During the Xmas break I built a set of Ripole subwoofers following Jazzmans's recipe with something thrown in from Axel Ridtahler's design. Basically it follows the former's construction details and dimensions except that the 2 Peerless SLS 12" woofers were installed in separate enclosures so to use them as a stereo set. This is where I used Axel's design information as far as the front of the drivers opening and baffle.
Jazzman uses a dual driver set for each channel with the purpose of having more output and as I understand less distortion and a more controlled output by virtue of having 2 drivers firing in phase towards each other.
I wanted to try these in stereo mode and that is what is happening so far. The room is fairly small; 12'x11' and the output is consistent with my single Vandersteen 2w subwoofer with the benefit of having a stereo output. I had never experimented with 2 subwoofer and it was really a good surprise. The bass quality or presentation is as described by Jazman himself in that it appears from nowhere without any apparent localization. It is not overblown but but not as tight as with some subwoofers I have heard; very musical and relax sounding, effortless one might say. And it goes deep. Even tried it with the first 10 minutes of the Prometheus DVD which has a very impressive bass sequence. It shook the room as well as the Vandersteen did.
It blends marvelously with the Spatials due to its open baffle design and I guess similar diameter of drivers. Bass from the Vandersteen could be localized sometimes in the room even with a low xover frequency.
I am using a Crown xls 1000 with a low pass filter set at 50 hz, with its 24 db/Oct. filter and connected to my First Watt F4 speaker outputs -high level connection- with a 500 ohm resistance in line so to connect the signal to the Crown's RCA inputs.
Highly recommended because they sound fantastic and easy to construct. ...
Home Depot visit for a nice presentable 3/4" plywood plus the needed cuts and for me the most difficult part was to do the round holes...