ok heres the thing i bought a box thats tuned to 38hz its 2.2cu(ported for 1 12")(obcongz121)and i was wondering since i have an id max v3 d2 i know it wants lower freq..i basically got this badboy for free so i wanna use it..will polyfill and my subsonic filter help me out here and if so how much fill and what do i set the filter at??? thanx in advance for the help.
polyfill only gives the impression of a box being about 10% larger than it is. you want to set your infrasonic filter to about 16-20Hz to prevent loss of damping and driver damage.
A 10% increase in volume to say 2.42 ft^3 in your case, would only give you about a 36 Hz tuning point with your existing ports. You're gonna need to extend port length if you want something lower.