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JL Audio Fathom f113v2 Subwoofer and CR-1 Active Crossover

JL Audio is one of those companies that does one thing and does it well. In JL’s case, that “one thing” is designing and building some of the world’s best subwoofers. Over its 38-year history, JL has fanatically pursued technological innovation with a single, laser-focused purpose: reproducing the lowermost 2½ octaves with the highest fidelity.

JL Audio holds an astounding 38 patents on woofer design (with six more pending), including those for a particular cone structure, a voice-coil cooling system, and a method of bonding the surround and cone assembly to the voice coil and spider, to name but a few. In addition to these patented proprietary techniques, JL Audio’s products are packed with non-patented innovations that are, in my experience, unique in the loudspeaker industry. If you read the extensive technical material on JL Audio’s website, you’ll get an appreciation for just how geeky and serious these guys are about subwoofers.

The result of this intensive focus on a single product category is a range of subwoofers that deliver reference-class performance. The first JL Audio subwoofer I heard in my own room was the original Fathom f113, about ten years ago. The system was dual-purpose (stereo and home theater) and equipped with reference-quality components. The f113 performed exceptionally in either two-channel or theater mode, integrating well with my stereo speakers for music listening and providing earth-shaking bass thrills on film soundtracks. A single f113 was markedly better, in every way than my previous reference subwoofer, which cost nearly five times more than the f113. The JL not only had more brute-force power; it also had much greater transient fidelity, better pitch definition, and was more refined and articulate. In the subwoofer world, those qualities are usually mutually exclusive. I’ve been using JL Audio subwoofers ever since. (My colleague Jonathan Valin, who has spent his life abhorring subwoofers, became a convert after hearing JL’s flagship Gotham. He now considers a pair of those mighty subs indispensable for music listening, even with large full-range speakers.)

Ten years after launching the Fathom, JL Audio has introduced an improved “v2” version of this outstanding sub. Two models are available, the $3700 f112v2 and $4500 f113v2, the differences being driver size and output power.

What’s new in the v2 models? For starters, the power output of the integral amplifier has increased by 20% from 1500W to 1800W in the f112v, and from 2500W to 3000W in the f113v2. I never thought that the originals needed more amplifier, but that extra headroom may come in handy under extreme conditions. The driver suspension has also been redesigned for greater linearity of movement. More importantly, however, the entire audio circuit has been upgraded for a shorter signal path and lower noise. This line-level processing circuit had been mounted behind the front control panel, requiring long cable runs between the audio jacks on the rear panel and the controls on the front. Now the circuits are in the back near the input and output jacks. In addition, this audio circuitry is now housed in a cast-aluminum sub-enclosure that is bolted to the rear-panel’s massive heatsink, isolating it from noise and vibration. There’s also better isolation between the power supply and audio signal circuits. Grounding has also been modified to further lower noise.

However, the most significant improvement is the vastly more sophisticated room-correction system called Digital Automatic Room Optimization (DARO) built into the updated v2 models. This new system is an evolution of JL Audio’s Automatic Room Optimization (ARO) circuit first used in the original Fathom. In the earlier model, ARO measured the subwoofer’s in-room response (with a supplied calibration microphone) and employed a single digitally controlled analog filter to flatten that response at the listening position. Although ARO removed bass bloat and increased definition, its single filter could only reduce the room’s highest response peak. By contrast, the new Digital Automatic Room Optimization in the Fathom v2 employs 18 one-sixth-octave digital filters. DARO provides significantly more precise attenuation of bass peaks, and at more frequencies, removing those peaks with extreme precision. Note that DARO doesn’t try to equalize out dips in the frequency response by boosting response at certain frequencies; it simply attenuates the peaks. The difference between a single band of analog filtering and 18 one-sixth-octave DSP filters is night and day.

In addition, calibrating the Fathom v2 is much faster and easier than it was in the original model. In the first Fathom, you had to juggle the test-signal level during the calibration to get just the right conditions needed by ARO. But DARO is truly a “one-button” operation; the subwoofer output level and microphone gain are adjusted automatically. In addition, the stimulus signal generated by the woofer during calibration is less susceptible to extraneous noise from things like air conditioners. Where ARO calibration would require several tries, accompanied by adjustments between each attempt, DARO works perfectly the first time.

One of the original Fathom’s many virtues was the comprehensive and well-thought-out front-panel controls. That hasn’t changed in the new models, which are functionally identical. A polarity switch and a continuously variable phase control work in tandem to time-align the subwoofer’s output with your main speakers (see sidebar). All subwoofers should have both these controls (realizing correct time alignment with just a 0°/180° polarity switch is a crapshoot). Similarly, the Fathom doesn’t just give you a continuously variable crossover frequency (30Hz–120Hz), it also provides adjustable crossover slopes (12dB or 24dB per octave). Again, the extra degree of control allows the subwoofer to better integrate and blend with your main speakers. The low-pass filter can be turned off if you are feeding the Fathom with the LFE output from a home-theater controller or receiver, or if you are using an outboard active crossover such as JL Audio’s CR-1.

Yet another thoughtful and useful adjustment is the “ELF Trim.” If you’ve spent any time struggling to set up a subwoofer, you’ve probably encountered the common condition of too much very low bass. The subwoofer simply overdrives the room at very low frequencies. The excessive output adds an annoying and amusical thump that makes the subwoofer stand out like a sore thumb rather than disappear. The Fathom’s Extreme Low Frequency (ELF) Trim control lets you cut or boost (–12dB to +3dB) at 24Hz to remove the thump.

Finally, the control panel’s center is dominated by the level control knob. If you are setting the subwoofer level with a home-theater controller or AVR, the Fathom’s level control can be bypassed via a switch.


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.


Every time I’ve added a subwoofer to a system I’ve felt that the available adjustments were relatively crude tools that allowed me to get close to ideal integration with the main speakers, but involved some guesswork, trial and error, patience, and just plain luck. The CR-1 is an entirely different story. This device provides extremely fine control over the critical hand-off between subwoofer and main speakers. The damping controls, in particular, give you an ultra-precise adjustment over how the sub and main speakers sum at the crossover point. In a remarkably short time, I had dialed-in the CR-1 so that the entire system was perfectly seamless from top to bottom. It’s amazing that it took so long for the industry to create a device like this; once you use it you’ll find it indispensable.

As I mentioned previously, the CR-1 confers a big advantage by splitting the frequency band with a true high-pass and a low-pass crossover. There’s very little overlap between the subwoofer and main speakers around the crossover point, eliminating the unpredictable result of having two different sources reproducing the same frequency band—the range of frequencies below the crossover point but above the lowest frequency the main speakers will reproduce. The combination of the high-pass and low-pass filter lets you decide, by listening, how much of the bass range is reproduced by the subwoofer and how much by the main speakers. If your main speakers have marginal bass quality below 100Hz, use a higher crossover frequency so that the main speakers never operate below 100Hz. Usually, a higher crossover frequency results in a more audible discontinuity at the crossover point. But the CR-1’s extensive controls provide seamless integration even at higher crossover frequencies.

I should mention that there are respected proponents of allowing the main speakers to run full-range and feathering-in the subwoofer so that it simply augments the main speakers’ output. Indeed, I’ve heard such systems sound superb. Although this approach can work well under ideal conditions, you have very little control over how the subwoofer integrates with the main speakers, with less-than-predictable results. Moreover, running the main speakers full-range erases the advantages mentioned earlier of freeing your main speakers and power amplifier from the burden of reproducing bass and the attendant increase in dynamic headroom.

Finally, the CR-1 has an extremely useful knob that very slightly shifts the balance between the main speakers and subwoofer. After you get the subwoofer’s level set at what you think is the right volume, the CR-1’s “Sub/Sat” adjustment provides fine tuning of the relative levels between subwoofer and main speaker. The sensitivity of all these adjustments is perfectly tuned; a tiny turn of the knob doesn’t produce too much change, yet the knob’s entire range is greater than would ever be needed. Between them, the Fathom and CR-1 provide a huge range of adjustments; getting them right is paramount to realizing the products’ potential. Fortunately, the two owner’s manuals are unusually comprehensive and well-written, guiding you through the set-up process.

The JL Audio Fathom f113v2 is a significant improvement over what I already considered to be the “go-to” subwoofer in the price range. In one sense the Fathom isn’t inexpensive; you can find lots of subwoofers for under $1k. But in another sense the Fathom is an amazing value, delivering reference-class performance for a far less-than-reference-class price. I wouldn’t hesitate to add a Fathom f113v2 and CR-1 to the most demanding playback system.

In addition to the specific sonic qualities described, the Fathom and CR-1 greatly elevated the system’s overall sound, not just the bass. The system opened up, with a cleaner midband (the result of removing midbass bloat), punchier dynamics, and an effortless quality on peaks.

I don’t know how much improvement the v2’s revised driver and increased amplifier power rendered, but I can tell you that the new DARO room-optimization system is a vast improvement over its predecessor in the original Fathom both in sound quality and ease of use.

If you’re thinking about adding a subwoofer to your system, I encourage you to audition the Fathom f1112v2 or f113v2, with and without the CR-1 crossover. If you own any brand of subwoofer, you need to hear what the CR-1 will do for integrating the sub into your system. And if you’re thinking about upgrading your speakers, you may want to first hear how adding a subwoofer can transform the sound of your existing speakers. In my view, no subwoofer anywhere near the price approaches the Fathom f113v2’s sound quality, build quality, engineering prowess, and value.

Specs & Pricing

Driver: One 13.5″
Loading: Sealed
Frequency response: 20Hz–86Hz +/–1.5dB; 18Hz–127Hz +/–3dB
Integral amplifier power: 3000W RMS short-term
Inputs: Stereo or mono or dual RCA jacks; stereo or mono on dual XLR jacks
Adjustments: Level, low-pass filter in/out, filter slope (12/24dB per octave), polarity, phase, extreme low-frequency (ELF) trim (–12dB to +3dB at 24Hz)
Calibration: Digital Automatic Room Optimization (DARO)
Dimensions: 16.5″ x 19.25″ x 19.25″
Weight: 133 lbs. (net)
Finish: Gloss black
Price: $4500

By Robert Harley

My older brother Stephen introduced me to music when I was about 12 years old. Stephen was a prodigious musical talent (he went on to get a degree in Composition) who generously shared his records and passion for music with his little brother.

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