Abstract: A humidity resistant device (24 and 78) for reading a meter having multiple dial faces and a rotatable meter hand (17-18) and axle (19) for each dial face that includes for each dial face (a) a plate (16) disposed between the dial face and the meter hand; (b) an array of spaced apart excitable electrodes (11-1 through 11-10) on one surface of the plate confronting the meter hand and defining an array about a center portion that includes the axle (19) of the rotatable meter hand; (c) a center electrode (12) in the center portion forming a part of a plate capacitor between each excitable electrode and the center electrode, the center electrode connected to and monitored by a receiver circuit (24), for sensing current amplitude through each such plate capacitor and spaced apart from the array of excitable electrodes and the axle (19) of the rotatable meter hand; (d) an A.C. voltage signal source (25) for placing a predetermined voltage signal on a pre-determined one of the excitable electrodes; and, (e) a D.C.

Abstract: A bimorph bender acoustical transducer driver or motor element in which no center vane is necessary. Elimination of the vane reduces the dynamic mass of the driver so that a thicker, more rugged piezoelectric wafer can be used to achieve the same acoustical response characteristics as were possible with prior art drivers having vanes and thinner piezoelectric wafers subject to damage.

Abstract: An improved acoustic impedance for a direct radiating dynamic loudspeaker having a natural Q greater than about 1.2, is substantially planar and is positioned in front of and covers the projected frontal radiation area of the diaphragm or cone of the loudspeaker. The acoustic impedance element is supported about its periphery and comprises a fibrous felt material having an air flow resistance in the range of about 50-100 cu. ft. per min. at 0.5 p.s.i. pressure drop, a density in the range of about 6-12 oz. per sq. yd. and a thickness in the range of 0.03-0.09 in. The acoustic impedance element is an air permeable continuous sheet and is comprised substantially entirely of fibers of synthetic materials, such as, for example, polyester, which are relatively impervious to moisture. The Q of the speaker including the damping element is in the range of about 0.75-1.0.

Abstract: A direct radiating dynamic loudspeaker has an apertured impedance frontal loading element for improving its acoustic impedance. A planar sheet of nonrigid, fibrous air-permeable material has an apertured area and is positioned in front of the diaphragm of the loudspeaker. The sheet of air-permeable material is supported only at its periphery. A sheet of acoustically transparent material is bonded to the sheet of air-permeable material to cover the apertured area.

Abstract: A padring for a loudspeaker is formed of a hot melt type material. The padring is easily attached to the housing by applying heat and also serves as a means of attaching a screen to the speaker. In the method of forming the padring, the hot melt type material is extruded into a continuous flat sheet and the padrings are cut from the sheet. Any scrap formed when the padrings are cut from the sheet can be recycled to the extruder reservoir since the hot melt material exhibits little thermal degradation. Consequently, the method of manufacturing the padring of the invention is a scrapless method.

Abstract: A solderless connector for joining the flexible electrical moving leads connecting the voice coil of a loudspeaker to the electrical input terminals located on the loudspeaker frame. The connector supplies electrical continuity between the flexible conductor and the terminal, and mechanically secures the flexible conductor without the need for solder or other mechanical means, thereby improving efficiency of assembly and improving quality by eliminating problems attributable to poor workmanship in soldering operations. These movable leads are known as pigtails, and their length is adjusted to insure long life and to eliminate distortion. A pigtail that is too short will limit cone excursion by becoming taut and introduce distortion into the acoustical output. A short pigtail will also result in early failure of the loudspeaker due to the excessive stress. A pigtail that is too long will also introduce distortion due to the generation of spurious noise.

Abstract: A method for the manufacture of loudspeakers having a ferromagnetic fluid contained in the voice coil magnetic air gap and being confined by the loudspeaker magnet field thereby enveloping the portions of the voice coil that are within the magnetic air gap. A critical viscosity range of the ferromagnetic fluid is required, the viscosity determined by the viscosity of the liquid phase and the concentration of the colloidal ferromagnetic particles which provide the viscous damping forces on the voice coil effective at low and high frequencies. The damping forces are due to shearing stress set up in the fluid by motion of the voice coil in response to electrical excitation and result in surprisingly improved acoustical performance, higher electrical output and freedom from hiss in the loudspeaker. The ferromagnetic fluid also provides an improved heat sink for the voice coil thus improving the electrical power dissipation capability of the voice coil.