Bob Katz is a world renowned Mastering Audio Engineer whose accomplishments read like a who's who in the industry. You can read all about his remarkable facility (and his inventions, and his books, highly recommended) here: www.digido.com. He has just installed a pair of JL Fathom 112's in his facility in Florida.

Here is his endorsement, word-for-word:

"I am a professional mastering engineer. I recently purchased a pair of Fathom F-112 subwoofers to replace my previous subwoofers for my mastering room. Everything about the construction and circuitry of these woofers is first rate, but most important to a professional, was the ability to linearize my room, to get the flattest, tightest, most even bass that I've ever heard. They have every control I consider essential to a subwoofer — level, continuously-variable phase, polarity switch, 12 or 24 dB per octave slope, continuously-variable low pass frequency, and extreme low frequency EQ. In addition, they come with a test microphone for an automatic room optimization feature that I was initially skeptical about, but now I'm convinced it works great. The A.R.O. was able to correct a measured +9 dB 65 Hz bump in my room with no audible artifacts. After A.R.O., every well-made recording now sounds correct in my room, whether it has sustained bass or rhythmic bass. The masters that I've previously made for my clients sound even better than before, and with the Fathoms it's much easier and less fatiguing to make new masters, as I can identify any bass errors with great certainty.

As a bonus, in addition to playing music cleanly, these woofers are able to reproduce the most demanding low-frequency recording anyone has ever made! There is a very clean, wide range 24 bit 96 kHz recording that I made of the Space Shuttle Discovery from the Press site, which is the closest anyone is allowed to the rocket during launch. I can reproduce the recording in my room at exactly the measured SPL of the launch, without audible distortion! This is one helluva low-frequency demonstration. Needless to say, I'm a happy camper."

Basically, this is a big step upward for me, bigger than I had imagined it might be. I was able to make the flattest, most even bass response in my room ever, with seemingly infinite bass headroom. The flat bass completes the Lipinskis, the total sound result is warmer, definitely more correct than ever, without having to do any tricks for "more bass" or overlap or anything. It helps make them a bit more musical on a wider range of material without losing their discrimination ability.

The bottom end is so correct now it gives you goosebumps. There's not a note out of place. I can hear bass notes that I didn't know were there... I've re-optimized the room, tweaked the listening position for flattest response, not one stone left unturned. I invite you all to drop in for the experience. The sound is accurate, tight, clean, powerful... I've been listening to everything I have to play for hours and hours, it's habit-forming!"