What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Technics SB-4500

 The SB 4500 Linear Phase Speaker
After extensive research into the way sound travels at different frequencies, Technics engineers designed the "staggered" speaker. A totally new concept, linear phase speaker have become an instant sucess with music lovers throughout the world.
The price of £ 84,95 each speaker is just another example of how Technics can satisfy your love of high fidelity at a reasonable cost.

Type:  2-way, 2-speaker bass-reflex system
Woofer : 250 mm cone type
Tweeter :  60 mm cone type
Impedance:  6 Ω
Instantaneous Max. Power Input:  75 W (peak)
Output Sound-pressure Level:  92,5 dB/W (At 1,0 m)
Crossover Frequency:  2,000 Hz
Dimensions (W x H x D):  350 x  631 x 325 mm (13-3/4" x 24-7/8" x 12-3/4")

Weight:  14,5 kg  (32,0 lbs)

Fisher 514

 The new Fisher  Studio-Standard 514 Stereo/4-Channel Receiver
Every Fisher receiver is designed for people who love to play music; but the new Fisher Studio-Standard 514 goes a step further. It's designed for the active audiophiles who get their kikcs out of playing with the music, the people who can't even wait to get a new component out of the box and up on the shelf before trying it out.  These are people who listen with their hands as much as their ears, and while others are snapping their fingers and stamping their feet, they're flicking switches, pushing plugs, and twirling knobs.
If you are as concerned with what goes on inside the box as you are concerned with what comes out, if you're still shifting speakers and splicing wires long after the party's over, chances are you just won't be satisfied by anything less than the Fisher 514.
 We left out nothing.
Both to keep up our reputation of having the latest and teh most, and to make sure that you can listen to as much 4-channel as possible, the 514 has a new CD-4 discrete disc demodulator as well as an SQ matrix decoder. CD-4 has the potential for greater channel separation than SQ. This means that the musicians and studio people can do trickier stuff, and that listeners can wander around the room and still hear everything in its proper position.
SQ is a cinch to broadcast on FM while CD-4 is just about impossible right now; SQ is used on many more records than CD-4, and the decoding circuit doubles as a 4-channel synthesizer for stereo recordings. With the Fisher 514 you do not have to make the difficult choice between CD-4 and SQ; we give you both.
 In addition to all the knobs and buttons you'd expect to find on any receiver of this caliber, the 514 has a sophisticated and highly useful "joystick" balance control similar to the pan pot used in professional recording studios. The joystick is much simpler to use than the two or four knobs found on most other 4-channel receivers, yet it permits extremely precise adjustments of the acoustical field to suit music, personal preference, room acoustics, or seating arrangements.
An elaborate tone control and filter system, centering on studio-style slide potentiometers, provides further fine tuning of the audio environment.
As you might expect, there are separate bass and treble controls for front and rear, but Fisher has added a midrange presence control, with maximum effect at about 1,5 kHz. It's just about the most useful and potent control you could add to a component, and can dramatically highlight a vocal performance against an instrumental background.
Although primarily designed as the control center for an elaborate 4-channel sound system, the 514 uses an exotic Fisher-invented "strapping" technique to combine front and rear amplifiers for stereo use, with a significant increase inpower over what you would expect by just adding up the per-channel wattages.
 What's inside.
Fisher has spared no effort to utilize the latest high-technology devices and manufacturing techniques in the 514. the FM tuner section incorporates dual-gate MOS/FETs. Lumped selectivity circuitry, and a ladder-type ceramic filter to provide the highest possible signal-to-noise ratio, interference rejection, sensitivity, selectivity, and immunity to overload. A Phase Locked Loop multiplex decoder insures high separation and low distortion through temperature changes and extensive use.

It comes from a fine family.
In addition to the 514, we're very pround of our new Studio Standard models 414 and 314. they have a bit less power and not as many controls, but the music is every bit as good.
If, however, you're not ready for, or not sure about, the new CD-4 system, we strongly recommend you consider our 504X, 404X and 304X receivers. They're identical to the "14" series models, except that instead of having a built-in CD-4 demodulator, they have space for it, and sell for $100 less. Should you wish to add CD-4 later on, any of our serice stations can do the job, and the total cost of the "04X" series receiver plud decoder will not exceed the cost of the complete "14". Anybody's 4-channel receiver can be converted to CD-4 with an external add-on demodulator, but Fisher accepts an  internal circuit board - for simplicity, convenience, and reliability.
Total Power RMS (8 Ω, 20-20,000 Hz)
Stereo : 180 W
4-channel : 128 W
Total Harmonic Distortion:  0,5% (at rated power, 4 Ω)
IM Distortion [60 and 70,000 Hz 4 : 1]:  0,8% (at rated power, 4 Ω)
Damping Factor:  than less 30 (4-channel operation, 4 - 8 Ω)
Input Senitivity/Impedance:
Phono :  2,7 mV/47 k Ω
Aux :  200 mV/100 k Ω
Monitor :  200 mV/100 k Ω
Recorder Output:  350 mV (30 % FM modulation)
Hum and Noise (below rated RMS output, volume control at minimum):
Phono :  56 dB
Aux : 65 dB
Monitor : 65 dB
Frequency Response:
Phono :  30 - 15,000 Hz (RIAA equalized ±2 dB)
Aux, Monitor :  20 - 20,000 Hz
Max. Input Signal RMS (at 1% THD, 1 kHz):
Phono : 60 mV
Aux : 5 V
Monitor : 4,5 V
Dimensions (W x H x D): 23" x 6 ¾"  x 17" 

Weight:  43 lbs

Pioneer PL-400

 Pioneer PL-400 fully Automatic  Quartz-Controlled Turntable
There are a lot of turntables you can buy for less than $200. Many  of them are fully-automatic. Some of them have Quartz Reference Systems. Others feature sophisticated suspension systems. Or have specially-designed motors to make sure the sound of your turntable doesn't interfere with the sound of music.
But at Pioneer, we believe, that if you're going to pay $200 for a turntable, you shouldn't just get one of these features. You should get all of them.
While other turntables with some of these advancements may look the same as the PL-400 on paper, they don't sound at all alike in your home. Because all these advancements act together to keep an imperfect environment, like your home, from getting in the way of perfect sound.
In your home, simply slamming a door can be more jarring to your turntable than it is to you.
 Pioneer's PL-400 has a sophisticated suspension system that isolates the paltter and tone arm from the rest of the turntable. Which means you can shake, rattle and roll a lot more with a lot less worry that your turntable is doing the same thing.
The PL-400 also has the world's thinnest direct drive motor. This ultra-thin motor does a lot more than give the PL-400 an ultra-sleek appearance. It keeps the turntable platter perfectly steady at all times. Thoough platter wobbling isn't a problem that can be easily seen on most turntables, it can be easily heard. It results in shifts of musical pitch.
Something the PL-400 is never bothered with.
What's more, the PL-400 also has Quartz control like that found in the finest  Swiss watches.
Which means you're guaranteed to get the maximum in rotational accuracy.
So if you want a turntable that sounds great, there's any number you can buy. But if you also want the price to sound great, there's only one.
The fully-automatic Poineer PL-400. we bring it back alieve.
Drive System:  Direct-drive
Motor:  Quartz PLL Hall motor
Turntable Platter:  310 mm ø, aluminum alloy die-cast
Moment of Inertia:  180 kg/cm² (including platter mat)
Speeds:  33 and 45 rpm
Wow & Flutter:  0,025% (WRMS)
Signal-to-Noise Ratio:  75 dB (DIN B)
Build-up Time:  Within 120° rotation at 33 rpm
Speed Deviation:  less than 0,002%
Speed Drift:  less than 0,00008%/h at 33
Less than 0,00003%/degree temp. Change at 33 rpm
Type:  Static-balance type, S-shaped pipe arm
Effective Arm length:  221 mm
Overhang:  15,5 mm
Usable Cartridge Weight:  4 g (min.) to 9 g (max)
Full auto-mechanism; Anti-skating force control; Stylus pressure direct-readout counterweight; Cueing device, Strobe light; Free stop hinges
ICs :  3
Transistors :  3
Diodes :  6
Hall Elements :  3
Power requirements:  AC 110/120 220/240 V 50/60 Hz
Power Consumption:  8 W (at 120 V)
Dimensions (W x H x D):  420 x 96 x 365 mm (16-1/2" x 3-3/16" x 14-3/8")
Weight:  6,5 kg (14 lb 5 oz)

PC-135 Specifications (only model PL-400X KU)
Type:  Induced magnet type
Stylus:  0,5 mil diamond (PN-135)
Output Voltage:  3 mV (1kHz, 50 mm/s peak velocity, LAT)
Tracking Force:  1,5 g to 2,3 g

Frequency Response:  10 to 25,000 Hz

Technics RS-615 US

 Whether your love of music is a passionate affair or a light hearted pastime, the latest offerings from Technics will more than satisfy your desire for high fidelity.
The RS-615US Stereo Cassette Deck
 Sound enthusiasts will love its attractive features. For example the famous Dolby noise reduction suystem to reduce tape hiss.  The electronically controlled DC motor to keep wow and flutter down to a sweet nothing. And a tough, durable tapehead. Its high performance will last long beyond the honeymoon period.
Being a front loader, the panel controls make it ideal for bookshelf installation. And the oil damped door provides easy access to the cassette and tapeheads.  Music lovers will appreciate the convenient timer recording/playback facility. With an automatic timer you can record programmes unattended. There is also a large 41 click/stop control for easy recordings.
If all this makes the RS-615US sound desirable, the price of £ 129,95 will make it irresistible
Track System:  2-channel, 4-track
Tape Speed:  4,8 cm/s
Motor:  DC motors, electronic controlled
Head:  1 Ferrite Erasure head; 1 Super-permalloy Playback/Recording head
Rewind Time (C-60):  ca. 90 sec.
Wow and Flutter:  0,10% (WRMS)  ±20% (DIN)
Frequency Response:
CrO₂ :  30 - 16,000 Hz; 30 - 14,000 Hz (DIN)
Normal :  30 - 14,000 Hz;  30 - 13,000 Hz
Signal-to-Noise Ratio:  50 dB;  (60 dB with Dolby)
Input Sensitivity/Impedance: 
Line-In :  60 mV/100 k Ω
Mic :  0,25 mV/400 Ω - 20 k Ω
Output Sensitivity/Impedance:
Line-In ;  420 mV/ 50 k Ω
Headphones :  65 mV/ 8 Ω
Semiconductors:  24 Transistors; 2 FET, 18 Diode
Power Requirement:  110/120/220/240 V, 50/60 Hz
Power Consumption:  10 W
Dimensions (W x H x D):  410 x 140 x 305 mm

Weight:  6,3 kg

Technics ST-8080

 With the remarkable advance in audio technology achieved within recent years, and the ceaseless striving of an elite team of engineers devoted to the task of producing perfect sound reproduction equipment, Technics has succeeded in achieving very high standards in its audio equipment, as can be seen in the case of the ST-8080 stereo tuner. This high standard will inevitably become the norm in future years, but that is hardly welcome news for audio enthusiasts looking for the best their money can by now.
The ultimate aim in any top grade stereo tuner is the perfect reproduction of the original waveform of the radio signals transmitted from the broadcasting station. This is certainly no easy task, since, besides other things, this involves the complete banishment of all interference and noise signals and the ability to mainta in stereo separation at exactly the same level as in the original signals.
The waveform of the signals comprising any musical expression is usually very complex, and cannot be used effectively to point out the differences between original and reproduced signals. In normal analysis, the tuner's ability to reproduce these signals is shown by using simple square wave and tone burst signals.

The results shown here illustrate the marked differences between the ST-8080 (in which the ultimate design priority has been placed upon waveform fidelity) and a conventional tuner (conspicuous for the lack of emphasis on waveform).
Photograph A.

The results shown in this photograph highlight the difference in response to a composite signal of a 50Hz square wave signal plus 1kHz sine wave signal. The very steep "sag" in the square wave output signal from the conventional tuner is indicative of the poor amplification phase characteristics in the low frequency region (which introduces distortion into the signal), while the depressed sections at the start of the 1kHz sine waves signify a very small dynamic range at lower frequencies.
Photograph B.

5kHz and 15kHz sine waves are modulated and demodulated independently, but are shown here (upper half of photograph) on the same time axis in order to reveal any change in time relation between the waves. The output of the ST-8080 shows no time change whatsoever, while the 5kHz and 15kHz signals passed through the conventional tuner have arrived at the output at different times. lf these 2 signals are then combined( lower half of photograph) the loss of waveform fidelity in the conventional tuner is even more evident.

 High Sensitivity Front-End (10.8 dBf)with 2-Stage RF Amplifier and 4 -Ganged FM Variable Tuning Capacitor.
The adoption of two low-noise  4-pole dualgate junction FETs and linear 4-ganged FM variable tuning capacitor in the  2-stage  RF amplifier stage is  largely responsible for  the very high sensitivity in the  front-end.
Usable sensitivity is 10.8dBf (or 1.9 µV according to IHF '58) at 300 Ω antenna input impedance, while the 50dB quieting sensitivity (stereo) is 34.3dBf (or 28.4 µV  IHF '58) at 300 Ω. With this kind of sensitivity, together with the greatly reduced interference signal  levels, even very remote FM stations are received with great clarity and fidelity.
Of special importance is the suppression of the interference caused by RF intermodulation, and the consequent improvement in selectivity in the more crowded sectrons of the FM band. The RF lM interference rejection curves are shown here in graph form.
Naturally, the higher the values( in dB) the better, but such values are very difficult to obtain without sacrificing sensitivity in reception of distant stations. Albeit, as can be seen in the graph, Technics has succeeded in attaining avery high standard indeed, and this without compromising sensitivity at all.

 New Developments in Local Oscillator and Mixer Stage Further lnprove Stability and S/N Ratio.
The greater overall stability of the ST-8080 tuner is also due to the improved stability of the local oscillator and mixer circuits which incorporate special low-noise transistors, and a recently developed aluminum core oscillator coil. And circuit sections prone to the effects of changing humidity, etc. Have been further stabilized by the use of special point-to-point wirrng techniques.
The use of special low-noise transistors designed to eliminate noise in both high and low frequency regions, and the extremely strict selection of circuit components, have greatly attributed to the very high S/N ratio, and the noticeable lack of frequency drift.  Special care has been taken to separate oscillator's hot side from the foil on the printed circuit board, another innovation resulting in drift-free performance.

 Advanced Type Flat Group Delay Filters Solve the Conflicting Demand for High Selectivity and Low Distortion in lF Stage.
A selectivity rating as high as 85dB, and adistortion ratio as low as 0.15% (100% modulation, MONO) in the ST-8080 has been accomplished by some very clever electronic engineering. The four flat group delay filters (one narrow band type, and three wide types) feature  4 -resonator type ceramic filters of very high selectivity characteristics. In addition, the amplification stage consists of 3-stage and 2-stage differential  amplifiers (in two separate lCs) connected to a quadrature detector.  At  ±400kHz, a very impressive alternate channel selectivity of 85dB has been obtained.  And even at ±200kHz, selectivity is still in excess of 10dB, which means that no matter how crowded the band may be, the desired signal can still be singled out with a high degree of clarity. These filters also assit in maintaining excellen stereo separation.
Here again is ample evidence of the very careful attention that Technics pays to the performance of the audio equipment it designs, not only in terms of  audio requirements, but also in terms of performance as communications equipment. No matter how low harmonic distortion may be suppressed, it will have little significance if the system is still  subject to other forms of interference. Only when all performance requirements are fully met, can the equipment be honestly be considered as a genuine FM stereo tuner.

 Super Flat Frequency Response from 20Hz to 18kHz (+0.2dB,-0.8dB)
Needless to say, waveform fidelity would be impossible  to attain in a tuner suffering from phase inversion and poor frequency response.  In the ST-8080, the 19kHz pilot signal, required for stereo demodulation in the MPX curcuit, is cut out with razors harp precision by the pilot cancel circuit (a Technics invention now copied by many other manufacturers). Besides improving frequency response, it also reduces distortion, and escapes the problem of phase inversion associated with low pass filters (which also inavoidably cut off some of the high frequency portions of actual FM programs).
Excellent linearity is also obtained, the response curve being incredibly flat (+0.2dB; -0.8dB) all the way trom 20Hz to 18kHz.
Together with the improvements gained by the flat group delay filters in the lF stage, an extremely high degree of fidelity in waveform has been accomplished. Furthermore  the 38kHz subcarrier signal has also been cancelled by a similar circuit, reducing the possibility of interference from this source to zero.

 Superb Stereo Separation (45dB at 1kHz) Due to New PLL  IC in MPX Circuit
Although the PLL (Phase Locked Loop) system is now quite common in the MPX circuit (where the left and right stereo signals are retrieved from the transmitted "multiplex"signal), the ST-8080 has improved upon this system by accommodating it in a newly developed IC (AN363). The advantages include greater stability and reliability under varying external conditions, decreased distortion especially in the high frequency region, and higher stereo separation. The improvement in waveform transmission is quite marked (see photograph A and B), not only because of the greatly reduced higher harmonics, but also because of  the reduction of unwanted components caused by beating.
This IC employs a voltage controlled oscillator to generate a 76kHz signal, which is then divided into 38kHz, and 19kHz signals.  This 19kHz signal is synchronized perfectly with the pilot signal, passed out of the IC via pin no.12, and undergoes waveform shaping into a pure19kHz signal, which is then mixed with the composite signal at the input of the MPX circuit, resulting in the cancellation of the unwanted pilot signal. This further eliminates the occurrence of poroblems in the succeeding nonlinear circuits.

Low-Noise Amplification IC  in AF Stage
The thoroughness of Technics pursuit for waveform fidelity is further emphasized by the quality of the circuitry employed in the AF stage. The IC  adopted here includes a first-stage differential SEPP output for audio frequency amplification, and is operated by a stabilized power supply. Besides the variable level outout control, the ST-8080 also features a separate output for tape decks. The level volume control is the precision adjusted low gang error type. The fixed output terminals (for recording) include  a special type of  lowpass filter of excellent phase delay characteristics, and which suppresses carrier leak to less than  -70d8.

Built-in REC Level Oscillator for Level Setting Accuracy
This oscillator generates a 440Hz sine wave siqnal whose level corresponds to an FM radio signal of 50% modulation. This enables recording enthusiasts to adjust recording levels to a very high degree of precision.

High Grade Signal Strength Meter for Greater Precision and Versatility
Linked to the quadrature detector circuit, this extremely li near signal meter (fl at right up to 65dBf) is fully qualified to measure signal strengths  to very high levels. This will prove very useful in finding optimum antenna position and direction for weak and strong FM stations alike.

Two-Way Muting
With muting circuitry in the reed relay of the output stage, and in the quadrature detector IC, 2-way muting is provided to suppress inter-station and tuning noise to a high degree.

MPX Hi-Blend for Noise-Free Stereo Reception of Distant Stations
The multiplex hi-blend switch betters S/N ratios in reception of weaker and more distant FM stations. The ST-8080 also features multipath measuring terminals to which an oscilloscope may be connected. Optimum antenna position and direction can thus be determined with great accuracy in situations troubled by multipath interference.

Also High Quality AM Reception
Nor has there been any skimping in design considerations for AM reception. Incorporating a high-Q ferrite bar  antenna, an IC developed specifically for AM, and the very high selectivity of the ceramic filters in the lF stage, exceptronally high reception standards have been achieved.

Specifications (DIN 45 500)
Frequency Range:  88 -108 MHz
Sensitivity:  (± 40 kHz deviation)
S/N 30 dB :  1,8 µV (300 Ω); 0,9 µV (75 Ω)
S/N 26 dB :  1,6 µV (300 Ω); 0,8 µV (75 Ω)
S/N 20 dB :  1,4 µV (300 Ω); 0,7 µV (75 Ω)
IHF Usable Sensitivity:  10.8 dBf (1,9 µV, 300 Ω  IHF '58)
S/N 50 dB Quieting Sensitivity:
Mono : 13,6 dBf (2,6 µV, 300 Ω IHF '58)
Stereo :  34,3 dBf (28,4 µV, 300 Ω IHF '58)
Total Harmonic Distortion
Mono : 0,15 % (1 kHz)
Stereo : 0,3% (1 kHz)
S/N (40 kHz deviation)
Mono : 70 dB (75 dB, IHF)
Frequency Response:
Variable :  20 Hz - 18 kHz (+0,2 dB; -0,8 dB)
Fixed :  20 Hz - 15 kHz (+0,2 dB -0,8 dB)
(DIN) :  20 Hz - 18 kHz (±15 dB)
Alternate Channel Selectivity:  85 dB
Capture Ratio:  1,0 dB
Image Rejection at 98 MHz:  85 dB
IF Rejection at 98 MHz:  100 dB
Spurious response rejection at 98 MHz:  95 dB
AM Suppression:  55 dB
Stereo Separation:  45 dB (1 kHz),  35 dB (10 kHz)
Carrier Leak :
Variable :  -60 dB 919 kHz); -65 dB (19 kHz IHF)
Fixed :  -65 dB 919 kHz); -70 dB (19 kHz, 38 kHz IHF)
Limiting Point:  1,2 µV
Bandwidth :
IF Amplifier :  250 kHz
FM Demodulator :  820 kHz
Antenna Terminals:  300 Ω and 75 Ω
Frequency Range:  525 - 1605 kHz
Sensitivity (S/N =20dB):  30 µV
Selectivity:  25 dB
Image Rejection at 1000 kHz:  45 dB
IF Rejection at 1000 kHz:  40 dB
Output Voltage
Vriable :  0 - 1,4 V
Fixed :  0,6 V
Power Consumption:  14 W
Power Supply:  110/120/220/240 V 50/60 Hz
Dimensions (W x H x D):  450 x 140 x 367 mm (17-23/32" x  5-1/2" x 14-7/16")

Weight:  8,4 kg (18,5 lbs)

Tannoy System 8 NFM II

 The integration of all the features described HERE is what makes the whole loudspekaer system even greater than sum of the individual parts.
  • The style of the cabinet is not arbitrary, it has been arrived at by considering the acoustic principles of diffraction and energy storage.
  • The trim rings around the rubber surrounds are there to smooth out the otherwise discontinuous contour to the HF wavefront.
  • The smooth lines around the port tubes ensure laminar air flow at low frequencies where the air in the ports has maximum velocity.
  • The shapes of the LF cones contiune the hyperbolic waveguide for the HF energy propagation.
  • The cabinet bracing and internal construction ensures that the HF unit can deliver the detail into the sound field.
  • The application of the Differential Material Technology approach to component behaviour under vibration and magnetic fields has lead to custom crossover components, custom cabling and a split crossover design being employed.
 The result of all these innovations is a family of monitoring loudspeakers from Tannoy; speaker which are quite remarkable in resolving the finest detail over the whole audio spectrum.
The new Monitor Series loudspeakers prove that Tannoy still leads the world in applying the science of loudspeaker design to the practical monitoring situation. These monitors are tools to be used in producing even more artistic and satisfying developments within the live and recorded sound stage.
Specifications System 8 NFM II
Recommended Amplifier Power:  20 to 150 watt RMS
Peak Power Handling:  200 watt
Nominal Impedance:  8 Ω
Sensitivity (2,83 volts at 1m):  93 dB
Distortion:  less than 0,4% (47 Hz - 25 kHz)
Phase Response:  System behaves substantially as a frequency-independent time delay
Dispersion:  90 degrees conical
Crossover Frequency:  1,7 kHz
Crossover Type:  1st order LF, cascaded 1st order HF with impedance compensation. Positive acoustic polarity
Frequency Response (±3 dB):  47 Hz - 25 kHz
Drive Unit Type:  8 inch, 2036 Dual Concentric
Cabinet Internal Volume:  18,3 litres
Cabinet Material:  30 mm MDF front baffle and back;  20,6 mm Top, bottom and sides, with energy absorbing bracing matrix and TF-1 acoustic wadding
Cabinet Finish:  Velti shadow grey soft-texture finish. High pressure twin laminate in shadow grey with metallic speckled finish on top, bottom and sides.
Grille:  Single piece, black acoustically transparent material over a rigid frame
Dimensions (H x W x D):  460 x 300 x 230 mm (18,1" x 11,8" x  9,1")

Weight (net):  12 kg (26,4 lb)

Tannoy System 6 NFM II

 The Dual Concentric design philosophy is world known for its precise stereo imagery and for the ease of finding sounds within a sound stage. The presentation of the sound image makes long production sessions much less fatiguing than with other monitoring systems because the brain does not have to work as haard correcting for acoustic anomalies in the time and frequency domains.
The integration of all the features described HERE is what makes the whole loudspekaer system even greater than sum of the individual parts.

  • The style of the cabinet is not arbitrary, it has been arrived at by considering the acoustic principles of diffraction and energy storage.
  • The trim rings around the rubber surrounds are there to smooth out the otherwise discontinuous contour to the HF wavefront.
  • The smooth lines around the port tubes ensure laminar air flow at low frequencies where the air in the ports has maximum velocity.
  • The shapes of the LF cones contiune the hyperbolic waveguide for the HF energy propagation.
  • The cabinet bracing and internal construction ensures that the HF unit can deliver the detail into the sound field.
  • The application of the Differential Material Technology approach to component behaviour under vibration and magnetic fields has lead to custom crossover components, custom cabling and a split crossover design being employed.
Specifications System 6 NFM II
Recommended Amplifier Power:  20 to 150 watt RMS
Peak Power Handling:  175 watt
Nominal Impedance:  8 Ω
Sensitivity (2,83 volts at 1m):  91 dB
Distortion:  less than 0,75% (52 Hz - 25 kHz)
Phase Response:  System behaves substantially as a frequency-independent time delay
Dispersion:  90 degrees conical
Crossover Frequency:  2 kHz
Crossover Type:  2nd order LF, 1st order HF Hard-Wired, low-loss, Positive acoustic polarity
Frequency Response (±3 dB):  52 Hz - 25 kHz
Drive Unit Type:  6,5 inch, 1667 Dual Concentric
Cabinet Internal Volume:  10 litres
Cabinet Material:  30,6 mm MDF front baffle;  15 mm high density particle board lined with TF-1 acoustic wadding
Cabinet Finish:  High quality vinyl finish. Velti shadow grey soft-texture finish baffle
Grille:  Single piece, black acoustically transparent material over a rigid frame
Dimensions (H x W x D):  345 x 230 x 223 mm (13,6" x 9,1" x 8,8")

Weight (net):  5,7 kg (12,6 lb)

Tannoy NFT and DMT Series II

Of all loudspeaker manufacturers in the world Tannoy has the greatest number of loudspeakers in use for sound production in british and European studios. An enormous number of successful recordings have been produced on Tannoy Monitoring since the first introduction of the Tannoy Dual Concentric loudspeaker in the 1950s.
The Dual Concentric design philosophy is world known for its precise stereo imagery and for the ease of finding sounds within a sound stage. The presentation of the sound image makes long production sessions much less fatiguing than with other monitoring systems because the brain does not have to work as haard correcting for acoustic anomalies in the time and frequency domains.
During the lastest years great strides have been made in the analytical understanding of loudspeakers. In parallel, the explosion of computing power available to physicists, electronics, acoustics and mechanical engineers has resulted in loudspeaker design techniques advancing at a faster rate than ever before.
Tannoy's massive experience and its highly innovative and skilled design engineering team, has placed the company in a most enviable position. This is reflected for the 1990s in what is a frankly exceptional - revolutionary rather than evolutionary - range of studio monitors.

A loudspeaker design naturally splits into various parts; lower frequency, higher frequency, crosover network and cabinet. The design of these parts cannot take place in isolation as they are all interdependent.
Traditionally, Tannoy has used a single magnet driving both low frequency and high frequency magnetic air gaps. This gives a very compact drive unit with acoustic source alignment. In the new designs of Dual Concentric units the HF unit and LF unit now have separate, dedicated magnet systems. This is because the HF waveguide design has become so sophisticated it cannot be made by processes suitable for magnetic flux carrying materials.

High Frequency Drive Unit
The HF waveguide can therefore no longer be an integral part of the LF magnet system. In splitting the magnet systems an extra degree of design freedom allows for very high precision casting and moulding processes together with accurate self centring diaphragm assemblies. Both production processing and in-field repairs can then guarantee consistent performance.
A new design of waveguide has been arrived at by making extensive use of CAD. We call it waveguide because there is a direct analogy with electromagnetic radiation in that characteristicimpedances must be carefully matched without introducing standing waves. The Tannoy HF waveguide matches the acoustic source impedance at the HF diaphragm into the listening environment.
The waveguide shapes the wavefront as it travels down from the diaphragm ensuring that path lengths are equal, that the wavefront is perpendicular to the fixed surfaces and that wavefront is spherical. Only small errors of fractions of a millimetre can upset this condition and cause phase shifts in the waveguide. Accuracy of design and production are essential in achieving the correct conditions within the waveguide.
In this way, transvers modes are minimised and high frequency dispersion maximised. Wavefront shaping begins at the diaphragm surface and, because the compression ratio can be kept relatively low with this design, the distortions due to air non-linearities are minimised. A hyperbolic flare has been chosen for optimum low frequency performance at the crossover point.
The HF diaphragm is a new design. The waveguide requires total piston movement over the operating range since any breakup modes within the diaphragm will result in phase-shifted components at the start of the waveguide propagation. A rigid piston diaphragm operating to above 25 kHz is made from aluminium and magnesium alloy.
A special machine has been designed and built toform and extrude the diaphragm with a 2 mm skirt. This configuration gives the most rigid diaphragm and ensures reliable handling for production and field servicing.  Aluminium is notoriously difficult for adhesive working and we put the diaphragm through a special alkaline etching process followed immediately by the build process to ensure relibility.
The diaphragm assembly is suspended by a precision moulded, inert nitrile rubber surround. This has been designed and tooled using high-precision, numerically controlled machining techniques. Its very narrow roll eliminates resonances below 25 kHz and provides a very stable and consistent mounting. The roll form ensures high excursions can take place if necessary yet provides a fatigue-indestructible assembly.
The diaphragm is driven by a new design of voice coil assembly.high temperature polymide-insulated, copper-clad aluminium, rectangular ribbon conductor is chemically bonded onto a glass-fibre former fitting onto the outside of the HF diaphragm skirt. This gives a high temperature (polyimide), very low mass (aluminium wire, glass fibre), high rigidity (rectangular wire, former to outside of diaphragm skirt), high reliability (nitrile suspension, copper clad aluminium) assembly.
Leadout materials are crucial for HF units and our new design incorporates beryllium copper flat strip to eliminate fatigue breakages and prevent fusing on unsupported areas under overload conditions.
tehHF diaphragm assembly is factory mounted onto the waveguide by a newly designed high-precision productionprocess. This ensures that the spacing between diaphragm and waveguide is consistent and the whole assembly self centres under all conditions when placed on the magnet assembly. Field replacement is therefore extremely simple and no difficult soldering or centring techniques are required.
The HF magnet assembly uses an anisotropic barium ferrite magnet for maximum energy product (BHMAX), a newly developed magnetic air gap coolant for lowest viscosity and highest thermal rating, a copper flux stabilising ring around the pole piece to minimise voice coil inductance and control the highest frequency energy, and a cavity damper to control the rear cavity compliance beneath the diaphragm.
Physically, the whole HF assembly self centre mounts onto the back of the low frequency assembly using three screws carrying with it the self-centring HF diaphragm. Production and field service is therefore virtually foolproof and extremely consistent.

Low Frequency Drive Unit
The heart of the LF unit is the motor system comprising the magnet and voice coil. Computer optimisation of the low frequency magnet gives linear flux linking to the voice coil using low carbon steel pole pieces and an anisotroipc barium ferrite magnet. A specially designed pur copper stabilising ring fits over the outer pole where it reduces eddy current lossles, lowers midrange distortion and increases thermal cooling by a massive 50%. In this way both power compression and reliability are considerably enhanced.
The choice of magnet operating point parameters, air gap flux strength, voice coil details, moving mass, dynamic compliance and drive unit radiating area presents a very complex mathematical problem where the solutions can take many different forms. The optimum solution depends on the intended use of the drive unit in particular cabinet systems and the expectations of the and user.
This is the skill or "black-art." element of loudspeaker design. Reaching the correct answers is much easier if computers can be called on to assist with solving the equations. Tannoy has an in-house software facility producing purpose-written programs to solve these equations in both numerical and graphic terms.
The LF voice coil uses polyimide insulated, chemically bonded rectangular section copper wire wound onto a high temperature aluminium former for robustness and reliability in thermal conductivity. A specially designed heat barrier wound onto the end of the former protects the adhesive bond to the LF cone from excessive temperatures.
Robust, fatigue-free leadout braid connects to a polarised, vibration-proof, high-current ternminal barrier connector.
The shape and materials from which the cone pistons are made reflect the optimisation of drive unit to cabinet size and end use. System 6, 8, 10 and 12 LF units use a CNC precision injection moulded polypropylene cone. System 15 and 215 have a traditional pulp cone with apex treatment and air-dry felting process. For cones of this size there is no better alternative when mass, rigidity, piston movement and natural upper roll-off charactereistics are considered.
All LF drivers have their cones terminated by nitrile rubber, high-compliance surrounds. The characteristic cone termination impedance is matched by the surround material independently of the required suspension compliance. The unit system compliance is provided by the rear suspension where the best degree of mechanical control can be provided.
In all cases the shape of the LF cone has been calculated to match the HF hyperbolic waveguide ensuring the wavefront remains spherical and perpendicular to the cone surface throughout the propagation.
Brand new pressure dic-cast chassis have been tooled for the new range drawing extensively on new thinking for LF drive units. It is important to eliminate trapped air cavities as these can provide unwanted compliances, upset the mechanical Q design requirements and cause unwanted acousyic colourations because of Helmholtz resonances and reflections from the chassis surfaces smearing the energy/time response.
The new castings have a very open construction with vented rear suspension features to eliminate low Q cavites, improve thermal cooling and prevent major reflections. Rigidity has been optimised in the axial plane to complement the cabinet philosophy while the front surface profile has been designed to prevent diffraction at the cabinet surface.
The five sizes of chassis each have purpose-designed trim rings to blend the HF wavefront into the cabinet. This feature has been shown in our research to be the biggest single factor in providing smooth HF radiation in Dual Concentrics (assuming, of course, that the HF unit is well designed in the first instance).

Crossover Network
There are two philosophies in designing loudspeaker crossover networks; the minimal and the conjugate. The minimal approch requires that the drive units are inherently well behaved and that each section, LF and HF, require minimum equalisation to achieve a smooth flat amplitude response.  The conjugate approach requires that the drive units are accepted as they are but are well characterised. The crossover network is then calculated to provide inherent equalisation to ensure a smooth amplitude response.
The two approaches differ in design emphasis. The minimalist designer concentrates on the drive unit design in controlling the final performance, while the conjugate designer concentrates on complex electronic analysis of networks to achieve the same measured result.
Tannoy has always followed the minimalist philosophy as far as possible. This is because listening trials with loudspeakers always point to those with the least crossover design complexity as being more realistic, involoving and convincing in their reproduction. However, this makes the drive unit designer's task more difficult as it is much harder to control performance through the mechanical parameters than through the electrical crossover components. It also puts much greater constraints on production repeatability of processes and test methods. However, overall the result in our belief is a better loudspeaker.
In crossover networks it is vital to use the very highest quality components for series connected elements. Resin impregnated, air cored inductors,  very high grade film capacitors and DMT cpacitors are needed for best sound quality. Internal wiring has an effect and in the new Tannoy Monitor series high-purity, long-grain crystal, low-oxygen copper wiring is used.
DMT research showed when a capacitor was encapsulated in a vibration absorbing material it changed both the sound texture and dynamics. Every variable of capacitor construction was investigated and custom capacitors designed optimised for sonic performance and with high-purity copper leads.
Vibrations inside the cabinet can effect the performance of inductor coils.  Tests show that reducing the vibrations reaching the inductors can heve a marked effect on system bass end resolution. Coils vacuum impregnated with resin are chosen to reduce the effects of vibration.
Air cored inductors radiate a significantmagnetic field which affects nearby components. Similary inductors can be affected by a driver's magnetic radiation. For these reasons it was decided to produce a split crossover with the inductors mounted on the cabinet cross-brace away from the driver magnets and other crossover components. The sound quality improvements more than justify additional manufacturing costs.
The crossover networks in the new series use simple low order slopes 96 dB and 12 dB per octave0 mainly to control the power distribution and balance. The components are of very high quality with Hard-Wiring (no printed circuit boards) and mounted on the back of the terminal panel at the rear of the cabinet. There is no need to remove drive units to gain access.

Terminal Panel
The terminal panel is a new design especially tooled for the new series. The option of conventional wiring or Bi-Wiring is available by a unique high quality gold plated sliding mechanism with large diameter robust terminals. The benefits of Bi-Wiring for monitoring are easily heard where the extra pair of cables can be accomodated.
The new terminal panel on System 12, 15 and 215 also includes a sliding link which provides adjustment of the high frequencies on a shelving basis from 2 kHz to 25 kHz with plus or minus 1,5 dB adjustment. The systems are calibrated in production to be flat to within specification when set to the flat adjustment position. All terminals and contacts are gold plated to eliminate contact potentials and oxidation. The terminal panel carries the crossover mounting and can be removed from the outside of the cabinet.

With well designed drive units the majority of the aberrations in the loudspeaker system are due to the cabinet. Most of the irregularities heard and measured in the higher frequency areas are due to diffractions and reflections caused by the cabinet boundaries.
The amount of acoustic energy transfer that the drive units can lauch into the listener's space is dependent on rigid mounting since action and reaction are equal and opposite. When the displacements of the HF diaphragm are calculated for sound levels in the region of 80 to 100 dB sound pressure level, the movements involved are extremely small, often fractions of a thousandth of an inch. However tiny these displacements are they carry information that is required for accuracy in the resulting sound stage.
It stands to reason therefore that the drive unit must be held in space very rigidly so that the HF diaphragm displacements are not themselves modified by the LF displacements which have inherently much more energy associated with them. The obvius method of doing this is to mount the drive unit rigidly into a rigidly made cabinet. But in doing this, a new set of problems appears.
Rigid systems are characterised by high stiffness. The natural resonance of the high cabinet stiffness - achieved by, say, cross bracing and bracing the driver to the rear of the cabinet - and drive unit mass, brings the natural resonance frequency into the audio band, typically around 100 to 200 Hz. This produces an objectionable colouration which can be mitigated in aural terms by some listeners by the increase in "speed" and HF clarity provided by the rigid system. However, it is notan ideal solution.
In its new Monitors Tannoy has taken a radical approach pointed to by measured parameter research into cabinet systems coupled with listening tests. The Tannoy cabinets are stiff but with a high level of internal damping. A very complex internal bracing structure in each of the cabinets allows the drive unit to be held rigidly but also to be able to dump its resonant or reactive energy into the lossy couplings of the cabinet. The joints between the driver and the bracing structure have a special compound which is very stiff at high frequencies but will absorb energy in the critical colouration areas.
The cabinet panel are made from MDF but are laminated an each side to increase their stiffness. However, the layer of adhesive between MDF and laminate acts as a lossy energy absorbent medium.
The cabinet panels are coupled into each other through hardwood rails at the corners, the dissimilar materials providing further modification for any inherent reactive energy components in the cabinet caused by the drive unit.
The rigid crossbracing structure is floated inside the cabinet using an adhesive system which will absorb the redundant energy from the rear of the drive unit chassis and maagnet system and yet provide the stiffness needed to allow very fine HF resolutions from the HF unit diaphragm
In addition to the cabinet construction he volume and port tuning have been carefully calculated to give the best set of parameters for monitoring loudspeakers.
There is a fundamental relationship in loudspeakers between efficiency, cabinet volume and low frequency performance given that minimal amplitude variations can be tolerated (as in monitoring situations). The set of parameters that are arrived at as a solution are inevitably a compromise and the skill of Tannoy has always been shown to be getting these particular parameters correct for the application.

Cabinet Finish and Grille

The cabinet is finished in a high impact resistant, texture paint. The grille is held by plastic split dowels located in the grille frame which fit into rubber lined holes in the front panel.