. Elements of acoustical engineering. Electro-acoustics; Sound. COMBINATION HORN 133 other end opening in front or at the bottom of the cabinet within which it is folded (Fig. ). The labyrinth is a piston driven tube with absorb- ing walls. At the first half wavelength resonance the velocity at the open end is in phase with that at the front of the cone. The radiation, then, from both sources is additive and the response is increased. An increase in response can be obtained over about an octave. The rising absorption of the tube lining with increase in frequency damps out the higher reso-
. Elements of acoustical engineering. Electro-acoustics; Sound. COMBINATION HORN 133 other end opening in front or at the bottom of the cabinet within which it is folded (Fig. ). The labyrinth is a piston driven tube with absorb- ing walls. At the first half wavelength resonance the velocity at the open end is in phase with that at the front of the cone. The radiation, then, from both sources is additive and the response is increased. An increase in response can be obtained over about an octave. The rising absorption of the tube lining with increase in frequency damps out the higher reso- ABSORBING WALL EQUIVALENT STRAIGHT PIPE. (D20 a ul5 1« \t 1 ,*;> â / :^ lajj / 1 \ / f '⢠' / 1 1 L SECTION THROUGH A-A' FRONT VIEW Fig. Acoustical labyrinth loud speaker. The equivalent straight axis damped pipe is shown above. The pressure response characteristic of the labyrinth loud speaker is labeled B on the graph. The pressure response characteristic of the corresponding cabinet loud speaker is labeled A on the graph. (After Olney.) (Courtesy of The Blakiston Company from Olson and Massa, " Applied ;) nances. The transmission through the tube is very low above 150 cycles. An anti-resonance occurs when the tube is one quarter wavelength long. The deleterious effect of the fundamental resonance of the cone with its suspension system upon the response may be eliminated by choosing the constants so that fundamental resonance of the loud speaker coincides with the quarter wavelength anti-resonance of the tube. The response characteristic of a direct radiator loud speaker with and without a laby- rinth is shown in Fig. These characteristics show that the accen- tuated response due to cabinet resonance has been eliminated and that the low frequency range has been extended. Combination Horn and Direct Radiator Loud Speaker ^. â The combination horn and direct radiator loud speaker consists of a horn coupled to the back side of a d
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