A couple of recordings that really drove this home to me were provided by longtime TAS reader Jim Williams, a great pipe-organ aficionado. A pipe organ happens to be an exceptionally revealing instrument when it comes to evaluating the degree to which a multi-driver transducer or, as in this instance, main speakers and subwoofer speak with a single voice. Volume 2 of Kei Koito’s Claves recital of Bach organ music opens with
a literally stupendous recording of the Toccata and Fugue in D Minor. (The venue is the Frauenkirche Cathedral in Dresden, the instrument a Silbermann organ, originally installed in 1736, destroyed in 1945, and gloriously restored in 2005.) Jim tells me this CD is used by Diapason magazine as a reference for how an organ should be recorded. Little wonder: It’s almost unprecedentedly clean, clear, and transparent, hugely dynamic, airy, and spacious with some of the deepest, truest, most jaw-dropping bass I’ve heard in over forty years as an audiophile. When the 32-foot stops come in, you really do feel as if the music is welling up under and around you as if from the center of the earth. And as with Zarathustra, you certainly feel the fundamental and at least hear it as sound pressure on your ears. I must emphasize again that the presentation evinces no sense that there is a separate subwoofer, let alone a separate subwoofer that propagates sound differently from the main speakers. But that’s a misleading way to put it. What is more accurate is to say that there is a sense of the transducers disappearing and of your being transported to the venue. The same is true of Dorian’s Organ Encores. Though a very different organ, miking, and acoustical setting, there is the same seamless, organic presentation and thoroughly natural impression of huge size and space. If you love pipe organs, I would urge you to run to your nearest REL dealer for an audition. At the very least, you’ll come away with a better idea of what is really down there on some of your favorite recordings.
There are probably as many different kinds of advice when it comes to setting up a subwoofer as there are subwoofers. Regardless of the method, the job goes much faster if you have a helper. I did it both ways—on my own and later with fellow TAS reviewer Robert E. Greene (REG). The REL method, which was actually devised by the folks at Sumiko, is unusual but it does work—sort of. First, you’re advised to place the woofer in a corner behind one of the speakers. This is good advice for two reasons: efficiency (from boundary reinforcement) and the fact that corner placement drives all the room modes equally. (Corner placement does not in and of itself yield a boomy bass unless your listening position happens to coincide with a spot where a standing wave is at or near maximum pressure.) Put on material with a lot of bass response, switch the phase between 0 and 180, and leave it in whichever position is louder. Then start to move the woofer out from the corner diagonally by increments until it reaches a point where—I am quoting from the manual—“the REL will go lower, play louder, and, if it truly locks on to the room and is fully pressuring it, the air around the REL will seem to be energized, stop right there! This is the correct position from the corner for the REL.” Once this is achieved, you orient the woofer physically (i.e., firing forward, to either side, presumably also to the rear or at any point around the center axis) so that the playing is “loudest and lowest.” (That isn’t an intentional oxymoron, merely bad writing. What I think it means is that you stop when are get the loudest sound in combination with the deepest extension.)
Then you turn to the crossover and level settings. Sumiko’s recommended procedure is to start at the lowest setting, 32Hz, and bring the volume up slowly to the point where you achieve “a subtle balance, i.e., the point at which you can hear the REL even with the main speakers playing. Now, bring the crossover point up until it is obviously too high; at this point, bring it down to the appropriate lower setting. For all intents and purposes, this is the correct crossover point.” If those instructions sound unhelpfully vague to you, you’re not alone. I have no idea what the “subtle balance” point is, and even less what constitutes “an appropriate lower setting” of the crossover. As for when the woofer “locks into” the room, a little more description, fellas, as to the effect you’re talking about would be helpful. But the truth is, using music to determine optimal settings for any of these adjustments is not so much hopeless as simply inefficient and more time consuming than necessary, because the settings will vary with program content.
Sumiko has long recommended Track 4 from the soundtrack of the movie Sneakers (Sony), because it has a repeating bass-drum motif that goes on long enough to allow for several adjustments without having to repeat the cut. This is a rather good recommendation inasmuch as the bass drum here actually sounds more like a very narrow cluster of frequencies than a single frequency. Using it according to Sumiko’s instructions, you can probably get a good enough result initially. The trouble is that what you’re really doing is adjusting the subwoofer for that cluster of frequencies as they appear at your listening position. A few hours after the initial adjustment and more listening, I found the level was too high for most other music. What I wound up doing over a few days is using a variety of familiar recordings, raising and lowering the crossover vis-à-vis the level until I achieved a result that sounded right on most music. Or, at least, right enough that I could stop fiddling and get back to enjoying music. This, by the way, is as good as you’re ever going to get. You’re never going to achieve perfection, and no subwoofer, no matter how good, will change the bass signature of your room: The primary modes will always produce maximum intensity at some frequencies in some places and minimum at others.
I wish I could give you specific numbers for my settings, but I can’t because REL has chosen not to identify the crossover values apart from the lowest and the highest. Nor do they put any markings on the level control except minimum, maximum, and high noon. This is a real mistake and the only serious criticism I have of the design, especially as regards the crossover frequencies. Assuming the crossover spectrum is distributed linearly around the clock, as it were, then noon should be 76Hz. But this is precisely the sort of assuming we shouldn’t have to do. If you know the response characteristics of your speaker system, particularly the point at which the bass slopes to its -3dB point, then you can get a considerable leg up on the whole process by setting the crossover frequency of the subwoofer to match, which is a good starting point. At least, this has been my experience with most subwoofers.