Acoustat X Brochure

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Acoustat X Brochure

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Acoustat presents outstanding
“State of the art” sound
electrostatically at a conventional
cone system price

WHY AN ELECTROSTATIC?

The electrostatic approach to
sound reproduction has been called
"the sound of the hrture." and at
the risk of beiaboring the obvious
perhns a brief review at the three
dillerent loudspeaker design can
ccptt and their atutndant faults
and virtues is in order.

The dynamic cone (or dome)
speaker has been around for a long
time. Here the cone or vibrating
structure (usually stiflened paper of
relatively high maul is energized at
its apex by attachment to a voice
coil placed in the m ol a maglel.
The cone/voicecoli structure has
high mass and thus significant
inertia Even il sufficient voicecoil
drive and damping can keep it mov‘
ing in an accurate replica of the
electrical simal. there is a strong
probability that the movement at
the many portions ol the cone will
duller signifiamly from the dual
due to the distance between the
numet/voicecoil energizing source
and the cone's surface radiating
area. A bit like trying to play the
piano with chopsticks! Drawbacks:
nor-linearity. cone breakup and
unacceptable levels ol harmonic
and intermodulation distortion.

The dynamic duct (or planari
speaker is a much more recent con’
cept. Here a plmic diephragn
physically incorporating numerous
wires is placed in a large screen type
enclosure containing numerous
small magnets. In a sense the voice
coil wire of the conventional cone
spedter has been ”read out over a
large vibrating surface and the map
net structure has been similarly
dispersed. This design is caminly a
distinct improvement over the con
ventional cone if only became the
diaphrawn is energized close to

the point where it radiates. Faults?
Perhm a law. The mass of the
vibrating dimhr‘agrt is still rela
tively him because of the abundant
wires and other structural consider-
ations. In general, the higher the
mas ol the vibrating surface the
poorer the transient md high lre~
ouency response. Also. because of
diaphragm excursion limitations,
bass rename frequently requires
auwnentation with cone woofers.

The electrostatic desim concept
has a few similarities with the
planar type. but it is lundarnentally
different. And it has been around a
great deal longer. Here a very lid“
plastic diaphwn is placed between
a conductive grid structure (sorry.
no rrtagtets) placed front and had:
in relation to the diaphragm The
diaphragn is usually supplied a con-
stant charge and is driven nusfvpuli
by other charges on the front and
back grids going alternahly positive
and negative in response to the
audio eigtal. But. in order to ac-
complish this. voltage requirements
are much wearer. Where; a dynat
mic speaker system requires tens of
volts the electrostatic requires thou-
sands.

Potential advert are numen
00!. The low mass 0 the diaphrawn
provides an opportunity for un~
equaled transimt and hidl fre
quency response with excellent
linearity. And there Is an advantage
completely unique to electrostatics.
As far as we know. the electrostatic
is the only transducer where the
sound always ananates from the
exact point where the uterp'zing
force is merited. even down to
the molecular level. (Note that even
planar dynamic speakers have de-
linite stretches of undriven die
phrep'n area between the conduc-
tive wires.) Additionally. there it an

opportunity for phase coherence
with no parasitic mechanical ele
ments between the drive ltd
radiating element and for an ex-
cellent acoustic impedance match
to air. The electrostatic concept it
probably the closest thing yet
devised to being able to turn an
electrical signal directly into sound!

THE PROBLEMS

Practical electrostatic speakers
made their ddsut in the early
1950's with Arthur Jansten's snail
tweeter array. This bold innovation
was enormously successful and is
still available irt much thetarrle lor-
mat today.

But. the fur/m electrostatic
speaker that could hrllill all the
obvious design goals was another
story. There have more than a law
attempts at lull rang electrostatic
design driven by conventional em-
pllfr‘ers over the years. and they
have all had three problems in
common:

”inadequate sound output levels
even when driven by wading
iy hifir powered amplifiers.

2) generally inedeqrete bass respono
ta

3) distortion and non-linearity car
ted by therteceefitytousehloh
voltage stepup transformers.

In addition. by trying to sauce"

out more level with more and more

power in this inefficient m-

ment, panels are frequently over-

driven and hunted out.

THE SOLUTION: AOOUSTAT’S
SSRVO-CHARGE AWLIFIER

The Acoustn research teltt
came to the conclusion that the
crux ol the problem lay not so
much with the electrostatic wait-
are themselves ltd their one“