The design of the speaker cab was based on the compact size I wanted, the specifications required by the Deltalite-II 2512, namely 1.5 to 3.0 cubic feet of internal volume and the need for a built in rack for the few pieces of rack gear I use. I wanted it all in one cabinet. I was prepared for it to be heavy because I wanted it built like a tank. I also had to have room for the tweeter and two 4 inch x 5 1/4 inch long ports. I wanted to incorporate a crossover so I had to plan a spot for it away from the sound insulation so the heat from the crossover didn't cause a fire.
I had a 4x8 sheet of 3/4 plywood left over from another project so that became my choice of wood for Sound Critter One. BTW, my son, a 7 year Navy veteran, came up with that name. I kinda like it myself. This plywood was not my first choice for this project. MDF and or Baltic Birch plywood wood have been great. The stuff I used is not void less, ie., free from knot holes and empty spaces between the laminated plys which cause unwanted resonances. It is not 12 ply and made especially for acoustic applications. It was however, very strong and heavy, it was very cheap (free) and it was sitting here in the way. I measured the rack I currently used (also homemade) to get the dimensions for the cab. I built it 14" deep. It is 25.5 inches high without the 2 inch casters. It is about 21 inches wide. The speaker cab measures 18x13x15 internally. This gave me a volume of about 2.4 cubic feet, well within the specs for the Delta-Lite II.
The baffle and the rear of the sealed cab were from 1/2 inch MDF. This is a much better choice for the sound baffle than the plywood. 1/2 inch or 3/4 inch works fine. A half inch inside the front and back of the cab I installed 1x1 bracing around the perimeter of the opening to give purchase for the rear panel and speaker baffle screws. Once the bracing was installed I sealed every joint, crack and seam with 100% Silicone sealant to stop air leaks. I ran a bead along the front side and the back side of all the bracing. I wanted to make this puppy air tight! All the joints in the cabinet were glued and screwed during assembly for strength.
Next I installed the rear panel. I used a bead of adhesive weather stripping around the perimeter of the door again to get a good air tight seal. I pre-drilled pilot holes for the 1 1/4 inch wood screws and fastened the rear panel. Once the door was installed I used 2 inch thick pieces of fiberglass insulation to line the interior of the speaker cab to stop unwanted resonances. I stapled it just to the inside of the case in the corners and in the centers so as not to completely crush the 2 inch thick panels. I left a gap in the insulation on the bottom to mount the crossover.
The trickiest part was cutting out the holes for the speakers and the 4 inch ports. But it wasn't really all that bad. I first cut the soundboard or baffle to fit the opening. Next I laid everything out on the panel to get a sense of spacing and what goes where. When you do this remember to allow for the internal bracing thickness inside the cab. Draw a line diagonally across the baffle from each corner. Where the lines intersect is the exact center of the baffle. Once you get everything centered and laid out, mark everything well with a pencil. I used a jigsaw to cut out the openings. I used a fine metal blade for a fine smooth cut. Once cut out I marked and drilled all the mounting holes for the speakers and the 5" long by 4" diameter PVC ports. I glued the ports flush to the front panel with Silicone adhesive.
With the back on, sound deadening insulation installed and the baffle cut out I was ready to do the electrical part. I drilled a hole in the top of the speaker enclosure to pass the speaker wire into the box from the rack area. Wiring a crossover is easy. In a two-way crossover you typically have two input connections, + and -. You have two + and - connections each for the woofer and tweeter which are sometimes marked w-, w+, t-, t+. Simply attach the input + and - wire from the amp to the corresponding points on the crossover. Same with the Ws and Ts. Attach the + and - terminals on the crossover to the + and - terminal on the woofer and tweeter. Depending on the type of crossover you have you may have to do a little soldering. Once all the wires were attached I installed the crossover in the box away from any insulation. It is much easier to do the soldering outside the cab.
With all the holes drilled and cut and the speakers and port tubes mounted on the baffle, and the wiring done, I removed all the components and spray painted the baffle flat black. I used spray can flat black truck bed liner to paint the outside of the main box. While it was drying I attached the four swivel casters to the bottom. Once dry I screwed the speaker baffle to the box. I did not use any adhesive when I attached the baffle because I want to be able to remove the baffle to replace\tinker with components. I did use a touch of Silicone to seal the hole that I had cut in the top of the box around the speaker cable.
Standing back and looking at Sound Critter One my first thought was this thing is a tank! LOL! It looks like I have finally built the guitar rig I have been pondering for 3 years! All that was left was to hook it up and see how it played.
No comments:
Post a Comment