Projection engineering (Sept 1929-Nov 1930)

Projection Engineering, September, 1929 Page !tl New Musical Effects Produced by Electrical Means New Freedom of Musical Expression Gained Through the Use of High Power Sound Reproducing Devices By Edward W. Kellogg* ONE of the most striking recent developments in the art of sound reproduction is that of loudspeakers capable of delivering large volume of sound. The gain from this increase in loudness is not simply that the ears are relieved of strained attention to catch what is said or played, but a change of quality as judged by ear occurs as the loudness is altered, even when the actual sound wave shapes are kept the same.1 For this reason, reproduced speech and music will not sound natural unless the reproduction is at approximately the same loudness as the original. The advent of the Radiola No. 104 brought radio music into the home with a volume about equal to that of a piano in the room. Electrical reproduction was then applied to phonographs, and the Brunswick "Panatrope" and Victor "Electrola" far exceeded the machines depending on direct or mechanical reproduction, in point of sound power. Auditorium Speakers More recently there have been evolved loudspeakers of much higher 1 "Auditorn Maskino of One Pure Ton'' by Another," R. L. Wepel & C. E. Lane. Phys. Rev., Vol. 2.3, P. 266, 1924. "Physical Measurements of Audition " B. F. Fletcher, Bell System Tech. Jour , Oct. 1923, P. 145. Jour. Franklin Inst.. Sept. 1923. "High Quality Transmission and Reproduction of Speech and Music," W. II. Martin and H. Fletcher, A. I. E. E., Vol. XLlll, 1924, P. 385. MR. KELLOGG convinces us that the art of musical expression is to be enriched by means of electrical reproduction. That a purely commercialized device will hitch itself to the purely aesthetic and remain as a contribution to the art of all sound expression appears far fetched. The fact remains, hoicever, that with tlir aid <>)' superpower reproducing devices, qnnlitii and volume can be controlled independently and an entirely new form of musical expression obtained. That point of development has been reached where we can "make the heavens resound to a whisper." We shall yet experience the thrill of our bodies vibrating under the power of "a soft musical passage'' rising alinre the orchestral background —Editor. Co. 'Research Laboratory, General Electric power lor use in auditoriums or outof-doors. In these devices no pains are spared to secure faithfulness or high quality, and amplifiers of ample capacity are employed to avoid distortion. Speakers of this class have for the most part been of two types, one employing a large horn, perhaps 12 to 20 feet long, with a bell opening of (he order of 8 feet by 8 feet, while the other type employs a number of cone type speaker units. As an example of the cone type auditorium speaker a model buill about two years ago under Mr. Edward W. Kellogg, and the high-power amplifier and bank of dynamic speakers employed in the interesting experiments discussed in this article. the writer's direction may be briefly described. It employed nine coil-driven cones such as used in the Radiola No. 104, the units being arranged in three racks, of three cones each. The power stage of the amplifier consisted of a pair of UX-851 tubes, each drawing .3 ampere plate current at 2000 volts. The amplifier could supply about 150 times the power without distortion which the UX-210 tube can supply to its cone in the Radiola No. 104 or the Panatrope. This equipment was used in a number of public gatherings at which orchestras or bands were present. It could, with pleasing effect, be run at a setting at which it was definitely louder than a ten to fifteen-piece dance orchestra, or comparable with a military band. Violin at Band Volume In the course of these demonstrations one characteristic of the music, produced by means of the high power speaker, impressed itself on those of us who were present. It is as easy to get a powerful sound from a single voice or instrument as from a large number of voices or from a whole orchestra. In fact we can with a given equipment put out considerably more sound power when reproducing a single voice or instrument than when reproducing the highly complex sounds of a large chorus or orchestra. Phonograph records are usually so cut that a vocal or instrumental solo is practically as loud as a hand recording. What this means with the household phonograph is that the BOlO numbers are reproduced with somewhere near their original volume, hut that the orchestra and hand numbers, while loud enOUgh to he enjoyed. ;ire faint Imitations of n iglnals. The high power auditorium speaker can practically duplicate the orchestra, chorus. or band, but it can do something which has not been possible before sing n tenor or soprano solo, or play a violin Si band volume. Sew Musical Expression such reproduction It of course nol exactly "natural," bul the function of :i mUSlCBl device, such as the loud speaker, is not necesarily limited to Imitation I although II musl be capable of Imitation) bul to afford pleasure to the listener. And one of the elements which brings a thrill to the listener is the flood of sound that shakes his whole body, that in some passages Beema even deafening, The