Subsonic Filter

Hello gentleman!

Question about a subsonic filter. I get how it works, that it basically blocks out low frequencies.

I have a power acoustic LT720 running Phoenix gold tantrun 5.25" doors and boston acoustics FX series 6x9's in the rear.

the rear speakers are set to full range, but what do I set the subsonic filter to? I've played wiht it and it does not seem to make any difference at all. is it disabled when the crossover isnt set to a low pass filter

and that brings me to my next question whats the difference between a subsonic filter and a lowpass filter.

Amp Specs say:

For the front speakers I have it set to high pass filter at 500Hz, then for the rears I have it set to Full frequencies, but the low pass and subsonic filter do not seem to make any difference.

I take it the subsonic is only acticated in low pass mode? or am I just not hearing it right lol

Boston Acoustics FX9 3 way

Frequency Response (3dB in car)

so does that mean I would want to set the crossover to full and the subsonic filter to the minimum setting of 60? or is that setting only active in LPF mode?

Phoenix Gold Tantrum 5.25"

So I should try and set the high pass filter right around the 80 mark??

sorry for all the Q's, but one more

what should bass boost be set at when using 6x9's? I have it set at about 1/2 right now so that I am getting bass to the rears and not the fronts. I think the crossover in my amp just sucks lol because even with a high pass filter set to 500, if I play with the factory headunit and turn the bass up I am getting a ton of bass out the front speakers.

you cannot turn the subsonic range off, you can only do the adjustments that I listed, that's what is puzzling me :(

i'll set the 6x9 to high pass, wont that take all the bass away from them though?