How to Make a Bandpass Subwoofer Box

While the quality of the subwoofer and the amplifier play a major role in determining the overall sound quality produced by a car stereo system, a poorly constructed subwoofer box will negatively impact the subwoofer's performance. Ensuring the quality of the subwoofer box is especially important when bandpass subwoofer boxes are involved as bandpass boxes are essentially a sealed subwoofer box connected to a ported subwoofer box. Any miscalculation in the design of the box or a construction mishap can severely decrease the effectiveness of the box.

Things You'll Need

• Subwoofer box specifications from manufacturer
• Jigsaw
• Drill
• 3/4" or 1" medium density fiberboard
• 2" drywall screws
• Panhead sheet metal screws
• Carpenter's glue
• Silicon caulk
• Tape measure
• Speaker wire

Instructions

1. Consult the documentation that came with the subwoofer to determine the specifications for the subwoofer. Every subwoofer requires a different sized box in order to function properly. Separate figures will be provided for the volume of the sealed section of the enclosure as well as the ported section. Additionally, the specific size of the subwoofer opening will be provided.

2. Using the volume calculations obtained from the subwoofer manufacturer, cut the MDF with the jigsaw. At the end of cutting, there should be a bottom panel, two side panels, two end panels, a top panel and a subwoofer mounting panel.

3. Cut an opening for the subwoofer using the jigsaw in the panel where the subwoofer will be mounted. The exact size needed for the opening will be provided in the specifications from the manufacturer.

4. Cut an opening in the MDF that will be the back panel for the sealed section of the subwoofer. The speaker terminal cup will be mounted in this opening.

5. Cut openings for the ports in the MDF panel that will be used on the end of the ported section of the box.

6. Align the sections of MDF required for the construction of the box except for the top panel and subwoofer mounting panel. Use the drill to pre-drill holes to connect the sections as well as holes for the mounting of the speaker terminal cup.

7. Apply the wood glue liberally between each contact section, and then use the drywall screws to assemble the box.

8. Affix the speaker terminal cup within the opening cut for it in the back panel using the drywall screws.

9. Line the interior joints of the box with the silicon caulk and set the box aside to cure for 12 to 24 hours.

10. Insert the subwoofer mounting panel inside the larger box to create a sealed section of the box and a ported section of the box. Verify that the appropriate volume is established in each separate section using a tape measure. Secure the mounting panel using the drywall screws.

11. Mount the subwoofer in the mounting panel so that the magnet end of the subwoofer is located in the non-ported section of the box. Attach the subwoofer using the sheet metal screws.

12. Connect the subwoofer to the speaker terminal cups using the speaker wire.

13. Secure the top panel onto the box using the drywall screws. The completed box should now have a sealed section divided from a ported section with a subwoofer mounted between the two sections.

Tips & Warnings

• Carefully review the subwoofer box specifications provided by the subwoofer manufacturer in order to ensure that the box has the correct volume in each section as well as the correctly sized port holes. Any deviation from the manufacturer's specifications can severely compromise the subwoofer's performance.

References

• Crutchfield: How to Build a Subwoofer Box
• Car Audio Help: Building Subwoofer Boxes
• Mobile Electronics Certified Professional: Box Building 101