Sorry to jump in Wayne, but there are technical details for the "Pros" on the Shunt Lightbulb Circuit down in here. T. Moore;
The compression is good because the sound doesn't fail (it turns dim in a light-and-less prononced scale, at the same time protecting the compression speaker) as oposed to PTC, fuse or rele. Like in a live event where "they" can't turn off the sound not even for a few seconds even if for speaker protection.
Ps. at first I tought you where really seeing some "Madonna lights" only after Wayne' I got they where xover lightbulbs.