Had a nice exchange with my speaker maker, Jim Salk. Salk had not heard the RELs and he has nothing negative to say about them. He commented to me about the differences he saw between REL at the T9x level and the Rythmik 12SE.
The REL T9 lacks phase control other than 0/180. What he likes about more adjustable phase control is that it helps dial in the phase correctly. As he put it, "If the subwoofer driver is not in the exact same plane as the woofers in the main speakers, you must set the phase such that the two are in phase with one another over the crossover region. If not, you may have nulls in the overall output." I'd only add that give one's rooms nodal regions, one might not *want* to put the woofers on the "exact same plane" as the mains. After all the measuring I did, I'd hate to have to do that with my subs.
He also noted that the REL subs I was looking at (not the more expensive RELS) use A/B amplifiers but better subs are now using digital Class D amplifiers (Hypex's Ncore amps or Purifi, etc.) He likes these amps because they run cooler and have a lot of power for the size while doing a good job of controlling the woofers. Finally, he likes subs with direct servo control. As he explained it, on a sub's two voice coils, one drives the woofer cone while the other is fed back to the plate amp’s servo circuitry. "The servo circuit monitors in the input and calculates exactly where the cone needs to be to produce the signal at the input. Using the second voice coil, it determines exactly where the cone is. If it is not in the position is needs to be in, the gain is automatically increased or decreased as necessary. All of this happens in real time. So you end up with very accurate response that is very musical as well." Finally, he likes that in the direct servo system [for the models I am comparing] the sub plays deeper. You can easily get flat response down to 20Hz with a 12” sub."
People love REL's and whether these technical differences make a difference is up to everyone's ears. But for the same price as the T9/x, it seems the Rythmik is quite amenable to careful adjustments. Until I'm in a room where I can get a swarm, I have the chance to get a sub which is easier to blend with my mains; I have technical know how about use REW along with the added technologies on the Rythmik to dial it in. And a 45 day window for return. It's very tempting.
The REL T9 lacks phase control other than 0/180. What he likes about more adjustable phase control is that it helps dial in the phase correctly. As he put it, "If the subwoofer driver is not in the exact same plane as the woofers in the main speakers, you must set the phase such that the two are in phase with one another over the crossover region. If not, you may have nulls in the overall output." I'd only add that give one's rooms nodal regions, one might not *want* to put the woofers on the "exact same plane" as the mains. After all the measuring I did, I'd hate to have to do that with my subs.
He also noted that the REL subs I was looking at (not the more expensive RELS) use A/B amplifiers but better subs are now using digital Class D amplifiers (Hypex's Ncore amps or Purifi, etc.) He likes these amps because they run cooler and have a lot of power for the size while doing a good job of controlling the woofers. Finally, he likes subs with direct servo control. As he explained it, on a sub's two voice coils, one drives the woofer cone while the other is fed back to the plate amp’s servo circuitry. "The servo circuit monitors in the input and calculates exactly where the cone needs to be to produce the signal at the input. Using the second voice coil, it determines exactly where the cone is. If it is not in the position is needs to be in, the gain is automatically increased or decreased as necessary. All of this happens in real time. So you end up with very accurate response that is very musical as well." Finally, he likes that in the direct servo system [for the models I am comparing] the sub plays deeper. You can easily get flat response down to 20Hz with a 12” sub."
People love REL's and whether these technical differences make a difference is up to everyone's ears. But for the same price as the T9/x, it seems the Rythmik is quite amenable to careful adjustments. Until I'm in a room where I can get a swarm, I have the chance to get a sub which is easier to blend with my mains; I have technical know how about use REW along with the added technologies on the Rythmik to dial it in. And a 45 day window for return. It's very tempting.