With such dissimilar subs, this may be working out well for you, particularly with your DSP. But, as cel4145 pointed out, you are using the subs to cover completely different frequency ranges. You are only getting the room taming benefits that are afforded by multiple subs in that range of frequencies where the output of the two subs overlaps. Any other frequencies are still being reproduced by one or the other subwoofer. Likewise, nor are you getting any of the output and headroom benefits that running multiple subs affords. Your setup may sound great to you and that is, of course, all that matters. But I would posit that you are underutilizing your RW-12d. It is basically only covering a single octave, from 20Hz to 40Hz. True, that is an important octave for bottom feeders, but the little HK is covering an octave (40Hz - 80Hz) that has much more overall information encoded in it than that lower octave does. I don't understand why you would think that it could do a better job there than the RW-12d could. I guess you could argue that since the workload is being split across both subs, they each will perform better over the range of frequencies that they are asked to perform. Still, I am skeptical that the benefit that the RW-12d gains by not having to reproduce frequencies above 40Hz warrants not using it to reproduce the octave above that and using the much less capable HK, instead.
You've got that RW-12d's nuts in a vice just so you can use the HK. I understand sentimental attachment, but c'mon, man!
Now, most people utilizing dissimilar subs do not have your situation where a stratification of duties is so easy to configure. More often than not, the subwoofers' outputs end up overlapping considerably more. And this is where the issues can arise with dissimilar subs. True, you may tame some room issues in the range of frequencies over which the subwoofers' outputs overlap, and that is, indeed. what the Geddes approach relies upon. But, even with EQ, you will almost always underutilize the more capable subwoofer, both in terms of output and particularly in terms of depth. Properly calibrated, the more capable sub will not be performing at the same output level it would be were it being used alone and its depth advantage is not only not being utilized, it is being stifled.
It is also important to realize that depth is not at all a goal with Geddes's methods. He does not really approach this stuff from a HT point of view; certainly not with the mindset of many of the people who post in this subwoofer subforum. If you can do the Geddes setup properly, with overlapping dissimilar subs, that's great, but it is not so easy and you will almost always do it at the expense of the depth of your most capable subwoofer. And very rarely does someone truly and properly implement Geddes's methods with their setup. The output of your subs in your setup, for example, doesn't overlap significantly enough to even implement his approach. He also is a strong proponent of using very capable front speakers and a LARGE speaker setting, something that does not exactly fall in line with the usual dogma around here.
Edited by sivadselim - 4/10/13 at 1:03pm