I don't see it. If you individually EQ each sub so that the phase, distance, amplitude, and freq spectra is what you want at the main listening positioning, and then you add them together, their responses should just add together. Where's the interaction? The 2 subs' physical locations are different. But what EQ'ing is supposed to be doing, is to make it so that they sound the *same* at the main listening position. (Or as much as possible the same, given their different physical locations.) Essentially, you're just co-locating 2 different sound fields over top of each other. (Hard to explain.) As if you had one speaker exactly where you're located, and then you add another one in the same exact spot. All you're doing is doubling the volume of something that should be "correct" in the 1st place: the soundfield of each sub at the main listening spot.

Gary- with your virtual sub idea: if each individal EQ system is doing what it's supposed to, the new virtual sub created from one plus another would simply be the two fields added together. No interaction. The only way *interactions* occur is if things *aren't* in phase so they don't add together properly. And let's say that there are some phase issues introduced by EQ'ing those 2 subs individually. The responses of each sub are still smoother than w/o 1st individually EQ'ing then, and yet still, that's why you run Audyssey over top of their combined response to deal with that.

And if it was such a "bad idea", why are there solutions out there in the market?

And why would SVS have told me that it can work both ways?

Does Velodyne say in their manuals, for example, that if you have two Digital Drive subwoofers not co-located, *not* to use the EQ system because it's a "bad idea"?