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I Just finished my GR subwoofers and got them hooked up. Man do these things sound great! They are by far the best subwoofer I have heard to date! I used 2 Sw12A subwoofers with 4 of the passives, and a rythmic a350 amplifier in a large enclosure.
I added 500grams of weight to each PR to get the tuning down around 14hz. This should provide a response that is -4db at 16hz and -6db at 12hz. If you use the boost/rumble filter on the amplifier set to 14hz you will get a -2db point near 14hz, but sacrafice a few decibels of total output.
I decided to break it up into 2 seperate enclosures to make them easier to move( each one weights well over 100lbs. Each enclosure measures 14"x24"x48" or 5cuft net.
The front and rear baffle is 2.25" thick using 2 layers of mdf and 1 layer of birch ply. The front baffle holds the subwoofer and 1 PR, while the rear baffle holds the 2nd PR directly opposite the PR on the front, and the amplifier. The amplifier was sealed off from the rest of the enclosure by building a 5" deep by 14" long chamber. This chamber also needs to be built into the box without the amplifier so they contain the same internal volume.
Braces were put every 6". The inside was then sprayed with a rubberized sound deadening spray, and the walls were lined with acoustic foam. I placed a small bit of fiberglass insulation behind the subwoofer, but left the area between the passives open. I stained them in 2 coats of minwax bombay mahogany to match the rest of my speakers. For some reason they turned out a little darker though.
This thing is solid. There is no cabinet vibration at all. My center channel is sitting on top of them with just some little felt pads and nothing. You can sit on the cabinets and not hardly feel a thing, even when the subwoofers are really moving.
I havent got a chance to measure the response or do an impedance sweep yet, but as soon as I get a chance I will. After watching war of the worlds on it, I can tell you the output below 20hz is very high. You really can feel it now with this subwoofer. Here are some pictures!
Thanks alot Danny!
http://www.audiocircle.com/index.php?action=gallery;area=browse;album=699
