Trying to use Acid and FL

kinda stuck. okay, so im using acid 5.0 and fruity loops for this. im taking a beatbox acapella of MF Doom – Hoe Cakes that i found on the site. anyways…
im trying to extract the beatbox sound just to have the vocals, so i tried this:
i loaded the track in fruity loops and exported it as an mp3, then i reverse the polarity in fruity loops and export the same track again. now i have the same tracks, but one with a reverse polarity. i then load both tracks into acid, i chop the reverse poalrity beatbox loop from the beginning of the track to layer it under the regular vocal/beatbox… now all that happens is that the bass/low end is gone, but the beatbox sound is still there. so what am i doing wrong?