Beomaster 901, by 1977/78 was Bang & Olufsen’s simplest receiver. However, no compromises were made on quality. The tuner section covered Long, Medium and FM wavebands with a very high standard of reception quality.
Tuning was by ways of a slider which moved smoothly along a clearly marked scale. An illuminated indicator and AFC (Automatic Frequency Control) circuit helped to make tuning easy and accurate. The MONO control button disconnected the built-in stereo decoder when correct stereo reception was impaired by bad weather conditions or other interference.
Beomaster 901’s large tuning scale had tuning facilities for FM, Long and Medium wave stations. The tuning slider had small thumbwheels to aid fine tuning. AFC locked the receiver to the desired station
The stereo amplifier had a powerful output of 2 x 20 watts RMS and special Darlington-coupled transistors in the output stages kept distortion to a minimum – less than 0,3% at full power. There were connections for two pairs of loudspeakers and a pair of headphones. Sockets were also provided for the connection of a tape recorder, a record-player and AM and FM aerials. Easy-to-use sliders controlled volume, balance, bass and treble and there were slim push-buttons for selecting waveband or tape or record input.
FM room aerial
In order to receive FM programmes, an FM aerial must be connected to the Beomaster 1001. Within a certain radius of the transmitter you could use the Bang & Olufsen FM room aerial, type 8902010. This aerial was easily fitted and the telescopic elements could be pulled out and positioned favourably.
Beomaster 901 could be made up as part of the Beosystem 901 including the the Beogram 1102 record player, Beocord 1101 cassette deck and 2 Beovox Uni-Phase S25 or P30 loudspeakers.
The amplifier section of this receiver had outstanding technical data: harmonic distortion was less than 0.1% at maximum power output and 0.06% at 50 mW. Frequency range was 20-30.000 Hz and effective bandwidth 10-35.000 Hz.
Frequency correction facilities were the LOW filter which reduced rumble on records (12 dB per octave at 80 Hz) and the HI filter which damped hiss (12 dB per octave at 4000 Hz). With the LOUDNESS control you could switch between objective and subjective linear reproductions. Beomaster 4000 had facilities for stereo and ambio reproduction. There were sockets for a record player and two tape-recorders, one allowing A\B monitoring. The headphone connection was placed on the receiver’s front. All inputs could be adjusted to give equal volume from all programme sources. The FM section had six pre-set stations. A light indicator assisted accurate tuning and an illuminated meter indicated the strength of a station. Field effect transistors, ceramic filters and integrated circuits were used.
When combined with a built-in record deck, the music centre was known as Beocenter 3500.
Receivers and amplifiers with the ambio function were products which, apart from stereo, could also reproduce the ambience or sound information of a room. Ambient information was included on most stereo vinyl recordings but could not be reproduced by a sound system with two loudspeakers or an ordinary stereo amplifier. Bang & Olufsen systems with the ambio function had facilities which electronically subtracted the difference signal (i.e. the difference between left and right channels) which contained ambient information. This information was fed into two extra loudspeakers which were placed as side speakers in a room. Ambiophony was an extension of stereo reproduction and enhanced the sense of realism. It could be used with nearly all stereo programme materials.
“Ambio is an extension of the type of sound reproduction known today as stereo.
Ambio is reproduced through four loudspeakers – two more than required for stereo.
Ambio is sensed as being more spatial and acoustically more life-like than conventional stereo. The sound picture has greater depth because you get the added feeling of being present of the concert hall, listening to the actual performance. Ambio is based on the principle that in the concert hall you not only receive sound impressions directly from the performing group, you also get reflections from the wall and ceiling. The spatial sensation is instrumental in providing the auditory experience and even a two-speaker stereo system will not bring it out fully. And you cannot accomplish the effect by connecting additional speakers to a conventional stereo amplifier because you still have the same left and right front signals merely distributed to more speakers.
In the Beomaster 4000 the left and right channels are subtracted from each other electronically and the resulting difference signal contains a certain amount of spatial information which is fed to the two new side speakers.
Many existing stereo records, FM broadcasts and tape recordings contain this spatial effect to a greater or lesser extent. In a concert hall, room acoustics will be recorded together with the actual programme material, appearing as time-delayed signals in both left and right channels. Recordings made in a strongly damped studio contain few time-delayed signals and the spatial sensation will therefore depend on how the producer mixed the sounds from the various instruments, perhaps adding acoustical effects by electronic means.
Multi-channel records such as SQ records, which are intended for use in a four-channel matrix system in order to bring out the sound effects , can be played successfully through the Beomaster 4000.
A good quality stereo turntable will provide ambio reproduction of both stereo and SQ records through your Beomaster 4000″
Beocord 900 was the simplest of Bang & Olufsen’s range of cassette-recorders.
Your only task was to choose the type of tape to put in: Cr02 or normal. Beocord 900 had large easy-to-read VU meters and recording controls were separate for left and right channels. There was a socket for a microphone and a push-button for mono recordings.
Tape-heads were made of Super Permalloy, a hard and extremely durable material which ensures a long useful lifetime. Wow and flutter was less than 0.28% (JIS method). Signal-to-noise ratio was better than 50 dB with chromium dioxide tapes.
The Beovox 1001 was a very similar loudspeaker to the Beovox 1200 (Beosystem 1200 version), but to match the new black finish of the Beomaster 1001 the metal grille was made black.
Sadly, the designers did not take the opportunity to fit a dome tweeter (as fitted to every other Beovox loudspeaker of the period), so the original (and outmoded) 2.5” cone type remained. As the Beomaster 1001 offered the facility of Ambiophonic stereo, 4 Beovox 1001s could be connected, and the model was also suggested for use with the Beogram 1500-1 record player.
Beovox 5700 high fidelity loudspeaker was of studio monitor quality with minimum distortion and maximum power handling capacity.
The loudspeaker was designed to handle 60 watts RMS or 100 watts music power with a distortion of less than 1% over the entire frequency range of 25-20,000 Hz. In order to produce these qualities, Beovox 5700 was fitted with a 25cm ABR (Auxiliary Bass Radiator) unit and a 25cm bass unit which together produced a clear powerful bass reproduction. Its mid-range dome was 5,5cm in diameter and its dome tweeter was 2cm. Dispersion was 160 degrees.
Trumpet stand
Owing to its size, Beovox 5700 could be preferably used as floor-standing speakers. For this reason Bang & Olufsen designed the trumpet stand, type 8906007. This stand had a top on which the loudspeaker could be placed, not only elegantly, but also practically so that a good sound dispersion could be achieved.
Beovox 5700 could be used with Beosystem 4000, an uncompromising stereo system, top of its range in the mid-1970s.
Beovox 3702 Type 6244 was a high-fidelity pressure chamber loudspeaker with high specifications and intermediate power handling capacity.
It was a three-unit loudspeaker system, which means that the entire frequency range was covered by three separate units: bass, mid-range and tweeter or treble unit. Its frequency range was 40-20 000 Hz and it had a power handling capacity of up to 40 watts RMS or 75 watts music. Distortion was lower than 1% over the entire range.
The bass unit had a 20cm diameter speaker, the mid-range 8cm, the tweeter 2,5cm. Beovox 3702 met DIN high-fidelity norms.
Beovox 5700 high fidelity loudspeaker was of studio monitor quality with minimum distortion and maximum power handling capacity.
The loudspeaker was designed to handle 60 watts RMS or 100 watts music power with a distortion of less than 1% over the entire frequency range of 25-20,000 Hz. In order to produce these qualities, Beovox 5700 was fitted with a 25cm ABR (Auxiliary Bass Radiator) unit and a 25cm bass unit which together produced a clear powerful bass reproduction. Its mid-range dome was 5,5cm in diameter and its dome tweeter was 2cm. Dispersion was 160 degrees.
Trumpet stand
Owing to its size, Beovox 5700 could be preferably used as floor-standing speakers. For this reason Bang & Olufsen designed the trumpet stand, type 8906007. This stand had a top on which the loudspeaker could be placed, not only elegantly, but also practically so that a good sound dispersion could be achieved.
Beovox 5700 could be used with Beosystem 4000, an uncompromising stereo system, top of its range in the mid-1970s.
