[DML] Re: Speaker Grounds vs Electrical Grounds

["Elvis Nocita" <elvisnocita@xxxxxx>]

Bill - a speaker will make a sound when connected to DC - the sound of
burning paper and plastic !

When you connect one output of the stereo to ground you will get a
similar sound...but this time of a burning amplifier !

Old radios only had cheap simple low power outputs (I am not going
to explain this in detail, it takes too much time to begin with Adam
and Eva) therefore they could use ground as the return line.
Just let me say - the positive line used 2 transistors for push/pull.
(And they also had a capacitor in the positive output line to prevent
the speaker from DC voltage.)

Newer Radios with almost 50W (yeah we really do believe in those 50W...)
have four transistors - feed and return line of the speaker each need
2 transistors for push pull - their outputs are inverted. I think that's
enough explained to understand that if you connect any output to ground
or +12V the amplifier will get fried within seconds.
Well, I think this is stuff of first or second year electronics engineering.

I wonder how a experienced electronics engineer wouldn't know this ?

The polarity of the outputs doesn't mean that there's only + or -, it's
there
to show you how to connect the speakers correctly. If you don't, then there
may
almost be no bass....

Elvis & 6548


Stereo speakers are actually low voltage AC devices, not DC. They
won't make a sound without alternating current on both sides from the
amplifier alone. Connecting their negative side to the car's battery
does absolutely nothing (nor for that matter does connecting their
positive side).

Check out this ShockWave graphic:
http://static.howstuffworks.com/flash/speaker-working.swf

What's happening is the polarity of the coil keeps changing, causing
it to attract to the magnet then repel away from it. That moves air,
creating sound waves.

Bill Robertson
#5939




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