So, I have a 2.1 system that sounds pretty ok, but yesterday I was running a test (https://m.youtube.com/watch?v=AC-ExFnAgXo&pp=ygUMc3BlYWtlciB0ZXN0) that revealed that I have some wild volume differences between certain frequencies all over the spectrum. I then listened to the same thing over my headphones (Beyerdynamic DT770 Pro) and there all frequencies had pretty much the same volume.

Is this normal or should I aim for equal volume over all frequencies for my stereo? If so, what’s the best way of attack? Room treatment?