What compromises would you accept?

[Feanor]

This is not correct or subs in cars would not be able to produce anything below 120hz or so. We know that is not true. In a 12x15x10' room, I am able to get a clean 19hz with my H-PAS sub
.

I stand corrected, Sir T, although I've heard the assertion made many times.

...
Feanor, Orchestra crescendo's come from you main speakers, not your subs. Are you referring to bass drum and organ pedal parts? That is where your subwoofer comes in.

Yes, I suppose. But perhaps I was really thinking of my Magneplanar MMG days when I had the high- and low-pass filters set much high, i.e. at 80 Hz, in which case the sub certainly did make a big difference for crescendos and loud bass in general.