Front view                                    Rear view                                      Side view
 

HE-15 T/S Parameters    Fs: 26 Hz     Qms: 6.0     Qes: .345     Qts: .326     Vas: 106.7 L     Re: 6 ohm     BL: 27.3 Tm     no: .529%     1W SPL: 89 dB     Cms: .145 mm/N     Mms: 257 grams     Rms: 7.0 kg/s     Xmax: 22.85 mm     Sd: 720 cm^2     Vd: 6.5L total     PEmax: ~ 2000W     3.5" p-p excursion     Dual 3 ohm VC     Aluminum cone

Cutaway view of the woofer

This is the box recommended by Stryke Audio, an inner box made of ¾" MDF measuring : 19 ½" wide, 43 ¼" high and 21" deep, OD. This is covered by an outer box of ¾" MDF. The net interior volume works out to be: 9 cubic feet or 258.7 liters.

I decided to make the inner box of 1" MDF and the outer box of ½" MDF, and add ½" MDF on the inside of the woofer mounting area. In addition 1½" diameter oak "hand rails" were installed as bracing.  I made the box deeper than recommended.  The net interior volume is: 9.7 cubic feet or 274.7 liters.

½" Fir plywood has been installed in the area where "T-nuts" will be used. The points on the "T-nuts" tend to bend when applied to MDF, but "dig in" the plywood nicely. The "T-nuts" have also been "staked" with wood screws so they can't be pushed out easily. The cabinet is 2 ¾" thick, while the woofer mounting area is 3¼" thick.
 

¼" Oak plywood has been applied to the entire exterior and a ¾" X ¾" groove left on all edges to accept ¾" quarter-round oak moldings.

The ¾" quarter-round oak moldings have been installed on the edges, and the entire unit sanded with 320 grit paper.

Views of the completed subwoofer, the two other sides look the same. The cabinet weighs 190 lb. empty and 300 lbs with drivers. The inlet terminals are on the bottom as are four casters.