Several months ago I purchased two Eminence Lab 12 drivers for $90 total. One of the drivers is brand new and the other was only used for some limited testing of a design idea. I decided to build a dual-opposed sealed subs for my office. I am currently using a Hsu VTF-1 MK-1 ported subs from about 2002.
The sub will be 15" wide, 21" tall, and 20" deep. Those proportions are similar to a Submersive.
According to the enclosure volume calculator
at HomeTheaterShack it has an internal volume of 2.173 cubic feet. The build will use 1 sheet of plywood. I used Cutlist to optimize the build for use with two 4x4 sheets if anyone wants to copy the build and can't get a whole sheet of plywood in their vehicle. I bought a piece of 3/4" 11 ply baltic birch veneer/poplar plys
at Menards for $30. I had used it before and really like it. It is cheaper, yet stiffer than the Arauco ply carried by Menards. It also has nicer outer veneer. I will have 1 1/2" thick baffles so the driver can be recessed. The sub will have a Neutrik Speakon connector with the drivers wired in series for a 12 ohm load. I will paint the sub with DuraTex
. The nice thing about DuraTex is that you don't need to prime the cabinet, it is easy to apply, and it is very durable. I have some speakers with DuraTex and really like it. You can get the DuraTex dyed other colors, but I am using black.
The sub will be powered by a Samson SX1200
amplifier that will be bridged. I bought the amp from MKTheater about a year ago. In bridged mode, it has 900 watts at 8 ohms. Since I am using a 12 ohm load it will probably output around 700 watts. This will be plenty for use in my office. I could make a 4 wire cable that goes into the Speakon on the sub and is branched to the two Speakons on the amp and use both channels of the amp. Each channel would then have a 6 ohm load. I get more power bridged and it is a simpler cable so I don't see any advantage to running the amp in dual mono mode. Any comments?
EQ and a Linkwitz Transform will be handled by JRiver Media Player. I've had a DCX2496 and miniDSP and JRiver is far more powerful and easier to use if the source is a PC.
The sub will be used mostly for music with an occasional movie during lunch. I also do some gaming during lunch and can route the game audio through JRiver so the EQ is still being used. I will probably shoot for a -3dB of around 25 Hz.
Tonight I will cut the plywood and hopefully cut the round openings in the baffles and braces. For the braces I will cut 3 rectangles that fit in the sub and then cut a large circle out of each rectangle. If you read any shelf deflection tests in a wood working magazine you find that a strip of plywood mounted vertically along the bottom front edge of a shelf measures to the least deflection. It is stronger than doubling the shelf. My braces are similar in that they are placed around the entire inside of the cabinet and stiffen the walls. They are only about 3" apart, too, so the cabinet becomes incredibly inert. They are easy to make - you just cut a rectangle and then a circle. It is a lot less time consuming than some of the post or dowel bracing system. It also has the most surface area support with the outer walls.