@ewinskih01: Danny Richie uses a pair of OB subs in the front of his room and a pair of F12G's in the rear (in both his company's listening room and at hi-fi shows), the F12's in phase opposite that of the the OB's. I believe he uses 40Hz as the x/o frequency between OB and F12.
OB subs sound different from sealed and ported for a number of reasons. Not just because of their dipole SPL drop-off with listening distance characteristic, and not just because the woofers don't have an enclosure in which to produce resonances.
First, their dipole design produces a null on either side of the OB frame (for those who don't know, the waves from the front and rear wrap around the frame and meet in the middle of each side. Being in opposite phase, their combined output is zero---the two cancel each other). The result is that the sub---producing no output in the left-to-right plane, typically the room's width---does not energize the room's eigenmodes in that room dimension. Less "room boom"!
Secondly, sealed and ported subs "pressurize" a room; the sub enclosure creates a separation between the interior of the enclosure and the air in the room in which it resides. When the woofer moves outward (in response to a positive signal), the air pressure in the room is increased (compressed); when the woofer moves inward (a negative signal, of course), the room's air pressure is deceased.
OB subs, in contrast, do NOT pressurize a room. The air on both the front and rear of the OB frame is vibrated by the woofer, but the room's air pressure is neither increased nor decreased. How could it be? The air pressure is moved around within the room, but that's all.
Some people like the sound/feeling of the pressurization of the room (Rythmik's Brian Ding, apparently). An OB in the front of the room with a sealed in the rear produces a compromise between the two---the lean/"taut" sound of the OB (optimal for blending with planar loudspeakers), the weight of the sealed.
OB subs sound different from sealed and ported for a number of reasons. Not just because of their dipole SPL drop-off with listening distance characteristic, and not just because the woofers don't have an enclosure in which to produce resonances.
First, their dipole design produces a null on either side of the OB frame (for those who don't know, the waves from the front and rear wrap around the frame and meet in the middle of each side. Being in opposite phase, their combined output is zero---the two cancel each other). The result is that the sub---producing no output in the left-to-right plane, typically the room's width---does not energize the room's eigenmodes in that room dimension. Less "room boom"!
Secondly, sealed and ported subs "pressurize" a room; the sub enclosure creates a separation between the interior of the enclosure and the air in the room in which it resides. When the woofer moves outward (in response to a positive signal), the air pressure in the room is increased (compressed); when the woofer moves inward (a negative signal, of course), the room's air pressure is deceased.
OB subs, in contrast, do NOT pressurize a room. The air on both the front and rear of the OB frame is vibrated by the woofer, but the room's air pressure is neither increased nor decreased. How could it be? The air pressure is moved around within the room, but that's all.
Some people like the sound/feeling of the pressurization of the room (Rythmik's Brian Ding, apparently). An OB in the front of the room with a sealed in the rear produces a compromise between the two---the lean/"taut" sound of the OB (optimal for blending with planar loudspeakers), the weight of the sealed.
