The
Electrostatic speaker is based on that
two equally polarized charges
repel each other while two oposite charges
attract each other.
Electrostatic speaker element:
..... electrode 1
: )---------===-=-=-=-=-=-=-=
: ): ____ # #
o--) ): | | # foil membrane #
Si :) )--|-Up+|-----------------# frame
o--) ): |____| # #
: ): # #
: )---------===-=-=-=-=-=-=-=
:...: electrode 2
T1
The
power supply Up is supplying the polarizing
voltage(about
5000V). 'Si' is the signal from the driving
amplifier,
it is transformed up by T1 to a voltage high enough to move
the membrane, also the
elecrodes will always have an
opposite charge. The
electrodes are made from a
perforated metal
plate or
a metal mesh. When electrode 1 gets a
positive electric field
it will push the membrane and the
negative field from electrode 2
will pull on the membrane(The charge change according to Si).
The moving membrane will make the air
vibrate, and thus make
sound.
A variation on the electrostatic speaker uses the
an
electret membrane. This speaker doesn't need
a polerizing voltage and is most used in
headphones.
Since the electrostatic speaker needs a polerizing
voltage, it uses more power than a
dynamic speaker.
The membrane is relatively large but very light
giving these speakers good
frequency response at booth
low and high frequency. The electret
version is cheaper
but has a somewhat lower
sound quality.