How to Build a Subwoofer Box: A Step-by-Step Guide

A great subwoofer in the wrong box sounds like a bad subwoofer. After 30 years in the install bay, here is exactly how we build them, step by step.

• What you need
• 1. Sealed or ported
• 2. Box volume
• 3. Measure
• 4. Cut
• 5. Glue and brace
• 6. Seal
• 7. Wire it up
• Mistakes

What You Need Before You Start

• Your sub's spec sheetBox volume, cutout size and mounting depth.
• 3/4 in MDFDense, flat and it does not ring.
• Wood glue plus screws or bradsGlue makes the joint. Screws just hold it.
• Silicone or seam sealerFor every inside joint.
• Terminal cup and wireGrab bulk speaker wire or an amp wiring kit.
• Basic toolsSaw, jigsaw, drill, square, clamps and a tape.

Step 1 Pick Sealed or Ported

This is the biggest choice, so make it first. Sealed is smaller and tighter. Ported is louder and deeper, which is why most people chasing deep bass end up with a port.

From the bayCheck the spec sheet first. Many subs list a box for each type. New to the terms? Look them up in our 12 Volt Dictionary.

Step 2 Get the Box Volume Right

Volume is the number that matters most. Spec sheets list net volume, the air the sub actually gets, so your box has to be bigger to make room for the sub, bracing and any port.

Skip the mathOur free Box Buddy tool gives you the panel sizes, net volume and port size in seconds.

Step 3 Measure Your Space

Measure where the box will live. In a trunk, measure the opening, not just the floor. In a truck, measure with the seat in its normal spot. Leave room for carpet and mounting depth.

Step 4 Cut Your Panels

Most boxes are six panels. Square cuts matter, because gaps leak and leaks kill bass. Cut the sub hole with a jigsaw or a router and circle jig.

Step 5 Glue, Fasten and Brace

Glue every joint, then fasten with screws or brads and clamp until dry. On bigger boxes, add a dowel or MDF brace between the largest panels, and count it in your volume.

Step 6 Seal Every Seam

Run silicone or seam sealer along every inside joint. A box has to be airtight. Even a small leak makes a sealed box weak and throws off a ported box's tuning.

Step 7 Add the Terminal, Carpet and Sub

Mount and seal the terminal cup, wrap the box in carpet if you like, then wire and mount the sub with the screws snug, not cranked down.

Match the ampSee every wiring option in Woofer Wizard, then use Amp Matchmaker to pick a monoblock amplifier.

Common Mistakes We See

• Using gross volume instead of net
• Particle board or thin plywood
• Screws with no glue
• Unsealed seams
• A box that will not fit the trunk opening
• Wiring below what the amp can handle

Free 12 Volt tool

Let Box Buddy Do the Math

Enter your sub and your space. Box Buddy finds a box that fits, checks the airspace and hands you a cut list.

Design My Box

Build It or Buy It

Building a box is one of the best ways to learn car audio. If you would rather get straight to the bass, we have you covered.

Subwoofer Brands We Carry

Want more? The 12 Volt Install Bay has more install guides from our team.