Loudspeaker and electrodynamic acoustic transducer with bulbous waveguide tip
View Patent ↗An electrodynamic acoustic transducer has a diaphragm and a frame with a pole piece carrying a bulbous waveguide tip which reduces or eliminates high frequency distortions caused by destructive interference within the transducer. The bulbous-tip structure clears the moving parts of the transducer and minimizes diffraction of sound energy, extending forward approximately to the plane defined by the outer periphery of the diaphragm when the diaphragm and voice coil are at rest. The bulbous-tip waveguide member extends radially outward above the central radiating area of the transducer diaphragm or cone so as to obscure the center portion of the diaphragm.
1. An electrodynamic acoustic transducer configured for use in a loudspeaker system, comprising:
a pole piece comprising a first or distal end;
a voice coil comprising wire windings configured to receive electrical current, the voice coil being configured to move along the first end of the pole piece;
a magnetic structure comprising parts defining an air gap, wherein the voice coil on the first end of the pole piece is disposed in the air gap so that the magnetic structure creates a magnetic field in which the voice coil is configured to move along the first end of the pole piece;
a first diaphragm comprising an inner periphery defining a central opening and an outer periphery, the inner periphery of said first diaphragm being attached to the voice coil to move with the voice coil; and
a waveguide extension structure disposed on the first end of the pole piece, said waveguide extension having a bulbous tip that projects radially to a larger diameter than the pole to project laterally over the inner radiating area of said first diaphragm.
2. The electrodynamic acoustic transducer according to claim 1 , wherein the bulbous tip waveguide extension is configured to substantially attenuate high frequency sound radiation from the central portion of said first diaphragm.
3. The electrodynamic acoustic transducer according to claim 2 , wherein the bulbous tip waveguide extension is configured to substantially absorb high frequency sound radiation from the central portion of said first diaphragm.
4. The electrodynamic acoustic transducer according to claim 3 , wherein said first diaphragm's inner periphery incorporates an inner flexible roll seal.
5. The electrodynamic acoustic transducer according to claim 4 , wherein the bulbous tip waveguide extension is porous and said bulbous tip waveguide extension comprises a portion that reduces in diameter in a smooth arc.
6. The electrodynamic acoustic transducer according to claim 5 , wherein the bulbous tip waveguide extension of the pole ascends to a height substantially no less than height of said first diaphragm with the voice coil at rest, and substantially no more than height of said first diaphragm at maximum excursion.
7. The electrodynamic acoustic transducer according to claim 6 , wherein said waveguide extension structure includes a first coaxially aligned portion of a first diameter, a second coaxially aligned portion of a second diameter, and a third coaxially aligned, radially projecting larger diameter bulbous tip; and
wherein said second diameter is slightly smaller than the first diameter, so that a coaxial annular ledge is formed at the interface of the two portions, and wherein said first, second or third diameters are larger than the diameter of the coaxial pole piece.
8. An improved loudspeaker system, comprising:
at least one front-facing midrange or mid-bass bulbous-tip waveguide transducer mounted in a baffle in an enclosure to create a loudspeaker assembly;
said bulbous-tip waveguide transducer comprising a pole piece comprising a first end;
a voice coil comprising wire windings configured to receive electrical current, the voice coil being configured to move along the first end of the pole piece; a magnetic structure comprising parts defining an air gap, wherein the voice coil on the first end of the pole piece is disposed in the air gap so that the magnetic structure creates a magnetic field in which the voice coil is configured to move along the first end of the pole piece; a first diaphragm comprising an inner periphery defining a central opening and an outer periphery, the inner periphery of said first diaphragm being attached to the voice coil to move with the voice coil; and a waveguide extension structure disposed on the first end of the pole piece, said waveguide extension having a bulbous tip that projects radially to a larger diameter than to project laterally over the inner radiating area of said first diaphragm.
9. The improved loudspeaker system according to claim 8 , wherein the bulbous tip waveguide extension is configured to substantially attenuate high frequency sound radiation from the central portion of said first diaphragm.
10. The improved loudspeaker system according to claim 9 , wherein the bulbous tip waveguide extension is configured to substantially absorb high frequency sound radiation from the central portion of said first diaphragm.
11. The improved loudspeaker system according to claim 10 , wherein said first diaphragm's inner periphery incorporates an inner flexible roll seal.
12. The improved loudspeaker system according to claim 11 , wherein the bulbous tip waveguide extension is porous and said bulbous tip waveguide extension comprises a portion that reduces in diameter in a smooth arc.
13. The improved loudspeaker system according to claim 12 , wherein the bulbous tip waveguide extension of the pole ascends to a height substantially no less than height of said first diaphragm with the voice coil at rest, and substantially no more than height of said first diaphragm at maximum excursion.
14. The improved loudspeaker system according to claim 13 , wherein said waveguide extension structure includes a first coaxially aligned portion of a first diameter, a second coaxially aligned portion of a second diameter, and a third coaxially aligned, radially projecting larger diameter bulbous tip; and
wherein said second diameter is slightly smaller than the first diameter, so that a coaxial annular ledge is formed at the interface of the two portions, and wherein said first, second or third diameters are larger than the diameter of the coaxial pole piece.
15. The improved loudspeaker system according to claim 10 , wherein said bulbous waveguide tip blocks sound radiation coming from said inner radiating area of said first diaphragm.
16. The improved loudspeaker system according to claim 15 , wherein said blocked radiation coming from said inner radiating area of said first diaphragm is prevented by said bulbous waveguide tip from creating destructive interference with sound radiation from an outer radiating area of said first diaphragm.
17. The improved loudspeaker system according to claim 15 , wherein said loudspeaker improvements' effect, as compared to traditional loudspeakers, is reduced high frequency distortions caused by destructive interference within the transducer.
18. The improved loudspeaker system according to claim 15 , wherein said bulbous tip's effect, as compared to traditional loudspeakers, is to extend the useful frequency response by approximately ⅔ of an octave in the crucial crossover frequency band of 2 kHz to 4 kHz;
wherein the reduced high frequency distortion and a related frequency extension with the tip provides smoother response with steeper roll-off than without the tip, thereby providing a loudspeaker which makes well-behaved crossover design more straightforward.