B&W electronics 70, User Instruction Handbook

Page 1: ...Model 70 electronics B W WORTHING ENGLAND T e l W o r t h i n g 6 6 8 3 0 a significant advance on existing loudspeaker systems...

Page 2: ...S Page Assembly Instructions l Mains Voltages 3 Audio Connections 4 Position of Speakers 5 Operation Instructions 6 Service and Guarantee 7 Design and Development Story 8 Response Curves and Measureme...

Page 3: ...artons and remove the accessory bag from the underside of the main cabinet Unpack the electrostatic unit from the smaller carton We suggest you retain the special Polystyrene pack from the smaller car...

Page 4: ...leaving our factory A small red label is attached to the power supply panel rear main cabinet giving this indication Adjusted for European 200 240 volts 0 HzJAC Adjusted for American 110 125 volts 60...

Page 5: ...e connections to the three pin plug are illustrated in Fig 3 below An outer metal screen is built in to the electrostatic unit for safety purposes It is important therefore to ensure that three core c...

Page 6: ...ge is not as critical as with many conventional systems It will also be found that the stereo image is preserved over a wide listening angle The suggested placing for a pair of Model 70 reproducers is...

Page 7: ...on the reflective nature of the walls and furnishings behind the loudspeaker there will be a slight increase in sound level above 400 Hz with the electrostatic operating in this condition If it is de...

Page 8: ...tion pattern especially within the vitally important mid frequency region of 400 Hz to 5 kHz aiming towards exploring the advantages of a distribution pattern approximating to spherical 2 A mid freque...

Page 9: ...m should be split The precise division of frequencies to be handled by the various units and reasons for the crossover frequency chosen will be discussed later in this release but initially let us sur...

Page 10: ...y unmanageable quality both in terms of size and adequate screening to provide freedom from T V I For these reasons the Ionic method was dismissed and attention focused on Electrostatic and Moving coi...

Page 11: ...sured showed this to be two of their weaker features DETAILED DISCUSSION ON BASIC UNITS FORMING THE COMPLETED MODEL 70 SYSTEM Mid High Frequency Electrostatic Unit It is not the intention of this rele...

Page 12: ...n of the experimental plates illustrated were arranged in every imaginable combination As the majority of these units were individually produced this part of the development took some two months Whils...

Page 13: ...Parallel with the work which was being carried out on shape size and configuration of the Electrostatic unit the possibility of providing a curved free standing horizontal radiator became an increasin...

Page 14: ...14 FIG 5 General polar diagram of Model 70 illustrating wide and even horizontal distribution FIG 6 Horizontal distribution Model 70 at 15 kHz...

Page 15: ...athmatically that the ambient air provided 85 of the load on the diaphragm and this fact was confirmed empherically throughout the development We instance the original XP prototype which showed a drop...

Page 16: ...pe than this short article to deal with even a reasonable proportion of the subject matter The writer does however feel some satisfaction in setting out in print certain basic principles which few oth...

Page 17: ...its it may be of interest to note from Figs 7 1 0 how stray capacities have been reduced to a minimum by careful design and positioning of units This factor plays an important part in sensitivity and...

Page 18: ...e falling impedance characteristic of the capacity load the E L S presents different and somewhat exacting requirements in terms of filter network The remainder of the crossover unit on Model 70 is co...

Page 19: ...the 701 electrostatic unit The writer s colleague Mr Dennis Ward despite some twenty years experience in the design and manufacture of moving coil units felt that a distortion factor in the order 1 wi...

Page 20: ...affixed at critical positions on the front face of the cone One of the relatively untouched aspects of bass radiator design has been the effective Q at resonance A simple bridge method was evolved for...

Page 21: ...ding waves were built up and the response plot degraded In co operation with Messrs B K Laboratories these problems were thoroughly investigated and resolved We subsequently purchased the complete ran...

Page 22: ...limited number of alternative designs for public comment at both the Amsterdam and London International Exhibitions and from customer opinion sampled it was decided to produce the horizontal styling d...

Page 23: ...at ear level when seated To assist movement on a carpeted surface and to distribute the not inconsiderable weight the leg structure has a return member which may be seen from the side elevation of Fig...

Page 24: ...e room gain below 100 Hz and the Northern Polytechnic Fig 14 which is very much more accurate at these low frequencies All the following measurements are taken in our own anechoic chamber where allowa...

Page 25: ...method of measurement has been made As mentioned earlier in this release in order to fully illustrate the performance of a loudspeaker system a number of off axis response plots must be taken and the...

Page 26: ...ig 19 15 deg off axis in a Vertical Plane We now follow the range of frequency response plots with tone burst and pulse oscillograms These oscillograms have all been recorded in our own anechoic chamb...

Page 27: ...27 Fig 20 Group I T B Oscillograms on 8 off 10 kHz 15 kHz 20 kHz Bottom trace indicates input upper microphone output...

Page 28: ...28 Fig 21 Group 2 T B Oscillograms 64 on 32 off 500 Hz 1 0 kHz 5 kHz 3 5 kHz 10 kHz 15 kHz Fig 22 Pulse Response 300 Hz 500 Hz...

Page 29: ...table D tot with input pf 25 watts R M S 8 ohms B K 4113 J Quad 33 B K Line and Mic Amps 30 Hz 40 Hz 50 Hz 60 Hz 100 Hz 200 Hz 12 10 8 2 5 1 5 1 4 300 Hz 400 Hz 500 Hz 500 Hz 1 kHz 3 kHz 1 4 0 5 0 3 1...

Page 30: ...13 diameter circular Bass Radiator with laminated and specially reinforced cone Type DW 13 3 Eleven module wide dispersion electrostatic unit Type 701 covering freguencies above 400 Hz Model 70 power...

Page 31: ...foot assembly and 701 electrostatic unit covered in matching veneer of oiled Teak or oiled American Walnut with main cabinet body veneered on all surfaces including the back IMPEDANCE Nominal 8 ohms r...

Page 32: ...mally specified in the 8 ohms load should be used The following amplifiers have been used in our Laboratory and Listening Room throughout development and have proved completely satisfactory QUAD 33 DY...

Page 33: ...Printed in England The manufacturers reserve the right to amend or modify this specification without notice...