Loudspeaker system

Abstract

A loudspeaker system includes a 10-inch high compliance woofer in a 1.5 cubic foot substantially fluid-tight enclosure. A pair of smaller speakers functioning as upper frequency radiators are supported on the top of the enclosure closely adjacent to the front edge with the axes of these small loudspeakers subtending an angle of substantially 90° so that the angle of each axis to the rear surface of the enclosure is substantially 45°. These small loudspeakers face the rear of the system, and fiberglass behind these speakers attenuates back radiation from them while being transparent to low frequency radiation produced by the woofer so that such radiation does not deflect the small speakers. The woofer and small speakers are fed in parallel, the small speakers receiving their energy through a network that allows increased transmission with increasing frequency. Both woofer and small speakers radiate energy over a common middle frequency range.

What is claimed is: 
     
       1. A loudspeaker system comprising, means defining .[.a substantially fluid tight.]. .Iadd.an .Iaddend.enclosure having generally parallel back and front panels,   .[.high compliance.]. woofer means secured to said front panel facing outward from said enclosure for radiating energy directly into a listening area,   a source of at least first and second upper frequency radiated beams supported on the top of said enclosure outside said enclosure and oriented for radiating energy having rearward components and oppositely directed sideward components comprising first and second loudspeakers respectively facing rearwards and sidewards to opposite sides,   a pair of input terminals,   means for connecting said woofer means to said input terminals,   and frequency sensitive passive attenuating means for coupling said loudspeakers in phase to said input terminals for transmitting signals from said input terminals to said source only above a predetermined low frequency while providing said loudspeakers more energy as a function of increasing frequency to coact with said woofer means to establish for said loudspeaker system a substantially uniform radiated power response as a function of frequency when normally positioned in a room with said back panel adjacent and substantially parallel to a wall and said front panel facing the listening area.   
     
     
       2. A loudspeaker system in accordance with claim 1 wherein said woofer means and said source comprise means for radiating sound energy over a predetermined common range of middle frequencies, said woofer comprising means for exclusively radiating sound energy below said common range.   
     
     
       3. A loudspeaker system in accordance with claim 2 and further comprising means for establishing the radiation of more sound energy from said source than from said woofer means in said predetermined common range. 
     
     
       4. A loudspeaker system in accordance with claim 3 wherein the ratio of the energy radiated by said source to that radiated by said woofer means in said common frequency range is of the order 2.5:1. 
     
     
       5. A loudspeaker system in accordance with claim 1 .Iadd.wherein said top has front and rear edges near said front and back panels respectively .Iaddend.and further comprising, acoustical attenuating means between said source and said front edge for attenuating upper frequency energy directed toward the front of said loudspeaker system from said source while being acoustically transparent to low frequency energy radiated by said woofer means.   
     
     
       6. A loudspeaker system in accordance with claim 1 wherein said source comprises first and second small loudspeakers seated on said top with their axes pointing in a direction having a rearward component and opposed sideward components. 
     
     
       7. A loudspeaker system in accordance with claim 6 wherein the angle between each of said axes and the plane of said front panel is within the range of 30°-45°. 
     
     
       8. A loudspeaker system in accordance with claim 7 .Iadd.wherein said top has front and rear edges near said front and back panels respectively .Iaddend.and further comprising fiberglass acoustical attenuating means between said small loudspeakers and said front edge for attenuating upper frequency energy directed toward the front of said loudspeaker system from said small loudspeakers while transmitting low frequency energy produced by said woofer means. 
     
     
       9. A loudspeaker system in accordance with claim 8 and further comprising a top cover of said loudspeaker system above said small loudspeakers, and means for covering the sides of the region between the latter top and said top of the enclosure with material that is optically opaque and acoustically transparent.   
     
     
       10. A loudspeaker system in accordance with claim 9 and further comprising front cover posts between the front corners of said tops and a back plate between the centers of the back edges of said tops for supporting the latter top on said top of the enclosure while presenting a substantially acoustically transparent opening to said first and second beams. .[. 
     
     
       11. A loudspeaker system in accordance with claim 1 and further comprising, frequency sensitive passive attenuating means for coupling said source to said input terminals while imparting progressively less attenuation with increasing frequency..].   
     
     
       12. A loudspeaker system in accordance with claim 1 and further comprising, the parallel combination of an inductor and resistor between said woofer means and one of said input terminals for slightly attenuating signals within a predetermined middle range of frequencies.   
     
     
       13. A loudspeaker system in accordance with claim 12 wherein said predetermined range is substantially 100 to 800 Hz. 
     
     
       14. A loudspeaker system in accordance with claim 12 wherein the value of said inductance is within the range of 1 to 4 millihenries and that of said resistor is within the range of 2.2 - 8 ohms and said woofer means has a nominal impedance of substantially 4 ohms. 
     
     
       15. A loudspeaker system in accordance with claim 1 wherein said source is located closely adjacent to the front edge of said top. 
     
     
       16. A loudspeaker system in accordance with claim .[.1.]. .Iadd.15 .Iaddend.wherein said woofer means and said source comprise means for radiating sound energy over a predetermined common range of middle frequencies, said woofer comprising means for exclusively radiating sound energy below said common range.   
     
     
       17. A loudspeaker system in accordance with claim 1 having only three loudspeaker drivers, one of which is said woofer means and the second and third of which are said first and second loudspeakers respectively. 
     
     
       18. A loudspeaker system comprising, means including woofer means defining .[.a substantially fluid-tight.]. .Iadd.an .Iaddend.enclosure,   said woofer means being for radiating acoustical energy .Iadd.to the front directly into the listening area .Iaddend.having spectral components at least in the low range of audio frequencies below a predetermined crossover frequency,   first and second like upper frequency driver means with means for attenuating rear radiation therefrom supported upon but outside said enclosure and having their axes pointing toward opposite sidewards directions for radiating acoustical energy having spectral components in the upper range of audio frequencies above said predetermined crossover frequency toward opposite sides of said enclosure,   the region to the side of each of said upper frequency driver means being substantially completely acoustically transparent,   said first and second upper frequency driver means being connected together for cophasally radiating substantially the same signal,   an input terminal pair for receiving an audio electrical signal,   and crossover network means for coupling energy from said input terminal pair with spectral components below and above said predetermined crossover frequency to said woofer means and the connected-together upper frequency driver means respectively while substantially blocking spectral components below said predetermined crossover frequency from the latter driver means including means for coupling to said first and second like upper frequency driver means more energy as a function of frequency to establish the on-axis pressure response thereof increasing with increasing frequency to coact with said woofer means to establish for said loudspeaker system a radiated power response as a function of frequency when normally positioned in a room that approaches uniformity more nearly than if said on-axis response were substantially uniform.   
     
     
       19. A loudspeaker system in accordance with claim 18 having only three loudspeaker drivers, one of which is said woofer means and the second and third of which are said first and second upper frequency driver means respectively. 
     
     
       20. A loudspeaker system in accordance with claim 18 wherein said means defining .[.a substantially fluid-tight.]. .Iadd.an .Iaddend.enclosure has generally parallel back and front panels with said woofer means being high compliance and secured to said front panel facing outwardly from said enclosure whereby said loudspeaker system is normally positioned in a room with said back panel adjacent a wall and said front panel facing the listening area. 
     
     
       21. A loudspeaker system in accordance with claim 18 wherein said means for coupling comprises a resistively shunted capacitor connected intermediate said connected together upper frequency driver means and said input terminal pair. .Iadd. 22. A loudspeaker system comprising, cabinet means for supporting loudspeaker drivers and having a front panel perpendicular to side panels,   first loudspeaker driver means supported by said cabinet on said front panel for radiating sound energy to the front directly into the listening area before reflection from a reflecting surface over a first frequency range and having a first polar response,   second loudspeaker driver means supported by said cabinet for radiating sound energy to the side for reflection first from a reflecting surface and then into the listening area along a path after reflection that intersects a plane perpendicular to said front panel and parallel to said side panels in said listening area over a second frequency range mostly higher than said first frequency range and having a second polar response different from said first polar response,   the axis of said second loudspeaker driver means being generally parallel to a normally vertical plane that bisects the angle between said front and side panels,   an input terminal pair,   and means for intercoupling said input terminal pair and said first and second loudspeaker driver means for providing spectral components in a common frequency range to said first and second loudspeaker driver means so that the difference between the frequency response of energy radiated by said first loudspeaker driver means and the frequency response of energy radiated by said second loudspeaker driver means in said common frequency range is not appreciable,   said means for intercoupling coacting with said first and second loudspeaker driver means to comprise means for dissimilarly radiating from first and second locations defined by said first and second loudspeaker driver means respectively spectral components over said common frequency range to provide a spatially diffuse source,   said common frequency range being at least half an octave. .Iaddend. .Iadd.23. A loudspeaker system in accordance with claim 22 wherein said common frequency range embraces 1 to 3 kHz. .Iaddend. .Iadd.24. A loudspeaker system in accordance with claim 22 wherein said first loudspeaker driver means supported by said cabinet for radiating sound energy comprises a woofer facing the front and said second loudspeaker driver means supported by said cabinet for radiating sound energy comprises tweeter means for radiating sound energy to the rear and side. .Iaddend. .Iadd.25. A loudspeaker system comprising,   means including front and side panels with woofer means seated in said front panel for defining an enclosure,   said woofer means being for radiating acoustical energy to the front directly into the listening area before reflection from a reflecting surface having spectral components at least in the low range of audio frequency below a predetermined crossover frequency,   at least one upper frequency driver means having its axis pointing in a sideward direction at an angle to the axis of said woofer means for radiating acoustical energy first upon a reflecting surface and then into the listening area along a path after reflection that intersects a plane perpendicular to said front panel and parallel to said side panels in said listening area having spectral components in the upper range of audio frequencies above said predetermined crossover frequency to the side of said enclosure,   an input terminal pair for receiving an audio electrical signal,   and crossover network means for coupling energy from said input terminal pair with spectral components below and above said predetermined crossover frequency to said woofer means and to said upper frequency driver means respectively while substantially blocking spectral components below said predetermined crossover frequency from the latter driver means including means for coupling to said upper frequency driver means more energy as a function of frequency to establish the on-axis pressure response thereof increasing with increasing frequency to coact with said woofer means to establish for said loudspeaker system a radiated power response as a function of frequency when normally positioned in a room that is substantially uniform over nearly the entire range of audible frequencies. .Iaddend.