M-AUDIO AV40s snapping when shut off

Unfortunately this is not uncommon in (active) speakers. The better ones will have timed switch-off or other protective measures. Although not the nicest sound, I have had a set of PA speakers that did that for the 6 years  I owned them and now someone else has been using them for 2. So, it won’t kill your speakers normally.

Perhaps someone can give you a clearer explanation of what exactly happens technically and why.

Greetinx.