an Eminence BP102 in reverse mount position. (Basket toward the horn exit). I used 3/4 baltic birch for the baffle with #8 hurricane nuts for mounting. Note we glued in the nuts. We used some hex cap bolts for mounting the driver and haqndles. Sexy, but a major pain to drive them with a hex key. The plywood is 1/2" "medite" (basically a luan veneer) Cheap and light. But we had some definite warping isssues with it.

Here's a shot of the door side. Much easier to add the support strips while adding in the panels. It allowed us to use the brad nailer from the back of the panel for mounting. We used the same 1", square drive, trim screws for most of the assembly.


Here's a 3/4 shot of the rear before final assembly. I added the glue block adjacent to horn slot to help straighten and square our warped plywood. I also had to "repair" a panel. I can't understand it, I cut the darn thing twice, and it was still too short.


None of Adam's friends believed he actually helped build the DR250. So here's proof.


Here's a thru shot before we mounted the side and bottom. We cut the slot on the back panel for the rear handle first. Then matched the cut on the top. We should have mounted the braces for horn throat before we added the throat panel. We didn't. As a result, I had to make some "compromises". I used a router to flush trim the sides and bottom.

Here's a shot of the front. Not the best carpeting job, but nothing that can't be fixed with a little patience. Adam designed and cut the braces. Adds a bit of artistic flair.


Here's a rear 3/4 view. The side handles are bolted thru the door and the side. We were able to reach this side thru the baffle hole . We used wood screws for the handle on the back. The casters are mounted using 1/4" bolts and hurricane nuts. Just plain nuts could be used as the panel is accessible thru the throat. We used closed cell foam strips to seal the back handle, the door, and the cable plate. I found the casters locally.

The crossover board is mounted inside the box. I ran four wires thru to the cable plate. The "IN" uses a 4 pole Speakon plug (only two poles are hot). The OUT uses a 2 pole Speakon. We have a dual 4 pole cable to go from the head unit to the IN. A 2 Pole cable feeds the DR250. This way we don't have to remember which is IN.

The IN feeds a 9mh Erse coil (10's were out of stock) attached to the negative terminal of the BP102. It also goes thru 210 uF of caps to the "OUT" plug - a 2 pole speakon. I used four 200 uF NP electrolytics (Two pair of parallel 200uF in series, all in parallel with a 10 uF GE poly cap) I did this to increase the voltage handling.

Cranking Up the Rig
We hauled the Tuba 24 home, hooked it up with DR250 and ran it off Adam's Behringer head unit.

The smile on that young man's face when he hit that low string told me everything I needed to know.

Adding the Tuba to the 250 is one killer rig. Clean and effortless reproduction. I was concerned about the sensitivity match between the Tuba and the DR250 --especially with 102 in the Tuba and a Beta 10 in the DR-250. It really isn't an issue. A bit of twiddling with the equalizer smoothed things out nicely.

Partial List From Parts Express

290-471 EMINENCE LEGEND BP102 10" BASS SPEAKER
262-820 DAYTON MH110 STEEL BAR HANDLE
262-305 SURFACE MOUNT HANDLE BLACK
027-428 DAYTON DMPC-10 10uF-250V POLYPROPYLENE CAPACITOR
266-946 ERSE SUPER Q 10.0mH 16 GA 500W INDUCTOR
027-366 200 uF -100V NON-POLARIZED CAPACITOR
262-028 DISH FOR (2) NEUTRIK D/NL4MP BLACK 4" x 4-3/8"
092-059 NEUTRIK NL2MP SPEAKON 2 POLE PANEL MOUNT
092-058 NEUTRIK NL2FC SPEAKON 2 POLE CABLE MOUNT
092-050 NEUTRIK NL4FC SPEAKON 4 POLE CABLE MOUNT
092-067 NEUTRIK NL4MP-UC SPEAKON 4 POLE PANEL MOUNT
081-1080 #8-32 HURRICANE NUT 50 PCS