Being that dc is by it`s very nature only going in one direction.
Does everything go quiet and vehicle fill with the smell of cooking electronics (varnish burning)odor ? The obvious thing here is without alternating current is the speakers will either move all the way out or all the way in. Hence, if it`s not going in and out/forward and backward, at most you will hear speaker come to rest.
A . . . "P F F F T"
p.s. I witnessed a suv leave ABC Warehouse and by the time they got to stoplight, they jumped out ran to rear of vehicle and opened . . . Smoke just poured out.