Intelligence level is hellier than treble peaking on speakers in the ghetto

from Eminem (Ft. Royce Da 5'9") – Bad Meets Evil Lyrics on Rap Genius

He is referring to himself throughout this entire verse, including this line.
Hellified means extreme or a large amount of something, hellier is a derivative of this.
Also, since he uses the term “peaking” after treble, he means the treble is high.
He is implying that he has a high level of intelligence.

Sometimes people do turn their treble down and bass up but they don’t put tweeters in their cars for nothing.

To help improve the meaning of these lyrics, visit "Bad Meets Evil" by Eminem (Ft. Royce Da 5'9") Lyrics and leave a comment on the lyrics box