The Goal: The client was interested in a very compact solution for delivering a versatile low-end fill in his 1994 Chevy Silverado. The woofer decided upon was the 6W3v3 from JL Audio:
The woofer was sent to me directly by the client for more precise T/S parameter measurements (and thus, a more accurate design.) The woofer was also to be wired up and loaded in to the enclosure so that it’s plug ‘n’ play ready immediately upon receipt.
The Design: The most immediately apparent characteristic of the available working space was it’s lack – a wedge shape allowing for roughly 0.39 cubic feet internally… Anything beyond a sealed enclosure would require a very careful balance of volume alignment, tuning, and compression control. In the end, an off-axis bass-reflex design was chosen.
The Build: Our target tuning / compression profile called for a substantial amount of air to travel along a relatively small cross-section. To maintain a suitably linear velocity profile, very large entry and exit flares were required; three times the internal vent diameter along the outside and two times along the inside. Obviously, no such vents are readily available so one had to be fabricated.
You can think of the picture above as a block of MDF from which a very heavy-duty port (similar to the type used in my audiophile HT builds) is “chiseled” out. In front of the block, there is a single cross-sectional template layer of the port.
Moving right along, the port is beginning to take shape (mainly in length.) Behind it is a partially assembled wedge shell that will make up the body of the subwoofer enclosure:
Once all the rings are stacked and traced to the proper length, the port is attached to the side baffle and beveled to the target geometry along both ends:
The side baffle is also routed to accept a flush-mounted terminal cup–seen covered in saw dust behind the enclosure, further back along the table saw:
As a finishing touch, the sides of the wedge were beveled with a 0.375″ radius round-over and the woofer mounting hole was inset for a flush alignment with the outer edge height of the woofer’s mounting ring.
Finally, the woofer and the terminal cup is mounted onto the enclosure. As you can see in the picture below, both components’ mounting rings are shallow enough to where a flush inset is possible even with just 0.75″ wood thickness: