Are the JL Fathom subs really that good....

Johnnyb53, the speaker position in a room gives the most natural midrange will almost never yield also the best bass response. Whether or not one will obtain good results by placing the subwoofers close/next to the main speakers depends entirely on the room geometry - it is certainly not a given. Having the ability to place the midrange-high frequency source in the ideal place and the bass source in its (different) ideal place is the main advantage of using a subwoofer.

Irv, you may have hit on something. I am less than 12' from my speakers due to my smaller room so there is less chance for the sound to blend before I hear it. I wouldn't call my setup nearfield but it isn't "farfield" either. I thought that when I went to full range floorstanders the subs might be too much in the room but that is not the case with the proper (to my ears) adjustments.

Interesting. Since your post, Bizango1, I've more carefully listened to see if I could tell where the subwoofer is in my room. I have to admit the results inconclusive, for two reasons. First, my sub is positioned about midway between my main speakers (though not exactly midway), making the sub more likely to appear blended. Second, a lot of recordings are mixed with mono bass. Perhaps most recordings. This, of course, means that a centrally placed sub will blend even better. So it possible that the only reason I can't tell where my sub sits is because that's how the bass would sound even if the sub weren't present.

NVP: All very good points. I was thinking more in terms of getting the easiest in-phase blend wherever your listening position. With a sub in a different place than the the mains, the phase relationship changes as you change listening positions. But as you say, the subs may need a different position for smoother response and better room coupling.

In my own setup I have a compromise between the two. I run a stereo pair of subs, but they need back wall reinforcement for any meaningful low bass, so I position them as stereo pairs against the wall and directly behind the R-L mains. That way I get the room reinforcement and only have to adjust the phase control a little bit, and the frequency range stays pretty uniform throughout the listening area.

Another advantage of separate subs is that the mains and the subs can be built and optimized to their frequency ranges, and it keeps the internal vibrations produced by very low notes (and contained within the sub) from smearing the cabinet vibrations handling the midrange and treble.

Irv, I have a large aquarium in between my speakers so I have never been able to locate the sub near the middle. Who knows, if I had I might never have been driven to try stereo subs. I guess the plot thickens as our system details come out. In my setup with the tank in the middle two subs to my ears are conclusively better. I suppose the bass blend across the soundstage could be inhibited by the half-ton body of water in the middle!