BIPOLAR SPEAKER WITH IMPROVED CLARITY

• US 20120014544A1
• Filed: 06/16/2011
• Published: 01/19/2012
• Est. Priority Date: 06/16/2010
• Status: Active Grant

• Current Assignee: Definitive Technology
• Original Assignee: Definitive Technology
• Inventors: GLADWIN, Timothy, Cochrane, Jason B.
• Granted Patent: US 8,995,697 B2
• Time in Patent Office: Days
• US Class Current: 381/304
• CPC Class Codes: H04R 1/26 Spatial arrangements of separate transducers responsive to two or more frequency ranges
• CPC Class Codes: H04R 1/403 loud-speakers
• CPC Class Codes: H04R 2201/34 Directing or guiding sound by means of a phase plug
• CPC Class Codes: H04R 3/12 for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04R 3/14 Cross-over networks
• CPC Class Codes: H04R 7/02 characterised by the construction
• CPC Class Codes: H04R 9/04 Construction, mounting, or centering of coil

Abstract

A forward focused bipolar loudspeaker system includes a front-facing driver array and a rear facing driver array with substantially identical front-facing and rear-facing midrange or mid-bass drivers voiced and driven so that the measured SPL curves of each of the arrays, when measured individually, are tonally balanced. The front array and rear array have substantially identical on-axis and off axis frequency response and the rear array'"'"'s output power (SPL) is reduced by, preferably, about 6 dB with respect to the output power produced by the front-facing array, while retaining a flat tonal balance for both the front and rear speakers, to produce a sound power ratio of about 2:1 as measured by comparing the front and back SPL levels of the speakers. This bipolar speaker system and method for voicing was discovered to provide greater clarity and improved localization while retaining the spacious envelopment of the bipolar sound field.

Claims

1. An improved bipolar loudspeaker system, comprising:

at least two front-facing and one rear-facing substantially identical midrange or mid-bass loudspeakers mounted in opposing baffles in an enclosure to create a bipolar speaker assembly; and

said loudspeakers being interconnected to an audio signal source of power so that the rear sound power that is produced by the rear-facing speaker is about 6 dB below the sound power produced by the forward-facing loudspeakers, thereby improving localization while retaining the spacious envelopment of a bipolar sound field.

2. The improved bipolar loudspeaker system of claim 1, further including:

a forward-facing tweeter and a rearward-facing tweeter in said enclosure; and

a crossover network connecting said tweeters to said audio signal source.

3. The improved bipolar loudspeaker system of claim 1, further including:

at least one woofer mounted in said enclosure; and

a crossover network connecting said woofer to said audio signal source.

4. The improved bipolar loudspeaker system of claim 3, further including:

a forward-facing tweeter and a rearward-facing tweeter in said enclosure; and

said crossover network also connecting said tweeters to the audio signal source.

5. The improved bipolar loudspeaker system of claim 1, wherein said at least two front-facing and said one rear-facing substantially identical midrange or mid-bass loudspeakers are mounted in respective compartments within said enclosure to create said bipolar speaker assembly, and wherein said front and rear speakers have SPL curves that are substantially flat and as tonally identical as possible, except for their level.

6. An improved, front or forward focused, bipolar loudspeaker system, comprising:

(a) a front-facing loudspeaker driver array including at least a first midrange or mid-bass driver mounted in a front baffle in an enclosure;

said front-facing array further including at least a first tweeter driver mounted in said front baffle in said enclosure;

(b) a rear-facing loudspeaker driver array including at least a second midrange or mid-bass driver which is substantially identical to said front array'"'"'s first driver, said second midrange or mid-bass driver being mounted in a rear baffle which opposes said enclosure'"'"'s front baffle;

said rear-facing array further including at least a second tweeter driver mounted in said enclosure'"'"'s rear baffle;

(c) a crossover configured to receive an audio signal from an audio signal source and connected to said front array drivers and said rear array drivers;

(d) wherein said crossover, said front-facing array'"'"'s drivers and said rear-facing array'"'"'s drivers are interconnected to said audio signal source so that when said audio signal source provides said audio signal, the rear array'"'"'s sound power is less than the front array'"'"'s sound power by a selected forward focused power ratio being in the range of 2 dB-10 dB, thereby improving localization while retaining the spacious envelopment of a bipolar sound field.

7. The improved bipolar loudspeaker system of claim 6, wherein said front array drivers and said rear array drivers are interconnected to said audio signal source so that when said audio signal source provides said audio signal, the rear array'"'"'s sound power is less than the front array'"'"'s sound power by a selected forward focused power ratio of one-to-two or 6 dB, thereby optimizing localization while retaining the spacious envelopment of a bipolar sound field.

8. The improved bipolar loudspeaker system of claim 7, wherein said front-facing array includes first and third substantially identical midrange or mid-bass drivers and said rear-facing array'"'"'s second midrange or mid-bass driver is substantially identical to said front array'"'"'s first and third midrange or mid-bass drivers.

9. The improved bipolar loudspeaker system of claim 8, wherein said front-facing array'"'"'s first and third substantially identical midrange or mid-bass drivers are aligned vertically with said first tweeter in an M-T-M array.

10. The improved bipolar loudspeaker system of claim 9, wherein said crossover comprises a passive frequency dividing network configured and tuned to segregate the audio signal into

(a) a front-facing array midrange or mid-bass driving signal,

(b) a rear-facing array midrange or mid-bass driving signal having the same voltage level as said front-facing array midrange or mid-bass driving signal,

(c) a front-facing array tweeter driving signal,

(d) a rear-facing array tweeter driving signal which, compared to said front-facing array tweeter driving signal, is attenuated by said selected forward focused power ratio of one-to-two or 6 dB.

11. The improved bipolar loudspeaker system of claim 6, wherein said crossover comprises an active frequency dividing network configured and tuned to segregate the audio signal into (a) an amplified front-facing array driving signal, and (b) an amplified rear-facing array driving signal having a selected power ratio compared to said front-facing array midrange or mid-bass driving signal such that, compared to said front-facing array driving signal, said rear-facing array driving signal is attenuated by said selected forward focused power ratio.

12. The improved bipolar loudspeaker system of claim 6, wherein at least one of said midrange or mid-bass loudspeakers comprises:

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 diaphragm comprising an inner periphery defining a central opening and an outer periphery, the inner periphery of the 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 over the inner radiating area of the diaphragm.

13. Loudspeaker according to claim 12, wherein the bulbous tip waveguide extension is configured to substantially attenuate high frequency sound radiation from the central portion of the diaphragm.

14. An acoustic transducer according to claim 13, wherein the bulbous tip waveguide extension is configured to substantially absorb high frequency sound radiation from the central portion of the diaphragm.

15. An acoustic transducer according to claim 14, wherein said diaphragm'"'"'s inner periphery incorporates a inner flexible roll seal.

16. An acoustic transducer according to claim 14, 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.

17. The electro-acoustic transducer of claim 16, wherein the bulbous tip waveguide extension of the pole ascends to a height substantially no less than height of the diaphragm with the voice coil at rest, and substantially no more than height of the diaphragm at maximum excursion.

18. A method of enhancing the sensation of spaciousness while preserving localization and minimizing the sound in a bipolar loudspeaker system, comprising:

mounting a pair of substantially identical front-facing midrange speakers and a single rear-facing midrange speaker that is substantially identical to the front-facing speakers back-to-back in an enclosure;

connecting said speakers to a source of audio power to play together, thereby creating a bipolar speaker assembly; and

driving said speakers from a common source of audio power so that the rear sound power that is produced by the rear-facing speaker is between 2 dB and 10 dB less than the sound power produced by the forward-facing speakers, thereby improving localization while retaining the spacious envelopment of the bipolar sound field.

19. The method of claim 18 further including;

mounting woofer and tweeter loudspeakers in the enclosure; and

interconnecting the woofer and tweeter loudspeakers to said source of sound power through crossover network connections.

20. The method of claim 19, further including maintaining a flat tonal balance for each of said front-facing and rear-facing speakers.