Exodus Audio Maelstrom 18" Subwoofer

zingo
zingo Posts: 11,258
in DIY, Mods & Tweaks
A few month ago purchased an unfinished Exodus Audio Maelstrom-X Gen II 18" with dual Maelstrom-x 18" passive radiators build locally from Craigslist. The seller had built and tested the cabinet a few years back after purchasing the drivers from Exodus (when they were still in business), but he never finished the project after moving to an apartment.

When I bought it, the drivers had been removed from the cabinet, and were stored in their original foam, and in great condition; including all the weight hardware for the passives. The box condition was a little rough, but overall well made with 1" MDF (doubled up on the driver faces) internal cross bracing. I lugged the 200lbs box home, and used my furniture dolly to wheel it out to the cabin. The design is down-firing with the two passive radiators front and back facing, so the first work I did on the box was mount 2" risers on the bottom with industrial casters; with the addition of the drivers, the entire enclosure weights about 300lbs.

Mounting the drivers was as easy as a 65lbs can be, but the cabinet was built with threaded inserts for all of the woofers, so it was only a matter of lining up the holes and torquing the bolts down. The original binding posts had been stripped off, so I ran speaker wire through the holes for testing purpose, and wire everything up. I knew the box wasn't airtight, and the weight needed to be adjusted on the passive radiators for proper tuning, but the original building said it tested strong down to 15Hz when he first assembled it, and I just wanted to make sure everything worked. The subwoofer driver is dual 2ohm coils, and I wired them in series for a reasonable 4ohm load. I hooked up a two channel amp I had, and the subwoofer came to life! This subwoofer was huge, and the sound that came out of it was huge-er!

The cabinet is not air tight at some seams, but it was also never caulked, and I need to use some body filler on the exterior of a few joint spots. I have binding posts on order, as I'm going to wire the woofer with both coils separate, and can be jumped externally. I haven't decided if I need any foam or stuffing on the inside, and I'll probably roll the exterior with a black truck bed liner or similar.

As far as final amplification, I have a pair of mono Buttkicker BKA1000-4A amps which do 1000w at 4ohm and 1900w at 2ohm. I don't think I'd buy these amps again as one is still on the bench from blowing a cap (poor quality control), but one is currently powering the subwoofer very well, and I'd love to feed the unit almost 4kW from the two amps. The amps do offer adjustable gain, adjustable and defeatable crossover, defeatable subsonic filter (although not applicable in my application because it of the very low tuning of the system), and auto-on.

I know I need to tune the PRs because the system actually seems to roll off before 80hz, but I want to get everything air-tight and mechanically tuned on it before I run the auto-EQ processing for it. I'll snap some pictures, but so far a fun project that provides more than enough LFE for movies.
Jake
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