Acoustat SPECTRA 1100 User manual

Table of Contents
Introduction
Break - In Period .............................................................................. Page 1
UsingThisManual Page 1
.........................................................................
OWNER’S MANUAL
SPECTRA
1100
ELECTROSTATIC
Assembly & Installation
GettingStarted/assembly .............................................................. Page 2
Disassembly .................................................................................. Page 6
Audio Input .................................................................................... Page 7
LOUDSPEAKER SYSTEM
Power imput ................................................................................... Page 11
High FrequencyContour Switch .................................................... Page 11
Acoustat
A Division of Rockford Corporation
613 South Rockford Drive
TempeArizona
65281 USA
602 . 967 . 3565
spiked Feet ................................................................................... Page 11
The Listening Environment
Room Size ..................................................................................... Page 12
Wall BehindThe Speakers ............................................................ Page 12
The Orientation of The Speaker SystemWithinThe Room .......... Page 12
Position InThe Room
Page 12
DistanceFrom Rear Wall .............................................................. Page 13
DistanceFrom Side Walls ............................................................. Page 13
Toe - In and DistanceBetweenSpeakers ....................................... Page 13
Area BetweenThe Speakers ......................................................... Page 13
Specifications ................................................................................ Page 14
Impedance Curves ........................................................................ Page 15
Amplifier Recommendations ......................................................... Page 17
Theory and Practice of SpectraOperation .................................... Page 18
Warranty Statement ....................................................................... Page 19
InCaseof Difficulty
Page 20
Electrical Schematic ...................................................................... Page 21
....................................................................
Additional Information

Congratulationson your purchase of AcoustatSpectra
Technology
I
INTRODUCTION
I Break - in Period
Your new Acoustat budspeaker requires a break - inperiod
before
full performance may be realized. Eyenthough the
speaker
will beginto play within a few moments of being
energized,and willsoundquitegood, abrand
new speaker is
characterizedby a lower efficiency, reduced dynamic capa-
bility,andagenerally"flat" dimensionality.
To
" break - in' the speaker, simply play music through the
systemat moderatevolume levels. The most dramatic im
-
provement will occurwithin the first 20 hours of operation,
although
slight improvements may be noticedeven at 50
hours of playingtime.
The
break - inperiodmaybeconductedallatonce (i.e. leaving
the system playing continuously) or may be accomplished
overanumberof playingsessions.
This break - inphenome-
non
occurs only when the speaker is brand new. Even if a
broken
- in speaker has been de-energizedfor an extended
period,
it will again reachfull performancewithin a few mo -
mentsof being re - powered.
I Using This Owner's Manual
We all have a tendency to read instruction manuals only if
somethingdoesn't work as intended. However,the assem -
blyandinstallatiinofthe Spectraloudspeaker,though simple,
may not be obvious at first glance. Therefore, to maximize
your enjoymentof thisloudspeaker,pleasereadthroughthe
entire manualbefore beginning.
This manual contains step
- by - step informationfor assem -
blingyour Spectra, installationinthe listeningenvironment,
and hook - upto the amplifier. We have also includedaddi -
tional informationin an attempt to answer those most com-
monly askedquestions.
1
ASSEMBLY & INSTALLATION
Getting Started
There are a few warningswe will make nowwhichwillsave
you trouble later:
1) Spectraarraysare MIRROR IMAGE, i.e. there are LEFT
Each
is identifiedbyasmalllabellocatedonthe rearedgeof
the top wood trim, as well as a colored dot on the bottom
surface of the array:REDfor right,andGREENfor left. The
two woofer boxesand twointerfacechassisareIDENTICAL.
2) The clotharraysare easily soiled, and arevery proneto
pickingup
lint frombeinglaidonacarpet. The protective
plasticbag should be lefton them untilthe arrays are
brought intofinalinstalledupright position
3) Spectra'ssectoredoperationrequiresacomplexconnec -
tion - set from interface lo array. Care isrequiredwhen
makingthe connections.
and RIGHTarrays.
We
will repeatthesewarnings when appropriate.
Assembly
Tool Required: Large (#2) PhillipsScrewdriver
1) Gently pry off the grilleframe fromthefront of thewoofer
box. It isheldonby four plasticfasteners. Set asidethe
grilleframe for laterre-attachment.
Referto Figures 1 and 2 for the followingsteps.
2) Removethe two large bolts at thetop-frontof the enclo -
sure, andset aside. These boltssecurethe electrostatic
array as wellthe front edge of the interface chassis.
2

3) Remove andset asidethe two smallPhillips - head
screwsontopof the interfacechassis,
at theouter
rear edges.
4) Slidethe chassis rearwardabout 2 " , andlift - upthe
front edge. Remove the plasticpartsbaglocated
underthe chassis. Pluginthe whiteconnectorto
the matingreceptacleontopof the woofer box.
Notethat this connectoriskeyed
so that it inserts
only one way. Insertfully untilitsnaps.
5) The partsbag should contain the following:
(1) WallTransformer
(2) 1/4" Washers
(4) SpikedLeveling Feet
(2) 1/4" - 20 x 2 " Bolts
(2) 1/4" - 20 Nuts
6) Placethe electrostatic array in positiononthe
front of the woofer box,withthe wires hanging
down infront of the woofer, and the seam inthe
grilleclothtowardthe rear.
It is recommendedthat
an assistantsupport the array inpositionuntil
step
#7 iscompleted.
Note: If the speaker is beingassembled near its
final location,you may want tochoose the appro -
priate Left or Right array.
7) lnsetta large bolt in each of the LOWER holes
located on the prongs extending from the array,
and adjust the position of the array
so that the
screws insert fully throughthe front of thewoofer
box. Placeawasher and nut onthe bolts fromthe
rear
and tighten. The arraywill now be self-sup-
potting.
8) Feed the arraywiresthroughthe holeinthe front
of the woofer box, with the blacktubingcovering
thewires betweenthe array andhole.
5
9) Again lift - upthe front edgeof the interfacechassis, and
locate
the 5 colored jacks (RED, BLUE, BLACK, YEL -
LOW,WHITE)ontheprintedcircuitboard. Plugthearray
wires into these jacks, PERPENDICULAR TO THE
BOARD,followingthe colorcode. Referto Figure
3.
10) Slidethe interlacechassisforward, makingsurethat the
11) Insertthe remaininglargeboltsinthe upperprongholes,
arraywires are not pinchedor strained.
threadintothe interfacechassis, andtighten.
12) insert and tighten(but do not overtighten) the Philips head
screwsontop of the chassis.
13) Re - install thewoofer grille, aligning it tothe front of the
woofer box by first lining up the top edge of the grille
against the plastictrim plateat the bottomof the array.
Then seat the fasteners by pressing each of the four
corners.
14) Repeat steps 1 - 13 for the other speaker.
We recommendthat
you keep all the boxes if possible. If
storage space is limited,keep allof themfor awhile untilyou
are satisfiedthat bothspeakers are performingproperly.
Experiencehasshownthat
if serviceor afactorymodification
is ever needed, it is most likelyto involvesendingONLY the
interfacesto Acoustat. Our packagingmaterials are top-of
the - lineand much more protectivethan most home - made
arrangements. (SeeInCase of Difficulty.)
Disassembly of Speaker
Shouldyour Spectra ever require disassembly for the pur -
pose of movingorrepair, simplyfollowthe assemblyinstruc-
tions in reverse order,
with one very important exception.
After unboltingthe interface chassis,
but BEFORE discon -
nectingany internalwires, the speaker must be discharged.
(cont.)
6

WARNING: Always unplugthe AC (POWER) input
and audiofeeds beforeaccessingthe insideof the
Interface.
1) Evenafter the power isremoved, a highvoltage charge
remains onthe array for
at least many hours.
2) To dischargethe array, remove the REDcodedarraywire
andtouch its
tip (while holdingthewire's insulation, NOT
the metalplug)
to any otherarraywireconnection. Unless
the speakerhasbeende
- energizedforsometime,expect
to see a spark andheara snap fromthe speaker.
3) Thespeaker will now be safelydischarged, anddisassem-
bly
may procedd.
Audio Input
The red/black input terminals are standard, 3/4" spacing,
bananajacks. They may acceptsingleordualbananaplugs,
spade lugs, pinplugs, or barewires.
There are four
possible ways to connect the loudspeaker to
the system amplifier(s). For all connections, be sure to
observepolarity markingsfor bothchannels: Red (+) to Red
(+), andBlack ( - ) to Black ( - ). AllAcoustat Loudspekaers are
designed to preserveabsolute phaseintegrity: i.e. when the
redinputterminalispositivewith respect to the blacktermi -
nal,the electrostat's diaphragmwillmoveforward.
Standard Connection: See FigureFour. This configuration
allowsasinglestereo amplifier to power boththe electrostatic
array andthewoofer. To implement,connectthe amplifier's
output to the 'ESUSYSTEM INPUT " terminals, and set the
switch to 'SINGLE AMP " . No connection is made lo the
" WOOFER INPUTterminals.
Bi - Wire Connection: See Figure Five. This configuration
allowsasinglestero amplifier topower both the electrostatic
array andthe woofer. butallowsuse of two separatecables
to feedeach section. To implement, connect the amplifier's
7
output to the " ESUSYSTEMINPUT " terminalsusing
one cable, and using another cable, connect the
same amplifier channel's
output to the WOOFER
INPUT
" terminals. Set the switch to the "BI-AMP/BI-
WIRE " position.
Bi-AmpConnection: See FigureSix.Thisconfigura-
tionallowsone stereo amplifier to powerthe electro -
static array, and a second stereo amplifier to power
the woofer. To implement, connect one amplifier's
output to the " ESLSYSTEMINPUTterminals, and
connectthe secondamplifier's output to the
" WOOFER
input" terminals. Set the switch
to the "BI-AMP/BI-
WIRE " position. The two amplifiers need not be
identical,but should havesimilar power ratings, and
must have identicalgain (sensitivity).
Alternate Bi-Amp Connection: See Figure Seven.
Thisconfigurationallowsonestereoamplifiertopower
the
left speaker, and a second stereo amplifier to
powerthe rightspeaker. Theadvantage of thissetup
is that
it allows each power amplifier to be placed
close
to the corresponding speaker, avoiding long
speaker cable runs. To implement, connect one
channel of the
" left " amplifier to the left speaker's
" ESUSYSTEM INPUT " terminals, and connect the
other channel
to the left speaker's WOOFER IN -
PUT " . Repeatthe processforthe rightchannel. Set
the switch
to BI-AMP/BI-WIRE" positiin. The two
amplifiersMUSTbe identicalfor this configuration.
Note that the BI-AMP/BI-WIREswitch disconnects
both
(+) and (-) woofer terminals from the ESU
System terminals, avoiding possible problems be
-
tweenamplifiersdue to commonconnections.
Forconnectionsusing
two amplifiers, a means must
be providedfor splittingthe signalfromthepreampli-
fiertoeachamplifier.Somepreampsprovidemultiple
outlets;othersrequirethe usea
"Y" adapter. Consult
your dealerfor availableoptions.
8

I Power Input
The miniature (3.5 mm) phone jack connects to the ul-
trasonicbiaspowersupply, whichcreatesthe +5000
volts necessary for electrostatic operation. The
suppliedwalltransformer
is to beconnectedto this
input jack arid plugged into an
ALWAYS ON line
outlet. Makesurethat there are
no wall switchesor
light dimmersassociatedwiththeoutlet. All Acoustat
loudspeakersare intendedtobelefton at alltimes lo
maintainfullcharge: powerconsumption is minimal
(aboutas muchas a small night light).
NOTE: Beforeplugginginthewalltransformer,make
surethat it isratedforyour local line(mains)voltage.
The export transformer, labelled for 220 volts, is
suitable for use with 220 to 240 volts, 50 to 60 Hz.
High Frequency Contour Switch
A threepositionswitchhasbeenprovidedonthe rear
of the interface chassis to adjust the top
- octave re -
sponse. Most situations will call for the " medium "
setting. However,there is no " correct " setting:adjust
this switch
to suit your own preferences. Each step
ofthe switchcauses a change of about 2 dBat 20kHz.
1 Spiked feet
Four spikedfeet have beenincludedfor installation
oneachspeaker. The feet serveto firmly couplethe
speaker to the floor, yielding more solid bass re
-
sponse. The feet can also be used to level the
speaker,as well as to "bite" through deep pile carpet-
ingto better stabilize the speaker.
The speakers
should be set - up intheir final listening
positionsbeforeinstallingthe spiked feet,as moving
the speaker with the spikes installedcan be more
difficult. Neverdragthespeakeracrossthe
floor with
the spikes installed. To install,simplyscreweachfoot
into the receptacle located on the bottom of the
woofer cabinet. Insertthe threads fully unless the feet are
beingusedto levelthe speaker, inwhch case
one or more
feet can
be backed-out to eventhe speaker onthefloor.
The use ofspikedfeetonnon-carpeted floorsisgenerallynot
recommendeddue
to the highchance of scratchingor dent -
ing the floor. It is possible to level the speaker on non-
carpeted flloors by substituting a hex- he ad 1/4"-20x1" bolt for
the spikedfoot. availablefromhardwarestores.
THE LISTENING ENVIRONMENT
I Room Size
The Spectra 1100is best suitedto smallto mediumrooms:
those with minimum dimensions of12 to 18 feet (3.5 to 5.5 me-
ters).Quiteacceptableperformancewillbeobtainedinlarger
rooms, but with aslight loss of total volume capabiliiy.
Some
of the principalconsideratiinswhichwilldeterminethe
performancepotentialof the speakersystem
as installedare
listedbelow. Remember, these aregeneral guidelinesonly.
Room shape, furniture type, and personal taste are all impor-
tant variables. Everylisteningenvironment is different, and
experimentation
is the key to satisfaction.
The Wall Behind The Speakers: The walls should be neither
excessivelyabsorptivenorreflective.
A highlyreflectivewall,
suchas large
glass windowsorsmoothhardplaster,willtend
toaccentuatehighfrequencies.
A highlyabsorptivewallsuch
as heavydrapes or excessive applicationof specific sound
absorbingmaterials, will tendto muffle highfrequencies, as
well as constrictthe apparent depthof the soundstage. The
HighFrequencyContour switch can help
to compensate for
some of thesevariables.
The Orientation Of The SpeakerSystem Within The Room:
For deepest low bass performance, the speakers should
project
sound alongthe longer axisof the room. This is true
of allloudspeakers, and
is in no way uniquetoSpectra. If this
is not possible in your room, the performance will not be
significantly compromised other than a slight
loss of deep
bass.
11
12

Distance From The Rear Wall: Sincethe Spectra isa
dipoleloudspeaker(producingsoundfrombothsides)
placingthe speakertoocbse
to the rearwallwillyield
reducedbass
output, due to rear - wavecancelations.
A minimumspeaker - to - rearwall distanceof 3feet (1
meter) is recommended, as measuredfromthe rear
center of
thearrayperpendiilartothewall. Note also
that thedistance to the rearwallcan be used insome
situations
to adjust the low frequencybalance inthe
room.
Distance From The Side Walls: Some space isdesir -
ablefromthesidewalls, buttheasymmetricnatureof
Spectra's horizontalhighfrequency radiationmakes
sidewall reflectionless of a problemthan with
most
otherspeakers. Aspacingof 1 foot (30 cm)is the mini-
mumrecommendeddistancefromthe sidewall to the
array's outer edge. Inwide rooms, of course, this
distance may be muchgreater.
Toe - In And Distance Between Speakers: There are
numerouscombinationsof toe
- inangle anddistance
betweenspeakers that willyield excellent sonic per
-
formance. In most situations, the distance between
speakersshouldberwghlyequaltothedistancefrom
each speaker to the listeningposition. The speakers
shouldalso
be toed - inat anangle so that they more -
or - lessface the listeningposition.
The Area Between TheSpeakers: This area should be
kept clear of majorobstructions to airflow if optimum
imaging
is to be achieved. The size, shape, and
materialof any objectsplacedbetweenthe speakers
will determnie
theextentofanynegativeeffects onim -
aging.
ADDITIONALINFORMATION
Specifications
PHYSICAL DIMENSIONS:
Height ........................................ 67.5 " (171.5 cn)
Width ......................................... 16' (40.6 cm)
Array Depth ............................... 3 " (7.6 cn)
Woofer Depth
............................ 16.75 " (42.5 cn)
RECOMMENDED AMPLIFIER POWER:
75 - 100 wattsperchannelor greater (basedon 8 ohm
amplifier rating). See further discussion under
" AmplifierRecommendations " .
BIAS POWER SUPPLY CONSUMPTION:
Lessthan 10 watts.
EFFICIENCY 88 dB SPL'
(400 Hz, 1 wattinto 8 ohmsequivalentatone meter,
extrapolatedfrom measurementstaken at
10 watts
into
8 ohmsequivalent, measured at a distance of
3.16 meters.)
IMPEDANCE: Typically greater than 6 ohms, mini -
mumof 2 ohms at highfrequencies (see graph).
FREQUENCYRESPONSE: - 3dB at 30 Hz, - 3dBat
19 kHz ( " High " setting)
CROSSOVERS:
Electrostat:
Woofer:
250 Hz. - 6 dB per Octave electrical,
- 12 dB effective acoustic rolloff.
250 Hz. modified - 1 2 dB peroctave,
internalphasereversal.
14
13

IMPEDANCE PLOT
20
100 lk 10k 20k
FREQUENCY - Hz
NOTE: VALUES PLOTTED FOR " MEDIUM " SETTINGOF HIGH FREQUENCY
CONTOUR SWITCH. IMPEDANCE SLIGHTLY LOWER ABOVE
10 KHZ FOR
" HIGH " SETTING, AND SLIGHTLY HIGHER FOR " LOW " SETTING.
PHASE SHIFT PLOT
20
100 lk 10k 20k
FREQUENCY - Hz
NOTE: VALUES plotted FOR " MEDIUM " SETTING OF HIGH FREQUENCY
CONTOUR SWITCH. PHASE SHIFT SLIGHTLY GREATER ABOVE
10 KHZ FOR
" HIGH " SETTING,AND SLIGHTLY LESSFOR " LOW SETTING.

AMPLIFIER RECOMMENDATIONS
As compared to most electrostaticloudspeakers,the
Spectra 1100possesses
good efficiencyand is rela -
tivelyeasy to drive. However,compared to traditional
magnetic loudspeakers, the 1100 possesses only
mediumefficiency,andcanoccasionallyposedriving
difficultiesat highfrequencieswhere impedancecan
dip to as low as 2 ohms.
Therefore, when choosing a power amplifier, afew
factors must be considered. The recommended
minimumof 75
- 1 00 wattsperchannelwillyieldgood
results, but will not realizethespeakers'fullpotential,
especiallyinlargerrooms. Amplifiersaslargeas
200
watts per channel may be used, as bng as good
common Sense
is employed: the speaker/a,plifier
should not be pushed to the limitof distortion. The
Spectra 1100
is very rugged, and the electrostatic
panelitself cannot
be damaged by excessivedrive,
but the interface electronics and woofer system do
havefinitepowerhandlingcapacity. The advantage
inusingalargepoweramplifieris not so much to allow
thesystem to playmuchlouder,butrather to allowfor
unrestricteddynamic headroom. Inbi-ampingcon
-
fgurations, the powerrequirementsforeachamplifier
can be somewhat lower.
Inaddition to the 8 ohmpowerratingof the amplifier,
the amplifier'sability
to drivelowimpedancesshould
be considered. Despite the speaker's rating of 2
ohmsat highfrequencies,the ampliiierdoes not nec -
essarily have to be rated for 2 ohms, since this
minimumoccurs over only avery narrow frequency
range. However,
to yieldoptimumperformancefrom
theloudspeaker,the amplifier should
beratedtodrive
4 ohm loads, and/or be advertised as beinga'high
current
" design.
Acoustatdoes
not generallyrecommendthe usedof
mono
- bridgedamplifierswithSpectraloudspeakers.
When astereo amplifier is bridged
into mono, each
17
half of the amplifier
" sees " only half the bad imped-
ance. Therefore,that 2 ohmminimumthenbecomes
a
1 ohm minimum,which can cause overheatingor
instabiliiy insome amplifiers. At thevery least, very
few amplifierscandelivermorepowerat 1 ohm:most
deliverconsiderablyless.
Thechoiceof amplifierdevicetechnology(transistor,
MOSFET vacuum
tube, etc.) isanentirely personal
one. Acoustat does not favor one technology over
another. Eachamplifier
must beevaluatedon its own
particular merits. The
same commentsholdtrue for
the choiceof speaker cable.
THEORY & PRACTICE OF SPECTRAOPERATION
Spectra 11 00 representsavery highstate of perfec -
tionof electrostatic hybridloudspeakers.
Theintedacetechniquesallowing the Symmetric
Pair
Electrically CurvedTransducer (SPECTRA) mode
of operationwere only perfectedinlate 1986.
At that time Acoustat made a quantum leap in the
productofSTEP
- UPEFFICIENCY andBANDWIDTH
which allowed for fhe first time a combination of
traditionalAcoustat highpedormancewith the half-
centuryoldidealof VARIABLE GEOMETRY opera -
tion.
This breakthroughsolvedthe longstandingimpasse
which had
not allowedhighSPL electrostats to have
optimum behaviorat allaudio frequencies.
YouwillfindSpectrahaswide,pleasantdispersionat
all frequencies, razor
- sharp high - frequency time
alignment,andclean low bass.
Spectra achieves this by effectively changing size
andshape at differentfrequencies. Spectra
is about
3" wide at highestfrequencies andabout 9 " wide at
middle frequencies. The lowest frequencies are
18

smmothytransitioned to an 8" dynamicwoofer.
Spectra's excellent midrange resultsfromthe magic
of wave physicswhichcausesthe 9
" of array opera -
tiinal at these frequencies to act dispersively for
waves leavingboththefront andthe rearof the array.
Spectra
is devoidof the midrangebeamingcommon
inplanarspeakersusinglargeflatmidrangeradiators.
For those wishing more in
- depth information about
electrostats in generaland specificallyspectra,contact
thefactory andaskfor our
" White Paper " entitled " Full
Range ElectrostaticLoudspeakers. "
An electriial schematic is included in this owner's
manual. However,the schematicisintendedonlyfor
the academically curious: field repair
is not recom -
mendedand not authorized.
The Spectra loudspeaker has beendesignedfor a
lifetime
of trouble-freemusicenjoyment. Ontherare
occasions that an apparent malfunction should oc -
cur, be sure to check all system signal sources,
fuses, and connecting cables.
If investigationpin -
pointsthe Spectra as the source of difficultyplease
contact
(by telephone, preferably) our Customer
Service Departmentbefore sendingany equipment
for service. Very often,we canofferfurthertrouble
-
shooting hints that simplify or even eliminate the
needfor factoryservice. Shouldyour Spectraloud
-
speaker requirefactory service, please useoriginal
factory packaging for shipment andincludea copyof
a
dated Bill of Sale and a brief note describingthe
difficulty.Everyeffortwillbemade to perform service
in atimely manner, withtypicalturn - aroundtimesof
about one week, exclusiveof transit time.
I ALL RETURNS TO THE FACTORY, REGARD -
LESSOFWARRANTY STATUS,REQUIRE PRIOR
RETURNAUTHORIZATION.
Acoustat
A Divisionof Rockford Corporation
613 South Rockford Drive
Tempe, Arizona
85281
602 - 967 - 3565
WARRANTY STATEMENT
The electrostatic elements of the Spectra 11 00 are
warrantedagainst defective materialsandworkman-
shipforthe lifeof the product. The electronic
compo-
nents contained inthe interface and the woofer are
warrantedagainstdefective materialsandworkman-
shipfor aperiodof fiveyearsfromtheoriginaldate of
purchase.Thiswarrantyextends
to theoriginalowner,
purchasedfrom an authorizedAcoustat dealer only.
A dated proof of purchasemust accompany allwar -
rantyclaims.
For subsequent owners, the electrostatic elements,
electroniccomponentsandthe woofer arewarranted
against defective materials and workmanship for a
period of five years from the date of manufacture.
Manufacturingdate shallbedeterminedfromacode
containedinthe serial number.
During the warranty period, defective parts will be
repaired or replaced, at Acoustat's option, without
chargefor laboror materials. Thewarranty does
not
covertransportationcosts to therepairsite. Acoustat
will return warranty repairs to the owner freight
19
20