Re: FM8 setup advice for use in 'Music' and 'Home Theater'
If you are using Audyssey, then you want to keep the crossover knob set at max, or 200 Hz in this case. It just makes sure that there is only one filter being applied with one slope instead of the one in your receiver and the ones in the subs fighting each other. Only use Audyssey or the knob to control, never both.
If you set either of them to 120, your sub will play up to 120 and your speakers will either play everything or will start at 120 and play up from there if they are set to "small" in your receiver. If they are set to "Large" they will play everything. I'd probably set them to small first and try large and see which one you prefer. I run my Sierra Towers as Large.
You don't need to change the extension or the slope for movies. You should be able to find a setting that works for both music and movies. If anything you can change the extension but there shouldn't be a need to change the slope.
PS4/Nvidia Shield --> Emotiva XMC-1 --> Emotiva XPA-5 --> Ascend Acoustics Sierra Towers and Horizon Center w/ RAAL tweeters (L/C/R), HTM-200 SE (Surrounds), 2x Rythmik F12 subwoofers