NONRESONANT SOUND TRANSDUCER/RADIATOR SYSTEM

Abstract: The present invention relates to a sound transducer/radiator system and, more specifically, to a sound transducer/radiator system in which the problem of resonant frequencies is completely eliminated. According to the present invention there is provided a nonresonant sound transducer/radiator system comprising a cabinet (1) having mounted therein different types of loudspeakers (5, 6, 7), particularly designed to reproduce tunes having different frequencies wherein each side wall (2) of said cabinet (1) has at least one slant opening slot (8) cut therein.

Description: TITLE: "NONRESONANT SOUND TRANSDUCER/RADIATOR SYSTEM" Background of the Invention The present invention relates to sound transducer/radi. ator systems and, more specifically, to an improved cabinet par- ticularly designed to eliminate the resonance problem in a sound transducer/radiator system. Sound transducer/radiator systems, generally referred to as acoustic boxes, are acoustic devices used to reproduce sound waves and usually comprise one or more loudspeakers moun- ted in a cabinet designed to enhance the efficiency of the loud¬ speakers. Typically, a sound transducer/radiator system, herein¬ after referred to as acoustic box, is provided with a loudspeake to reproduce low frequencies, called 'woofer', designed to repro duce the bass tones produced by instruments such as the base drums bassons and the like, a loudspeaker to reproduce middle frequen- ciies such as the human voice and those produced by most musical instruments, called 'midrange', and a loudspeaker to reproduce high frequencies, called 'tweeter', designed to reproduce the high pitched tones produced by instruments such as the violin. Additionally, in the acoustic boxes using two or more different types of combined loudspeakers, the use of a frequency crossover to monitor the frequencies is necessary so that any loudspeaker is only allowed to reproduce frequencies within the range it was originally designed for, in order to prevent a high frequency from being directed to a low frequency loudspeaker and vice-versa. As it is known to any person skilled in the art of a- coustic boxes, when the cone of a loudspeaker vibrates in res- ponse to a signal it radiates sound on both sides. That is, the forward movement of the cone causes a pressure build-up on its front surface and a rarefying of the air on its back while the backward movement of the cone causes an inverse condition. The continuous repetition of these movements generates two opposed sound waves 180° out of phase which tend to annul each other, which effect is aggravated at the lower frequencies. The solution to this problem is to completely separate the front and back, surfaces of the cone by means of a plate upon which the loudspeaker is mounted, called 'baffle' . The ideal di¬ mensions for this baffle should be infinite in order to complet ly separate said front and back surfaces but this is not a fea¬ sible solution and therefore the experts in acoustics were forced to look after other solutions to solve this problem. A first solution proposed for this problem consisted in the use of a completely closed cabinet as the acoustic box in an effort to reproduce a baffle having infinite dimensions complete ly separating said front and back surfaces of the loudspeaker. This design principle is known as sealed system. According to this design, the interior of the cabinet is completely coated with a sound absorbing material, such as glass wool, so that all the energy radiated from the back surface of the loudspeaker is absorbed and dissipated within the cabinet, as heat. This sealed system, however, notwithstanding the fact that it provides a low harmonic distortion and allows the anu- facturing of acoustic boxes having small dimensions while still presenting a good response at low frequencies, has a major dis¬ advantage in that it requires the use of high quality loudspea¬ kers, which together with the necessarily rigid construction of the acoustic box, raise its manufacturing costs. A second solution previously proposed for this problem was the vented, ported duct acoustic boxes, also known as 'bass reflex', which, function according to the principles of the Helm- hotz' resonator, which consists of a closed hollow cavity having a single opening with very small dimensions called duct. In the acoustic • boxes manufactured according to this design principle, it is necessary that both the cabinet and the loudspeakers mounted therein be tuned in order to obtain a line¬ arity of resonance frequencies in which there are no peaks, where by the performance of the acoustic box results are good. However, it is difficult to tune these frequencies so that the air in the duct moves inwards and outwards in phase with the loudspeaker. The use of several openings or ducts was one of the s£ lutions proposed to allow this tuning, as several ducts would cause a rupture in the concentration of the resonance frequencies. Another solution proposed to allow this matching of phases was the use of several baffles defining a labyrinth within the acou¬ stic box, but the dimensions of these baffles change according to the type of loudspeaker used in the box and this, again, results in a high manufacturing cost problem to this design. The objective of the present invention is to solve thes problems of the prior art and to provide a sound transducer/radi¬ ator system wherein this problem is solved in a simple and reli¬ able manner while at the same time not adding a cost factor to the manufacturing of the acoustic boxes. According to the present invention, these objectives are fulfilled by providing a sound transducer/radiator system com prising a cabinet having mounted therein loudspeakers particular ly designed to reproduce tones having different frequencies, wher in each side wall of said cabinet has at least one slant opening slot assymetrically cut therein. •The present invention will now be described in further details, as a non limitative example, with reference to its em¬ bodiment shown in the attached drawing which is a top perspective view of the acoustic box according to the invention. With reference now particularly to the drawing, a non- resonant sound transducer/radiator system or acoustic box accor¬ ding to the present invention comprises, basically, a cabinet 1 having four side walls 2, top and bottom walls 3,4 and a pluraii ty of loudspeakers 5,6,7 mounted therein, said side walls 2 hav¬ ing slant opening slots 8 cut therein. Cabinet 1 is a body made from laminated wood or plywood having a thickness of about 19mm and a substantially square cross- section, formed by four side walls 2, a top wall 3 and a bottom wall 4 interconnected to define a substantially closed cabinet, except for the slant openings 8. As it can be better seen from the figure, the acoustic box according to the present invention has feet or supports 9 in each of its corners to maintain it slightly above the floor and the 'woofer' loudspeakers 5 to reproduce the bass tones having low frequencies are mounted on the top and bottom walls 3,4 of the acoustic box, with their cones facing away from each other. This arrangement provides a partial cancellation of the resonances from these 'woofer' loudspeakers, in a first step towards the complete elimination of any resonance in the acoustic box. The 'midrange' and 'tweeter' loudspeakers 6,7 are moun ted on the side walls 2 of the acoustic box, as usual, and their mounting and/or installation and connection will not be discussed in further details hereinafter because they are well known to any person skilled in this art. The resonance problem in the acoustic box according to the present invention is completely eliminated by the provision of the slant opening slots 8 cut on the side walls 2 of the cabi. net 1. These opening slots 8, which degree of inclination can range from 30° to 70 from a horizontal plane, act as a system having an infinite number of vented, ported ducts. In other words, each resonant frequency finds a corresponding exit at a certain point of the opening slots, whereby said resonant frequency does not resound or echo due to the presence of a natural exit opening tuned therewith. This eliminates the problem of the concentration of resonances. Additionally, these opening slots 8 allow the loudspea kers to vibrate freely, in contrast with the sealed or vented, ported duct systems of the prior art, whereby loudspeakers having lower quality requirements and, accordingly, lower cost, can be used in the acoustic boxes according to the present invention. The width of these opening slots 8 depends on the pre sure created by the loudspeakers. In other words, it depends on the inner volume of the acoustic box and, as cited above, must be at least big enough to allow the loudspeakers to vibrate freely. Another important feature of the present invention is the assymetricalness of the slant opening slots 8 in each side wall, which cannot be symmetrically cut in said side walls 2 ex¬ actly in order to provide an exit to each resonant frequency. Additionally, in order to provide a better performance to the sound transducer/radiator system of the present invention, the passive frequency crossover of the prior art can be substitu ted by an active element placed before the amplifiers, whereby each type of loudspeaker is directly energizated by an amplifier only with the frequencies for which, it was designed. Having thus described the invention, it is to be under stood that it may undergo several modifications and changes in its embodiments as long as these modifications and changes do not depart from the true spirit and scope of the invention as claimed in the attached claims.

Claims: CLAIMS : 1. Nonresonant sound transducer/radiator system com¬ prising a cabinet having mounted therein different types of loud speakers particularly designed to reproduce tones having diffe- rent frequencies, wherein each side wall (2 ) of said cabinet (1) has at least one slant opening slot C8) cut therein. 2. Nonresonant sound transducer/radiator system accor¬ ding to claim 1, wherein the degree of inclination of said slant opening slots (8) ranges from 30 to 70 from a horizontal plane. 3. Nonresonant sound transducer/radiator system accor¬ ding to claim 2, wherein the degree of inclination of said slant opening slots (.8) ranges from 35 to 65 from a horizontal plane. 4. Nonresonant sound transducer/radiator system accor¬ ding to claim 3, wherein said degree of inclination of the slant opening slots (8). is 55 . 5. Nonresonant sound transducer/radiator system accor¬ ding to claim 1, wherein the width of said slant opening slots (8) is at least big enough to allow the loudspeakers (5,6,7) to vibrate freely. 6. Nonresonant sound transducer/radiator system accor¬ ding to claim 1, wherein said different types of loudspeakers (5, 6,7) comprise at least a loudspeaker (5) to reproduce lower fre¬ quencies. 7. Nonresonant sound transducer/radiator system accor- ding to claim 6, wherein said loudspeaker (5) is mounted on the top C3)_ or bottom wall (4) of said cabinet (1) to reproduce lower frequencies.

Inventors: MAZUZA GEORGE, MAZUZA, GEORGE
Applicants: MAZUZA GEORGE, MAZUZA, GEORGE
Application year: 1989
Main classification: H04R1
IPC codes: H04R1