I am curious...I suspect that bad things would happen since it is DC current. Since I am not willing to try this out experimentally, does anyone know what would happen?
Would the cones just bulge out a little and stay there? Or would they bulge out A LOT to their extremes and really be hurting themselves? I don't think the voice coils would burn up because 9V is still only 10 watts of power or so to an 8 Ohm speaker.
When I refoamed the woofers on a pair of my speakers recently I noticed that woofers inherently have some spring-like resistance to being extended or pushed in, even without the foams on. What generates this resistance? Is it just the spider?
I used to think that the current/voltage signal running through my speakers was proportional to their cone position. Thus, if I looked at a computer WAV-file I would be seeing driver displacement vs time. But now I think the current/voltage signal, and the WAV-files, are actually graphing driver acceleration/force vs time. If that is so, even a tiny DC offset applied by either a 9V battery or a faulty recording source might continually order my speaker cone to "bulge out" until it bursts....
I worry about this because I have played poorly recorded things before that have had moderate DC offsets in the signal. I have never had any problems but I wonder how bad even a tiny DC offset is for a woofer.
