While doing a spring tune up on my system I noticed that my X-over covers were melted in the upper right corner. There is a lightbulb looking device in this corner which is obviously the culprit. Aplime SPX-137s.

Checked the owners manual but it doesn't mention this device at all.

Anyone know what it does? Maybe I have been overpowering my speakers and the buld is used to burn off extra power?