THIEL SmartSub 1.12 Subwoofer Reviewed
By: Brent Butterworth,
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The THIEL SmartSub 1.12 raises a fascinating question: How smart does a subwoofer need to be? For the most part, a subwoofer merely pumps out about an octave of sound, between 40 and 80 Hz. Our hearing isn't attuned to bass frequencies, so we don't notice the sonic differences among subwoofers as readily as we notice the differences among speakers. AV receivers have subwoofer equalization circuitry built in to correct for the effects of room acoustics. So why has THIEL--both under its current leadership and under its namesake founder--always strived to make its subwoofers "smart" and marketed them as such?
There's no denying that the SmartSub 1.12 is one of the smartest subs ever designed. Most impressive is its built-in room correction, a five-band parametric equalizer that uses an included microphone to automatically optimize the sound for your room and your seating position (or for multiple seating positions). If you don't like the results, you can manually alter each filter's frequency, boost/cut level, and bandwidth.
The SmartSub 1.12 can be calibrated and controlled through a computer connected via USB or through an iOS/Android smartphone/tablet app. The smartphone or tablet connects wirelessly to the SmartSub 1.12's built-in Wi-Fi access point.
This subwoofer also offers nice connection options. The back panel has XLR and RCA stereo line inputs and outputs, plus an internal subwoofer crossover. Thus, if your stereo preamp has no built-in crossover (almost none do), you can use the SmartSub 1.12's crossover, which lets you set the high- and low-pass filters individually in one-decibel increments and also choose from Butterworth or Bessel filters in 12-dB, 24-dB or 36-dB-per-octave slopes, or Linkwitz-Riley filters in 12-dB, 24-dB or 48-dB-per-octave slopes. This means the lows can be filtered out of your main speakers, which will give you smoother bass response and better integration with the subwoofer, and it will improve the main speakers' power handling.
There are separate delay settings for the high-pass and low-pass filters, adjustable in one-millisecond increments (up to 50 ms), a feature found in all modern AV receivers but few stereo preamps equipped with subwoofer crossovers. Thus, if your sub is three feet farther from you than your main speakers, and you're using the sub's crossover, you can time-align them by delaying the main speakers by three milliseconds. This feature should eliminate the need for a phase control, but there's one on the control panel anyway, and it's adjustable in one-degree increments to 180 degrees.
A monochromatic, luminescent front-panel display shows all the operating information, including the settings on the EQ. THIEL also includes a small IR remote control that adjusts volume, phase, mute, etc., and lets you flip through the display screens. The remote also scrolls through four different sound modes (Music, Movie, Game, and Night). Plus, THIEL throws in a wireless transmitter that connects to the line outputs of your system so that you don't have to run a cable to the sub if you don't want to.
I almost forgot to mention that the SmartSub 1.12 employs a high-excursion 12-inch driver and a 1,250-watt Class D amp. The relatively compact cabinet is available in a gloss black or wood finish.
I placed the SmartSub 1.12 in my room's "subwoofer sweet spot," a position just to the left of the right-channel speaker, which is where most subs tend to sound best from my usual listening position. Because I got a very early sample of the subwoofer, the iOS/Android control app wasn't ready yet, so I used the Windows PC app, which THIEL says has the same functionality. The app is a couple of steps above anything similar that I've used, with friendly graphics and an intuitive design that actually made it fun to use and easy to adjust. Following the onscreen prompts, I ran the auto EQ routine, placing the microphone on a photo tripod at my ear height (the mic has a standard ¼-20 mounting socket on the bottom), and running five response sweeps. The display then showed me the in-room measurement, the correction curve it calculated, and the settings it applied on its five parametric filters. As stated before, I could go in and adjust any of those settings.
I connected the subwoofer to my system in three different ways. I tried it in what I think will be its most common setup in two-channel systems, with long Wireworld Eclipse 7 XLR balanced interconnects running from a Classé CP-800 preamp/DAC to the sub's inputs, and shorter XLRs running from the sub's outputs to a Classé CA-2300 stereo amp. (This setup works best, with fewer long cables required, if you keep your amp up front between the speakers, as I do.) I also tried using the Classé preamp's internal subwoofer crossover, with the XLRs going straight to the amp and a long RCA-tipped interconnect running from the preamp's subwoofer output to the SmartSub 1.12. Then I tried a conventional home theater setup, using my Denon AVR-2809Ci AV receiver and an AudioControl Savoy seven-channel amp, with the receiver's RCA subwoofer output connected to one of the sub's RCA inputs.
I used three different sets of speakers: my Revel Performa F206 towers, a visiting pair of Bowers & Wilkins diamond 804 D3 towers (review pending), and a set of small Sunfire home theater speakers, with CRM-2s in the front and CRM-BIPs used for surrounds. I used the subwoofer's Music mode (which I found measures the flattest) for all music listening, and I switched between the Music and Movie modes for movie listening.
I have two relatively minor complaints about the SmartSub 1.12's design. First is that the sub itself has no controls at all. You have to control it through the remote, through your smartphone or tablet, or from a connected computer. Second is that the gain could stand to be maybe six decibels higher. There were times when I wanted to push the level of the bass up higher relative to the main speakers, but the sub's volume was already at maximum.
It seems to me that one of the main reasons why many audiophiles don't like subwoofers is that, too often, the subwoofer sounds like a separate component in the system, rather than a natural extension of the left and right speakers. This is, of course, unnatural: When you play a double bass, the low fundamental tones and the upper harmonics both come from the same instrument, not from separate places with their own sonic character.
So far, it appears the solution to this problem that audiophiles embrace the least reluctantly is to connect the subwoofer to the speakers or to the output terminals of the amp, as seen in Sumiko and REL subwoofers, and adjusting the subwoofer's response so that it picks up where the main speakers' bass response starts to roll off. The upside is that the hookup and setup are simple, and in my experience it's easy to get a good blend between these subs and the main speakers. The downside of this approach is that the main speakers still have to handle a full load of deep bass, which limits their power handling, increases distortion, and increases the deleterious effects of room acoustics because the main speakers have to be placed for optimum midrange and treble performance, not for optimal bass performance.
Using the SmartSub 1.12's internal crossover is, in my opinion, the best solution I have found. I used the Sunfire speakers because their limited low-frequency response makes it hard to get them to blend with a subwoofer. But with the SmartSub 1.12's internal crossover, it was easy. I guessed that using Linkwitz-Riley 24-dB/octave filters at 100 Hz would give me a good blend, and indeed it was a good start. The double bass on "Mistreated but Undefeated Blues" from legendary jazz bassist Ray Brown's Soular Energy album sounded so much like a real instrument in my room, with a solid stereo image, no booming or distortion, and a generally even response from note to note. That's a rare result.
I noticed, though, when I played Mötley Crüe's "Kickstart My Heart" that, while the bass was extremely tight, precise, and well-defined, there did seem to be a little less impact in the upper bass, near the 100-Hz crossover frequency. So I plugged in the computer, sat in my listening chair, and tried some different adjustments, such as bringing the high-pass filter frequency lower, bringing the low-pass filter frequency higher, and using the different filter profiles. I ended up getting the best result by sticking with the Linkwitz-Riley filter profile, pushing the high-pass frequency up to 110 Hz, and going with a shallower, 12-dB/octave response for the high-pass. This gave me an impeccably smooth response; the little Sunfires sounded like a colossal, kick-ass tower speaker system, but with much flatter bass response than non-EQ'd tower speakers could possibly achieve.
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