Audio speaker

• US 4,924,504 A
• Filed: 11/19/1987
• Issued: 05/08/1990
• Est. Priority Date: 06/18/1987
• Status: Expired due to Fees

• Current Assignee: Highwood Audio Incorporated 1 Alberta
• Original Assignee: Highwood Audio Incorporated
• Inventors: Burton, Paul
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Byrd, Danita R.
• Application Number:
  US07/123,191
• Time in Patent Office: 901 Days
• Field of Search: 381/199, 381/193-196, 381/200, 381/201-203, 181/173, 181/174
• US Class Current: 381/427
• CPC Class Codes: H04R 2440/01 Acoustic transducers using travelling bending waves to generate or detect sound
• CPC Class Codes: H04R 7/04 Plane diaphragms
• CPC Class Codes: H04R 7/24 Tensioning by means acting directly on free portions of diaphragm or cone
• CPC Class Codes: H04R 9/047 in which the windings of the moving coil lay in the same plane
• CPC Class Codes: H04R 9/063 using a plurality of acoustic drivers H04R1/24 and H04R1/403 take precedence

Abstract

An audio full range speaker which achieves the propogation of a peaked wavefront from the diaphragm instead of generating a substantially planar wavefront as in the case of the common speaker construction utilizing a diaphragm driven as a piston. The speaker has a substantially planar, thin, flexible film forming the diaphragm mounted within a frame. The diaphragm is driven by a driver which imparts motion to the diaphragm at a small source area, the motion being imparted in a direction normal to the plane of the diaphragm so that ripples radiate from the drive area and travel at the same time across the flexible diaphragm, one behind the other, towards the frame. The rest of the diaphragm is driven by the central moving portion, endowing it with a built-in time delay. Because of the time delay involved in spreading the energy across the diaphragm, the wavefront radiated by the speaker ges a head start at the center and lags towards the edges. The result is that of a spreading spherical wave front for a point source and a cylindrical wave front from a line source, and allowing a large diaphragm to behave as a small virtual audio source. The full range transducer requires no crossover, equalization or time delay circuits.

Claims

1. An audio transducer comprising:

a frame having a central open area,

a substantially planar, thin, flexible film forming a central portion thereof supported by said frame within said open area of said frame,

means for imparting a motion to a drive area of said diaphragm in a direction normal to the plane of the diaphragm, said drive area being small relative to the supported portion of the diaphragm whereby waves are created in said diaphragm and radiate away from said drive area in the form of a number of waves travelling at the same time toward said frame,

said motion imparting means being a line source drive in the form of a centrally disposed linear coil provided by a plurality of juxtaposed, parallel conductors affixed to and extending for a distance along said diaphragm,

a stationary elongated magnetic means supported adjacent said coil and defining a gap receiving said coil, and

a pair of members varying a mass along their lengths provided on immediate opposite sides and extending the length of said linear coil.

2. An audio transducer comprising:

a frame having a central open area,

a substantially planar, thin, flexible film forming a central portion thereof supported by said frame within said open area of said frame,

means for imparting a motion to a drive area of said diaphragm in a direction normal to the plane of the diaphragm, said drive area being small relative to the supported portion of the diaphragm whereby waves are created in said diaphragm and radiate away from said drive area in the form of a number of waves travelling at the same time toward said frame,

said motion imparting means being a line source drive in the form of a centrally disposed linear coil provided by a plurality of juxtaposed, parallel conductors affixed to and extending for a distance along said diaphragm,

a stationary elongated magnetic means supported adjacent said coil and defining a gap receiving said coil, and

a pair of members which vary in distance from said linear coil length along their lengths being provided on opposite sides and extending the length of said linear coil.