JL Audio Fathom f113v2 Subwoofer and CR-1 Active Crossover

A Great Subwoofer Made Better

Equipment report
JL Audio Fathom f113v2
JL Audio Fathom f113v2 Subwoofer and CR-1 Active Crossover

JL Audio is a proponent of multiple subwoofers, and not just because it wants to sell more subs. Each subwoofer in a distributed subwoofer system drives a room’s resonant modes differently, resulting in smoother bass response. Moreover, with two subs in a room, each one has to work only half as hard for the same total acoustic output, ensuring that each subwoofer operates within its linear range while also delivering greater dynamic headroom. For these multi-sub applications, JL has included a method of allowing multiple Fathoms to work together as a unit. One of the Fathoms can be designated the “Master.” Changing the Master’s level will change the level (and other settings) of the other Fathoms connected to it.

These adjustments and controls are about as extensive and complete as you’ll find in a subwoofer. But if you want the next level of fine-tuning, JL Audio makes an active outboard line-level crossover, the CR-1, with a few tricks up its sleeve. The $3000 CR-1 replaces the Fathom’s low-pass filter and offers more precise tuning of the critical transition between the subwoofer and your main speakers. Specifically, the CR-1 has finer crossover-frequency adjustments, a knob for setting the subwoofer/main speaker balance, and a pair of “damping” controls: one for the signal driving the subwoofer at the crossover frequency, and one for the signal driving the main speakers. These provide a slight boost or cut right at the crossover frequency, giving you that extra ability to get the handoff between subwoofer to main speakers just right. This pair of damping adjustments allows you to surgically dial-in the response at the all-important transition between main speakers and the sub.

The most important aspect of the CR-1, however, is that it not only has not a low-pass filter to remove mid and high frequencies from the signal driving the subwoofer, but also a high-pass filter to remove bass from the signal driving the main speakers. This is an important difference from the Fathom’s integral crossover, which is simply a low-pass filter that removes mid and treble frequencies from the signal driving the subwoofer but has no effect on the signal driving the main speakers. With just a low-pass filter on the subwoofer and the main speakers run full-range, the main speakers and the subwoofer will both reproduce the same signal over some band of frequencies. The outputs from the main speakers and the subwoofer will combine in unpredictable ways, creating peaks and dips in the response. The range of overlap is determined by how low in frequency your main speakers extend and the crossover frequency selected on the subwoofer. Ideally, the subwoofer comes in just as the main speakers are rolling off in the bass. But in practice, this transition is never that simple. Things can get very messy around the crossover point when two disparate speakers, located at different points in the room, are reproducing the same frequency band.

These problems are obviated by employing a line-level crossover (the CR-1) that divides the frequency spectrum into two parts (subwoofer and main-speaker signals) before the power amplifiers. First, adding the CR-1 avoids the overlapping bass problem when the main speakers and sub are both reproducing the same frequency band. Second, keeping bass out of your main speakers and amplifier (the CR-1 operates before the power amplifier) relieves the amp and the speakers of reproducing energetic low frequencies. The dynamic headroom of both amplifier and speaker is increased. Third, filtering low bass from the signal driving your main speakers reduces woofer excursion, increasing upper-bass clarity.

We’ll explore later how the CR-1 performs in the real world, but let’s first consider the Fathom f113v2 on its own. I set it up in two rooms, one a small theater system based on PSB T3 speakers in the left and right positions, with the Fathom driven by the LFE output from a Classé home-theater controller (the low-frequency effects output of a controller is a mono mix of the “.1” LFE channel on film soundtracks along with bass from any speakers designated “small” in the home-theater controller’s set-up menu.) The second system, in a different room, is a stereo system built around Piega C711 speakers driven by an Esoteric F-03A integrated amplifier.

After finding the right placement for the Fathom and dialing in the crossover frequency, crossover slope, and phase controls, I listened to the system before engaging the DARO room-optimization routine. As expected, the system’s bass was deeper and fuller with the Fathom, but the penalty was some smearing, bloat, and boom. Any time you pressurize a room with low frequencies, that energy is going to excite room resonance modes, which you hear as excessive weight, loss of articulation, smeared transients, and tonal colorations. Yet three minutes later all these problems magically vanished; that’s how long it takes DARO to measure the response of the Fathom in your room (at that particular subwoofer location, and that particular listening position) and apply the 18 DSP filters to attenuate those response peaks. The transformation is dramatic. By removing midbass bloat, I could hear more low bass, with much greater pitch definition. DARO simply makes you unaware of the subwoofer as a separate entity. The midrange also becomes cleaner, clearer, and less “thick.” Transient fidelity improves, with less overhang on kickdrum. Hearing bass start and stop faster better communicates music’s rhythm and flow, on a wide range of music. The walking bass line on Errol Garner’s “The Man I Love” from Encores in Hi-Fi was so much better defined after DARO that I could clearly hear the fascinating rhythmic fluidity between Garner’s left and right hands and the beat. It never ceases to amaze me how an audio technology can clarify a musician’s intent.

As powerful as DARO is, it’s not a panacea. You should still position the subwoofer so that it best integrates with your room before running DARO. Poor placement will introduce large peaks and dips in the response; as noted, DARO only knocks down the peaks and doesn’t try to boost the dips. Still, DARO is a significant sonic advance over ARO, and easier to use as well.

The Fathom f113v2, once set up and dialed in, displayed a range of virtues with which I’m very familiar. Even after all these years of using JL subwoofers, I was struck by the Fathom v2’s unlikely combination of powerful and effortless extension with unfettered dynamic impact on one hand, and exquisite agility, finesse, timbral resolution, and pitch definition on the other. The Fathom has a remarkable ability to add a subtle weight and bass foundation to some recordings—so subtle that you don’t know the sub is working—and then with other music to explode out of nowhere with concussive bass impact and deep extension—the bass drum impacts on the Reference Recordings The Rite of Spring in MQA, for example. For fun, I cued up E. Power Biggs performing Bach’s Toccata and Fugue in D Minor, a subwoofer guilty pleasure if there ever was one. The Fathom reproduced the lowest pedal tones with tremendous authority and power, accompanied by a complete sense of ease. Moreover, the pedal tones had distinct pitches rather than being low-frequency mush. Another great thing about the Fathom is that you don’t hear port artifacts (it’s a sealed design) such as chuffing, the onomatopoetical word describing the sound of air rushing in and out of the port. The Fathom delivers low bass with no sense of strain, no smearing of pitch, no dilution of timing information, and no port-induced artifacts. In fact, the Fathom exhibits no single character that imposes itself on the music; instead the Fathom is chameleon-like in its ability to perfectly blend into a wide range of music. Going back to the Bach organ recording, this track also beautifully illustrates how adding a subwoofer increases the sense of space, soundstage depth, and the ability of a system to portray a large acoustic space. This was true even during passages with no low-bass notes; the Fathom still reproduced the subtle low-frequency cues that convey dimensionality and size. Try comparing a system with and without a subwoofer, and you’ll discover that virtually all music, regardless of its spectral content, sounds more spacious and open with a subwoofer.

As good as the Fathom f113v2 is, and as well as it integrated with main speakers, the system’s overall sound is transformed by adding the CR-1 outboard crossover. Although I’m the first to regard with suspicion the idea of inserting an active piece of electronics into the signal path, I found that the CR-1 is extremely clean and transparent. If it weren’t, the CR-1 would be a non-starter. The signal path to which I inserted it was the Berkeley Alpha Reference Series 2 MQA DAC driven by an Aurender W20, the 30Wpc Esoteric F-03A Class A amplifier, and Piega C711 speakers with their extraordinary and unique coaxial planar-magnetic driver. Although this amplifier and speaker combination is not a powerhouse in terms of scale and impact, it is nonetheless extremely transparent to sources. The CR-1 introduced no noticeable degradation to timbre, soundstaging, or dynamics.

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