<font color='#000000'>For 2 channel music, there is perfect solution for this, by REL subwoofers. They have adjustable LFE and High Pass inputs. So you can use the 'high pass' to blend the sub with the main speakers with NO frequency gap!
But for movies with DD/DTS where LFE is mandatory, there is no way you can defeat the fixed x-over without some compromise. Well again, sound quality is not as demanding for movies as for music.
so bottom line is: for movies use the fixed x-over, e.g. 90Hz. for music use adjustable x-over.
Abe</font>