Sumo Samson subwoofer & Delilah crossover
Along with graphic equalizers, subwoofers are the classic example of a product being widely promoted and bought as the solution to problems which may or may not turn out to be real. To quote recent ad copy from that purveyor of dream machines, DAK Industries (footnote 2), "You'll hear the awesome effect of thunder rumbling through your home. You'll hear a depth and dramatic fullness to your music that won't be heavy but will thrill you with its massive strength." Whether or not subwoofer customers have a need for low-bass extension, or even a listening room suitable, that doesn't appear to be relevant to sales, particularly when the customer owns a pair of small minimonitors. "TRY AUDIOPHILE'S BEST FRIEND RISK FREE," encourages DAK Industries (with somewhat peculiar syntax).
"Come on," I hear you saying, "What's wrong with that? Surely minimonitor owners are the people who would most benefit from subwoofers?" "Ha!" reply I. "Let me tell you a tale . . ."
Way back in the early '80s, one of my speakers of choice was the Rogers LS3/5A. (In fact, I still have a pair.) Natural candidates, you might think, for use with a subwoofer. I thought so too, and spent most of the Spring of 1983 experimenting with a Janis W3 subwoofer (footnote 3). Ultimately, however, I admitted defeat. That vintage and model of Janis I found to be a little too colored in the midrange to form a successful match with the '3/5As.
"Colored in the midrange?" Why should that matter with a speaker only destined to handle music's grunt region? It does, however. I found that you should cross over to the main system at as low a frequency as you can manage. The '3/5A pretty much dies below 100Hz, implying a crossover frequency to the subwoofer of around 125Hz. A typical crossover slope of 12dB/octave will mean that any lower-midrange information will still be emitted by the subwoofer only 1224dB down, to the detriment of the stereo imaging. And if the subwoofer is colored in that regionthe Janis I found to have a somewhat woody sound, a slight "honk"or has a rising response through the midrange, that coloration will be audible.
In addition, most bass and tenor instruments have a considerable part of their spectrum in the 70140Hz region. Placing a crossover frequency, with the attendant problems of phasing and integration, toward the higher part of this region will not be the formula for the best sound of these instruments.
All such problems can be ameliorated by positioning the crossover frequency lower. Dropping an octave to 63Hz helps a lot by suppressing midrange spuriae by at least another 12dB. I used the Janis in this manner with some success with both Celestion SL6s and old Quadssadly, my second wife got custody of the latter when we divorced. Lowering it to 50Hz would help even further. You get my drift? In true Zen manner, subwoofers are best suited for use with speakers that ostensibly don't need their help. Those that could do most with low-bass reinforcement are the hardest to make work, if at all.
In addition to the direct problems, I also found placement of the subwoofer in the room to be critical. You can read in almost any mainstream audio publication that subwoofer placement is noncritical, the ear/brain not being able to determine the direction of low-frequency soundwaves. To quote that DAK ad again: ". . . the subwoofer can be placed anywhere because low-frequency material is totally non-directional." The latter part of that statement may be true (assuming that by "material" Mr. Kaplan meant "sound"), but it isn't strictly relevant. As you move your head, the pattern of standing waves set up by the subwoofer's excitation of room resonances will tell your ears that there is a soundsource in that particular position in the room.
In general, stereo subwoofers placed adjacent to the main speakers, a single subwoofer positioned directly between the main loudspeakers, or, in the worst case, a single subwoofer directly behind your listening seat, are the only positions which I have found to work.
The Janis was eventually replaced by an AudioPro Ace-Bass subwoofer. This offered a cleaner, if less powerful bass, but was let down by an integral electronic crossover that was, sonically, a woeful underachiever. This underlines the fact that no matter how good your electronics, the signal has to be passed through the crossover, which may or may not be of high-end pedigree. Ultimately, I found that better amplification rather than a subwoofer gave me more of what I was looking for in terms of bass, and I bought my first Krell KSA-50.
Thus the matter lay; I devoted my attention to maximizing the intrinsic performance of whatever speakers I chose to use, mainly Celestion SL600s. The results were sometimes surprising, considering the limited low-frequency extension of these speakers, and always musical, which explained my surprise when Anthony H. Cordesman put forward in Stereophile the notion that such speakers had no place in a high-end system (footnote 4).
However, I wouldn't argue that the Celestions never suffered from their lack of the bottom octave. I never hear from them, for example, the ability to move air that you occasionally get livethe sound of a pipe-organ's 16' and 32' stops flat-out, for example, or the bass guitar of the Grateful Dead's Phil Lesh, or, a propos this review, a Linda Ronstadt concert some years back in Los Angeles I had attended with Cambridge Audio's Stan Curtis and Randy Patton, then with JBL.
Not only was Linda's band superbit included Bill Payne, once with Little Feat, on piano, and Andrew Gold and Danny Kortchmar on guitarsbut the quality of the music-making was matched by that of the sound. Bass guitar and kick-drumreproduced by a horn PA system with multiple JBL LF drivershad a weight to their sound that I hardly ever hear from live rock.
These days, Randy heads up the Sumo division of Califone. Maybe the quality of the bass at that Universal City Amphitheater concert had stuck in his mind alsoor maybe it was just his need to add some low bass to his KLH Nines. Whatever, one of the first products to be introduced by Sumo after Randy joined them was a subwoofer, Samson, designed by JBL's Greg Timbers, and a matching line-level crossover, Delilah.
Samson . . .
Daniel Reilly, pugilist, philosopher, and Stereophile's shipping and receiving clerk, is not one to shirk grunt work; indeed, he almost seems disappointed when mere pickup cartridges or small parcels of interconnect pass his desk on their way to the appropriate reviewer. But when the truck arrived at the Stereophile building with two Sumo Samson subwoofers for him to deliver to my home, each on its own wooden pallet, even he was surprised at their heft: "Good gracious!", he was heard to mutter. He had no choice but to concede defeat and ask my help in getting these monsters in the pickup.
For a monster the Samson surely is. The generous-sized enclosure is constructed from ¾" Medite (MDF), with a 1½" Medite front baffle (covered by a wraparound grille). In addition, the top is concealed by a 1"-thick hardwood boardin the review samples, this was of oakand the whole sits upon a small plinth, the edges of which are finished to match the top. Add in a 15" drive-unit with an 18.675 lb magnet, and you have a sturdy piece of furniture that doesn't take kindly to being moved around in a frivolous manner.
The drivera version of the classic JBL paper-cone 15" unit that I used to use to amplify my Fender bass when I played professionallyis centrally placed on the front baffle and reflex-loaded via two large, 4"-diameter, 19"-deep ports toward the back of the right-hand side. Fitted with a foam-roll surround and a 4"-diameter voice-coil, made from edgewound copper ribbon, moving in a magnetic field shaped for low distortion (the pole-piece is fitted with a flux-stabilizing ring), this is a high dynamic-range driver, capable of moving a lot of air. Sumo recommend a minimum amplifier power of 200W and a maximum of 1000 RMS watts!
Electrical connection is via true five-way, gold-plated binding posts on the rear. The passive Samson lacks any kind of low-pass filter, so must be used with a separate power amplifier . . .
. . . and Delilah
Delilah is a remarkably versatile line-level crossover, housed in a slim 19" rack-mount enclosure styled to match other Sumo components. From left to right, the front panel contains the mains on/off switch, three rotary controls for subwoofer level, low-pass and high-pass crossover frequencies (50, 63, 80, 100, 125Hz, with Bessel functions specified), and three pushbutton switches, these selecting 12dB/octave or 18dB/octave slopes for the low-pass outputsthe high-pass output is fixed at 12dB/octaveand bypass, more of which later. The back panel carries the output jacks, all gold-plated, for: high-pass outputs, inverting and non-inverting stereo low-pass outputs, to feed a pair of subwoofers, and inverting and non-inverting summed mono low-pass outputs for feeding a single subwoofer.
Footnote 1: The introduction to the Spica Angelus loudspeaker review in Vol.11 No.2 (February 1988).
Footnote 2: Stereo Review, January 1988
Footnote 3: We are sad to report that John Marovskis of Janis passed away at the end of 2011.Ed.
Footnote 4: "Who Stole the Bass?", Vol.10 No.3.