Maybe I'd buy into it if two things happened:
1. Someone could come up with a good reason for mixing full range bass cabs other than "15"s go lower and 10"s go higher," which is entirely based on looks.
2. I ever heard a mixed cab rig that sounded as good as a matched cab rig.
Yeah, I'm sure everyone who uses mixed cab rigs will say, "But you never heard MY mixed cab rig!" Don't care...I've heard plenty enough mixed cab rigs to know that I don't like them and I don't think they work nearly as well as matched cab rigs.
With one exception...if you use separate amps for each cab, you can dial complimentary tones into each separate rig, like a clean/dirty or what I call the poor man's biamp. But since I only bring one rig to every gig, I see no good reason to mix cabs when matching cabs that you like are a sure thing.
A good enough reason is that it's very possible that 2 different cabs will complement each other by having strengths where the other has weaknesses and vice versa. And a lot of 15s do go lower than a lot of 10s and vice versa (10s going higher than 15s). But go ahead, market your 5" sub and see how it does.
Just because YOU haven't heard a mixed setup that you liked, doesn't really mean all that much. I wouldn't exactly call your tastes typical or varied from what I've seen of them. Traditional Fender bass into Ampeg tube amp seems to be your primary goal, and the potential benefits of a mixed setup don't come into play very much in that situation.
Like in the Ashdown popularity thread, you conflate YOUR preference for the "truth" which is anything but universal.
And with the "poor man's biamping" (which is actually more expensive because you need 2 separate heads and 2 cabs), what you fail to take into consideration is, again, sometimes 2 cabs will just naturally complement each other, and you don't really need to do much if any tweaking.
Think of it this way, do people have basses with 2 different pickups that they play mixed together? It's the EXACT SAME THING. The Carvin bass I've been borrowing has the MM style bridge HB and a Jazz in the neck (plus a piezo bridge PU). I almost always play with the blend of the 2 mags dead center, because it just has the fattest, warmest tone that way, but without being too boomy or anything like that. Each pickup tends to accentuate a different part of the mids, that alone can be less than ideal, but together they sound killer.
