Acoustic system

• US 5,821,471 A
• Filed: 11/30/1995
• Issued: 10/13/1998
• Est. Priority Date: 11/30/1995
• Status: Expired due to Fees

• Current Assignee: Mark A. Mcculler
• Original Assignee: Mark A. Mcculler
• Inventors: McCuller, Mark A.
• Primary Examiner(s): Dang, Khanh
• Application Number:
  US08/565,119
• Time in Patent Office: 1,048 Days
• Field of Search: 181/148, 181/151, 181/152, 181/156, 181/199, 381/88, 381/90, 381/158, 381/159, 381/160
• US Class Current: 181/156
• CPC Class Codes: H04M 1/035 Improving the acoustic characteristics by means of constructional features of the housing, e.g. ribs, walls, resonating chambers or cavities
• CPC Class Codes: H04R 1/1008 Earpieces of the supra-aural or circum-aural type
• CPC Class Codes: H04R 1/227 using transducers reproducing the same frequency band
• CPC Class Codes: H04R 1/2834 for loudspeaker transducers
• CPC Class Codes: H04R 1/2842 for loudspeaker transducers
• CPC Class Codes: H04R 1/2853 using an acoustic labyrinth or a transmission line
• CPC Class Codes: H04R 1/2857 for loudspeaker transducers
• CPC Class Codes: H04R 1/30 Combinations of transducers with horns, e.g. with mechanical matching means , i.e. front-loaded hornshorns in general G10K; transducer enclosures or mountings using a back-loaded horn H04R1/2861; application of horns as guiding means to obtain a predetermined directivity characteristic H04R1/345
• CPC Class Codes: H04R 25/48 using constructional means for obtaining a desired frequency response H04R25/652 takes precedence

Abstract

The present acoustic system produces sounds over a broad range of frequencies, and includes an enclosure, a speaker acoustically connected to the enclosure, for generating, almost simultaneously, two sounds, a forward sound, and a rearward sound. It further includes a waveguide enclosed at least partly within the enclosure, and acoustically connected to the speaker, for defining an acoustic path along which the rearward sound travels. The waveguide includes a plurality of inner panels that are positioned inside the enclosure for optimizing the length of the travel path. The inner panels and the enclosure define a plurality of inner passageways having generally similar cross-sectional surface areas, and a plurality of inner openings, for causing a selective cancellation of sounds at predetermined frequencies, while preserving sounds at other frequencies.

Claims

1. An acoustic system comprising in combination:

an enclosure;

a speaker acoustically connected to said enclosure, for generating two sound waves, a forward sound wave, and a rearward sound wave;

a waveguide formed at least partly within said enclosure, and acoustically connected to said speaker, for defining an acoustic path along which said rearward sound wave travels;

said waveguide including a plurality of inner panels positioned inside said enclosure for lengthening the length of said travel path;

said plurality of inner panels and said enclosure defining a plurality of inner passageways, and a plurality of inner openings, for causing a selective cancellation of said rearward sound wave traveling along said acoustic path at predetermined frequencies, while allowing sound waves at other frequencies to propagate with minimal attenuation;

wherein said enclosure includes an output port through which said rearward sound traveling along said acoustic path exits;

wherein said speaker has a piston area S_D ;

wherein the surface area of said output port is equal to a portion of said piston area S_D ;

wherein said waveguide and said enclosure define a first compartment adjacent to said speaker;

wherein said first compartment has a predetermined volume;

wherein said speaker has a rear surface, at least partly enclosed within said first compartment; and

wherein said volume loads said rear surface of said speaker with back pressure, in order to reduce a cone excursion of said speaker.

2. The acoustic system according to claim 1, wherein said waveguide has a substantially uniform sectional surface area along generally its entire length.

3. The acoustic system according to claim 2, wherein said inner panels are made of acoustic material;

and

wherein said acoustic material may be any of;

plastic, wood, clay, marble, or metal.

4. The acoustic system according to claim 1, wherein said acoustic path is serpentine.

5. The acoustic system according to claim 1,

wherein said plurality of inner panels and said enclosure cause a selective cancellation of said rearward sound wave traveling along said acoustic path at high frequencies, while allowing sound waves at lower frequencies to propagate with minimal attenuation.

6. The acoustic system according to claim 1, wherein said uniform sectional surface area of said waveguide is substantially equal to the surface area of said output port.

7. The acoustic system according to claim 1, wherein said speaker is oriented outwardly away from said waveguide.

8. The acoustic system according to claim 1, wherein said forward sound propagates through said speaker;

and

wherein said rearward sound propagates through said waveguide and exits through said output port.

9. The acoustic system according to claim 8, wherein said volume (AV) is defined by the following equation:

##EQU2## where FS represents the free-air resonant frequency of said speaker;

QTS represents the Q of said speaker at FS in free air considering both its electrical and mechanical resistance;

Q represents the system losses or relative damping ratio of stored to dissipated energy or ratio of reactive to resistive energy); and

VAS represents the volume of air having the same compliance as the suspension of said speaker.

10. The acoustic system according to claim 9, wherein said waveguide has a length generally calculated from the center of a voice coil of said speaker, along said acoustic path, up to said output port;

and

wherein said waveguide length (Lwg) is generally defined by the following equation;

space="preserve" listing-type="equation">Lwg=k. FS,

where k is a constant and FS is a free-air resonant frequency factor.

11. The Acoustic system according to claim 10, wherein said rearward sounds traveling in said waveguide are reflected by said inner panels to create standing waves within said enclosure;

wherein a straight line center to center (CTC) measurement is taken between said speaker center V and a center C'"'"' of said output port; and

wherein said CTC is generally proportional to said waveguide length (Lwg), as set forth in the following equation;

space="preserve" listing-type="equation">CTC=m/Lwg,

where m is a constant factor.

12. The acoustic system according to claim 1, wherein said inner panels and said enclosure define an air volume compartment in which said speaker is at least partially housed for loading the rear surface of said speaker with back pressure to increase the efficiency of a speaker driver, and to reduce the excursion of said speaker.

13. The acoustics system according to claim 1, wherein said enclosure further includes one or more outputs ports.

14. The acoustic system according to claim 8, wherein said volume (AV) is a function of FS, QTS, and VAS, where FS represents the free-air resonant frequency of said speaker;

QTS represents the Q of said speaker at FS in free air considering both its electrical and mechanical resistance;

Q represents the system losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy); and

VAS represents the volume of air having the same compliance as the suspension of said speaker.

15. The acoustic system according to claim 14, wherein said waveguide has a length generally calculated from the center of a voice coil of said speaker, along said acoustic path, to said output port;

and

wherein said waveguide length (Lwg) is a function of FS, where FS is a free-air resonant frequency factor.

16. The Acoustic system according to claim 15, wherein said rearward sounds traveling in said waveguide are reflected by said inner panels to create standing waves within said enclosure;

wherein a straight line center to center (CTC) measurement is taken between said speaker center V and a center C'"'"' of said output port; and

wherein said CTC is generally proportional to said waveguide length (Lwg).

17. The Acoustic system according to claim 1, wherein the surface area of said output port is generally equal to one half of said piston area SD.

18. An enclosure for use with a speaker, the enclosure comprising in combination:

the speaker being acoustically connected to said enclosure, for generating two sound waves, a forward sound wave, and a rearward sound wave;

a waveguide formed at least partly within said enclosure, and acoustically connected to the speaker, for defining an acoustic path along which said rearward sound wave travels;

said waveguide including a plurality of inner panels positioned inside said enclosure for lengthening the length of said travel path;

said plurality of inner panels and said enclosure defining a plurality of inner passageways, and a plurality of inner openings, for causing a selective cancellation of said rearward sound wave traveling along said acoustic path at predetermined frequencies, while allowing sound waves at other frequencies to propagate with minimal attenuation;

wherein said enclosure includes an output port through which said rearward sound traveling along said acoustic path exits;

wherein said waveguide and said enclosure define a first compartment adjacent to the speaker;

wherein said first compartment has a predetermined volume;

wherein the speaker has a rear surface, at least partly enclosed within said first compartment; and

wherein said volume loads the rear surface of the speaker with back pressure, in order to reduce a cone excursion of the speaker.

19. A method for producing sounds over a broad range of frequencies using a speaker, the method comprising the steps of:

acoustically connecting the speaker to an enclosure for generating two sound waves, a forward sound wave, and a rearward sound wave;

forming a waveguide including a plurality of inner panels, at least partly within said enclosure, and acoustically connecting said waveguide to speaker for defining an acoustic path along which said rearward sound wave travels;

positioning said plurality of inner panels inside said enclosure for lengthening the length of said travel path;

said plurality of inner panels and said enclosure defining a plurality of inner passageways, and a plurality of inner openings, for causing a selective cancellation of said rearward sound wave traveling along said acoustic path at predetermined frequencies, while allowing sound waves at other frequencies to propagate with minimal attenuation;

wherein said enclosure includes an output port through which said rearward sound traveling along said acoustic path exits;

wherein the speaker has a piston area S_D ;

wherein the surface area of said output port is equal to a portion of said piston area S_D ;

wherein said waveguide and said enclosure define a first compartment adjacent to the speaker;

wherein said first compartment has a predetermined volume;

wherein the speaker has a rear surface, at least partly enclosed within said first compartment; and

wherein said volume loads said rear surface of the speaker with back pressure, in order to reduce a cone excursion of the speaker.