This is how we describe our approach to the components in a no-compromise audio system. No unnecessary frills or emblishments, but each component in the series does the job that it was designed to do far far better-since part of its value wasn't frittered away on useless gimmicks. We don't believe in selling a consumer tone controls which won't allow him to make an effective correction on frequency unbalanced source material - because adding them to a preamplifier would mean that we would have to subtract something from the specification of the preamplifier. Everything must be paid for, either in money or performance. If frequency correction must be made, there may also be a need for scratch and or rumble filtering - and all these functions are provided on our Graphic Equalizer - and not at the 6 6db/ octave rate found on most preamplifiers but at a really usefull 18 db and 24 dB octave respectively.

Our SPS preamplifier is the best basic preamplifier we know how to make and where only a single tape recorder is used will handle virtually all of the requirements of an audiophile working with carefully chosen records and tapes -the former played on a normal output level phono cartridge.

Where a low output level moving coil cartridge is used, our DW 535 pre-preamplifier is ideal, preserving the very low distortion characteristics of the moving coil cartridges. While expensive, it does the job without compromise in circuitry which could lower the price but which would be easily audible as lowered definition or a muddy mid range.

As an alternate, and where two tape machines are used, our SPL preamplifier uses a circuit derived from the basic circuit of the SPS, but which requires considerably more circuit board room to ensure proper stability margains at ultrasonic frequencies. It has the DW 535 pre-preamplifier built in, and has a separate low power stereo power amplifier which permits it to drive even electrostatic earphones.

For frequency response corrections on material of musical merit but less than ideal recorded characteristics, our SG Graphic Equalizer is the Black Box of choice, permitting exacting frequency compensation with the ability to filter out scratch or rumble.

As the user might very well be preserving valuable material on tape recordings we felt that this was the proper place to bring-out internal system circuits onto the front panel - as well as their usual position on the case.
Two items are still missing from our line up, one is a stereo metering unit which we have designated SMP unit - in design at present it will have true VU meters meeting proper balistic specifications combined with a pair of strip-line bar displays which will indicate true peak levels - over a range (unswitched) of 50 dB. The unit will interface with both the SPL and the SG units with front panel source switching.

The second missing item is the Power Amplifier. In the past we have built power amplifiers to order, but have felt that it must be possible to build a unit having total reliability with exceptional performance. We have never made any secret of the fact that as yet we have not found such a unit on the market. We do think, after several false starts that we at least have the circuit and the mechanical packaging system - but the most we will say is that it's in the works.

This brings us to our speakers - which started us in business. It is not generally realized that the very first full range electrostatic speakers manufactured in North America in 1958 were designed by personnel now with this company. However our designs diverged from the mainstream in 1965 so that our full range units are unique in that they have no crossover networks from below 30 Hz to above 15+ kHz - about nine octaves. Thus, with all cells carrying the entire range there is Total Coherence of sound without phase distortion to modify wavefronts, and to introduce coloration.

In spite of this, Patented operating principles allow our 3rd Generation Speakers to operate at concert-hall levels at reasonable efficiencies. This is expensive, but we have tried to keep the designs as simple as possible, paying a premium to obtain components which behave as close to the ideal as possible. In this respect we feel that we have solved problems both psycoacoustic and electroacoustic that our competitors don't even realize that they are going to have to solve.

Our speakers are now available in two finishes; the internal design is essentially identical.

One is a distinctive black-cloth belted design, capped top and bottom with rosewood and having a sunken black band bisecting the cabinet around the sides and across the top. Internally, the driver cells are hermetically sealed into a welded steel frame with mylar front and rear diaphragms.

The other is derived from the enclosure used for our Mark 2 and 2A units. This uses a 1/8" thick aluminium extrusion as the case. It is inert gas welded into an exceptionally rigid frame, and lined with mastic bonded dampening material. The frame is pebble finished in black anodizing having a muted sheen which does not fingermark. This style of cabinet permits units to be stacked in multiple for sound reinforcement or other professional use. It is admittedly too modern for some environments, but totally functional.

Either type of speaker operates from a revised ST-300 A matching unit. We are unique in using a separate matching unit with special cables and connectors. However in our market, many of the speakers are used in physical ways, (such as being hung from ceilings) in which an additional 50 lbs of electronics would preclude. The ST-300 A is heavy (over 95 lbs.) out of necessity, for we use matching transformers which are of a size that shock our competitors, by keeping core flux densities low we avoid distortion.

We don't attempt to design our equipment for everyone. If you have a feeling that part of the prestige of owning a stereo system comes from the complexity of the control panel, then you probably wouldn't be happy with our equipment. But if you're choosing components for what they don't do to excellent sound source material, then our equipment is matchless.


Noted for exceptionally low distortion and ultra high definition, a state-of-the art device employing discreet semiconductor augmented integrated circuitry.


Inputs: Phono 1, Phono 2, Tuner, Aux. 1, Aux. 2, Tape. Input Sensitivity: Approx. 400 uV for 1.5 v out. (phono) Approx. 600 mV for 1.5 v out. (high level).
Phono Overload: 105 mV at 1 kHz.
Distortion: Harmonic well under.002% 20 to 10 kHz, @1.5v out. Intermodulation under.002% @ 1.5 v out.
Signal to Noise Ratio: Better than 80 dB referenced to 10 mV on Phono Input.
Frequency Response: High Level ± 1.5 dB from 4 Hz to.7 mHz. RIAA Phono ± .2 db 40 Hz to 20 kHz.
Square Wave Performance: Rise Time: Typically under 950 nanoseconds.
Settling Time: Typically under 1400 nanoseconds 1/2 % error. Overshoot: Well under 1/2 of 1% at 20 kHz.
Controls: Balance, Volume, Input selector push button group, Stereo/stereo reverse, Stereo/Mono, Tape Monitor, Power Switch.
Earphone Provision: Output Jack for medium impedance earphones.
Power Outlets: Three switched, one unswitched.
Dimensions: Faceplate 6" x 6 l/2", case 5" x 5 ½" x 10, Weight 9 lbs.
This is a very low noise low input impedance stereo pre-preamplifier designed to be used as a pre-preamplifier for moving coil phono cartridges. It has unexcelled performance with audible superiority in this application. It is line powered.

Inputs: Low level magnetic, Load Impedance approx. 8.2 ohms; 47 ohms or 100 ohms.
Outputs: Z-out ranges from 200 ohms to 5 kOhm depending upon setting of internal level adjustments.
Input Sensitivity: 50 uV for 2.5 mV out, 200 uV for 10 mV out.
Input overload: 200 mV
Distortion: Under 0.002% at Rated output 20-20,000 Hz.
Frequency Response: ± .1 db 30 hZ to 130 kHz, ± 1.5 dB 9 Hz to 500 kHz.
Square Wave Performance: Rise time under 600 nanoseconds. Settling time under 400 nanoseconds for 1% error band.
Overshoot: None
Dimensions: Main Case: 2" x`10" x 7"
Transformer case: 3 "  x 2 1/2" x 2 1/2".  Weight: 31/2 lbs.

A refined and developed SPS type circuit with the addition of an infranoise pre-preamplifier for use with moving coil cartridges, and a low power stereo power amplifier for use with earphones. Also provides more flexibility on tape recorder use.

Inputs: Low Level Magnetic 1,2; Normal Magnetic 1,2; Tuner, Aux. 1, Aux. 2, Tape 1, Tape 2.
Input Sensitivity: Low Mag. 30 uV for 1.5 v out, Normal Mag. 1.5 mV for 1.5v out, High Level &Tape, 400 mV for 1.5vout.
Phono Overload: Low Mag. 2.5 mV to 100 mV (depending on internal gain set), Normal Mag. 130 mV.
Maximum output: 25 volts peak to peak.
Distortion: Harmonic, well under 0.002% 20 to 10 kHz @ 1.5 v out
Intermodulation, well under.002% @ 1.5 v out. 
Signal to noise ratio:
Low Mag. better than 70 dB referenced to 10 mV at output of Pre-preamp, RIAA weighting. 
Normal  Mag. better than 80 dB referenced to 10 mV at input.
Frequency Response: High Level, ± 1.6 dB 1 Hz to 0,7 mHz.
Low Level Input Impedance 8.2 ohms or 47 ohms.
RIAA Equalization Accuracy: ± 0.15 dB 40 Hz to 20 kHz.
Square Wave Performance: Rise time: High Level In: Under 950 nanoseconds, Norm Phono Input: Under 1100 nanoseconds, Low Level Phono In: Under 1600 nanoseconds
Settling time: High Level In: Under 900 nanoseconds.
Normal Phono Input: Under 1300 nanoseconds.
Low Level Phono Input: Under 1500 nanoseconds, 1/2% error band.
Overshoot: None

Controls: Balance, Volume, Separate left and right channel controls only for earphone input; Input Selector Pushbutton Tape: Monitor 1, Monitor 2, Tape Dub 1 to 2, 2 to 1;
Stereo/Mono, Stereo/Stereo, Reverse, Left Channel Input only, Right Channel input only; Mute, Earphone on/off, Power on/off.
Earphone Provision: Stereo Power amplifier approx. 2 watts/ channel max for low impedance/medium impedance ear- phones, jacks on front panel dual phono-type connectors on top of case. Power Outlets: 2 switched on main case, 3 switched on  transformer case, 1 unswitched on transformer case.

Dimensions: Panel 13"x6 1/2", Case 11" x 5 1/2" x 10", Trans- former case 4" x 6" x 6". Total weight under 18 lbs.

A versatile equalizer/filter unit designed primarily for the correction of frequency response errors in source material.

Connections: Preamplifier input and output; Tape 1 in, Tape 2 in, Aux 1 in, Aux 2 in, Tape and Aux. inputs brought out on top of unit using RCA-type Jacks, and on front panel using earphone type jacks. Tape 1 out, Tape 2 out, Aux. 1 out, Aux. 2 out. Tape and Aux outputs brought out on top of unit using RCA-type jacks, and on front of unit
using Earphone type jacks.
Operating Level: 1.5 Volts RMS in/out all controls flat.
Maximum Output Level: 15 volts p. p.
Distortion: Harmonic, under 0.007%.
Intermodulation under 0.01%.
Signal to noise Ratio: Better than 90 db at 1.5 volts.
Frequency Response: (all controls flat) ± 1.5 db 10 Hz to 700 kHz.
Square Wave Performance: Rise Time under 1200 nanoseconds (all controls flat). 
Settling Time under 1200 nanoseconds for 1% error band. 
Overshoot: Under 2% at 20 kHz. 
Controls: 8 Pairs of center detent slide controls (left 
right channels brought out side by side) controlling boost and cut (up to 12 db cut or boost) at center frequencies of of 45 hZ 100 Hz, 225 Hz, 500 Hz, 1150 Hz, 2500 Hz, 6000 Hz & 13,500 Hz.

H.F. filter at 8 kHz or 11 kHz, 18 db/octave cut off rate (Bessel type filter).
L.F. (Rumble) filter at 25 Hz or 50 Hz, 24 db/octave Tape Monitor 1, 2; Tape Dub 1 to 2, 2 to 1.
Equalizer connection: Normal (cut into preamplifier circuit), Tape 1 to 2,  Aux. 1, Aux. 2.
Equalizer In/Out.

 Dimensions: Panel 13" x 6 l/2", Case 11" x 5 1/2" x 10". Wt.12lbs.

Now available in two finishes and styles, these units are the third generation series of a design type first manufactured in 1970.They have increased efficiency and reduced distortion as well as low frequency response surpassing most conventional speaker systems. They are sealed against dust and moisture, and are designed for demanding service conditions.

It is difficult to express the performance of these speakers in specifications, much of the psycoacoustic art used in their design is apparent only upon listening, and no definitive parameters as yet exist in this area of perception. As an example, the large radiating area used results in a very low sound gradient in the listening field of the speaker, that is there is only a very small level change from the area right in front of the speaker, to the area at the rear of the average an actual listening room. This approximates the gradient field in an actual concert land this absence of "acoustic glare" results in an apparent ability of the listener's hearing to increase the apparent ability of the listener's hearing to increase its discrimination between subtle tonal differences, and do this without listening fatigue. The resultant sound has an effortlessness which is lost where the sound is projected from 10" diameter holes as in most speakers. (or 14", or 8" as you will have it). The combination of a crossover free 9 octave region, the very wide frequency response, and the excellent high frequency dispersion result in a sound that is closer to the source in fidelity than ever before achieved.
Operating Level: Average levels of 100 dB can be realized in the listening field with amplifier powers of 250 watts/channel (at 4 ohms). The speakers are of 
capable of producing peak levels of 115 db when driven from stable amplifiers. We suggest the use
an amplifier with sufficient power that it does not enter the clipping region of protection, as the excellent transient response of the speakers will make this all too obvious. Thus a 200 watt per channel amplifier wil be sufficient for most rooms, unless very high sound-pressure-levels are necessary.

Input Imperence: The input impedance (contraryto general belief) is quite smooth from 600 Hz through 14kHz being 2.7 ohms ± 0.2 ohms.This median level will rise to approx. 3.8 ohms after 4 months of operation. The anomalies in the impedence response is a 70% rise at 16 kHz (the upper crossover point to the ultrasonic units), a rising characteristic above 25 kHz (approx. 17 ohms at 100 kHz) and a smooth rise below 600 Hz which peaks at about 22 to 40 ohms depending upon room loading at 110 Hz. At low frequencies the impedence does not drop below 8 ohms (even at DC).

Frequency Response: With the necessary qualification that frequency response below 100 Hz will be dependent on its smoothness on room characteristics and speaker placement, it is generally possible to obtain a response lying within ± 4 dB from 30 Hz to 18 kHz. The high frequency response smoothness will be somewhat dependent upon the number and level of room reflections.

Distortion: Generally under .1%, there is a rise above 10 kHz to .3% at 16 kHz, and a rise below 55 Hz to about 2% at 37 Hz, at a level of 85 dB 1 meter on axis. We have found that the most prominent distortion characteristic noticed will be the transient intermodulation distortion characteristics of the power amplifier used. Having tested a number of commercially available power amplifiers we have found that there is far less ringing at square wave inputs (from 5 kHz to 20 kHz) than would be inferred from the trade literature and power amplifier reviews.

Size: Aluminum  1 meter x 1 meter x 24cm.
                           39 3/8 x 39 3/8 x 9 1/2 
                           Approx. 64 lbs/speaker
Size: Wood Trimmed Steel 1.05 meters x 0.98 meter x 24 cm
                               41 x 39 x 91/2
                               Approx. 104 lbs/speaker

ST-300 A 10 1/2 H x 19 W x 11 D same
                   26 cm x 49 cm x 27 cm same

The ST-300 A unit comes complete with 25 foot cables for each speaker and weights 105 lbs.


P.O. BOX 419, THORNHILL, ONTARIO, CANADA L3T 4A2 Phone (416) 884-3244
Please note: The above address and telephone number are no longer valid - they are included as they were on the original!


© 1980, 1999 Wright Electroacoustics

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