Is this achieved by increasing back pressure? I never knew that it was the resonance in the pipe that caused the drone, always thought it was the muffler?. I'm just the kind of guy who really likes to know what's going on before I spend cash.. (Read cheap! Lol)
Let's think about that for a moment.
Your muffler uses deflectors to bounce the exhaust gasses and their accompanying sound waves in one or more chambers. The pulses bounce and bobble around just enough to attenuate the unpleasant frequencies.
Resonators open up more paths for bouncing sound waves to follow. That attenuates more of the unpleasant frequencies.
Due to the shape of the glass packs the exhaust flows straight through with little interruption while the sound waves get trapped in the packing.
