01-09-15: TrcnsThis is the point where the sub adds to what your speakers can do. IMO this is also the perfect spot to make sure your phase/timing is correct (neither leading or lagging the main speakers).
I dropped the Crossover from 35 to 25 and then even to 20 hz and started to increase it little by little. At 20 to 25 Hz I had to increase the volume from 6 to 9 but after 25 I had to go back to 6 otherwise the bass was too high.
At 40 Hz sound stage does improve as compared to at 25Hz. There are some songs which have more bass than the others but overall the result is pretty good.Yes the sub is adding to the soundstage because it is crossing into the frequency range your main speakers already do. You have found some tracks with bass that seems too much because you are adding is there.
That said as my speakers are breaking in the bass is getting a lot deeper. My speakers are rated 40hz to 50khz. I initially I had my sub set to 36hz. Sounded pretty good until the lows opened and tightened up. With certain songs the bass is too heavy. So I have since went back on the crossover setting to 28hz just so I am only adding what the speakers can't do. Whats pretty amazing is I only have about a dozen songs where I can hear when the sub kicks in.
Just my opinion and my preference. Glad you have it setup they way you like it because in the end that's all that matters. So if you ever decide you too much bass for certain songs you can always re-adjust back.