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





JBL4425 monitor loudspeakers

Bi-Radial Studio Monitor

The success of the models 4430 and 4435 Bi-radial studio monitor loudspeakers has prompted JBL to introduce a smaller model based on the same principles for use in smaller studios and for a variety of demanding audio production applications.

As in the case of the larger Bi-Radial monitors, the 4425 maintains a 100-degree-by-100-degree coverage pattern from its crossover frequency (1200 Hz) up to 16 kHz. Smooth power response is ensured from the lowest frequencies up to 1200 Hz, and flat power response is maintained above that frequency. At the same time, axial response is remarkably smooth, and the combination of controlled power and axial response ensures that the reflected sound field in the control room will be free of coloration. The model 4425 also addresses the requirement for accurate stereophonic imaging. The mirror imaged pair creates absolutely symmetrical sound fields, and this is the essential requirement for precise imaging. There is no lobbing for normal off-axis listening positions in the horizontal plane, and vertical lobbing is minimized over the preferred listening arc.

The model 4425 can handle program power inputs of 200 watts, more than enough to accommodate the high acoustical levels demanded in critical listening to today's digital recordings.

 

High-Frequency Horn and Driver

The BI-Radial horn used in the model 4425 is a scaled down version of the model 2344 horn used in the 4430 and 4435 monitor loudspeakers. It is made of high-impact structural foam and is acoustically inert. The high-frequency compression driver is a completely new design making use of a computer-machined phasing plug. Tolerances are held to a high degree, and unit-to-unit variation is small. The disphragm assembly is JBL's unique titanium design, with its advantages of extended frequency response relative freedom from mechanical fatigue, and high acoustical output capability. A copper shorting ring plated on the pole piece controls high-frequency impedance and improves high-frequency response.

As is the case with the larger Bi-Radial monitors, the 4425 system maintains precisely aligned phase response over a forty-gegree wide arc in the horizontal plane. The preferred listening arc in the vertical plane is between zero (on-axis) and ten degrees up.

 

Low-Frequency Transducer

A newly designed driver, the model 2214H, is used in the 4425 monitor loudspeaker. This transducer incorporates JBL's symmetrical field geometry (SFG) magnet structure for low distortion. The 76 mm (3-in) voice coil is made of edge-wound copper ribbon wire for highest sensitivity and power handling. The inner suspension of this transducer has been designed to exhibit a progressive increase in restoring force with increasing displacement. This controls dynamic offset for low-frequency, large excursion signals, and results in reduced distortion at low frequencies. A composite coating on the cone optimizes both damping and stiffness, resulting in smoother response and lower distortion.

 


Frequency Dividing Network

In addition to the normal function of frequency division, the network in the 4425 provides power response compensation for the high-frequency drier. Two controls allow the user to contour both mid and high frequencies to match various room characteristics. While the network slopes are 12 dB/octave, the combination of inherent roll-off characteristics in both high- and low-frequency components of the system with the electrical characteristics yields quite rapid transitions in the crossover frequency. Network components are of the most rugged, low-loss type, and high-quality bypass capacitors are placed in parallel with the larger capacitors in the signal path for increased linearity.

 


Specifications

Frequency Response:  40 Hz - 16,000 kHz ±3 dB

Sensitivity:  91 dB SPL

Efficiency:  0,8%

Dispersion Angle

Horizontal :  100° (+10°; -30°)

Vertical :  100° (+0°, -30°)

Impedance:  8  nominal

Max. Power Input:  200 W

Continuous Sound Pressure Level:  114 dB

Crossover Frequency:  1,200 Hz

Driver Complement:

Low Frequency :  2214H

Compression Driver :  2416H

Horn :  2342

Enclosure Volume:  53,8 l (1,9 cu. Ft.)

Resonance Frequency:  34 Hz

Dimensions:  406 x 635 x 311 mm (375 mm deep w/horn)

Weight Net:  26 kg (57 lbs)


 

Acoustic Research AR-28BX speakers


Specifications:

System Type:  Floor standing acoustic suspension 2-way system with drive units in a vertical array

Drive Units:

LF :  250 mm (10") acoustic suspension woofer

HF :  25 mm (1") liquid cooled high range driver

Voltage Sensitivity:  2,83 volts produces 89 dB SPL at 1 meter on axis

Efficiency:  1 watt produces 89 dB SPL at 1 meter on axis

Power Requirement:  10 watts per channel minimum

Power Handling Ability:  May be used with amplifiers rated at up to 100 watts per channel

System Frequency Response: -3 dB points at 42 Hz and at 22,000 Hz

System Low Frequency Performance:  -3 dB at 42 Hz with an effective Q at resonance of 74

Impedance:  8  nominal; 5  minimum point

Crossover Network: 

Both woofer and high range have second order electrical networks High range has a second order electrical network

Crossover Frequency:  1800 Hz

Cabinet Internal Volume:  35 liters (1,25 cu lt)

Cabinet Finish:  Walnut grain vinyl veneer

Cabinet Dimensions (H x W D):  689 x 330 x 257 mm (27-7/8" x 13" x 10-1/8")

Weight: 15,9 kg ( 35 lbs) 1 speaker net


 

Acoustic Research AR-8BX speakers


 

Specifications:

System Type:  Bookshelf acoustic suspension 2-way system with drive units in a vertical array

Drive Units:

LF :  150 mm (6") acoustic suspension woofer

HF :  25 mm (1") liquid cooled high range driver

Voltage Sensitivity:  2,83 volts produces 87 dB SPL at 1 m on axis

Efficiency:  1 watt produces 87 dB SPL at 1 m on axis

Power Requirement:  10 watts per channel minimum

Power Handling Ability:  May be used with amplifiers rated at up to 75 watts per channel

System Frequency Response: -3 dB points at 62 Hz and at 25,000 Hz

System Low Frequency Performance:  -3 dB at 62 Hz with an effective Q at resonance of 88

Impedance:  8  nominal; 5,6  minimum point

Crossover Network: 

Woofer has first order electrical networks plus mechanical slope to give a total of 18 dB/octave

High range has a second order electrical network

Crossover Frequency:  4000 Hz

Cabinet Internal Volume:  9,8 liters (35 cu lt)

Cabinet Finish:  Walnut grain vinyl veneer

Cabinet Dimensions (H x W D):  394 x 244 x 187 mm

Weight: 6,6 kg ( 14,5 lbs) 1 speaker net


 

Akai M-10 tape deck

This Three Motors Auto-Reverse Solid State Stereo Tape Recorder offers you perfect stereo hi-fi tape recording and automatic reverse playback with concert hall sound.

 

Outstanding Features

4-track stereo/monaural recording and playback

3 speed  (7-1/2; 3-3/4; and 1-7/8 ips)

3 heads - Erase, Playback/Record and bias heads - Crossfield Head System

3 motors -  A hysteresis synchronous 3-speed motor for capstan drive; Two 6-pole eddy current out rotor motors for supply and take-up reel drive.

Wide Cross-Field Frequency Response

40 W music power solid state amplifier with two integrated circuits

Sensing tape continuous reverse (Auto reverse)

Manual reverse

Shield type head for high Signal-to-Noise Ratio

Sound on sound

Automatic stop/shut off; Instant stop control with start button

Automatic pinch wheel release, Automatic lever release

Two lever system ensures dependable and durable operation

Track selector for simple operation between stereo and monaural

Tape lifter in fast forward and rewind operation

100 kHz biased for FM multiplex recording

Tape speed equalizer

Treble and Bass controls

DIN jack with selector switch for High Low input

Two stereo headphone jacks

4-digit index counter with reset button,

Two large VU meters

Vertical or horizontal operation

Fine oil finished wooden cabinet or vinyl leather wooden cabinet

Universal voltage selector ( from 100 V to 240 V, 50/60 Hz)

 

Cross-Field Head

On conventional recorders the signal and bias are applied to the same recording head. Therefore the frequencies recorded, especially the high frequency component of the recorded signal tend to be attenuated or erased by the effect of the bias field.

On the exclusive Akai Cross0Field Head which was developed by Akai for practical use the signal and bias heads are mounted in opposition with their centres slightly off. As the recorded signal is entirely unaffected by the prevailing effect of the entire frequency spectrum with maximum fidelity.

 

Sensing Tape Continuous Reverse

Automatic reverse with metallic sensing tape is used for playback only. Reverse operation will occur when metalic sensing tape on prerecorded tape makes contact with the Sensing PIN. Put metallic sensing tape as the desired reverse point on shiny side of the prerecorded tape and another metallic sensing tape at the desired reverse point  on dull side of the prerecorded tape. So, the M-10 will give continuous playback in both directions between two points

 


Specifications

Tape Speed: 7-1/2; 3-3/4; and 1-7/8 ips

Wow and Flutter

At 7-1/2 ips :  less than 0,08% rms

At 3-3/4 ips :  less than 0,12% rms

At 1-7/8 ips :  less than 0,20% rms

Frequency Response

At 7-1/2 ips :  30 - 26,000 Hz

At 3-3/4 ips :  30 - 19,000 Hz

At 1-7/8 ips :  30 - 9,000 Hz

Distortion: within 2% 1,000 Hz 0VU

Signal-to-Noise Ratio :  better than 50 dB

Input Level

Mic :  better than 0,5 mV

Line :  better than 50 mV

DIN :  better than 5 mV (Low); 50 mV (high)

Power Output: 

15 W maximum per each channel at Undistorted Power, total 30 W

20 W maximum per each channel at Music Power, total 40 W

Equalization:  Correct equalization for playback of tapes recorded to the NAB curve

Recording Bias Frequency:  100 kHz

Recording Level Indicator:  2 VU meters

Recording System:  4-track stereo / monarual, Cross-Field bias system

Fast Forward and Rewind Time:  75 seconds using 1,200 foot tape at 50 Hz  (60 seconds at 60 Hz)

Recording Capacity: 

8 hours monaural recording at 1-7/8 ips (1,200 foot tape)

4 hours stereo recording a 1-7/8 ips

Max. Reel Size:  7" reel

Head: 3 heads - Erase, Rec/Pb, Bias

Motor:  3 motors- hysteresis synchronous 3-speed motor ; Two 6-pole eddy current out rotor motors

Speaker:  2 - 4" x 6" speakers

Semiconductors:  22 Transistors; 2 ICs

Power Requirements:  AC 100 to 240 V 50/60 Hz

Power Consumption:  165 W

Dimensions:  474 x 350 x 242 mm (18-3/4" x 13-3/4" x 9-1/2")

Weight:  22 kg (48,4 lbs)


 

Akai X-330D reel-to reel

Stereo Tape Deck with Multi-Purpose Program Minder

The X-330D enables to enjoy different music for 24 hours, in addition to selection and repeating your favourite tune forever.

 


All features:

Program Minder - Automatic Continuous Reverse

Sensing tape continuous reverse. Manual reverse

Cross-field head

3 motors -  A hysteresis synchronous 3-speed motor for capstan drive; Two 6-pole eddy current out rotor motors for supply and take-up reel drive.

3-speed  (7-1/2; 3-3/4; and 1-7/8 ips)

Magnetic brake with tach generator (stoppage occurs within 3seconds from F.F/RWD condition (10-1/2"  reel)

Up to 10-1/2 reel acceptable and back tension control

4-track stereo/monaural recording/playback. For playback the X-330D requires an external power amplifier and speakers

4 heads - Erase, Playback, Record and bias heads

All silicon transistorized pre-amplifier

12 hours continuous hi-fi stereo recording capacity at 1-7/8 ips (7,200 foot tape)

Shield type head for high Signal-to-Noise Ratio

Tape lifter in fast forward and rewind operation

Track selector for simple selection between stereo and monaural

Automatic stop/shut off, Automatic pinch wheel release

Sound on sound, sound with sound, sound over sound

100 kHz biased for FM multiplex recording

Remote controllable, AC outlet with automatic shut off switch

Standard/ low noise tape selector

Tape cleaner, 4-digit index counter with reset button, VU meters

Fine oil finished wooden cabinet

Universal voltage selector ( from 100 V to 240 V, 50/60 Hz)