HI so i have a nex8100 HU and I'm using the alpine mrp m2000 to power my 12' Alpine type r's.

If I'm using the crossover on the HU would i then switch off the subsonic filter on the mrp m2000? 

Would i leave the bass eq frequency on the amp at the highest 80 hz since the crossover on the HU will adjust it if need lower?

Do i leave the LP filter at the highest frequency on the amp 200hz so that it can be adjusted from the HU crossover?

mrp20

subsonic is like a bass boost.

Think of the subsonic like a high pass filter for your sub.  It is the point where your bass starts to roll off on the lower frequencies.  You would set it based on your box - are you running sealed or ported?

With a sealed box I would recommend setting that amp to the 30hz filter.

With a ported box you want to take your tuned freq x .75.  This ( or as close as possible ) is where you'd set it for a ported box.

I'm guessing here that BASS EQ is really BASS BOOST.  The EQ setting is the center freq.  The EQ LEVEL is how many DB increase centered on that freq.  In general this is where alot of distortion is introduced into a system.  I'd suggest leaving the center freq around 50hz and the level only +3db unless you really know what you're doing setting your gains ( IE scope or some other proven method - not just by ear or voltage reading ).

Lastly, I placed the LPF at just above the freq you intend to set the filter at on your HU.  This way if for some reason the HU settings were to get changed ( ie by a friend or w/e ) then you don't have to worry about them being TOO far off from your settings.  This really is more important with HPFs but it's still warranted with subs as well.

Hope this helps!