I hired a professional woodworker to build two Bill Fitzmaurice Autotuba subs. The output was pretty good, but I was not satisfied with the quality of sound. I also built two Rythmik Audio Servo subs in a sealed box. Cabinet was 2 inches thick with bracing and net internal volume of two cubic feet. Sound quality was about the same as the North Creeks, but output was not adequate even with the gain modified by Rythmik. Rythmik Audio does have good service if you happen to do business with them.

My top (though by no means only) priority was minimizing power compression. It's hard to find a subwoofer that can "keep up" with a good high efficiency system. I think one of the reasons is that while the high efficiency system is loafing along at a handful of watts, the less efficient subwoofer needs maybe 100 times as much power to keep up. This is one of the reasons a horn subwoofer works so well. But if you don't have room for a horn sub, or if you want bass extension south of 30 Hz, then a more conventional system optimized for minimimal power compression makes sense.

You can find 15" drivers that will significantly out-displace the Acoupower. But I don't think there are any out there that can match its motor when it comes to minimizing power compression.

I'm a subscriber to Voice Coil, a loudspeaker industry newsletter published by Audio Amateur Publications. Each month Vance Dickason, of "Loudspeaker Design Cookbook" fame, does a review of a couple of drivers. The only time I have ever seen him go beyond reporting "just the facts, ma'am" and indulge in outright praise was in his review of the Acoupower woofer.

At this point I am very happy with the Acoupower, and have plans to build a big bucks high-end commercial subwoofer system around it.

Duke

How low do you want to go, and how big a box can you live with?

Duke