How To Make Home Subwoofers
The final touch to a home theater is often the installation of a subwoofer. The subwoofer delivers the subsonic sensations experienced in a movie theater by using low-end effects that are felt as much as heard. Making your own home theater subwoofer is challenging, but the cost savings are significant, as is the satisfaction at accomplishing this task. While there are many considerations, from the shape of the enclosure to the size of the loudspeaker, you can find abundant plans, therefore help, online.
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Things You'll Need
- Speaker driver
- Thiele/Small parameters
- 3/4-inch to 1-inch medium-density fiberboard (MDF)
- 3/4-inch plywood
- PVC pipe (for port)
- Hack saw
- Power drill
- Router or circular saw attachment
- Speaker wire
- Binding posts
- Connection terminal
- Glue
- Silicone caulk
- Wood screws
Instructions
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1
Pick the size of loudspeaker that will be housed in the cabinet. Popular sizes range from 8 inches to 20 inches, but the best bass response will be produced by 12-inch, 15-inch, or even 18-inch loudspeakers. The subwoofer is generally a diameter larger than the woofers in your front speakers in a home theater setup.
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2
Get the Thiele/Small parameters. This are supplied with every component of any worth. They tell you that component's resonance frequency, which is critical to enclosure size. If they are not supplied with the component, you can find them easily online.
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3
Decide on your type of cabinet. There are five types of popular design, but the two most popular are sealed and ported/vented/bass reflex. Sealed enclosures are often self-amplified; ported designs yield a bit more low-end and are more efficient. They're also larger in cabinet size, though, and more involved as a DIY project.
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4
Get your enclosure material. Do you prefer a traditional wood rectangle? Or would you like the sub to double as an end table? Sonotube is a popular material for round subwoofer enclosures.
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Buy your enclosure material. The three main materials to consider are plywood, medium density fiberboard (MDF) or Sonotube (used to pour concrete columns). Saw the material to your enclosure measurements or have them cut wherever the material was purchased.
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Dry-fit your sides, bottom or top, and bracing. Bracing is a piece to increase cabinet rigidity and aid in minimizing vibrations. It's often the same size as the bottom piece, which is inset into the sides or walls of the enclosure.
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Glue the sides, bottom (or top) and brace. Additionally secure the connections with wood screws. If the screws are to remain, countersink them. Clamp the enclosure with furniture clamps, and let it dry for eight hours.
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8
Cut out the back panel. If you are building a powered sub, the cut-out should accommodate the plate amplifier. If you're building a sealed subwoofer, the terminal cup is what you cut out space for in the back panel. Dry-fit the panel, then glue, screw, clamp, and let dry as in the step above.
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Attach the top panel. This panel may be inset in a rectangular design, or be larger than the enclosure itself if being used as a table top. In either event, attach with glue and wood screws, clamp and let dry.
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10
Prepare and attach the front panel. This is the panel that needs to be cut out for the loudspeaker, and often for the port(s). Make those cuts. Before attaching the panel, caulk all inside seams with silicone caulk.
Allow at least 15 hours for the caulk to dry. Silicone caulk emits gases that can erode speaker surrounds (the rubber portion around the cone of the speaker).
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11
Constuct the port(s). (If the enclosure is a sealed design, skip this step.)
Ports can be square, constructed of the same plywood as the cabinet panels, or round. Round ports are often made with PVC pipe. Flare the ends of the port no matter what shape port you make. Glue the ports to the back of the front panel, allow the glue to set; then caulk around the ports to make a complete seal, and let the caulk dry.
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12
Glue, screw down, and clamp the front panel. From the opening in both front (for the loudspeaker) and rear (for the terminal cup or amp) caulk with silicone caulk all the seams of the front panel. Let this dry for at least 15 hours.
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13
Sand the cabinet. Router the edges if you are to have rounded edges. Fill all countersunk screw holes with wood putty. Sand again. The cabinet is then ready for the installation of the loudspeaker/driver and the terminal cup or plate amplifier.
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14
Install the back piece, be it a terminal cup or plate amplifier. If it is a plate amplifier, all the terminals are on the rear-facing part of the amplifier. Make sure all parts clear internal bracing. If there's not enough clearance, notch out the bracing. Secure the back pieces with glue. Once the glue is dry, caulk around the perimeter of the terminal cup or plate amplifier. Allow sufficient time for the caulk to dry.
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Attach connecting cables between the terminal cup or amplifier and the loudspeaker/driver. Then attach the front speaker. Use wood screws and a non-drying caulk around the cone's perimeter to make an airtight seal.
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Finish the cabinet with a wood veneer, paint or stain of your choice.
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Tips & Warnings
Use speaker design software for this project. Win ISD is one such program that can be downloaded free.
Ported designs are "tuned" to a resonating frequency of the driver and are also adjusted in their interior volume by the size of the driver and the port. For this reason, ported subwoofers tend to be larger than a sealed enclosure, but they deliver greater low-end response.
Thiele/Small parameters are the mechanical and electrical measurements that determine the ideal design for the speaker cabinet. They are also know as T/S, and they exist for any driver/loudspeaker. If such information is not provided with the loudspeaker (the driver plus the cone), it is available online for every size component. Having those components and the T/S parameters dictates the interior volume of the enclosure, or box, and also dictates the resonating frequency that the enclosure is "tuned" to, the amount of damping for the enclosure and the amount of bracing that might enhance the rigidity of the "box" inside.
Always use generous amounts of glue and silicone sealant in constructing the cabinet. No air should escape the cabinet, except through the port in a ported design.
