Are big subwoofers viable for 2 channel music?

@jon_5912  That is sort of like a rel six pack except you have different sizes and types of subs. I bet it would work well if it was properly setup.

For a large space like the one initially lined out by the OP (or be that even a smaller ditto), serving home theater duties to boot, I'd wager to keep the thing of it all the most "musical" - i.e.: with low distortion, effortless and smoothly distributed bass - is to go with two or more big, higher eff. subs. Many seem to be hellbent on the "multiple smaller subs vs. fewer or only a single big one" division. For Pete's sake, what's with the self-imposed limitations? Have your cake and eat it too with a bunch of large subs like the ones from the reasonably priced and quality items PSA, and make them no less equipped than with 18" diameter woofers. These are high eff. pro drivers with a moving mass to cone diameter and motor force ratio that in no way makes for "slow" bass, contrary to some high moving mass, very low eff. (<85dB's) woofers meant for ultra small sub cabs with a bass reproduction that never really "gels" with the mains. Yes, very generally large, high eff. subs to my ears sound somewhat more musically "right" and well-integrated, because you don't sense they're using any real effort reproducing bass with their large diameter cones that barely move. Sonically in some regards REL subs are one of the more notable exceptions from the small cab/low eff. "camp" being not least they don't try and squeeze out infrasonics from their designs, that would have otherwise necessitate a higher moving mass in the driver and thus resulted in even lower sensitivity and likely bass lag. But, again: big (higher eff.) subs are not only viable for music reproduction; they would seem wholly essential if you ask me, while providing for a very worthwhile impact watching movies as well. What people won't do to avoid size in subs, and the hassle this has a tendency to bring with it (sometimes unknowingly, because they haven't heard the difference). It may even come down to large size being judged as "not looking cultivated enough," or "too brute for hi-fi." 🙄 When you got the space, use it. Bass properly sized/scaled is all the better for it.  

@phusis I definitely am wrestling with this now. What if I got some 12 inch klipsch subs... maybe 4 or 6 of them and put them all over my room even at different heights. For that money I can buy 2x full marty gsg cabs with 21 inch mach 5 drivers (used pair has come up on canuck) and dual crown amps. Which would be better? I think you make a lot of good arguments.

Or if you look at something like rel for the price of even 1.5x of S812s I can get this dual 21 inch setup.

Has anyone heard of or had experience with Snap AV?  They are a custom install only brand that I had never heard of.  I ran across some used subs on ebay for dirt cheap and they appear to be well-designed.  They're sealed, and have phase knobs instead of the 0/180 switch.  I consider that to be a sign of serious design in a sub.

I wonder if the low name recognition results in them having terrible resale value even though they're pretty good.  I just bought one for a whopping $112.  Not much of a risk.

@smodtactical , For that space you are going to need at least two 12" subs with excursions over a cm or you will be pissing into a forest fire. 

The idea that music requires different subwoofers than theater I find very odd. Any sub system that can reproduce down to 18 Hz accurately is perfectly acceptable for both. 

What is speed when it comes to driver performance? What does "faster" mean? The faster a driver can move the higher the frequency it can reproduce. If a driver can move fast enough to reproduce 500 Hz then 100 Hz should not be a problem at all. What everybody is referring to when they say "fast" or "faster" is transient response. The diameter of a driver is only one factor that can influence transient response. There is also the stiffness of the suspension, the weight of the moving system, and the power of the drive motor. The point is, when it comes to reproduction under 100 Hz an q18" driver is no slower than an 8" driver. Anyone who thinks so is just falling prey to "lay intuition," 

There are many excellent subwoofer drivers available today. The driver is usually not the source of problems. It is that enclosure that separates the men from the boys.