So what is "dope?"
Doping is the shiny goop you see on the surround of a speaker. Besides extending the life of the surround, it also acts as a shock absorber to help keep the cone under control at higher volumes. The downside is that it also dampens cone vibrations and therefore reduces the potential character and texture of the speaker. If you are going to bend/sustain notes in the area above the 10th fret on the high E string and at high volumes with heavy distortion, then you need the doping to help prevent ghost notes and cone cry that could result from the extreme cone vibrations. Many players prefer the raw, undamped tone of the undoped speaker and they learn to modulate their finger pressure when noting in the area that causes cone cry.
Pre-Rola Treatment For this doping, the cone is artificially aged and chemically treated. Vibration dampner compound is also applied to the cone body and surround.
Put simply: the higher gain you use, the more dope you should have on your speaker.