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





B&W DM 4


The DM4 was released at the International Audio Fair, October 1972 in the firm belief that the design aims have been achieved, and from extensive comparasion with other systems currently available we believe the DM4 may well out-perform competitive loudspeaker systems of three times the size and twice the price.
The DM4 is a 3-unit loudspeaker comprising highly developed Bextrene coned Bass/Mid-range unit (designed and produced in our own factory), type HF1300 Mk II lower high frequency unit and a 19 mm plastic domed upper high frequency unit. Third oreder Butterworth filters are used throughout and the crossover unit closely integrates the optimum performance of the three units to give an exceptionally smooth response extending from 30 Hz to above 25 kHz.
The DM4 monitor is individually pen tested in anechoic chamber and supplied with automatic pen plot showing frequency response.

Stand-mount/Bookshelf loudspeaker system
Product Summary
The DM4 is a three-unit monitor loudspeaker system that produces high quality results from an incredibly small cabinet, making it perfect for home or small studio where space is at a premium. Acoustic loading is by a very dense, critically damped enclosure with a small controlling vent to optimise the response between 60 and 120 Hz. This also produces considerably reduction in cone excursion from 30 to 60 Hz.

Technical highlights
The bass/midrange units come in a critically contoured Bextrene cone configuration. This is laminated in a highly resistant damping compound that ensures linear frequency response to at least an octave above crossover.
The upper mid frequency unit offers wide dispersion from a virtual point source and a 19mm low diaphragm mass plastic dome unit extends frequency response to above 25 kHz
Cabinet
Constructed of 19 mm 750 density chipboard throughout with inside balancing  veneers. All battens pinned and glued , Choice of teak, Walnut or Rosewood veneers plus a satin white finish.

Specifications
Drive Units:
High Frequency :  1 x 19 mm voice coil
Mid Frequency :  1 x 34 mm mid/high frequency unit
Low Frequency :  1 x 164 mm bass/midrange unit
Frequency Response30 Hz 25 kHz. Better than ± 2dB,
Sensitivity4,8 watts into nominal impedance (i.e 6.2 volts) for a sound pressure of 95 dB pink noise at 1 metre
Nominal Impedance8 Ω
Power Handling:  10 W – 30 W
Dimensions (H x W x D):  531 x 255 x 255 mm (21" x 10" x 10")
Weight:  11,1 kg (24 lb 6 oz)
Finish
Standard:  teak or walnut
Special:  satin white or selected veneersof rosewood or black ash

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