I use a single REL T5i in a 12' x 20' room with Harbeth P3esr small monitor speakers. A REL is designed to augment the performance of FULL RANGE speaker systems in order to provide, in certain cases, linear response below 15Hz. REL Set-Up Made Simple RELs are not traditional subwoofers, but true sub-bass systems. With a throw distance of some 45’(13.7M) Arrow permits flexible placement without sacrificing sound quality. Compatible with Arrow™ is REL’s latest generation of zero compression wireless. I have somewhat limited options for monitor placement. I would have thought it best to set that to max 120 on sub but doing this distorts bass and is extremely loud. Super fast delivery of both High Level Bass and .1/ LFE ensures the rich, natural warmth that only RELs can deliver. Therefore, for the moment, set aside everything you’ve been A REL will take advantage of the physical room acoustics to provide deep pressurization as no traditional subwoofer can. This means you get the ideal levels for both hi-fi and AV, without the need to constantly change the settings. A single, high-quality alloy-fiber composite driver and down-firing orientation produces maximum coupling with the floor and eliminates the need for a grille. Arrow™ is an optional extra. A REL is designed to augment the performance of “full range” speaker systems, to provide linear response down to below 12 Hz (Studio III, -6 dB down at 9 Hz). For best results, the REL should be placed in one of the corners behind the speakers. With the REL fully into the corner, and pointed to the opposite corner, continuing to play the music, slowly pull the REL from the corner on the diagonal, line to opposite corner, equidistant from both side and rear wall. I have just bought a rel t5i sub. So REL takes the hardest challenge of trying to get your subwoofer placement right — maintaining domestic tranquility amid horrible visible wires — and solves that, while simultaneously crafting a gorgeous product that can melt into any well-designed home. So onwards: After placing and adjusting the x-over and the blend of the T5 to my mains, along with various room placement variations which took the better part of two weeks of minor changes to get correct, I now have a virtually seamless presentation. At a certain point the REL will audibly play louder, go lower in frequency extension, and truly pressurize the room. The specifications indicate the Harbeths start to roll off at 75 hz. Simplicity is its own reward, and the REL T/5i subwoofer reduces the classic cubic sub to its bare essence. Whatever the specs, the influence of the room will dominate the perception of bass. This not only maximizes room gain but allows “for the most linear low bass wave launch…the ability to tune the sub to the axial node of the room, or longest throw distance.” In my small room, this procedure works but don’t be shy about experimenting. Corner placement is suggested by REL to begin, facing on a room diagonal. Faster and Deeper: A 360° Update T/5i is the purest expression of REL. High quality finish With REL's legendary build quality and finish, the T5i has to be one of the most attractive-looking subwoofers in its class. Hi folks sorry if this has been answered already but cant find it anywhere. Just a bit confused with the LFE crossover. With a range of some 45-feet, Arrow permits flexible placement without sacrificing sound quality. With the REL T5i you have separate level controls for stereo and LFE .1 surround.