How to Build a Sealed Sub Box
1990-1994 Lexus LS400

This tutorial provides general guidance for building a sealed sub box. I will also show how I mounted the box in my 1991 LS.

Tools Needed:

• Screwdrivers
• Circular saw
• Jig saw
• Drill
• Drill bits
• Countersink bit (if you want to be fancy)
• Tape measure

Parts/Supplies Needed:

• 3/4" MDF
• Screws
• 1" fiberglass insulation
• Silcone caulk
• Liquid nails
• Spray glue/cement
• Box carpeting
• Plastic box port (if you're making a ported box)
• Cardboard & tape (if you want to make a mock up)

1) Plan your box design. Each sub has a recommended box type and size. My Infinity Perfect 10.1 sub needed a .6 cubic foot box. I chose to build a sealed box because I was looking for accurate tight bass. I have used this box dimensions calculator several times to build sealed boxes. It is helpful during this thinking & planning stage. I figured that my box needed to be 9.5"x11"x15.1875" using 3/4" MDF fiberboard.

2) Buy supplies. The basics you'll need are: MDF, Liquid Nails, a box of 2" screws, Silicone, and box carpet.

3) Before you start cutting you may want to make a cardboard mock up of the box. This will help you visualize how the box will fit and look in the trunk. If things don't fit the way you want them to now is the time to change them.

4) Start cutting the pieces for your box.

5) The front and back of the box should be screwed into the sides of the box. This design will make the box stronger. When assembling use Liquid Nails on all joints. Screws should be placed every 2-3 inches. It may seem excessive but this box will be subjected to a lot of pressure, it needs to be strong. Let the Liquid Nails cure for at least 24 hours.

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Cardboard mock up and the real deal almost complete.

6) Once your box is assembled you can carpet the box. I added 1" fiberglass to the inside of my box because it was recommended by the sub manufacturer. I used Liquid Nails to glue it on. You'll also want to run the speaker wire during this stage. I bypassed the whole speaker terminal thing because I was permanently mounting the box.

Here's a close-up of the top of my box. I used these large bolts for mounting the box to the rear deck. It was a challenge to find a good place to mount the box, but it can be done.

7) Mount the sub in the box. I sealed it in with silicone. 8 screws hold it in. During this stage I also sealed any gaps around the speaker wire in the back.

8) Install speaker cover if desired. I need this cover over my sub because I use my trunk so much. Let the silicone dry for at least 24 hours. The box is done!

I ended up being able to use 4 of the bolts. Each is secured with washers and a thin piece of rubber to prevent vibrations.

Another angle.

Even though the box was strongly secured to the rear deck I wanted a little more. I had to build a new back panel so I designed it to fit snugly under the box. The box is connected to the panel, everything is solid.

This is why I designed everything I way I did. I needed to be able to fit this stuff in my trunk!

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