Rythmik Audio F12/F12-400 vs JL Audio E-Sub e112

Yeah @harpo75, the "regular" Rythmik (and GR Research) subs---like most (all?) others---will play up to little more than 100Hz. The woofers in the OB/dipole Sub are designed to work in "free air", and the Rythnik Audio plate amp included with the kit is modified specifically for dipole use, with a dipole cancellation compensation circuit.

Since the woofer in the ET LFT-8 plays up to 170Hz, a "normal" sub (whether Rythmik, GR Research, or any other brand) cannot take the place of the LFT's dynamic driver, which is a woofer not a subwoofer. However, the Rythmik F8 (a pair of 8" drivers in a sealed enclosure)---which will play up to 250Hz---CAN be used in place of the stock LFT-8's woofer. But the F8 is priced higher than the OB kit, and appears to be nearing discontinuation anyway.

@harpo75: Excellent! Now consider using a pair of the Rythmik Audio/GR Research OB/Dipole Subs in place of the woofers in the ET LFT-8b! The OB Sub can play up to 300Hz (the ET's dynamic woofers are used up to 170Hz), and will turn the LFT-8b into a completely dipole loudspeaker.

It's easy: just leave the stock woofers unconnected at the binding post terminals, and use the controls on the Rythmik A370 plate amp as your low-pass crossover filter..The OB sub contains either two or three (your choice) 12" woofers, and is a remarkable woofer system. You can use your F12's as well, for a DIY "swarm" low frequency system.