Took a quick look at that thread and see that it is Randy Rash, who I've corresponded with in the past, especially about his Type 10 amp from Greenvalve.
It's a small world, this DIY audio hobby, thanks to the internet. Randy a great guy and very knowledgeable. I'm glad you know him....
I still have to figure out which speaker is going to go where in my house before I make any decisions on subs. I generally don't like subs, but OB is another thing altogether. I recently convinced my wife to let me move the office part of my office into another room, which means I can dedicate the existing office to a listening room, however, e ven though the room is 10.5' x 16.5', I really only have a 10.5' square with which to work, so I'm not sure how well an OB will work in that setup. If it does, it will do so just barely and with the listening chair rght up against the back wall.
I'm coming out of a 10'x13' listening room where I had to set up the short distance, too. I found that I could get what I wanted better with OB than box, but I had to add a bunch of room treatments. For me (and your milage may vary), I found a combination of diffusion and bass traps were necessary. I placed a rear wall diffusor behind me listening chair that helped a little but if I had the space, a poly diffusor behind the chair would have helped tremendously, I believe. I just didn't have the foot of depth needed to accomplish that. I also found that a single front wall poly diffusor was very beneficial to the imaging with OB.
Another item was pulling the speakers out much closer than I expected they would be. The issue here is balancing the the front wall first reflection with the direct sound...in a small space you can get some fuzziness and when you find the sweet spot, it is like everything comes into focus. I found equal distance between the listing chair and the front wall was needed in the 10' space.
I used four 15" augies for a while in this room and it was wonderful. I had lots of bass traps, however. I had a bunch of Owens Corning 703 and a bunch of R-13 rolls in various configurations. Once I tamed the bass a bit with the traps, the four augies were effortless and detailed. Of course I was always playing at low levels given the room size (relatively speaking), so the added air movement really made an impact. Just something to consider.
FYI, the GR-Research SA-1 plate amps also have the OB shelving filter and 20 hz HP filter and are intended for sealed or OB subs.
Danny is also now in production of the first run of his new 8" servo OB driver, alongwith a purpose designed amp from Brian Ding. That may be the only setup that has a prayer of keepin up with the Lowthers (dx-55s with aluminum VCs and high-ferric). I would probably also use a single enclosure with two drivers and place them between the mains, as I'm told this will not kill the soundstage as with other types of subs.
Danny and Brian are good guys and very helpful/knowledgeable. I have other Danny designed speakers and of course the Rythmiks. I found that running my OB augies in stereo made a significant imaging difference, particularly with the drums, but also with other areas such as a double bass. I think with OB the idea that bass isn't directional is a wrong. I can A/B and always prefer the stereo set up. You may want to consider this idea, as well.
Wonder if anybody has ever built a full 10" trio -- seems like that would be really quick and articulate with decent enough bass for my small room. Oh well, then I'm back to the question of whether the OBs will work in this room at all... :-)
They current "best of class" with the 10" series is a Penta: four 10" augies per side with a 10" mid-woofer rounding out the five speakers. See below (Jim, I've attached photos for folks to look at but will link you to the thread to read the build which will give you a good idea of the product here:
http://www.hawthorneaudio.com/forums/viewtopic.php?f=2&t=3709 ). I would think you would be very happy with 10" trios.
And yes, we are bit O/T....
John
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