<s>
An	O
electrostatic	B-Device
loudspeaker	I-Device
(	O
ESL	O
)	O
is	O
a	O
loudspeaker	O
design	O
in	O
which	O
sound	O
is	O
generated	O
by	O
the	O
force	O
exerted	O
on	O
a	O
membrane	O
suspended	O
in	O
an	O
electrostatic	O
field	O
.	O
</s>
<s>
The	O
speakers	O
use	O
a	O
thin	O
flat	O
diaphragm	B-Device
usually	O
consisting	O
of	O
a	O
plastic	O
sheet	O
coated	O
with	O
a	O
conductive	O
material	O
such	O
as	O
graphite	B-Application
sandwiched	O
between	O
two	O
electrically	O
conductive	O
grids	O
,	O
with	O
a	O
small	O
air	O
gap	O
between	O
the	O
diaphragm	B-Device
and	O
grids	O
.	O
</s>
<s>
For	O
low	O
distortion	O
operation	O
,	O
the	O
diaphragm	B-Device
must	O
operate	O
with	O
a	O
constant	O
charge	O
on	O
its	O
surface	O
,	O
rather	O
than	O
with	O
a	O
constant	O
voltage	O
.	O
</s>
<s>
This	O
is	O
accomplished	O
by	O
either	O
or	O
both	O
of	O
two	O
techniques	O
:	O
the	O
diaphragm	B-Device
's	O
conductive	O
coating	O
is	O
chosen	O
and	O
applied	O
in	O
a	O
manner	O
to	O
give	O
it	O
a	O
very	O
high	O
surface	O
resistivity	O
,	O
and/or	O
a	O
large	O
value	O
resistor	O
is	O
placed	O
in	O
series	O
between	O
the	O
EHT	O
(	O
Extra	O
High	O
Tension	O
or	O
Voltage	O
)	O
power	O
supply	O
and	O
the	O
diaphragm	B-Device
(	O
resistor	O
not	O
shown	O
in	O
the	O
diagram	O
here	O
)	O
.	O
</s>
<s>
However	O
,	O
the	O
latter	O
technique	O
will	O
still	O
allow	O
distortion	O
as	O
the	O
charge	O
will	O
migrate	O
across	O
the	O
diaphragm	B-Device
to	O
the	O
point	O
closest	O
to	O
the	O
"	O
grid	O
"	O
or	O
electrode	O
thereby	O
increasing	O
the	O
force	O
moving	O
the	O
diaphragm	B-Device
;	O
this	O
will	O
occur	O
at	O
audio	O
frequency	O
so	O
the	O
diaphragm	B-Device
requires	O
a	O
high	O
resistance	O
(	O
megohms	O
)	O
to	O
slow	O
the	O
movement	O
of	O
charge	O
for	O
a	O
practical	O
speaker	O
.	O
</s>
<s>
The	O
diaphragm	B-Device
is	O
usually	O
made	O
from	O
a	O
polyester	O
film	O
(	O
thickness	O
2	O
–	O
20µm	O
)	O
with	O
exceptional	O
mechanical	O
properties	O
,	O
such	O
as	O
PET	O
film	O
.	O
</s>
<s>
By	O
means	O
of	O
the	O
conductive	O
coating	O
and	O
an	O
external	O
high	O
voltage	O
supply	O
the	O
diaphragm	B-Device
is	O
held	O
at	O
a	O
DC	O
potential	O
of	O
several	O
kilovolts	O
with	O
respect	O
to	O
the	O
grids	O
.	O
</s>
<s>
This	O
causes	O
a	O
force	O
to	O
be	O
exerted	O
on	O
the	O
charged	O
diaphragm	B-Device
,	O
and	O
its	O
resulting	O
movement	O
drives	O
the	O
air	O
on	O
either	O
side	O
of	O
it	O
.	O
</s>
<s>
In	O
virtually	O
all	O
electrostatic	B-Device
loudspeakers	I-Device
the	O
diaphragm	B-Device
is	O
driven	O
by	O
two	O
grids	O
,	O
one	O
on	O
either	O
side	O
,	O
because	O
the	O
force	O
exerted	O
on	O
the	O
diaphragm	B-Device
by	O
a	O
single	O
grid	O
will	O
be	O
unacceptably	O
non-linear	O
,	O
thus	O
causing	O
harmonic	O
distortion	O
.	O
</s>
<s>
In	O
one	O
recent	O
design	O
,	O
the	O
diaphragm	B-Device
is	O
driven	O
with	O
the	O
audio	O
signal	O
,	O
with	O
the	O
static	O
charge	O
located	O
on	O
the	O
grids	O
(	O
Transparent	O
Sound	O
Solutions	O
)	O
.	O
</s>
<s>
The	O
electrostatic	O
construction	O
is	O
in	O
effect	O
a	O
capacitor	O
,	O
and	O
current	O
is	O
only	O
needed	O
to	O
charge	O
the	O
capacitance	O
created	O
by	O
the	O
diaphragm	B-Device
and	O
the	O
stator	O
plates	O
(	O
previous	O
paragraphs	O
referred	O
to	O
as	O
grids	O
or	O
electrodes	O
)	O
.	O
</s>
<s>
Most	O
often	O
a	O
transformer	B-Algorithm
is	O
used	O
to	O
this	O
end	O
.	O
</s>
<s>
Construction	O
of	O
this	O
transformer	B-Algorithm
is	O
critical	O
as	O
it	O
must	O
provide	O
a	O
constant	O
(	O
often	O
high	O
)	O
transformation	O
ratio	O
over	O
the	O
entire	O
audible	O
frequency	O
range	O
(	O
i.e.	O
</s>
<s>
The	O
transformer	B-Algorithm
is	O
almost	O
always	O
specific	O
to	O
a	O
particular	O
electrostatic	B-Device
speaker	I-Device
.	O
</s>
<s>
To	O
date	O
,	O
Acoustat	O
built	O
the	O
only	O
commercial	O
"	O
transformer-less	O
"	O
electrostatic	B-Device
loudspeaker	I-Device
.	O
</s>
<s>
In	O
this	O
design	O
,	O
the	O
audio	O
signal	O
is	O
applied	O
directly	O
to	O
the	O
stators	O
from	O
a	O
built-in	O
high-voltage	O
valve	O
amplifier	O
(	O
as	O
valves	O
are	O
also	O
high	O
impedance	O
devices	O
)	O
,	O
without	O
use	O
of	O
a	O
step-up	O
transformer	B-Algorithm
.	O
</s>
<s>
Advantages	O
of	O
electrostatic	B-Device
loudspeakers	I-Device
include	O
:	O
</s>
<s>
exemplary	O
frequency	O
response	O
(	O
both	O
in	O
amplitude	B-Application
and	O
phase	O
)	O
because	O
the	O
principle	O
of	O
generating	O
force	O
and	O
pressure	O
is	O
almost	O
free	O
from	O
resonances	O
unlike	O
the	O
more	O
common	O
electrodynamic	O
driver	O
.	O
</s>
<s>
For	O
example	O
,	O
typical	O
dynamic	O
speaker	O
drivers	O
can	O
have	O
moving	O
masses	O
of	O
tens	O
or	O
hundreds	O
of	O
grams	O
whereas	O
an	O
electrostatic	O
membrane	O
only	O
weighs	O
a	O
few	O
milligrams	O
,	O
several	O
times	O
less	O
than	O
the	O
very	O
lightest	O
of	O
electrodynamic	O
tweeters	B-Device
.	O
</s>
<s>
Since	O
many	O
electrostatic	B-Device
speakers	I-Device
are	O
tall	O
and	O
thin	O
designs	O
without	O
an	O
enclosure	B-Device
,	O
they	O
act	O
as	O
a	O
vertical	O
dipole	O
line	O
source	O
.	O
</s>
<s>
Typical	O
disadvantages	O
include	O
sensitivity	O
to	O
ambient	O
humidity	O
levels	O
and	O
a	O
lack	O
of	O
bass	O
response	O
,	O
due	O
to	O
phase	O
cancellation	O
from	O
a	O
lack	O
of	O
enclosure	B-Device
,	O
but	O
these	O
are	O
not	O
shared	O
by	O
all	O
designs	O
.	O
</s>
<s>
There	O
is	O
also	O
the	O
difficult	O
physical	O
challenge	O
of	O
reproducing	O
low	O
frequencies	O
with	O
a	O
vibrating	O
taut	O
film	O
with	O
little	O
excursion	O
amplitude	B-Application
;	O
however	O
,	O
as	O
most	O
diaphragms	B-Device
have	O
a	O
very	O
large	O
surface	O
area	O
compared	O
to	O
cone	O
drivers	O
,	O
only	O
small	O
amplitude	B-Application
excursions	O
are	O
required	O
to	O
put	O
relatively	O
large	O
amounts	O
of	O
energy	O
out	O
.	O
</s>
<s>
Recent	O
,	O
technically	O
more	O
advanced	O
solutions	O
for	O
perceived	O
lack	O
of	O
bass	O
include	O
the	O
use	O
of	O
large	O
,	O
curved	O
panels	O
(	O
Sound-Lab	O
,	O
MartinLogan	O
CLS	O
)	O
,	O
electrostatic	O
subwoofer	B-Application
panels	O
(	O
Audiostatic	O
,	O
Quad	O
)	O
,	O
and	O
long-throw	O
electrostatic	O
elements	O
allowing	O
large	O
diaphragm	B-Device
excursions	O
(	O
Audiostatic	O
)	O
.	O
</s>
<s>
a	O
subwoofer	B-Application
,	O
to	O
handle	O
lower	O
frequencies	O
,	O
with	O
the	O
electrostatic	O
diaphragm	B-Device
handling	O
middle	O
and	O
high	O
frequencies	O
.	O
</s>
<s>
Many	O
feel	O
that	O
the	O
best	O
low	O
frequency	O
unit	O
for	O
hybrids	O
are	O
cone	O
drivers	O
mounted	O
on	O
open	O
baffles	O
as	O
dipoles	O
,	O
transmission	B-Architecture
line	I-Architecture
woofers	O
or	O
horns	B-Device
,	O
since	O
they	O
possess	O
roughly	O
the	O
same	O
qualities	O
(	O
at	O
least	O
in	O
the	O
bass	O
)	O
as	O
electrostatic	B-Device
speakers	I-Device
,	O
i.e.	O
</s>
<s>
In	O
1992	O
Critical	O
Mass	O
introduced	O
the	O
first	O
electrostatic	B-Device
speakers	I-Device
for	O
use	O
in	O
the	O
mobile	O
environment	O
(	O
car	O
audio	O
)	O
.	O
</s>
<s>
Because	O
of	O
their	O
tendency	O
to	O
attract	O
dust	O
,	O
insects	O
,	O
conductive	O
particles	O
,	O
and	O
moisture	O
,	O
electrostatic	B-Device
speaker	I-Device
diaphragms	B-Device
will	O
gradually	O
deteriorate	O
and	O
need	O
periodic	O
replacement	O
.	O
</s>
<s>
Cost-effective	O
repair	O
and	O
restoration	O
service	O
is	O
available	O
for	O
virtually	O
every	O
current	O
and	O
discontinued	O
electrostatic	B-Device
loudspeaker	I-Device
model	O
.	O
</s>
<s>
Electrostatic	B-Device
speakers	I-Device
enjoy	O
some	O
popularity	O
among	O
do-it-yourself	O
(	O
DIY	O
)	O
loudspeaker	O
builders	O
.	O
</s>
<s>
Such	O
supplies	O
include	O
resistors	O
and	O
capacitors	O
for	O
RC	B-Algorithm
circuit	I-Algorithm
frequency	O
equalization	O
,	O
if	O
necessary	O
;	O
step-up	O
transformers	B-Algorithm
;	O
perforated	O
metal	O
sheets	O
or	O
grids	O
and	O
insulating	O
plastics	O
for	O
the	O
stators	O
;	O
polymer	O
film	O
and	O
conductive	O
paint	O
(	O
e.g.	O
</s>
<s>
a	O
liquid	O
graphite	B-Application
suspension	O
)	O
for	O
the	O
membrane	O
;	O
simple	O
tensioning	O
equipment	O
for	O
proper	O
membrane	O
tuning	O
;	O
and	O
a	O
frame	O
,	O
usually	O
of	O
wood	O
,	O
to	O
hold	O
everything	O
together	O
.	O
</s>
<s>
A	O
widely	O
read	O
resource	O
by	O
ESL	O
enthusiasts	O
is	O
The	O
Electrostatic	B-Device
Loudspeaker	I-Device
Design	O
Cookbook	O
(	O
)	O
by	O
notable	O
ESL	O
specialist	O
Roger	O
Sanders	O
.	O
</s>
<s>
Arthur	O
Janszen	O
was	O
granted	O
in	O
1953	O
for	O
an	O
electrostatic	B-Device
loudspeaker	I-Device
.	O
</s>
<s>
After	O
the	O
war	O
,	O
he	O
developed	O
manufacturing	O
technique	O
for	O
electrostatic	B-Device
speakers	I-Device
,	O
to	O
be	O
used	O
with	O
conventional	O
cone	O
woofers	O
,	O
known	O
as	O
electrostatic	O
hybrids	O
.	O
</s>
<s>
In	O
the	O
early	O
1970s	O
,	O
Electronic	O
Industries	O
of	O
Minneapolis	O
took	O
over	O
the	O
license	O
and	O
rights	O
to	O
make	O
JansZen	O
electrostatic	B-Device
speakers	I-Device
.	O
</s>
<s>
In	O
1974	O
,	O
Electronic	O
Industries	O
introduced	O
a	O
new	O
wire	O
wrap	O
around	O
ESL	O
tweeter	B-Device
that	O
great	O
lowered	O
the	O
cost	O
to	O
manufacture	O
.	O
</s>
<s>
Several	O
large	O
arrays	O
of	O
these	O
tweeters	B-Device
were	O
actually	O
used	O
as	O
public	O
address	O
systems	O
in	O
concerts	O
in	O
Minneapolis	O
.	O
</s>
<s>
Plans	O
were	O
made	O
to	O
offer	O
electrostatic	B-Device
speakers	I-Device
in	O
cars	O
,	O
but	O
never	O
came	O
into	O
production	O
.	O
</s>
<s>
Dave	O
Wilson	O
of	O
Wilson	O
audio	O
,	O
used	O
JansZen	O
tweeters	B-Device
in	O
his	O
famous	O
,	O
WAMM	O
,	O
Wilson	O
Audio	O
MOdulator	O
Monitor	O
.	O
</s>
<s>
The	O
developers	O
of	O
the	O
Tri-Ergon	O
sound-on-film	O
sound	O
film	O
system	O
had	O
developed	O
a	O
primitive	O
design	O
of	O
electrostatic	B-Device
loudspeaker	I-Device
as	O
early	O
as	O
1919	O
.	O
</s>
<s>
The	O
first	O
fully	O
successful	O
full-range	O
electrostatic	B-Device
speaker	I-Device
,	O
and	O
also	O
among	O
the	O
most	O
influential	O
,	O
was	O
produced	O
in	O
1957	O
:	O
the	O
Quad	O
Electrostatic	B-Device
Loudspeaker	I-Device
(	O
Quad	O
ESL	O
,	O
later	O
known	O
as	O
the	O
ESL-57	O
)	O
from	O
Quad	O
Electroacoustics	O
,	O
of	O
Huntingdon	O
,	O
England	O
.	O
</s>
<s>
Although	O
the	O
ESL-63	O
was	O
discontinued	O
in	O
1999	O
,	O
Quad	O
maintains	O
production	O
of	O
electrostatic	B-Device
speakers	I-Device
.	O
</s>
<s>
Popular	O
manufacturers	O
of	O
electrostatic	B-Device
speakers	I-Device
include	O
MartinLogan	O
,	O
KEF	O
,	O
Quad	O
,	O
SoundLab	O
.	O
</s>
<s>
Other	O
manufacturers	O
currently	O
producing	O
electrostatic	B-Device
loudspeakers	I-Device
include	O
Solosound	O
,	O
King	O
's	O
Audio	O
,	O
Panphonics	O
,	O
Cadence	O
Audio	O
,	O
T+A	O
and	O
Silberstatic	O
,	O
Blanko.nu	O
.	O
</s>
<s>
Audiostatic	O
claim	O
to	O
make	O
the	O
only	O
full	O
range	O
electrostatic	B-Device
loudspeaker	I-Device
.	O
</s>
<s>
MartinLogan	O
,	O
,	O
Metrum	O
Acoustics	O
,	O
Sanders	O
Sound	O
Systems	O
,	O
and	O
Sound-Lab	O
,	O
and	O
others	O
build	O
hybrid	O
designs	O
with	O
conventional	O
woofers	O
or	O
subwoofers	B-Application
.	O
</s>
