I'm playing my Ampeg V-4B through a friends Ampeg SVT410HEN cab and dialed in this insanely overdriven glass shattering distortion. I was looking at the speakers while playing, and the speaker surroundings were turning orange with heat when I would really let loose. I assume this is the voice coils heating up, but should the speaker surroundings be turning orange? At first I though I was imagining things, but i've repeated the experiment, and the speaker surroundings are truely turning orange. Is this damaging the cab? Should I stop playing with these settings?