16-mm sound motion pictures : a manual for the professional and the amateur (1953)

Record Details:

Something wrong or inaccurate about this page? Let us Know!

Thanks for helping us continually improve the quality of the Lantern search engine for all of our users! We have millions of scanned pages, so user reports are incredibly helpful for us to identify places where we can improve and update the metadata.

Please describe the issue below, and click "Submit" to send your comments to our team! If you'd prefer, you can also send us an email to mhdl@commarts.wisc.edu with your comments.




We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.

Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.

482 XIII. PROJECTION AND PROJECTORS Lansing 604 type (Fig. 114A) is used. This unit, when properly placed with respect to the space to be covered with sound, can cover not only the perspective center but also the boundaries. Other loudspeakers with sacrifices in performance of varying kinds may be obtained at lower cost. In comparing these, it would be well to use the Western Electric 755A as a performance reference if the price for the unit in question is between these two. The horn-type loudspeaker should preferably be used especially for the speech intelligibility frequencies that lie above 1000 cps. This type provides: (1) good efficiency (20% is not uncommon compared with 3 or 4% common for ordinary dynamic cones) ; (2) good and reasonably uniform directional radiation (over 60° is easily accomplished at 6000 cps compared with as little as 10° for the conventional dynamic cone) ; (3) good transient response on speech sounds, a result of good damping and uniform impedance characteristics (the horn-type design is almost ideal for the speech range, the single dynamic cone is one of the poorest, especially if it has the large diaphragm and the large-mass voice coil essential to good radiation of low frequencies) ; (4) a much smaller difference in sound pressure at the front row center compared with the last row at the extreme sides. (Sound from the horn-type should be almost as clear and distinct as up front, whereas the sound from the dynamic cone type will probably be low in volume and possibly unintelligible.) The advantages can be readily observed if the loudspeaker of a current model Bell and Howell sound projector is replaced with an Altec-Lansing 604 speaker in its box enclosure, or, should the additional bulk be no disadvantage, replaced by such speakers as the Bell and Howell Orchestricon (made for Bell and Howell by Jensen) or similar divided-range speakers made by Jensen, Stephens, Altec-Lansing, Klipsch, Western Electric, RCA, and others. Since the recent advent of Alnico V and other improved materials, manufacturers have been vying with one another in the design of loudspeakers that may be satisfactorily applied to 16-mm sound projection. The cost of Alnico V is but a small percentage more per pound than its predecessor Alnico III ; as the size and weight of the slug necessary to provide a specified flux is reduced to about one-fourth, a reduction in magnetic leakage has also been possible resulting in still better loudspeaker performance. Despite these improvements, the cost of a really satisfactory loudspeaker for 16-mm sound projection still represents a very appreciable percentage of the cost of the complete machine, and,