My stereo integrity ht 18" sealed 150l subwoofer build

Powered by Behringer Inuke 6000dsp



Finished subwoofer in black, I actually made two of these babies. Painted in matt black using a high quality roller.

Two Stereo Integrity ht 18" d4 subwoofer elements, I ordered them with dual 4ohm voice coils, so I could run them at 8 ohm nominal impedance for lower distortion. Amplifier is the Behringer Inuke6000dsp. Its a d-class amp with 2 x 1500 watts to 8 ohms so there's plenty of juice to go around.

Modeling how the 150 liter woofer cabinets would fit into our living room, dummy box made out of cardboard.

Quick 3D model of how I wanted to make the internal cross bracing, as I didn't want to waste precious internal volume of the enclosure. IMHO using heavy bracing also adds unnecessary weight.

On with the show, I used very old , should I say waste-quality mdf , in 22 mm. For two 150 litre subs you need lots of it!

After roughly cutting the sides, I went onto gluing the "face-side" of the sub, I used birch veneer for the doubling of the element side of the sub, as the recess for the element is quite deep.

After this point its just putting the pieces of the box together!

Glue has settled but the box is looking a bit rough around the corners, as was expected with so low quality mdf.

I "painted" the inside corners of the box with normal wood glue, to make the enclosure completely sealed.

Then onto making the internal bracing, 2cm strips of birch ply will do.

Internal bracing done, after the glue had settled I glued some packing foam to the walls for damping. Theres quite a difference when you do this, put your head inside the enclosure and listen to outside noises...

Like seen from previous pictures, the corners were still pretty rough, since the mdf I used was pretty low quality and bent out of shape. I made some wood plaster from wood glue and mdf powder, works like a charm. This plaster is the same material and color as the original mdf and tough as nails, really hard to sand.

Corners were rounded with a router bit, too bad I didn't take photos of this phase.

Next is the painting, with a good quality roller and furniture paint. White is the base coat, and then the top coat in matte black.

Painting with a roller is relatively easy, compared to painting with a spray gun. Applying a thicker coat is also more forgiving on the finished surface, and IMHO suits pretty well to a subwoofer of this size, gives that PA-look to the finished cabinet.

For sealing the element I used regular window sealing tape found in hardware stores, works nicely and you can be sure its airtight.

I topped the enclosures with polyester filling from cheap Ikea pillows. Some people would argue that this is not necessary, but I believe the filling adds resistance to the internal airflow of the cabinet, thus effectively increasing the volume of the enclosure. 

Finished sub.