Ok, issue confirmed. And I know the cause: "BAD!" was designed to improved IMD for bass tones, which is at least 95% of all the bass in music, and it works very well on that. But on random bass (bass noise, basically), it makes things slightly worse. (The improvements on bass tones is still much bigger than the detrimental effect on bass noise). I'll see what I can do to improve this, but even with this, you really should still keep it turned on for music.

BETA012 posted. There's a new slider, "Allow distortion on thunder bass (threshold)", probably not a great name for what it does... But that setting controls how strongly it tries to reduce IMD, which is bad for random (thunder) bass sounds, good for tones. 50 is bad. 30 and 35 are probably still ok, but I'm not really sure - see my previous post. 0 is old behavior ("BAD!" on in the previous few beta's).

maybe its just me but i prefer to use white noise to calibrate ST for music since its flat freqs all across.
can you imagine if a different type of white noise was used that emphasized upper freqs instead of lower freqs ?

I use it too, but also many other tones like sine sweep.

the problem is, music is completely random freqs at different amplitudes and waveform shapes.
i have different methods of testing and calibrating, such as injecting a sinewave based tone at the frequencies the MB is set to with white noise at the same dB level and observing the drops at certain frequencies and their bandwidth occupied by the drop.
the same type of testing applies to pre-emphasis, to hear no audible drop differences with pre-emphasis turned on/off but not applied on the output (pre-emph enabled but not to output).
so turning it on and off should produce virtually no difference, thats when pre-emph is calibrated properly, it produces the emphasis needed for AM/FM but without any push-downs on the lows from the mids/highs.

That's nice. However how about areas between bands?