Originally Posted by Ed Van Belkom
Brian thought it might be a good idea to have a seperate thread for the DIY Servo Subwoofer kits.<br><br>
This will help seperate the discussions between fully assembled units and DIY kits.<br><br>
Brian could you chime in and let us know what kits are currently available in the different configurations?<br><br>
Could you also let us know what is in the works and options available in the near future?<br><br>
This will help many of us that want to save money or have an custom finished enclosure made.
Rythmik audio DS1510HP CI build
I designed and will be building the cabinet for my DS1510HP myself, so I’m going to describe that. Most of the time will be spent on the actual build. My hope is that someone who needs some additional guidance on the details of building such a cabinet can get some use out of this.
This cabinet is going to be part of a wall of built-in bookshelves and cabinets, so that pretty much constrained the design to match the other cabinets. That, plus general acoustics and mechanics issues, led to the following design constraints:
Driver placement: as far as possible to the front and bottom of the enclosure while still ensuring that the driver won’t hit the speaker grill.
Back wall placement: far enough back to provide a minimum of 2” clearance to the back of the driver.
External dimensions: 36” wide x 15” deep x 24” high
External volume: 3-4 cubic feet, with 3.5 being the optimum (as provided by email by Brian Ding of Rythmik Audio).
Bracing placement: external wherever possible. Internal bracing will tend to obstruct the air flow in what will be a shallow box .
Amplifier placement. Since the speaker baffle is the only vertical surface exposed, the amplifier has to be mounted on the baffle. This means that either the amplifier is in the enclosure with the driver, or airtight connections have to be provided between the amplifier and driver, through the walls of the inner enclosure.
Materials: Nominal 3/4” plywood: cherry veneer with hardwood inner plies for all visible surfaces, and Baltic (or Russian) birch plywood for the rest.
There are two basic options for the cherry plywood. One has a layer of medium density fiberboard (MDF)underneath the cherry veneer, and the other has all wood veneers. The MDF gives a very smooth surface, but previous experience with using it for bookshelves has taught me that it’s not as stiff as all wood veneer plywood.
Many people like Baltic birch plywood for cabinets. However, I’m putting a clear finish on these, and I would have had to veneer all the exposed surfaces. That’s a lot of work. Since I have used the cherry plywood on a previous subwoofer (NHT 1259 driver in a cabinet similar to this one) with good success, I decided the benefits of using all Baltic birch didn’t justify the labor involved.
The first three attachments are the plans for the cabinet: front elevation (with the speaker/amp baffles treated as transparent), two vertical cross-sections looking from the side at the position of the driver and the amplifier, and a horizontal cross-section looking from the top at the position of one of the horizontal braces. I don’t use 3D software for my plans, so I don’t have them available for this one. I trust that the plans will make sense once we see the construction pictures, if not sooner.
Rythmik says a sealed cabinet for this driver should be between 3-4 cubic feet. Brian Ding of Rythmik told me in an email that that’s the external enclosure size, and recommended 3.5 cu ft. The external volume of this cabinet is 4.04 cu ft, larger than the optimal size. I could have made the enclosure smaller by putting the amplifier outside it, but I decided that the complications of making an airtight electrical connection were not worth it. Once I decided to include the amplifier in the enclosure, there was no practical way to make the enclosure smaller without exceeding other design constraints.
Rithmyk also says to line the walls of the cabinet with batting, which they supply with the rest of the parts. All the walls except the front will be so lined.
Bracing: Most subwoofer designers place heavy emphasis on bracing the cabinet. I agree that it is necessary for such large cabinets. However, we need to remember the purpose of the bracing. We want any resonance in the cabinet to be at a higher frequency than anything the subwoofer will be reproducing. I’ve chosen to do that by using braces that divide the various panels into sections small enough that the resonant frequencies will be high enough.
Bracing in general: I chose to use 2x4 lumber for the braces, for several reasons. First, they take up a lot of space, and I need to reduce the volume of the box considerably. Second, they’re wide that ¾” plywood, which makes driving screws through the wall into them much easier. Third, they’re much easier to make, since all I have to do is cut them to length.
On the inside of the enclosure the limited space pretty much dictated where I can put braces. In particular, I wanted to put one more on the back wall, but there just wasn’t enough room. On the top and right side I had complete freedom, so I chose a semi-random layout.
Front panel: This the baffle plate for the driver and amplifier. It’s a double plate, primarily to make the construction of the driver baffle easier, but also to add stiffness. There’s not much room to brace the baffle, so I wanted to reduce the chances of the entire baffle moving back and forth with the motion of the driver. The double thickness will help that (2 x thickness means 8 x stiffness). In addition, the edges of the baffle are inset in dadoes all around. That essentially keeps the edges from moving at all. In addition the large holes will force the panel to vibrate in small sections. The resonant frequencies should be high.
Top panel: It’s fairly large, and only a single thickness. However, it is extensively braced.
Left panel: These are the smallest, which raises the resonant frequencies, but not as well braced as the other panels. However, it will eventually be screwed to the cabinet to the left. I don’t foresee any issues.
Right panel: This is a single thickness, but small, and very well braced. Again, I don’t foresee any issues.
Bottom: This is extensively braced with the braces connecting to the bottom of the cabinet and should have no issues.
Back. This is extensively braced with the braces connecting to the back of the cabinet and should have no issues.
Construction: I’ve attached two files. One is the plans, with comments. The second is the detailed build process, showing the various steps of the construction. As I go, I will add photos, tied to these steps.