How to hook JL F112 sub to both preamp and pre/pro

texas, sorry to belabor the point, but i'm very curious on your position where multiple sources to the fathom subs are concerned. if you're still following this thread, would you mind expounding on the circumstances that would result in competing signals? i'm genuinely curious about this, as i ran this way with an F112 without any (perceived) ill-effects for a while after consulting with the tech at JL Audio. am i setting myself up for some issues down the road??

Jeffkad, yes, my preamp (aesthetix calypso) has multiple outputs. i ran the main L/R outs from the HT pre/pro into a bypass input on the preamp, and from there, one set of outs to my main amp, a second set of outs to the fathom sub. additionally, i ran the subwoofer out from the HT pre/pro to the second inputs on the fathom. i made sure the XOver point in the pre/pro was set higher than on the fathom and everything seemed to be fine. Do not get too hung up on finding a preamp with HT Bypass, as any preamp will do, you’ll just have to remember to run the volume up when you select the input from your HT pre/pro.

best to call JL Audio and speak to their tech (Barry) about your specific system. i've also talked with the tech at SVS and they suggested the same setup the JL did, noting no damage would occur.

Another option you might consider are Rythmik subs. they are FANTASTIC and their DI amp option (soon to be replaced by the PEQ3) is specifically designed to work with both a 2-channel preamp and a HT pre/pro.

to your comment on high end pre/pros, my aesthetix calypso was night and day better than my theta casablanca. to my surprise, using my Wyred4Sound DAC2 as a preamp was also better than the casablanca and very close to the aesthetix.

Srosenberg, thanks much for the input. I actually did have an email exchange with Barry at JL and he confirmed what you said, its perfectly fine to run both inputs, LFE/RCA out from pre/pro and balanced/XLR out from preamp.
Not surprised your calypso was better, as I have heard great things about that unit, but VERY surprised about the W4S being so good. What gear are you running? Wondering if there is a certain threshold of gear quality above which such distinctions become more pronounced. I'm running B&W N803 as mains (HTM1 ctr and DS7 surrounds), with Sunfire TGA5200 amp ( a very good and underappreciated amp) and a Sunfire TGP5 pre/pro fed by both a modded Denon 3930ci and a Sonos-BelCanto Dac2 combo. Although not heavy high end, would assume its good enough to hear a difference?

The below is from the JL Audio F112/3 manual. As you can see, they specify NOT connecting 2 sources to one sub, as the tech at JL Audio told me previously. I don't know who Barry is, but I would check for clarification. I don't think you can do this with a JL Audio, I think it could fry the crossover and amp, unless they have changed the electronics significantly. Look again at the last sentence of the setup from the manual below.

SYSTEM CONNECTION DIAGRAM 1:
One Fathom to
Home Theater Receiver or
Home Theater Preamp/Processor
Most home theater receivers and
preamp/processors provide a single
(mono) subwoofer output. When
connecting a mono subwoofer output
to your Fathom, you will only use the
Fathom’s “Left or Mono” input.
Two connection types are available
for connecting the Fathom to your home
theater system: balanced (XLR or 1/4-
inch TRS connector) and unbalanced
(RCA-type connector). Balanced
connections provide superior noise
rejection and ensure proper grounding
between components. If your receiver or
processor has balanced outputs, we highly
recommend that you use them.
In the connection diagram at left ,
balanced connections are shown as solid
lines, unbalanced connections are shown
dotted. You will only use one of these
input connection methods (not both).

texas,
that's really odd that the manual is SO explicit on this point, while their technician is clearly telling end users something different. point taken, thanks for your comments - perhaps the OP should bring this up with JL.

Jeff,
my rig isn't the final word in high end, but i've spent the last several years going through several different amps, preamps, sources, DACs, speakers, etc to get to a point now where i'm comfortable evaluating gear IN MY ROOM to MY PREDILECTIONS. those are important to note, as we all listen for different things, and my gear might sound dramatically different in another room.

i'm currently running Wilson speakers and VAC monoblock amps. the aforementioned DAC2 serves as DAC and preamp and is surprisingly capable in that role. that piece was really something of a surprise, as i never expected it to better my Weiss Minerva, and certainly never thought I'd be running it as a preamp.

Mac:

Barry Ober is a technical consultant for JL. Check out his own personal website at soundoctor.com ( a wealth of audio info and white papers). This guy has an uber-impressive resume, he's an audio engineer and has built recording studios. A very knowledgeable dude.

I think he's credible, to say the least.