I happily discovered that I could solve my problem today with too much bass coming from my new subwoofer by changing a setting in JRiver. I am very pleased that I can now play music with just the right amount of bass without my house rattling.
My new sub, the PSB 450, was causing the loose-fitting dummy doorknobs on my laundry closet to rattle loudly when I played some music with deep bass. The same with the wobbly doorknob to my garage. And a picture on the wall.
I tried reducing the level (volume) on the back of the sub as low as I could while still getting sound and lowering the crossover to 52 hertz, but the loud rattlings were still there. I put the sub on a padded platform (Subdude) and then added two of the low Isoacoustics stands designed for subwoofers, but this did nothing to reduce the rattling in my house.
So, although I did not think it would work with my powered speakers, I adjusted JRiver's DSP room correction setting for the subwoofer by reducing it by eight decibels. The distracting rattling in my house disappeared instantly. I also adjusted the distance setting.
I am not using a receiver or preamp. I have my subwoofer connected directly to the dual RCA outs from the back of my powered Audioengine HD6 speakers. Because of this system arrangement, I did not think that changing the setting in JRiver would do anything, but it worked. And I verified it by undoing the setting in JRiver, which immediately brought back the loud rattlings with the loose doorknobs. I did the setting again in JRiver, and the rattlings stopped. I used Pink Floyd's "Speak to me" song from the Dark Side of the Moon studio album as the test track.
I was then able to increase the crossover on the back of my sub to 59 hz, which is good because now my sub and speakers blend well and there is plenty of bass from my sub without causing any annoying rattlings. I also use my speakers and sub with my TV, and action movies sound awesome now.
I was pleasantly surprised that the one settings change I tried in JRiver did not cut the bass or level to my two speakers, only the sub just as I wanted. I verified with a frequency and level app, and by ear, that everything is as I want it to be with the speakers and sub now. I am running the HD6 speakers full range without any EQ in JRiver.
I expect that there must be many other people like me who are using powered speakers and subwoofers without any bass management options from receivers, external crossover devices or preamps. And just like I was, they must be frustrated with their subwoofers causing their their homes to rattle. JRiver software can be the solution.
How did JRiver make it possible to reduce the output to a subwoofer that is connected directly to powered speakers without altering the powered speakers' output or frequencies in any way? To my untrained mind this seems like some kind of magic that defies what should be possible.