hey! so i'm a decent bassist, but i'm a serious novice when it comes to technical issues (i mean, i know how to hook up a head to a cab in such a way that neither of them is blown up, but the extent of my knowledge pretty much ends there). i want that to change, but for the moment i just need my rig to sound good again. here's what i use: Head: Ampeg SVT350AV (200W at 8ohms, 350W at 4ohms, solid state) Cab: Sunn 215 (300W at 8ohms, two 15" speakers, this is a Fender Sunn, not an original) Bass: Musicman S.U.B. (passive, four-string, DR Hi-Beam strings 50, 70, 90, 110, possibly about to make the switch to 65, 85, 105, 125 to accomodate for a band i'm joining that tunes to drop A) Pedals: Ernie Ball VPJR (volume pedal), Boss TU-2 (tuner), Boss CS-3 (compression/sustain) now, normally i love the way my equipment sounds. it's really mid-rangey and at the 6 o'clock position across the board (gain, volume, bass, treble, high, no eq, no limiter, no pad) i haven't met a lone guitarist yet who can compete with me for volume without putting at least one 4x12 on either side of me. recently, however, my low notes have started to fart a lot and the tone just doesn't quite sound right anymore. i feel like it's a cab issue because a) the farting, and b) the head still sounds awesome on other cabs i've tried, but both speakers still seem to be putting out sound. does anyone have any idea what the issue could be? is there some inexpensive repair work i could do to my cab, preferably on my own? i've been flirting around with the idea of picking up an acoustic cab or an ampeg svt810e for a while, should i just cut my losses and do it? help! also, while we're on the subject, would the following buttons on the back of my head have anything to do with this, and even if they don't, where should i be setting them? button a: UP=PRE, DOWN=POST, button b: UP=0db, DOWN=-20db. like i said, my technical knowledge is low, and although these buttons seem pretty intuitive, realistically i don't know where they should be set or if either of them is causing damage to my cab by being incorrectly set. thanks!