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Electronics-World-1959-05

Enjoy Stereo Now! at LOW

Enjoy Stereo Now! at LOW COST! ordinary broadcast AM or AM -FM, or portables WITH FABULOUS NEW ea Easy to Install! Transistorized! Top Fidelity! No Drift ! No Hum f Compatible - Stereo /Mono No Extra Amplifiers or Speakers I Model SDK -101. Less cartridge. List, $16.75 Model SDK- 102CS. With E -V 126ST dual sapphire compatible cartridge. List $27.50 (above prices are less battery) See it at your distributor, dealer or record store; or order direct. *Trod* Mark THE STEREO -ETTE CO. 4908 N. Lincoln, Chicago 25, III. 26 Send FREE Bulletin No.CS101.N Send... .Model (n} $ Check or M.O. for S enclosed. (No C.O.D.) NAME ADDRESS CITY ZONE STATE Loudspeakers for Stereo (Continued froh page 44) respondingly different proportions of sound from the two units will be "located" somewhere between, although that "somewhere" may differ with different seating positions relative to the speakers. A directional loudspeaker is a useful adjunct for improving coverage, especially where provision is made for aiming it, independent of its location, as provided by the Jensen "Director" assembly both in separate units and the unitized variety, or by Goodmans in its "Stereosphere" (which can be used as part of an installation similar to the "Stereodot "). Directivity of the "stereo" units can be used either to improve the stereo effect in one's favorite listening seat, although the speaker symmetry is not ideal (due to room shape, for example) , or to cover a "long shot" position to improve uniformity throughout an area. One good way of getting a loudspeaker truly omnidirectional in the horizontal plane is to "point" it upwards. The Hegenlan- designed unit put out by EICO is an example of this design approach. If the Goodnlans "Stereosfere" is aimed straight up this does the same. But to give smooth omnidirectional radiation, such units should be close against a wall to avoid undesirable reflection effects from producing effective "double image." This way the reflected radiation merges completely with the direct radiation. A unit designed to have a highly dispersed radiation from its front only may actually be more uniform in its radiation in some situations- especially if the room arrangement prevents its being close to the wall -due to a radiator or window, for example. Another factor, besides shape of the area to be covered, is the furnishings although this can cut both ways in different circumstances. In a recreation - type room, with all hard surfaces, a directional pattern that spreads horizontally but restricts vertically is an asset. The JBL "Koustical" lens, with its appropriate driver and horn, provides one way of doing this. A less expensive way is to use a vertically aligned row of small direct -radiator units, connected in -phase as shown in Fig. 12. Otherwise, an essentially omnidirectional or diffuse radiation is best for this kind of room. Rooms with heavy drapes, wall -towall carpeting, and heavily upholstered furniture come at the other extreme. Generally speaking, these are more tolerant of loudspeaker types as regards radiation pattern, so concentrate on getting the smoothest response. But sometimes the room shape will tend to produce "dead spots" where the sound gets lost. By "beaming" the sound into these spots with a director system, more complete coverage can be obtained. That's the story with the well- established and by now familiar dynamic speakers, but this year several new names have appeared in the electrostatic (I prefer the term "electric" - there's nothing "static" about sound radiation) speaker field. Most of these, thus far, are tweeters or mid -range and tweeter, but at least two claim full - range with electric units only. Electrostatic Speakers One objection to electric units has been their directional property -a small, flat unit will send out a narrow - angle beam that gets narrower as the frequency gets higher. But this assumes a flat -or near flat -shaping. Actually there seems to be a good reason why this form should be more pliable in making a desired shaping than the more familiar dynamic. Even now, Electrocoustic claims a unit that has adjustable directivity by hinging both the radiator and the reflector. The firm says it includes the possibility of omnidirectional radiation. This does provide considerable variation which is a nice feature. In addition, Wright St. George is featuring a number of variations including an adaptable "modular" scheme. A question arises here about the size needed for adequate bass response. This depends on how far the diaphragm can move. Large movement will produce corresponding bass response from a smaller surface area but larger movement requires wider spacing between the fixed and moving elements, a higher impedance amplifier output (which can be provided in a transformer which comes with the speaker). and a very much higher polarizing voltage. This gets into insulation problems which, until recently, have seemed insurmountable. But at last it looks as if a break -through is being made. When the electrostatic speaker was thought of as essentially a small -movement device, the only way full -range response, including bass, could be visualized was by making at least one whole wall of your room a speaker - which is hardly practical for most of us. That got into a sound radiation concept that was quite the opposite of the conventional dynamic which uses a relatively small cone with large movement. Now the development looks as if it will be quite feasible for electric transducers of the future to optimize on the size question. This may well make them very adaptable units. Conclusion In this article I have departed from my usual rule of not mentioning specific names. I could not say what I had to say without being specific. But in mentioning these names, no endorsement or censure is intended. Some whose names I have not mentioned, but which appear in the table, represent as much work and achievement as many others. Now let's gather the pieces to see how to go about buying what you want. First, do you want a system to just sit ELECTRONICS WORLD

ack and listen to good stereo for some time to come or are you an experimental "bug "? Second, what kind of room do you have: size, shape, and furnishings? And, third, how much do you want to spend? If you don't want to play around, changing your system, and trying out different arrangements, get one that does a good job in your room and is as simple as possible. For the smaller rooms. a single- cabinet job, for the larger ones two separate cabinets of a size that "looks right" in the room: using types of unit that suit your room's acoustics. If you want to play around, experimenting with different arrangements . get one of the flexible systems, of which there is quite a variety, preferably to suit your room size. And about your budget, you don't need me to tell you. Stereo has produced a wider price range in speakers than monophonic hi -fi ever did! 3p'- LOW -DISTORTION SINE -WAVE GENERATOR By HERBERT COHEN General Transistor Corp. author has been considering TIIE the profilent of extracting the fundamental frequency fr a couve al neon - tube saw -1 th generator. The slow charge ' and the extrenuly rapid discharge produces a saw -t t h H.191. form whose usefulness i, limited but wIikh contains the fund: nlal and man. hat However. b parallel tuning the capacitor discharge eireuil, a low- distot- 1 sine wave can be obtained. The primary of a Staneor PS8416 power tr:utsfornur, paralleled by a .01 pfd. eapaw' , is used a. a high-"Q" tank eirruil. The tuned circuit appears as an exeeedingly high i111114.111111 re to the fund: neat fregtuniy but practically a short circuit lu ils hull With an oscilloscope acru.s the transformer primary, the put ie adjusted to sel the oscillator at the LC frequency of transformer and capar' , As the fundamental approaelles the tuned IA: frequene., the waveform ber s e und e sinusoidal with an increasing amplitude on approaching resonance. At resonance. the wavrform shows less than 3% hat distortion as measured with a distortion anal.zer. 'Flic see lacy of the transformer supplies many outputs for low- or high- iniped- :uue matching. One problem in this construction is Ilual ground i5 also a.c. ground. An isolation transformer can be used lu el' ale this problem. The stability of this unit is basically determined b. the stability of the a,e, bor. .t 1000 - e.elr o- eillator. constructed its the author and .b,,nit in the diagram below, puls out a w:neforun comparable to the Hartley type. -30- 117 V AC 130 V 20 MA 1SPST May, 1959 0 20 pf 50V 500K 003 Vid H NE51 en. r S ANCOR PS 9416 A LIFETIME WARR The responsibility of being the finest... wsvLVE ND TOVRC eE Tn.D[»A.+S VsED TO DENOTE TIE Ovslav or nCRUND Truly the finest stereo pickup ever made... the STANTON Stereo FLUXVALVE is hermetically sealed in lifetime polystyrene with all of the precision that has made Pickering a quality leader in the field of high fidelity for more than a dozen years. For instance...only the STANTON Stereo FLUXVALVE has the "7- GUARD" stylus assembly -so safe and easy to handle... so obedient and responsive to every musical nuance in the stereo groove. Only the STANTON Stereo FLUXVALVE has the parallel reproducing element contained in the 'T.GUARD "...assuring the proper angle of correspondence between recording and playback styli for maximum Vertical Tracking Accuracy. : :. ..»., .. a ». ., :.. . WAaa co»PANV r»vrNnDNS. And...because of this the STANTON Stereo FLUXVALVE reproduces music with magnificent sound quality...from both stereophonic and monophonic records...with negligible wear on record and stylus. In plain truth...the STANTON Stereo FLUXVALVE is by far the finest stereo pickup made...backed by a Lifetime Warranty`, assuring you a lifetime of uninterrupted, trouble free performance -with a quality of reproduction no other pickup can equal. We *mot you visit your Mato, paw wen -Prop rn ano ask lot a personal demonstration. NEWLY REVISED -"IT TNES TWO TO STEREO ADDRESS DEPT FE9 FOR YOUR FREE COPY for /hose who con heel Me difference PICKERING 8 COMPANY, INC., Plainview, N. V. Featuring Paracoupled windings, a new patent- ed design principle. These transformers use advanced pulse techniques to insure superior square wave performance and undistorted reproduction of transients. Dynaco transformers handle full rated power over the entire audio spectrum from 20 cps to 20 kc, without sharp rise in distortion at the ends of the band which characterizes most transformers. Conservatively rated and guaranteed to handle double nominal power from 30 cps to 15 kc without loss of performance capabilities. Specifications: Response: Plus or minus 1 db 6 cps to 60 kc. Power Curve: Within I db 20 cps to 20 kc. Square Wave Response: No ringing or distortion from 20 cps to 20 kc. Permissible Feedback: 30 db MODELS A -410 15 watts EL 84. 6V6. 6A05 14.95 A -420 30 watts 5881. EL 34. KT -66 19.95 A -430 GO watts KT -88. EL 34 29.95 A -440 120 watts KT -88. 6550 39.95 A -450 120 watts PP par KT -88. EL -34 39.95 1111 with lapped primaries except 5.440 which has tertiary for screen or cathode feedback/ Additional data on Dynakit and Dynaco components mailable on request including circuit data for roderni;ation of Williamson-type r amplifiers to 50 Rares of output and other applications of Dynaco transformers. nYNAf;(1 INC. Dept. RT, 617 N. 41st, Philadelphia 4, Po. F:p»rl aiii»D: 2111au..n "I.. 1oaL. N. S. i 127

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