I booted my LiveCD and saw that the dpkg output there is just the same as for my regular system (on solid-state drive). I'm glad to know that I have jack1 and not jack2, though I'm still not really sure I understand completely, since the jack process I get is named jackdbus. For now, I stopped using the jack_control shell script and am just using qjackctl to bring jack up, and still, the process name is jackdbus. I thought jackdbus was jack2...
Also, after considering your input on my password situation, I finally realized that in Linux there's not a separate admin user name, and I started the root terminal and was able to remember/specify the correct root password. So that problem is solved.
The most interesting thing is my mistaken idea that the low-pass filter was attenuating a lot. I think I have been misunderstanding the frequency content of those low notes on a piano. I was thinking for example the low A is a more or less pure 27.5hz, but now I think I see, duh, there are lots of resonances that you hear, that are higher frequencies. My 60hz low pass filter gets rid of those and sends them to the mid/high speaker, so all that is left for the big woofer is the lowest frequency content. That is a kind of strange sound; divorced from its resonances, the piano key sounds weird, and probably due to my woofers needing equalization below 50hz or so, it's not as loud. Have I got this right??
If so, I'm thinking, everything is actually working correctly!! Next challenge: to figure out how to add some equalization via ecasound (or other way you guys might suggest) to get good response out of my woofers, all the way down into the 20-30hz range. That should finally make my piano sound more like a real grand piano, I think.
Thanks!!
John