US 3213209 A
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Description (OCR text may contain errors)
Oct. 19, 1965 E. R. DOELITZSCH 3,213,209
LOUDSPEAKER Filed Aug. 7, 1962 E INVENTOR /0 5 E EDUARD R. DOELITZSCH F I 6'' WW ATTORNEYS United States Patent 3,213,209 LOUDSPEAKER Eduart R. Doelitzsch, 78 Summer St., Framingham, Mass. Filed Aug. 7, 1962, Ser. No. 215,336 4 Claims. (Cl. 179115.5)
This invention relates to an improved loudspeaker for a radio or a record player, the loudspeaker being designed to emit sound waves in a wide range of frequencies, a woofer and a tweeter being combined in a single unit. To this end the voice coil is mounted on a light-weight tube near the rear end thereof, the apex end of a woofer cone being secured to the tube near the voice coil. A tweeter cone is mounted on said tube at its forward end.
For a more complete understanding of the invention, reference may be had to the following description thereof, and to the drawing of which FIGURE 1 is a sectional view of a loudspeaker embodying the invention;
FIGURE 2 is a sectional view of a modified form of loudspeaker; and
FIGURE 3 is an elevational view of one of parts of the speaker shown in FIGURE 2.
The loudspeaker shown in FIGURE 1 includes a driver comprising a customary magnet which may be either a permanent magnet or an electromagnet to provide a magnetic field in which the voice coil 12 can vibrate. A basket 14 is mounted on the magnet 10 to support a woofer cone 16 by its rim at its larger end with the usual compliance 18. The cone 16 is shown on the drawing as a circular cone, but the term is intended to refer also to elliptical cones and to prismatic forms. The voice coil 12 is mounted on the rear end of a light-weight, elongated tube 20 which is made of suitable stiff material such as impregnated paper. A spider 22 surrounds the tube 20 just forward of the voice coil 12 and is attached to the tube and to the basket 14 to keep the tube and voice coil centered with respect to the gap between the pole-pieces of the magnet 10. The apex end of the woofer cone 16 is attached to the tube 21) just forward of the spider 22. At the forward end of the tube 20 the apex end of a reverse cone 24 is secured, the rim of this reverse cone being secured to the inner surface of the Woofer cone 16, thus forming with the tube 20 and a portion of the woofer cone an air-tight resonance chamber 26. The reverse cone 24 also serves to center the forward end of the tube 20.
Also secured to the forward end of the tube 20 is the apex end of a tweeter cone which is considerably smaller than the woofer cone 16 and is made of relatively hard material, such as molded phenolic resin, the woofer cone 16 being of softer material such as paper, wool or other fabrics impregnated with a heat-setting phenolic compound. The customary connectors 31 for the voice coil leads are mounted on the basket 14.
The loudspeaker illustrated in FIGURE 2 has several parts identical with parts of the loudspeaker illustrated in FIGURE 1. The pole pieces of a magnet 10 surround a voice coil 12 on the rear end of an elongated light-weight tube 20. A basket 14 is mounted on the magnet 10 to support the outer end of a woofer cone 16 by means of a compliance 18. A spider 22 is mounted on the bottom of the basket to center the voice coil 12, A tweeter cone 30' is secured to the forward end of the tube 20. A reversed cone 24' is secured at its apex end to the forward end of the tube 20, this reversed cone having holes 27 therein as it is employed merely as a support to center the forward end of the tube 20. In this embodiment of the invention a second reverse cone 32 is secured to the rim of the tweeter cone 30' and to the woofer cone 16', enclosing a resonance chamber 26.
In both embodiments the voice coil causes the tube to vibrate longitudinally at all frequencies. The woofer cone responds to the lower frequencies, while the tweeter cone responds to the higher frequencies. The result is the production of tones of high fidelity through a wide range of frequencies with an unexpected stereophonic effect of depth and brilliancy, generated in the chamber or chambers, in the form of harmonics of a wide range of frequencies.
The foregoing combination of cones is effective not only with dynamic loudspeaker systems employing permanent magnets, but also with electrodynamic and electrostatic systems. It has the further advantage of requiring no change in the frame structures now in use.
1. In a loudspeaker having a driver, a voice coil in the field of said driver, a woofer cone, and a support frame for said cone mounted on said driver; an elongated tube carrying at its rear end said voice coil, a spider attached to said driver and to said tube next to said voice coil, means securing the apex end of said woofer cone to said tube next to said spider, a tweeter cone carried by said tube at the forward end thereof, and a reverse cone secured at its apex end to said tube and at its rim to said woofer cone, said reverse cone, woofer cone and tube forming a resonance chamber.
2. Apparatus as described in claim 1, said reverse cone having holes therethrough,
3. Apparatus as described in claim 1, and a second reverse cone extending from near the rim of the tweeter cone to the woofer cone.
4. Apparatus as described in claim 3, the first said reverse cone having holes therethrough.
References Cited by the Examiner UNITED STATES PATENTS 2,231,479 2/41 Perry 179-115.5 2,641,329 6/53 Levey 179-l'l5.5
FOREIGN PATENTS 857,413 12/60 Great Britain.
ROBERT H. ROSE, Primary Examiner.
UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No, 3,213,209 October 19, 1965 Eduard R, Doelitzsch It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
In the grant, lines 1 and 12 and in the heading to the printed specification, line 3, name of inventor, for "Eduart R, Doelitzsch", each occurrence, read Eduard R.
Doelitzsch Signed and sealed this 19th day of April 1966 A (SEAL) Attest:
ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner of Patents