electric shock when you touch speaker

mozmax

Member
2013-09-22 1:37 am
hi everyone, i recently acquired a old set of final sound 900i electrostatic speakers that have some problems, the main one is when you touch the front of the speakers you get a electric shock, they are powered by a 12v dc power pack and use 300mh, the weird thing is they both do the same thing, anyway does anyone have any ideas what the problem could be, would it be worth fixing them etc, thanks in advance guys....
 
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mattstat

Member
2009-10-19 7:47 pm
A little more information might be necessary to provide guidance.

Is this a minor shock, similar to low-level static you'd get from sliding around on carpet?

Is this with no music playing (i.e., it happens any time the 12 V DC is supplied)?

When you say "front" are you talking about the frame or the stator itself (perforated metal)?

If on perforated metal, is it all over the perforated metal or just in one spot?

Final has a paper on their "inverter technology". In that, they claim to be putting the audio signal on the diaphragm and the bias voltage on the front and back stators (+3500 V on one, -3500 V on the other). If the shock is minor, you may just be experiencing this aspect of their design. I don't have direct experience with their units, so this is speculation on my part.

Obviously, err on the side of caution if you are uncertain, but a properly functioning bias supply is normally of limited danger since it is very current limited. It can be annoying to be shocked by them though.

There is a leakage current limit specified by CE/IEC. To measure it, you need a little circuit that models the impedance of the human body.
 

mozmax

Member
2013-09-22 1:37 am
ive not had the courage to touch them yet, its the front stator where you get the shock from, the person i bought them of said its when you touch the fronts of the speakers and a good party trick lol, its a shame because they look really nice and do work too apart from they cut out randomly, you can hear the relay clicking, ide love to get them working proper again