Subwoofer Reviews

My incommodious room favors small standmount and panel speakers that some audiophiles would say require a subwoofer.

But I was never inspired to try one until a new category of subwoofer appeared: the "micro" (aka soccer-ball) subwoofer. The minute I saw the little KEF KC62, a 10" cube, I imagined it could do 0–100Hz and back to zero in record time. I reported on the KEF microsub last month, in Gramophone Dreams #49.

Just after I completed that report, I spied the SVS 3000 Micro. It, too, looked like a well-tuned, high-revving four-cylinder racer. When my request for a review sample was approved, my mind began to ask itself: What makes one subwoofer better than another? What does it actually mean for a subwoofer to be "fast"? Do some subs sprint like greyhounds while others drag their hind paw?

I asked Technical Editor John Atkinson to define the word fast as it applies to subwoofers. His answer was perfect: "As a subwoofer reproduces a narrow frequency band, its drive-unit alignment should be overdamped if it is not to sound boomy or blurry." Then I called Sound & Vision Technical Editor Michael Trei, my old friend and an experienced subwoofer reviewer, and asked the same question. I got the same answer though in different words. "It's more about stopping than starting," Mike said. "Lack of overhang is key." He added that, in this respect, sealed boxes are usually best.

Description
SVS Sound's new, most compact sub, the $799.99 3000 Micro, is a supersmall (10.9" × 11.7" × 10.7"), 26.7lb sealed-box subwoofer featuring dual-opposing 8" aluminum-cone drivers equipped with dual-ferrite magnets. SVS's first micro sub is considerably smaller than its slightly more expensive siblings: the sealed-box SB-3000 ($999.99), which weighs twice as much (54.5lb), measures 15.6" × 15.2" × 17.8", and features 13" drivers, and the still larger, even heavier, ported, more expensive ($1399.99) PB-3000. All three use the same 800W RMS (2500W peak) Sledge STA-800D2 class-D power amplifier. The 3000 Micro's specified frequency response is 23–240Hz, ±3dB.

The SVS 3000 Micro can be adjusted with a Bluetooth smartphone app that works in Apple iOS and Google's Android. This exciting-to-use (!) app instructs and assists subwoofer installers in adjusting volume, low-pass frequency (30–200Hz), phase, polarity, room-gain compensation, and crossover slope (6, 12, 18, or 24dB/octave); the phase adjustment is performed with a slider calibrated in single degrees. There is also a DSP-powered parametric equalizer, which allows users to create and save as many as three custom EQ adjustments.

If you lose your smartphone, you can control most features of the 3000 Micro using the Intelligent Control Interface (ICI), a backlit user interface on the subwoofer's side plate. In addition to the obligatory On/Off switch and IEC power cord receptacle, this control panel features a 3.5mm trigger input and unbalanced (RCA) line-level inputs and outputs. There is no speaker-level input, nor is there an active, high-pass–filtered crossover output for rolling off the main speakers. One interesting feature is room-gain compensation, which allows the bass to be rolled off gradually (6dB or 12dB/octave, selectable) below a certain frequency (25Hz–40Hz) to keep the bass from rising at the lowest levels in small rooms. Also on the side panel is a USB Type A port for firmware updates and for powering SVS's $119.99 SoundPath Wireless Audio Adapter. An Auto/On button allows you to set the 3000 to stay on all the time instead of going into Standby mode.

The most important side-panel buttons are the [+] and [–] buttons, which allow owners to adjust subwoofer volume, raise or lower the low-pass frequency cutoff, select the frequency where room gain compensation kicks in, and fine-tune the phase angle; sometimes a bit of subtle-but-shrewd sub-to-satellite phase management can be the difference between subwoofers that completely disappear and ones that almost disappear, especially in multisub installations.

The 3000 Micro allows users to adjust the woofer's output phase in 10 discrete steps between 0° and 180°. An LED bar display indicates settings for each of those variables.

Setup
For me, adding a subwoofer is not a quick or simple exercise; it is a long-term, leisure-time project in which I aim to create a pair of three-way loudspeakers out of a pair of two-way loudspeakers and a sub.

Part of my brain says that this is an absurd task, one at which I'll never succeed. But another part remembers what Stereophile Senior Contributing Editor Kal Rubinson wrote in his review of the JL Audio Fathom f110v2 subwoofer. I paraphrase: Positioning main loudspeakers for imaging and tonal balance is very different than positioning stand-alone sources of low bass, which, for sophisticated music listening, should be positioned to minimize adverse interactions with low-frequency room-boundary modes. Kal's words encouraged me to try subwoofers again and motivated me to perform these careful setup experiments.

Armed with pink noise and warble tones from my trusty Editor's Choice CD and my now-discontinued dB Pro iPhone app, I did a lot of measuring when I reviewed the KEF KC62 subwoofer. I measured extensively because I did not yet know where to place the woofer for best blending with the satellites. At the start of that report, I connected the woofer to a 25' RCA cable and a long power cord and tried everywhere the sub could possibly go, including right next to my listening couch and under my desk. In most locations, boundary modes created irregularities in the frequency response that announced the sub's sound as separate from (and different than) the main speakers.

During those experiments, I supplemented listening with an FFT app on my iPhone called Octave RTA. I used it to look at dual-mono (uncorrelated) pink noise, with, without, and with only the subwoofer. It was interesting to observe, with the microphone fixed in my listening position, how the bass response morphed as I moved the woofer from place to place. My brain does not do room-mode math, but watching these changes on the FFT app helped me "see" my room as a complex (but stable) acoustical compliance.

Because of these experiments, when the SVS 3000 Micro arrived, I pretty much already knew where it should go. Between my speakers but off-center, I discovered a spot about 36" from my front wall that is what the late David Wilson might have called a "zone of neutrality," a place where the power of boundary reflections seems lowest.

Once the 3000 Micro was positioned, the SVS iPhone app made the remaining setup almost too easy: No crawling on the floor with a flashlight to change settings. No worrying or keeping notes or trying to remember how the last setting sounded. I just sat on my couch, iPhone in hand, iPad with Roon at my side, playing one recording after another and tweaking filter slope, volume, and turnover frequency one cycle or one dB at a time. For example, I spent one lazy afternoon adjusting the 3000 Micro's low-pass filter, 1Hz at a time, between 70 and 75Hz, simultaneously tweaking the level between –22 and –27dB.

One of the recordings I relied on was Maximilian Hornung playing Dmitry Shostakovich's Cello Concerto No.2 in G major, Op.126, on his album Cello Concertos of 1966 (16/44.1 FLAC, Myrios Classics/Tidal). The raw invention and surprise-filled drama of this composition make repeated listening more exciting with each repetition. Its relatively uncompressed dynamics are spread evenly over 10 octaves. I knew I was closing in on the right settings when the kettledrums and cello sounded like I thought they should. The smart design and subtle responsiveness of the SVS iPhone app made my setup efforts into pleasurable, music-filled learning experiences.

Listening
Some purists think adding a subwoofer to a BBC-licensed LS3/5a is heretical. But for me, using subwoofers to extend the bass of my Falcon Gold Badges has caused me to comprehend many of my favored albums in a deeper (pun intended) way—a way I'm certain their creators intended for them to be appreciated.