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40
Better Theatres Section
May 10, 19,
Announces
NEWβ
Theatre Horns
cf Special Design
Made of New Acoustic Properties
Amplion's new production methods now make possible any special size or design of exponential horn at considerably less than heretofore.
NO MORE
PROHIBITIVE PRICES
as formerly, for our new economical and practical method does away with the high cost of special moulds.
Amplion New 12-Ft. Air Column Horn of Glass Smooth Vibrationless Material. Will accomodate two Amplion Horn Units.
SPECIAL SIZE HORNS
to fit any requirement
BUILT TO ORDER
on short notice
AT MODERATE PRICES
New Amplion Tube Exciter Type EL-22
Can excite the fields of the speakers on the stage, from the projection room.
W rite for Special Literature and Prices
AMPLION CORPORATION
OF AMERICA
133 W. 21st St. New York
the back wall, until he gets the result shown in Fig. 3. This photograph shows that the curve of the rear wall has been sufficiently lessened to permit reflected sound waves to be nearly parallel, thus
If the difference in these distances . more than 35, it is a physical fact th f acoustical trouble over the area C-C c curs. This drawing does not show sous waves other than those which pa
FIG. 3
avoiding the confusing convergence at E.
The two diagrams (Figs. 4 and 5) represent longitudinal sections of the auditorium. Fig. 4 shows the original design of the auditorium. The double curve of the ceiling nearest the proscenium arch caused a convergence of sound waves at B. Passing over this point, the rays diverged and spread out over area C-C on the main floor, just in front of the balcony. In this cross section, pegs were inserted to simulate auditors along the floor and balcony surfaces. The third and fourth pegs from the stage along the floor surface cast two shadows. One, when prolonged past the peg, intersected the source (S) ; the other, similarly prolonged, touched a portion of the ceiling
surface at A. Lines drawn from S to the points where these prolonged shadows intersect the ceiling surface would properly represent the path of the sound. Since these sections are made to a definite scale, the distance traveled by the direct sound, and that traveled by the reflected sound, can be measured.
through the convergence at B, for th I reason that (as in the case of the floe I plan photograph, wherein the diverger I rays shown reflected from the side wall
caused no trouble) they cause no disturl ance to the auditor.
In Fig. 5, the ceiling surface A ha been changed. The new curve reflect the waves back into the balcony instea of down to the main floor, as in Fig. β The pegs along the area H-H cast doubl shadows, one of which, when prolonge from the peg, passes through the sourci The second intersects the ceiling surfac A. Again, if lines are drawn from th source to these points of intersection, th paths of the direct sound and reflecte sound may be measured. It will generall be found that in a case of this kind, th difference between the two paths is re atively small β less than 35 feet β an that the reflected sound acts as a reir forcement of the direct sound and in proves audition in the balcony seats.
Fig. 6 and Fig. 7 are transverse, o latitudinal sections, of the auditoriun