Acoustat Monitor Brochure

Page 1

Full Range,
Direct Drive,
ElectrOstatic
Speaker System
with: Integral

selfscontained
Servo-Charge amplifier

Page 2

the acoustat

monitor

A UNIUUE FULFILLMENT UP MUSICAL

ACCURACY

Fror'i he time the first generation 0t iull~range
electrostatic loudspeakers was introduced. about
two decanoa ago. it was apparent that someday
this technology could yield a speaker of t'uly
suucrt: purlormarruu

That may has arrived with the presence of the
Acoustat M01 tor.

It you have neard the Monitor system. the'e is
'eally very little that we need to say about ts sound.
fluwuver. yuu would probably like to know sumo oi
the reasons that its pcrlorrrla'tce surpasses other
speaker types and earl er generation electrostatics.

I'rr). Arfr)l.slal Mmulcr' had its origin in the party
1960's with a bold essumntian that it should be
possible to build an electrostatic speaker of no

common-15L: ll woulc b2: lull range; direct drive:

and have high sound pressure levels. no crossovers.
and no audio transformers.

It has taken this mary years [0 turn INS dream
unto the Annustat Mon-tor-ellnwmg fu 1 Ilment
of tho cloctrostuti: promise.

This. promise his long existed because tne
push-pull. constant charge electrostatic element
slarlds aluriu irr ils ubililv lu urrilurrrrly and linearly
drwr: largo diaph'am swtaucs 0| allrlcsl negligible
mass. Only an incrudrbly liglt conductive coating
need be applied to very ll\in rug-I!!! (imphmms to
drstrrmne charges nuer the anrtane

It is this unique epi ity :nat allows a fun-range-
ermm-r: design with the entire surface radiating
nll Irreqrmrrrtrn-W.

All observers agree that much of the superior
perfc-rmarce of electrc-statlcs Is due to the highs'
unrlorrr lorce fuel-:1 spread over the entire dzaohram
hour when me sound is radiating l'he result is
very close to converting electricity directly to
sound, as I [here were: '10 drfrohr'arn at all! In the

Acoustat Monitor. he dlNEII charges on the
drapltrant arr: closer together than a single wave-
length of light and fh(~ d aplrar. 5 only 055
lhousaniths of an inch thick (about one sixth r)! thr}
thickness 0! [He shout ul paper].

This liable illustrates the ditierences between
electrostatics am: the two prevalent types 01
magnolia or dynamic speakers in terms of the two
most Important parameters for a high performance
speaker system.

Urrilvrrnily cl
AUDI '20 Force

Mass 0 Q'm Hamming;
Radiator Area
-
Dynami: High Poor
{Cum-1
Planar Lower Better
Megretir.
Electrostatic Lowest Best

Couruarud to it planar Irlztg'rcliu spuekur wilh its
wrree spaced at intervals and bender! to its maphram
an eieciroetatic'e "intimacy oi duve' is approximately
1t)ll.l):1l) tunes greater Arrrl cljrrlp'drud w M ii lyp cal
cane driver. severe million hrres greater Al the
laws of physics confirm that low mass and inti'r'rate
drive will yielct superior transient response. less
cvlcrairuw. and allow duliuilion emu delail to be
reproduced even er very Jaw stoning r'nvols

Page 4

WHY AN INTEGRAL AMPLIFIER?
-

In the beginning. there were. lube amplifiers.
tubes are basically high inpedance nevioes Magnetic
eoeairere are low impedance lcads. Hence. STEP-
DOWN transformers were almost always p-ceont.

A ur'g cattle power transistors. which could
directly drive magnetic speakers. Tne first generation
of electrostatic designers then inverted the past
and put in STEP-UP translcrmers :3 get back to the
"ugh impnamcc Cl lhOSO speakers.

Wl'y wasn't it obvious that vacuum. tubes were a
much more natural and eficient match 1m
ernrt'ostancsl Actually, this was obvious to :i few
dillerent individuals involved in such research.

lr the early 1960s. we burll our rrst amplifier
using the tour quadrant uutput hr dge. which was to
become the mainstay of all Acoustat amplifiers.

Its immediate a-omisc was so obviwu that we have
never dev ated f'om this basic outth drive
connection.

Fva pusaible JU'litlllLKIU is utiiricu by tailor us;
the amplifier to the electrcstatic panels anc not the
other way around:

I OWN VOW-90$ can UC generated by this design
which are appropriate to the speaker: thus
cmnnlmely eirmmatinn the need lor audio
step-up transormers and crossounrs

2, Low generator impedance. compared to the triad

impedance. can be assured at all lrequencies:

providing excellent panel control n'id damping.

Higher eli-ziency is attained. 'educi'ig am: irer

requirements.

-1 Any desirable analiurion required to the "attest
UVG'EI" 'esponsu can hr: oca'iouuctillv
impremerren.

I'J

HOW MANY WATTS?

Aii iiitarestir'g uriansweranle quesriot in tn 3
case. Unanswerable because a full-range electrostatic
is essentially a very large capacitor. arc oower
carrot be measured into a capacitive lead. in the
laboratory. using a. dJ'hrny resistive load. the Servo-
Charge emolltler memurcs in the 1C0 wall "angel.

Because of high coupling etilclericv ol our high
impedance am: first to the high impedance capacitive
load which the panels icpruscrt a hundred watts
becomes marvelously effective in Dioducrng
srratterrngw large amounts 01 sound pressure level
and is able to Ur) lliis slay-rig well williiii llic pluli:
dissipation parameters of the output tubes. In an
average listening room on music material head at
[yo-cal listening distancus. a pair at Monitors will
produce over l to an betore amniitier clipping or
over 1% {rural limrnuui; disturlivn oi the total
system occurs.

SERVO-CHARGE AMPLIFIER
-

These units are contained in the pedestals ol the
Mcniter speakers and are of hybrid aeslgn employing
solid state circuitry for all low level functions and
tli, about: described direct drive output from high-
voltage tube elements. coupling directly to the
speaker panels.

The output drive tubes are high vonagc ponloues
which are used in a conservatively rater: application.
Even on the rrosl cemanding muarcal r'tater til it
is extremely Gilt-Cult to roach the maximum
dissipet on level or the tunes. oven momentarily.
TJba l to in an average application ha; [generally
exceeded our: year and the replacement cost is
mocest as. matched sets a": not ruqui'cd.

The Servo-Charge amplitier incarnoralcs the
ol owing leatures:

"Instant-On" Relay Circuitry

This feature. which eliminates the need for any
ncwer umh Ilccls trnm the preamplifier source.
canalsts at a unique aunio triggered automatic
turn-0n circuit. The ampl tier is lett ccrrecten in
Is wall Outlet at all times. A very I'Jw power is
let: on the four vacuum tube tllamonis when tt-u
arrplifiar lfi not l'l use This f8Cilllfllfi3 he. instant
lurn»un when an audio signal is supplied provides a
dti'iiu-cl'nscr clccl and because switcn'ng power
Surges artL eliminated greatly cxlcnus tub: I to. Two
cast 01 this stand-by operation is es: than 14 nor
day per speaker. After the audio Signal has been
runruveu [or a period 0" approximately five minutes.
the automatic cicuitry w ll shut down tne amplifier
to the low power start: by mace

Low frequency equalization

Active equaliealioi is user: let me ollfl ratlcn 0
low lruuucncv icspurisu uburraliuns causal; in
interaction of the reflecting wall sir-face WI'..'l the
dipole raciaticn pattern.

During extensive 1.53 octave frequency analySis n
testing the response at the system. it was veriliud
that a vliuriu'iicnori cl quarter wavelength
reinforcement and half wave-length cancellation
:aikes place in "5 luwer liequeiiuiee. Tlus is lruu
I3: nil Lunch} radiators in the :irnxrmity or a reflecting]
wal. Witl' typica speaker to rear wall cistances the
net effect cf this roinlorcci'nont canccllatiur'
phenomenon is to pruduuu: il liurrip ' in tin: response
a: 90-' 00 he due lo quarter w an) lurch rcmtarcnmenl
il'ld ti ' dip" at tall-:JIKI H7 matinee. nt hall
wave-lergt'i cancellation. The so'utiut to this
problem which i left uncsrmctnd causus it "vuvrriy"
50". at JPPU' tiltiti Cfitldl'cernulll and own mizlminn
"<1 mp-cut". was to prov de specific active ecualizatic'i
t: currecl llie rcspurisc.