Music in the Round #80
The matter of room acoustics itself relates to the Schroeder frequency: a transition point, usually between 200 and 300Hz above which a room will exhibit a high density of reflections that are analyzed statistically, and below which that room will display a limited number of discrete modal reflections. (Thus, it should not to be confused with the number of times that Beethoven's music appears in Charles Schulz's comic strip "Peanuts.") Above the Schroeder frequency, the sound is dominated by densely overlapping modes whose properties are easily addressed with such physical correctives as wall treatments. But in the frequencies below the Schroeder or critical frequency, the room's influence is dominated by discrete modes that depend on the room's dimensions and are more amenable to electronic correction. (Physical acoustical correction within this range would require the careful placement of structures whose own dimensions are mathematically related to sizable wavelengthsnot easy to achieve, unless one has a dedicated listening room.)
Since subwoofers always operate below the critical frequency, JL Audio's enhancement of the equalizer in their v2 range of Fathom subs is to be applauded; otherwise, owners of analog systems would have to buy a standalone equalizer. However, many of us multichannel fans have systems that already include room-EQ capabilities, and while these vary greatly in convenience and capability, we might not want to buy a sub with its own EQ, thus adding unnecessary complexity and cost. In my Manhattan system, I prefer to use Dirac Live for all playback, as my serious listening is to files via my Baetis server and exaSound multichannel DAC. In my weekend system, in Connecticut, I use Dirac Live to play files, and Audyssey MultEQ XT32Pro for discs.
So when my reliable Paradigm Reference Servo-15 subwoofer developed a hum, and I decided not to ship the 80-lb, 16-year-old sub home to Canada for evaluation and repair, I faced the issue of replacing it (footnote 2). All things pointed to getting a powered sub or subs capable of excellent bass extension that, more important, would integrate acoustically and aesthetically with my system. And there was no need for it to have built-in equalization.
My experience with JL Audio's Fathom line led me to get two of their E-Sub e110 subwoofers ($1499.99 each in Black Ash finish). The E-Subs, one step down from the Fathoms, have slightly less impressive specifications for extension and power than the Fathom f113. The f113 has a claimed frequency response of 2086Hz, ±1.5dB, and 3dB at 18Hz; the E-Sub e110, 25116Hz, ±1.5dB, and 3dB at 23Hz. The f113's built-in power amp is rated at 3000W RMS (short term), the e110's at 1200W RMS. However, the e110's smaller size opens up more placement options, its lower weight makes it easier to move, and the use of two will mitigate some of the differences in FR and power between it and the f113. In fact, the use of multiple subs, carefully positioned and set up and equalized, is a growing trend supported by research efforts (footnote 3) to produce flat, spatially uniform bass response in real rooms.
I was surprised to find that each e110's double-boxed carton was nearly as large as the f113's, even though the e110 measures only 14.24" high by 13.5" wide by 16.51" deep and weighs 52.7 lbs (compared to the f113's 19.25" by 16.5" by 19.25" and 133 lbs). I moved the old Paradigm Reference Servo-15 out of the room (with considerable effort), then placed one e110 to each side of my center Monitor Audio Silver 8 speaker, at the front of the room, so that the JLAs would be equidistant from my main listening position. The e110's construction and finish were of high quality, and an excellent match for the Silver 8s.
Each e110 has a 10" driver, a pair of RCA inputs, and a pair of RCA outputs. With the sub's crossover engaged, the output jacks provide a 24dB/octave, Linkwitz-Riley-filtered high-pass signal; when the crossover is defeated, they provide a buffered version of the same signal that appears on the e110's input jacks. Controls include level, filter defeat, filter frequency, polarity, and variable phase, but I defeated the filter and left the polarity and phase at 0¯. All I needed was the level controlAudyssey and Dirac Live would handle everything else, including EQ.
I began with Audyssey, because its first step in calibration is a handy subwoofer-level routine. Using the test tones and the e110s' level controls, l carefully set each e110 to 75dB, ±0.5dB. Audyssey may retrim the two sub levels during its calibration process, but because the server output to the Marantz AV8802A surround-sound processor is 5.1, Dirac Live on the server cannot. Measurements taken with Dayton Audio's Omnimic microphone-plus-software system showed that each e110 had an in-room response with a deep trough (at 53Hz right, 60Hz left), a broader hump (44Hz right, 42Hz left), and a smooth rolloff below about 6dB/octave, even though the left sub was about 4' from a corner and the right sub about 4' from an open doorway (fig.1).
The combined output of both e110s (green trace) was almost an algebraic sum of their individual responses. This is important, because Audyssey calibration (with nine measurement positions, using the array recommended by Dirac) applies the same correction to both subs. Looking at fig.2the results for the two e110s operating together, before and after calibration by Audysseyyou can see that the deep trough was reduced to less than 5dB, and the broad hump replaced by a nominally flat response from 30Hz down to below 20Hz. Useful response was maintained to below 15Hz. Pretty impressive for a pair of 10" drivers!
Unfortunately, Audyssey didn't set the sub levels properlya complaint I've often heard from others, but not something that had troubled me till now. It was immediately apparent by ear that the bass was very lean, and Omnimic confirmed that the subs needed 56dB more drive. That corrected, the e110s were getting the sub-40Hz bass from all five channels (plus LFE, where it existed), and it all seemed so right and so familiar. It sounded just like running the main speakers full range . . . until it didn't.
Any of a number of organ recordings revealed clean, deep sounds I hadn't heard from the Monitor Silver 8s sans subsat least, not with the power and weight they had now. The sub-Saharan subject of the title track of Béla Fleck's Flight of the Cosmic Hippo (CD, Warner Bros. 26562-2) threw his weight around, and organ pedals in the second movement of Saint-Saëns's Symphony 3, with Christoph Eschenbach and the Philadelphia Orchestra (SACD/CD, Ondine ODE 1094-5), were firmly supported. Kick drums had palpable kick, and the overall balance of symphony orchestras was appropriate. For example, in the first movement of Manfred Honeck and the Pittsburgh Symphony Orchestra's recording of Tchaikovsky's Symphony 6, Pathétique (see sidebar, "Recordings in the Round"), the lower strings provided a rich carpet, unobscured even by the bursts of brass.
The JL Audio E-Sub e110s meshed better with my system than had the 15" sub they'd replaced, and my ears couldn't identify them as discrete sources of sound; often, I needed to get up to feel, with my hands, where all that firm, clean, deep bass could be coming from. It seemed as if the five main speakers themselves had been endowed with greater capabilities. And, of course, in a sense, they had.
On the other hand, these two 10" subs didn't "load" the room as had their far larger predecessors. This might seem predictable, but a good part of the reason was that the e110s seemed much freer of resonant behavior. Indeed, the two 13" JLA Fathom f113s in my Manhattan system are equally tight and integrated with the rest of the system, yet provide more encompassing bass than the e110s. I intend to pursue this by supplementing the two e110s with the Paradigm Studio SUB 15 subwooferor, perhaps, with another e110 or two. (Maybe I could hide them behind the sofa . . . )
JL Audio's E-Sub e110 is a compact subwoofer that offers deep, powerful bass. Most important, with the use of a competent room equalizer it's easy to integrate into any system, to provide welcome and gratifying low-frequency extension. And two were even better.
Next Time in the Round
I have an Idof course!but this one is a music server and/or renderer from JRiver, based on an Intel NUC small-form personal computer. In addition, there will be a report on Classé's new Sigma Mono power amplifier, based on their proprietary class-D circuit designs.
Footnote 1: JL Audio, Inc., 10369 N. Commerce Parkway, Miramar, FL 33025-3962. Tel: (954) 443-1100. Fax: (954) 443-1111 (General). Fax: (954) 443-1108 (Technical Support). Web: www.jlaudio.com.
Footnote 2: I still have a Paradigm Studio SUB 15 subwoofer, which I reviewed in the January 2010 issue. While the SUB 15 includes Paradigm's Perfect Bass Kit EQ, I haven't used that facility for a while.
Footnote 3: Todd Welti and Allan Devantier's original paper for Harman International Industries is "Low-Frequency Optimization Using Multiple Subwoofers," JAES Vol.54 No.5, May 2006. A less formal presentation is available here.