JL Audio Fathom f113 Subwoofer - In The Welterweight Class!

      Date posted: November 13, 2009

JL Audio Fathom f113 Subwoofer

Sugg. Retail: $4000 CAD ($3700 US)
Canada Email: Canadian Website:

If you want a compact subwoofer, the Fathom f113 looks like a fine choice, if you’ve got a weightlifter friend: it weighs in at 115 pounds. If not self carrying (my limit is my Yamaha 9.9 outboard motor at 85 pounds), it is self calibrating, and comes with a microphone that you put at the listening position. We’ll show before and after measurements for our room below. This process is called Automatic Room Optimization, or A.R.O. More on all this later. The f113  is roughly 16.5 inches high and wide, and 19.25 inches deep.

The control panel can be seen to be across the top of the cabinet’s front, above the driver.  Adjustments include, from left to right, the A.R.O. calibration controls (including the balanced microphone input), Master/slave indicator light (that switch is on the rear panel beside the balanced Slave output, Slave meaning that the f113  is being used with a second JL sub); next is a slide switch that defeats the level control to its right (Reference defeats the control and Variable does the obvious opposite); Lights has 3 positions, off, mid and bright; a Low Pass filter is next right with 3 positions - Off, 12 dB [per octave] and 24 dB (this allows better matching of the sub’s upper response to the main speakers); the LP frequency can be adjusted in 7 steps from 30 to 130 Hz; the next circular switch in this group is for Extreme Low Frequency (E.L.F.) trim, adjusting 25 Hz output, with steps from -12 to +3 dB; the final rotary switch is a complex Phase control (for use most with multiple subs, but also helping in matching sub phase to the main speakers; there are 7 steps from 0 to 280 degrees, but a slide switch to its right allows 0/180 adjustment for those who want things simpler.

This is a complex, even professional subwoofer, and with its myriad adjustments tunable to both small rooms and very large ones. For audiophiles, it’s pretty complex, but at its price, I would expect the dealer to have his weightlifter/technician deliver it, find the right spot, and completely match it to the room and the main speakers. Once that’s done, you can dim the lights (those on the sub front panel too), and even put the grille cover back on, which hides the control panel completely, and start to listen. More on that below, but first, some measurements.

Fathom f113 Measurements (see text)

Looking at the chart, you can see 5 measurements. The first 3 are, top down - the sub right out of the box except for Level setting to about 85 dB; next down with A.R.O. correction completed and with the Low Pass switch setting at Off; the 3rd curve shows the Low Pass Frequency at maximum, 130 Hz. Though pretty good, in an average range of +/-4 dB, I thought better results could be achieved with some tweaking.

The first thing to do was limit the upper output of the sub using the Low Pass switch, so I set the Low Pass switch to -12 dB. Then it seemed time to bring the E.L.F (Extreme Low Frequency) adjustment into play; this I set at its maximum position, +3 dB. That measurement is the top of the lower pair, and one of the flattest responses I have measured for a subwoofer, +/-1 dB between 20 and 100 Hz. And cone movement with the broadband pink noise test signal suggested we were probably flat to about 16 Hz.

But did we want response that was just 5 dB down at 150 Hz? Well, maybe with mini-monitors, but with our Energy Veritas 1.8s (with their port output limited by PSB rubber plugs), perhaps the upper output could be tamed, which I set on the Low Pass switch to -24 dB per octave, a “Linkwitz-Riley alignment”, according to the manual. Again, the E.L.F. adjustment was set for 3 dB boost at 25 Hz. So now we had a curve that gently slopes above 50 Hz, down 5 dB at 100, but more important, down 15 dB at 150 Hz. It is, as you can see, still dead flat below 50 to 20 Hz and to the lower limits of the sub.

I’m sure these results could be achieved with a different combination of settings, but this worked for me. Perhaps the dimensions of my room offer some rationale for why these settings did work here. My listening room is 32 by 12  by 7 feet high, and well damped with Room Tunes and Tube Traps. Therefore, it will develop a full 32 Hz wavelength, but needs a little help below that frequency. The higher crossover needs to be below 100 Hz with my speakers, and about 55 Hz is optimum, which is what we managed in the lowest curve shown. These settings were used for listening tests.

Before making those subjective evaluations, a few more comments about the A.R.O. auto EQ system. My gut feeling is it would have been more successful in a room that was closer to square, less well “trapped” and damped, and, like many, with irregular boundaries on at least one end or side. This system also (again from the excellent manual), “serves to eliminate the single largest acoustic response peak…at the main listening seat”; that is, it is not quite as versatile as all the other controls I used, but my settings were, of course, facilitated by the LMS system I use for measuring speakers. But that is not to say A.R.O. isn’t a good starting point in setting up the Fathom f113, or any other JL Audio subwoofer. But careful tweaking with an RTA device or a sound level meter will be a big help.
f113 control panel
It’s also important to note that during the A.R.O calibration I was able to hear exactly what in my room would rattle at specific frequencies as the auto sweeps were run by the system over its 2+ minutes of calibration, which happens at a quite high level, somewhere just over 90 dB at 1 metre. And it was obviously audible that the f113  is capable of very high and clean levels at well above 90 dB with very low distortion.

Regular readers will know that I am very much a multi-subwoofer person, using 4 in my listening room (all were disabled during the measurement and listening period with the Fathom), and a pair in my home theatre. A pair of f113 s might be a stretch financially, but would provide more even deep bass in any room, and all the EQ and frequency contours offered on a sub like this can’t fully overcome the room with a single radiating point. Some other subs approach this problem by being bipolar or dipolar, but either way placement is very critical, and corners always the worst possible option. I set up the f113 just inside my right speaker, well away from room boundaries and facing directly forward.

In listening, I used the final two measurement settings, switching from -24 dB to -12 for some of my older Jazz and Classical recordings that need a little boost in the mid-bass. It’s nice to have that option at the flick of a switch, something I can do on a continuously variable basis with the pot on my Energy electronic crossover feeding the Sunfire True Subwoofers. In my room, the f113  provided very clean, tuneful, and powerful bass down to the lowest frequencies, with prodigiously clean sound at any level I could stand.

In sum, this is a very good subwoofer once you find the right spot for it. Listening to bass-heavy recordings like James Taylor’s Hourglass, I heard that sense of effortlessness that distinguishes a really good sub in the lowest octaves, without any intrusion in its upper range when properly set up. Some writers call this “disappearing”, but the word that comes to my mind is “foundation”, as the JL Fathom f113 adds the true basis of bass to any already excellent audio system. Need I say more?

Andrew Marshall

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