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AMPLIFIER RECOMMENDATIONS 

As compared to 

most 

electrostatic loudspeakers, the 

Spectra 1100 possesses 

good 

efficiency and 

is 

rela- 

tively easy to drive. However, compared to traditional 

magnetic  loudspeakers, the  1100 possesses  only 
medium efficiency, andcanoccasionallyposedriving 

difficulties at high frequencies where impedance can 
dip to as low as 

ohms. 

Therefore, when choosing a power amplifier, a few 

factors  must  be  considered.  The  recommended 

minimum of 75-1 

00 

watts per channel will yield good 

results, 

but 

will 

not realize the speakers' full potential, 

especially in larger rooms. Amplifiers as large as 

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 limit of distortion.  The 

Spectra 1100 

is very  rugged, and the  electrostatic 

panel itself cannot be damaged by excessive drive, 

but  

the  interface electronics and woofer system do 

have finite power handling capacity. The advantage 
inusingalargepoweramplifieris not so much to allow 

the system to play much louder, but rather to allow for 
unrestricted dynamic headroom.  In bi-amping con- 

fgurations, the power requirementsforeach amplifier 

can be somewhat lower. 

In addition to the 

ohm power rating of the amplifier, 

the amplifier's ability to drive low impedances should 

be 

considered.  Despite the  speaker's  rating 

of 

ohms at highfrequencies, the ampliiier does not nec- 

essarily  have to  be  rated  for 

ohms,  since  this 

minimum occurs over only a very narrow frequency 
range. However, 

to 

yield optimum performance from 

the loudspeaker, the amplifier should be ratedtodrive 

ohm loads, and/or be advertised as being a 'high 

current" design. 

Acoustat does not generally recommend the used of 

mono-bridged amplifiers with Spectra loudspeakers. 

When a stereo amplifier is bridged into mono, each 

17 

half of the amplifier "sees" only half the bad imped- 

ance.  Therefore, that 

ohm minimum then becomes 

ohm minimum, which can cause overheating or 

instabiliiy in some amplifiers.  At the very least, very 

few 

amplifiers can deliver more power at 

ohm: most 

deliver considerably less. 

The choice of amplifier device technology (transistor, 

MOSFET vacuum tube, etc.) is an entirely personal 

one.  Acoustat does  not favor one technology over 

another. Each amplifier must be evaluated on 

its 

own 

particular merits.  The 

same comments hold true for 

the choice of speaker cable. 

THEORY 

PRACTICE OF SPECTRA OPERATION 

Spectra 11 

00 

represents a very high state of perfec- 

tion of electrostatic hybrid loudspeakers. 

Theintedacetechniques allowing the Symmetric Pair 

Electrically Curved Transducer (SPECTRA) mode 

of  operation were only perfected in late 1986. 

At  that time Acoustat  made a quantum leap in the 
productof STEP-UP EFFICIENCY and BANDWIDTH 

which  allowed for  fhe  first  time  a  combination of 

traditional Acoustat high pedormance with the half- 
century old ideal of VARIABLE GEOMETRY opera- 

tion. 

This breakthrough solved the long standing impasse 

which had not allowed high SPL electrostats to have 
optimum behavior at all audio frequencies. 

You will find Spectra has wide, pleasant dispersion at 

all  frequencies,  razor-sharp  high-frequency  time 
alignment, and clean low bass. 

Spectra achieves this by  effectively changing size 

and shape at different frequencies.  Spectra 

is about 

3" 

wide 

at 

highest frequencies and about 9" wide at 

middle frequencies.  The  lowest  frequencies  are 

18 

Summary of Contents for SPECTRA 1100

Page 1: ...5281 USA 602 967 3565 spikedFeet Page 11 The Listening Environment RoomSize Page 12 Wall BehindThe Speakers Page 12 The Orientationof The Speaker SystemWithinThe Room Page 12 PositionInThe Room Page12 DistanceFromRearWall Page 13 Distance FromSideWalls Page 13 Toe In and DistanceBetweenSpeakers Page 13 Area BetweenThe Speakers Page 13 Specifications Page 14 Impedance Curves Page 15 Amplifier Recom...

Page 2: ...r 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 afew warningswe will make nowwhichwill save you troub...

Page 3: ......

Page 4: ...in lift upthe front edge of the interfacechassis and locatethe 5 colored jacks RED BLUE BLACK YEL LOW WHITE onthe printedcircuitboard Plugthe array wires into these jacks PERPENDICULAR TO THE BOARD followingthe colorcode Referto Figure3 10 Slidethe interlacechassisforward makingsurethat the 11 Insertthe remaininglargeboltsinthe upperprongholes arraywires are not pinchedor strained threadintothe in...

Page 5: ...ection To implement connect the amplifier s 7 outputto the ESUSYSTEMINPUT terminalsusing one cable and using another cable connect the same amplifier channel s output to the WOOFER INPUT terminals Set the switchto the BI AMP BI WIRE position Bi AmpConnection See FigureSix Thisconfigura tionallowsone stereo amplifierto powerthe electro static array and a second stereo amplifier to power the woofer ...

Page 6: ......

Page 7: ...nsertthe threads fully unless the feet are beingusedto levelthe speaker inwhch case one or more feet canbebacked outto eventhe speaker onthe floor The use ofspikedfeetonnon carpeted floorsisgenerallynot recommendeddue to thehighchanceo fscratchingor dent ing the floor It is possible to level the speaker on non carpeted flloors by substituting a hex head1 4 20x1 bolt for the spikedfoot availablefro...

Page 8: ...erwghlyequaltothedistancefrom eachspeakerto the listeningposition The speakers shouldalso betoed inat an angleso that they more or lessface the listeningposition TheArea Between The Speakers This areashouldbe kept clear of majorobstructions to airflow if optimum imaging is to be achieved The size shape and materialof any objectsplacedbetweenthe speakers will determnietheextentofanynegativeeffects ...

Page 9: ...R SWITCH IMPEDANCE SLIGHTLY LOWER ABOVE 10 KHZ FOR HIGH SETTING AND SLIGHTLY HIGHER FOR LOW SETTING PHASE SHIFT PLOT 20 100 l k 10k 20k FREQUENCY H z NOTE VALUES plotted FOR MEDIUM SETTING OF HIGH FREQUENCY CONTOUR SWITCH PHASE SHIFT SLIGHTLY GREATERABOVE 10KHZ FOR HIGH SETTING AND SLIGHTLY LESSFOR LOW SETTING ...

Page 10: ...tedtodrive 4 ohm loads and or be advertised as being a high current design Acoustatdoes notgenerallyrecommendthe usedof mono bridgedamplifierswithSpectraloudspeakers When a stereo amplifier is bridged into mono each 17 half of the amplifier sees only half the bad imped ance Therefore that 2ohmminimumthenbecomes a 1ohm minimum which can cause overheatingor instabiliiy insome amplifiers At the very ...

Page 11: ...vice please useoriginal factory packaging for shipment andincludeacopyof a dated Billof Sale and a brief note describingthe difficulty Everyeffortwillbemade to perform service inatimely manner withtypicalturn aroundtimes of about one week exclusiveof transit time I ALL RETURNS TO THE FACTORY REGARD LESSOFWARRANTY STATUS REQUIREPRIOR RETURNAUTHORIZATION Acoustat A Divisionof Rockford Corporation 61...

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