US 1786279 A
Description (OCR text may contain errors)
ADec. 23, 1930.- l. WOLFF I 1,786,279
REFLECTOR Filed March 31, 1927 III AT RNEY Patented Dec. 23, 1930 UNITEDk STATES PATENT OFFICE IRVIN G WOLFF, OF NEW YORK, N. Y., ASSIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE REFLECTOR Application filed March 31,
The invention concerns acoustic devices of the type generally known as loud speakers and has for its principal object to provide a sound reflector in connection with such a device A more specific object of the invention is to provide a sound reflector in combination with a loud speaker for reflecting the sound waves therefrom in order to modify the direction of the sound or to decrease or amplify certain frequency ranges.
In the construction of loud speakers it is often necessary for structural purposes or other reasons to so locate the sound emitting element that Athe direction of maximum sound intensity or of more nearly perfect transmission is not in the direction of the audience. It may benecessary for example to locate the vibratile element so that the sound waves emitted from it will be directed ina vertical direction whereas the listener usually will be located in a horizontal direc tion from the loud speaker. It is known that the low frequency waves will extend with a substantially equal intensity in all directions, that is there is a tendency for the low frequency waves to change their direction of propagation readily or in other words, to spread out in all directions. The high frequency sound waves, however, have a tendency to persist only in the direction in which they start. The high frequency waves, in other words, instead of spreading out in all directions have more or less the form of a beam which in the case of a loud speaker extends directly away from it. It is obvious, therefore, that if the vibratile element were placed horizontally that the low frequency tones would probably be of sufficient intensity in all directions but the high frequency tones would extend directly upward and would have little effect in the horizontalV di rection in the loud speaker. The resulting sound7 therefore, would have its high frequency components weakened so that the speech or music being produced would not correspond at all to that originally causing the vibration of the vibratile element. I propose to overcome this, defect by providing a sound reflector in proximity to the vbratile 1927. Serial No. 179,744.
element so that the high frequency waves will be directed from their original path into the direction which it is desirable that the sound from the loud speaker be heard.
The invention further contemplates the use of a reflector in connection with a loud speaker to amplify certain frequency ranges of the loud speaker or to decrease certain frequency ranges. It is well known that the usual sound emitting device has several frequency ranges that are unduly accentuated with respect to the others resulting in distortion of the original sound. On the other hand the element may respond very poorly to certain frequencies within its operating range resulting in a decided dip in its respense curve. By the use of a reflector of suitable construction and material it is possible to strengthen or decrease as desired the intensity of the sound of particular frequency ranges. This may be done by so` placing the vibratile element that it vibrates in a direction different from that in which it is desired'that the sound be heard and then providing a reflector which will reflect the sound waves into the desired direction. By suitably choosing the reflector it can be made to reflect some frequencies and absorb others from which it will result that the sound after it leaves the reflector will have certain frequencies of substantially the same intensity as they left the vibratile element and others will be decreased in intensity. In this manner a more uniform response over the entire frequency range of the vibratile element may be obtained.
A more particular use of the reflector occurs where a vibratile element is used hat7` ing a rise in its characteristic curve within the low frequency range. It is well known that the diaphragm or other vibratile elementemits sound waves from its two sides simultaneously and these waves are directly out of phase with each other. This effect is of no importance with respect to the high frequencies as they tend to persist in their original direction and the wave length is too short to give interference but the low frequency waves tend to spread out in all directions and if no means were taken to prevent it those i to actuate said diaphragm, a casing enclosing said means and said diaphragm, said casing having an opening substantially the same shape as said diaphragm, and a reflector mounted adjacent to said opening and angularlv disposed With respect to the plane of said diaphragm.
6. In combination, a loudspeaker device having a vibratile element, and an ellipsoidally shaped reflector mounted adjacent to said element.
7. The combination of an acoustic device and an elliptical reflector associated therewith.
8. The combination of an acoustic device and a reflector therefor, said reflector having a surface at least a part of which is an ellipsoid of revolution.
9. The combination of means forming a refleeting surface having the form of an ellipsoirl of revolution and an acoustic device positioned substantially at the focal point of said ellipsoid.