LOUDSPEAKER SYSTEM WITH BOUNDARY LAYER CONTROL

Abstract: A loudspeaker system, where the construction comprises a cabinet (12) that has two drivers (14, 16) mounted in the front face (18) thereof, controlled by an electronic crossover network (42). The front face of the cabinet slopes upwardly and rearwardly from bottom (20) to top (22), generally at an angle of about (20) degrees to the vertical; it is recessed from the forward extension of the sides, top and bottom, and is covered except over the drivers, with a compressed fibrous, sound absorbing material (24). The material is compressed by the grill cloth (32) which is stretched at least across the front of the speaker. The compressed fibrous, sound absorbing material attenuates surface waves that are propagated outwardly from each of the woofer and tweeter parallel to or at a shallow angle to front face of the cabinet, and any reflections from cabinet corners or the like are even further attenuated. Because of the sloped front face, the crossover network may be designed having constant group delay time differences over the first one or two octaves on each side of the crossover frequency, so so that there is better phase response and minimal interaction between the drivers.

Description: • LOUDSPEAKER SYSTEM WITH BOUNDARY LAYER CONTROL FIELD OF THE INVENTION; This invention relates to loudspeakers, and in particular relates to two-way speaker systems that have a woofer and a tweeter, and which may be " mounted in a relatively small cabinet. The construction of the loudspeakers of the present invention includes a compressed fibrous, sound absorbing material placed over the front face of the speaker cabinet — except where the drivers are mounted — which is held and compressed in place by the grill cloth which is stretched across the front. In an alternative embodiment, the sound absorbing material may be compressed by a frame that is held in place at the front of the speaker. BACKGROUND OF THE INVENTION: There has been some tendency, in the past, to look to the development of smaller, high fidelity speakers for use with stereo systems and the like, but with such developments has come a generally lower quality of sound reproduction. Moreover, there is a desire to provide speakers that can be produced inexpensively. One of the approaches that has been taken, in the past, to develop smaller sized speakers has been to provide folded columns or enclosures, such as that referred to in MITCHELL, United States Patent 4,235,301, dated November 25, 1980. That structure, however, is a complicated one, requiring at least six reflector panels which are mounted at 45 degree angles, and has a rather unique shape that may not be easily accepted in the market place. In any event, it is required that any good speaker should have acceptable low frequency response, which means not only that the speaker should have a response to a relatively low frequency such as 50 Hz or lower, but that it should have control over . the below resonance woofer cone movement, and also that it should not have a low rolloff rate below resonance. Still further, in any speaker enclosure having drivers such as woofers, mid-range speakers, dome tweeters, and so on, it "is a virtually inescapable fact that there is a component of the sound wave generated by each driver that travels parallel to or at a shallow angle to the face of the front panel of the speaker cabinet. To make matters worse, any of the surface waves that propagate outwardly from the drivers that are mounted in a speaker enclosure or cabinet will reflect from any discontinuity on the face of the cabinet, such as the corner or edge of the cabinet. Moreover, there are interactions between the surface waves propogating from the various drivers, with the overall result that there are a series of cancellations and reinforcements, which not only results in an irregular frequency and phase response of the speaker, it manifests itself in an uneven cosine pulse test response, blurs the stereo imaging when a pair of speakers are used from a stereo source, and blurs the transient attack of the speaker system. In other words, a speaker system, by virtue of the physical mounting of the drivers in the cabinet, can reduce its own accuracy and efficiency, and create "noise" by failure to accurately reproduce the electrical signals that have come to the speakers. This, in turn, can result in a loss of perceived stereo imaging due to the loss of physcho-acoustic information because of the aberrant out-of-phase sound infonmation received, which disturbs the mental "processing" required by the listener. That, in turn, can result in loss of stereo imaging, and "listener fatigue". The present invention seeks to overcome those difficulties, and does, by providing a relatively thick compressed fibrous, sound absorbing material on the front face of the speaker cabinet. Moreover, the sound absorbing material is held in place either • by the grill cloth or a frame that is mounted to the front of the speaker cabinet, where the front face of the cabinet is recessed from the forward extensions of at least either the sides of the cabinet or the top and bottom of the cabinet — usually the sides and top and bottom. Other prior art that addressed several of the problems overcome by the present invention includes BAITCHER, Publication 82-00543, dated February 18, 1982. That publication, however, relates to a structure where signals, and particularly high frequency components from the back surface of a mid- range diaphragm, are attenuated, while the mid-range components are- phase-delayed and redirected through a part of the housing so as to enhance mid-range signals being heard from the front of the speaker. ISHII ET AL, in United States Patent 4,015,089, dated March 29, 1977, teach a commercially popular multi-way speaker system that has at least three drivers each of which is arranged in a staggered relation along their respective radiating axes at predetermined spacings from each other. An appropriate crossover network is then required, so that the sound waves radiated from the various drivers are substantially flat — at least when tested with a synthesized signal. The phase and .frequency characteristics of the speaker construction are considerably more linear than previously. However, that speaker construction is relatively expensive — at least compared with speakers built according to the present invention - having substantially similar frequency and phase response characteristics with substantially similar power handling capacities. A further patent is that of DEXTER, United States Patent 4,249,037, dated February 3, 1981, which teaches a truncated pyramidal housing having an open top and a plurality of drivers suspended in the housing with a woofer in the bottom, and at least a pair of mid-range speakers. The open top channels sound out from the speaker housing, and the non- parallel sides which are tapered preclude the sound that goes out the top port from coming back into it, thus reducing internal resonance. One further patent of interest is HUMPHREY, United States Patent 4,325,454, dated April 20, 1982, which teaches a speaker housing having two chambers, the first of which is air-impermeable. There are two speakers or driver, that are mounted with the rear surfaces of their diaphragms facing inside of the air-impermeable chamber and with their axes perpendicular to each other, and there is a slant board oriented at an angle to the axis of the second speaker in the second chamber. A pressure wave of the rear surface of the diaphragm of the first speaker is coupled from its chamber through the second speaker, thereby maintaining the pressure within the air-impermeable chamber constant, and the sound wave from the front surface of the second speaker diaphragm reflects off the slant board with phase reversal so that it is substantially in the same phase as the sound pressure wave from the front surface of the diaphragm of the first speaker. None of the above prior art, however, addressed the question of attenuating surface waves, of their reflections, on the front face or parallel or at a shallow angle to it, of a speaker enclosure. Any attempt that has been made in the industry to address that question has been simply the application of a felt " ad or surround in the immediate area at the periphery of the tweeter or mid-range drivers, but this has generally merely introduced further points for creation of reflection and more distortion. The principal purpose for the present invention is to present a loudspeaker system which overcomes the problems of frequency and phase response due to the presence of surface waves that propagate from the .drivers along or parallel to the surface of the cabinet face in which the drivers are mounted, or at a shallow angle to it. Moreover, the present invention provides a loud speaker system that has superior perceived low frequency response to either ported or ducted cabinets or folded columns, especially those of comparable physical size. Still further, the present invention results in a speaker system for use with stereo signals that gives a much better transient response, better stereo imaging and more improved detail and ambience, all at relatively low costs. All of the advantages and objectives are met by the provision of a cabinet having two drivers mounted in the front face thereof, a woofer and a tweeter, and a crossover, where the front face of the cabinet slopes upwardly and rearwa-rdly from bottom to top, with the woofer being mounted below the tweeter. A compressed fibrous, sound absorbing material covers the front face of the speaker cabinet except at the two openings that are provided for the active areas of the drivers — their diaphragms or domes — and has an appreciable thickness. Due to that structure, surface waves that propagate outwardly from either of the drivers parallel to or at a shallow angle to the front face of the cabinet are substantially attenuated . BRIEF DESCRIPTION OF THE DRAWINGS : " The objects and advantages discussed above, and others, are more clearly described hereafter in association with the accompanying drawings, in which: Figure 1 is an isometric view of a typical speaker cabinet according to the present invention, as constructed, but with a portion of the speaker grill cloth having been removed; Figure 2 is a partial cross-section in the plane 2-2 of Figure 1j Figure 3 is a partial cross-section in the plane 3-3 of Figure 1; and, Figure 4 is a schematic of a typical crossover network for use with the -loadspeaker system of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS: One of the principal objectives in the preparation of speakers according to the present invention is that the speaker should not necessarily be physically very large. This, of course, presents problems because of the almost contrary requirement .that the speakers should have good low frequency response and accuracy. As it happens, speakers in keeping with the present invention, and manufactured as in the manner of the examples discussed hereafter, are ' substantially only twenty to twenty-two- inches high, ten to fourteen inches wide, and thirteen to fifteen inches from back to front at the bottom dimension which is the longest from front to back. Given that ' the speakers according to the present invention have a frequency response of plus or minus 3 dB in the range of 50 Hz to 17kHz, • it will be appreciated that the physical size of the speakers is quite small. Referring to Figure 1, a loudspeaker 10 is illustrated, which comprises a cabinet 12, a first low frequency driver (woofer) 14, and a second high frequency driver (tweeter) 16. An electronic crossover network is not shown, but is mounted within the speaker enclosure or cabinet 12. In the usual manner, the crossover network discussed hereafter in association with Figure 4 — controls the frequency cut-off and rolloff characteristics of the drivers 14 and 16. The front face 18 of the cabinet 12 slopes upwardly and rearwardly from the bottom 20 to the top 22; and- the woofer 14 is mounted below the tweeter 16. The back panel 19 is perpendicular to the top and bottom of the cabinet. A compressed fibrous, sound absorbing material 24 covers the front face 18 of the cabinet 12, except that openings are provided in front of the woofer 14 and the tweeter 16; at least, openings are provided in front of the active areas — the diaphragm, of the woofer 14 and the dome of the tweeter 16. The sound absorbing material 24 has an appreciable thickness; which means that the thickness of the sound absorbing material 24 is considerably greater than, say, the thickness of the diaphragm material of the woofer 14 or the thickness of ordinary grill cloth used with speakers, as discussed hereafter. It will be noted that the front face 18 of the cabinet 12 is recessed from the forward extensions of at least the side pieces 26 of the cabinet 12; and in an alternative embodiment " it may be that the front face 18 is recessed only from the forward extensions of the top piece 28 or the bottom piece of the cabinet. However, in general, all of the side pieces, top and bottom pieces of the cabinet 12 extend fo ' rwardly of the front face 18; that is to say, the front face 18 is recessed .from all of their forward extensions. (In a minimum cost embodiment of the speaker of the present invention, the sound -absorbing material 24 may simply be placed on the front face of a speaker and compressed, as discussed hereafter.) In the general construction of the speaker 10, the woofer 14 and the tweeter 16 may be mounted on or in the panel 30 which provides the front face 18. During the assembly of cabinet 12, the woofer 14 and the tweeter 16 are mounted in the front face 18. They may be mounted through appropriate openings in the panel 30, so that they are screwed or secured to the front face of the panel 30, or they may be secured to the rear face of the panel 30, or otherwise; so long as they are well secured and in place. Thereafter, the sound absorbing material 24 is put into place and is compressed such as by stretching and tightening a grill cloth material 32 across the front of the ca'binet 12 and particularly over the forward extensions of the side, bottomland-. top pieces of the cabinet; thereby compressing the sound absorbing material 24 which was previously uncompressed when first placed on the front face 18 of the cabinet. The sound absorbing material is conveniently glass fibre material of the sort which is commonly used for providing insulation in the walls of buildings such as residential homes, and the like. Moreover, the glass fibre material that is used should be of a thickness that it will be compressed to about one half to one third of its uncompressed thickness. In an alternative embodiment, the sound absorbing material 24 may be compressed by placing a frame over it and securing the frame within the forward extensions of the side pieces 26, top piece 28 and bottom piece of the cabinet 12. In a further (low cost) embodiment, the sound absorbing material 24 may simply be placed on the front face 18 of the speaker cabinet that is not recessed from the forward extensions of the top, bottom or sides. In that event, the sound absorbing material is compressed by stretching and tightening the grill cloth material in such a manner that the edges of the front face ha ' ve a tapered or rearwardly sloping appearance. Moreover, a"somewhat similar but less striking rearwardly sloped appearance may also be achieved in the more usual embodiment of the speaker of the present invention, by having the forward extensions of the top, bottom and sides to a somewhat lesser extent; or, in the alternative, by using even thicker sound absorbing material 24 so that it is more 'compressed at the edges than in the centre of the front face. It follows, from that, that the present invention also contemplates the instance where the sound absorbing material need not be homogenously compressed across the entire width of the front face, but can be more compressed towards the edges. It may be that the dimensions of a typical cabinet, as shown in Figure 1, are twenty inches high, ten to eleven inches wide, and fourteen inches deep at the bottom. The cabinet is approximately seven inches deep at the top, thus the angle of the sloping front face 18 and of the sloping forward extensions of. the side pieces 26 is approximately 20 degrees from the vertical or 70 degrees from the bottom. Of course, those dimensions and angles are not absolute, in that the speaker could be made somewhat larger — although not too much smaller without deleterious effect on the low frequency response. Also, the angle of the sloping front face ma Y generally be from 15 degrees to 25 degrees from the vertical (75 degrees to 65 degrees from the bottom) . Typical drivers are a woofer that is seven to eight inches in diameter, preferably having a diaphragm made of Bextrene (TM) or polypropylene, and a one inch soft dome tweeter. The crossover network, discussed hereafter, provides a crossover between the two drivers at about 3.5 kHz; and, as noted, the speaker has a response that is plus or minus 3dB in the range of 50 Hz to 17 kHz. Given the above, and having a crossover network where both the high pass and low pass sections have a relatively constant group delay time difference over the first one or two octaves on either side of the crossover frequency, the sloping front face 18 accommodates the fact that the tweeter 16 should be set back physically from the woofer 14. Also, allowance is made for the fact that the centre of radiation for a dome tweeter is further forward with respect to the mounting in the panel 30 than for a woofer. A further advantage of the sloping face that is realized is the fact that the so-called dome dimple frequency wobble that may occur in a dome-type tweeter would be aimed, on axis, upwards and therefore in the usual instance over the head of the listener. Moreover, to permit an otherwise unimpeded forward radiation from the tweeter, i , is normal to shape the opening in the sound absorbing material 24 around the tweeter 16 by bevelling it as at 34 in Figure 2. By bevelling the sound absorbing material ,24, the opening is made to increase in size forwardly of the front surface of the front face 18 and forwardly of the tweeter 16. The unimpeded forward radiation path may then be at least plus or minus 45 degrees from the axis of the tweeter 16, circularly around the axis. As seen in Figures 2 and 3, the mounting of the tweeter 16 and the woofer 14 is such that each is substantially on the centre line of the front panel 30, (for the purposes of symmetry). Moreover, the grill cloth 32 is shown stretched across from the forward extensions of the two side pieces 26, in each Figure, thereby compressing the glass fibre, sound absorbing material 24 against the front face 18. The uncompressed fibre is shown in ghost lines at 36 in each of Figures 2 and 3. (It has also been noted above that the sound absorbing material 34 may be more highly compressed at -the edges, if it has been placed over a substantially flat front face, or one having extensions of the top, bottom and sides to a lesser extent than in the preferred embodiment.) If desired, the drivers — especially the tweeter 16 — may be mounted to one or the other side of the central vertical axis of the cabinet 12. In that case, however, two mirror-imaged speakers would 'be required, properly mounted and phased, to realise stereo imaging. There is also shown in each of Figures 2 and 3 a further component that is inserted into the cabinet 12 before it is closed. That is a plurality of discrete chunks of uncompressed glass fibre material, shown at 38 in each Figure. Conveniently, each of the chunks 38 may be a cube of about 3.5 to 4 inches per dimension, and may be easily cut batts of glass fibre material of that thickness. It will also be seen that, for such reasons as appearance, it is convenient that the grill cloth material 32 may be stretched across the front of the speaker 10 and also along the sides 26 and across the top of the cabinet. That leaves only the bottom and the rear surfaces of the cabinet uncovered with the grill cloth, and they may be spray painted or covered with a cardboard or other * material covering of a similar appearance and colour to the grill cloth; thereby making a loud speaker enclosure and cabinet that has no external wood finish. This means that the cabinet is not manufactured, in those circumstances, using cabinet-finished hardwood, and the like, and is therefore more easily and inexpensively prepared and manufactured. Indeed, the side pieces, the top, the bottom, the front and the back pieces of the cabinet 12 may all be made of sheet panel material such as particle board or plywood. Those material are generally quite inexpensive, especially particle board, and they are very strong. They are also hard, and there may be back waves reflected from them. For those reasons, and also to decrease the resonance of the cabinet, a further panel of relatively soft and slightly compressible sheet material such as pulp board — especially that sold in association with the Trade Mark "Ten-Test" — may be secured to the inside surfaces of at least each of the side pieces 26 of the cabinet 12, ' as shown at 40 in Figures 2 and 3. The pulp board 40 may be secured to the inside surfaces of the side pieces 26 such as by contact cement. The contacting edges of the sides, top and. bottom, with the front and back panels, may all be substantially airtight. It may sometimes also be helpful, in the event of any irregularities of backwave from the woofer 14, to secure a small piece of pulp board to the inside of the front panel 30 in the area below the opening through which the woofer 14 is mounted. Likewise, the sound absorbing material 24 may be secured to the front face 18 by several dabs of contact cement , placed in the corners and elsewhere as required . It should also be noted that the present invention also contemplates the possibility that there may be a single, coaxial, driver mounted in the front fact of the cabinet. Usually, in such a speaker, the centre of radiation for the tweeter element is mounted further forward than the centre of radiation for the woofer element — and, indeed, there may also be a mid-range element — but the bevelling as at 34 in Figure 2, to accommodate the woofer element as in Figure 3 does provide for an unimpeded primary forward radiation path. Also, because of the angle of the sloping front " face, any on-axis frequency wobble or other distortion that may occur in the tweeter element is, again, aimed upwards and therefore in the usual instance over the head of the listener. Turning to Figure 4, a typical crossover network 42 is shown, having connecting points 44 for connection of the crossover to the amplifier which drives the speaker on that channel to which it is connected if it is in stereo. In any event, the high pass section is shown to comprise a capacitor 46, a choke 48, and an RC network 50, connected to the tweeter ' 16. The low pass section comprises a choke 52 and an RC network 54, connected to the woofer 14. The particular network shown, having the values as indicated, provides a crossover of about 3 * 5 kHz, with an even and relatively constant group delay time difference for the first one or two octaves on each side of the crossover frequency of 3.5 kHz. For ease of construction and mounting, the crossover network components may be mounted inside the cabinet 12 such as by securing them to the inside surface of the back panel of the cabinet with such material as the silicone sealant material that is used for sealing around bathtub enclosures. This provides a mounting for the crossover network components that is substantially free of vibration, so that it will neither rattle or buzz, nor fall off. Speakers have been built having the general construction as discussed and described above, and with the dimensions as mentioned, and a crossover network as shown. Those speakers have demonstrated excellent square wave response and cosine pulse test response, thereby demonstrating the ability of the speakers to faithfully reproduce a fast rising signal. Excellent low frequency rolloff is exhibited, with substantially flat response (plus or minus 3 dB) and with good clarity of signal reproduction. Because of the presence of the .compressed sound absorbing material 24 — generally compressed glass fibre batts that have been compressed from, say, three and a half or four inches thick to approximately one and one quarter to one and three quarter inches thick — not only are -surface waves that propagate from the drivers (the woofer 14 or the tweeter 16), parallel to or at a shallow angle to the front face 18, attenuated by the compressed sound absorbing material 24, any reflected waves are even further attenuated, so that there is substantially no irregular frequency or phase response of the speakers. That is, there is no frequency phase anomaly over substantially the entire frequency range of the speaker. It has been noted that the frequency above which very acceptable response is attained is approximately 50 Hz; that is not to say that that there is no response below 50 Hz, but that the response below 50 Hz is not as flat as above. It can be expected that, in some circumstances, the speakers of the present invention may be used with and coupled to sub-woofers that work in the very low frequency ranges. In any event, a loudspeaker system having boundary layer control of sound waves propagated across the surface of the speaker cabinet from the drivers,- parallel to or at a shallow angle to the front face thereof, has been discussed and described with illustrations of alternative constructions. An advantage of the present invention is that surface waves are attenuated and surface reflections even more so, and there is minimal interaction between the drivers; and thus there is a cabinet frequency response and phase response that is quite smooth. Due to the construction, especially the assured absence of surface sound wave anomalies, phase coherency through the crossover region — the crossover frequency plus or minus at least one octave on each side thereof — is more easily achieved; giving, of course, a much improved transient response. Because of that, stereo imaging is improved when a pair of speakers is used, one connected to each of the stereo channels from a stereo amplifier, and with a better sense of detail and ambience. Speakers "may be driven having a response of about 80 Db at one metre on axis by amplifiers having as little as 25 to 60 watts per channel. The accompanying claims define the ambit of the present invention.

Claims: CLAIMS 1. A loudspeaker system, comprising a cabinet 12 having at least one loudspeaker driver 14,16 mounted in the front face 18 thereof; where said front face of said cabinet slopes upwardly and rearwardly from bottom 20 to top 22; a compressed fibrous, sound absorbing material 24 covers said front face except forward of the active area of said at least one loudspeaker driver; and said sound absorbing material has an appreciable thickness; whereby surface waves that propagate outwardly from said at least one loudspeaker driving to or at a shallow angle to said front face, are substantially attenuated. 2. The loudspeaker system of claim 1, where said at least one loudspeaker driver is a coaxial driver having at least a first, tweeter element and a second, woofer element. 3. A loudspeaker system, comprising a cabinet and two drivers 14,16 mounted in the front face thereof, the first driver 14 being a low frequency driver and the second driver 16 being a high frequency driver, and a crossover network 42 to control the frequency cut-off and rolloff characteristics of the drivers; where " said front face 18 of said cabinet slopes upwardly " and rearwardly from bottom 20 to top 22, and said first driver is below said second driver; a compressed fibrous, sound absorbing material 24 covers said front face except forward of openings where said front face is occupied by the active areas of said drivers; and said sound absorbing material has an appreciable thickness; whereby surface waves that propagate outwardly from either of said drivers parallel to or at a shallow angle to said front face, are substantially attenuated. 4. The loudspeaker system of claim 1 or 3, where said front face is recessed from the forward extensions of at least the side pieces 26 of said cabinet or from the forward extensions of at least the top and bottom pieces 20,22 of said cabinet. 5. The loudspeaker system of claim 3, where said front face is recessed from the forward extensions of the side pieces and the top and bottom pieces of said cabinet. 6. The loudspeaker system of claim 5, where the opening in said sound absorbing material at said second driver 16 is bevelled 34 so as to increase in size, forwardly of the front surface of said front face and said second driver. 7. The loudspeaker system of claim 2, where said sound absorbing material 24 is compressed as a consequence of a grill cloth material 32 having been stretched and tightened across the front of said cabinet and over said sound absorbing material which was previously uncompressed 36. 8. The loudspeaker system of claim 6, where said sound absorbing material 24 is compressed as a consequence of a grill cloth material 32 having been stretched and tightened ^ across the front of said " cabinet and over said sound absorbing material which was previously uncompressed 36. 9. The loudspeaker system of claim 7 or 8, where said front face 18 slopes rearwardly and upwardly from the bottom 20 at an angle of from 15 to 25 degrees from the vertical. 10. The loudspeaker system of claim 8, where said first and second drivers 14,16 are each mounted substantially on the vertical centre line of said front face 18. 11. The loudspeaker system of claim 2 or 5, where said sound absorbing material 24 is compressed by a frame fitted between the forward extensions of at least the side pieces of said cabinet or from the forward extensions of at least the top and bottom pieces of said cabinet. 12. The loudspeaker system of claim 1 or 3, where said sound absorbing material 24 is glass fibre material. 13» The loudspeaker system of claim 1 or 3, where said cabinet is filled with discrete chunks 38 of uncompressed glass fibre material. 14. The loudspeaker system of claim 1 or 3, where all of the side, top, bottom, front, and back, pieces of said cabinet are made of sheet panel material such as particle board or plywood. 15. The loudspeaker system of claim 1, where all of the side, top, bottom, front, and back, pieces of said cabinet are made of sheet panel material such as part-icle board or plywood, and where a further panel of relatively soft and slightly compressible sheet material 40 such as pulp board is secured to the inside surfaces of each side of said cabinet and substantially covers the same. 16. The loudspeaker system of claim 3, where all of the side, top, bottom, front, and back, pieces of said cabinet are made of sheet panel material such as particle board or plywood, and where a further panel of relatively soft and slightly compressible sheet material 40 such as pulp board is secured to the inside surfaces of each side of said cabinet and substantially covers the same. 17. The loudspeaker system of claim 16, where a further piece of said soft sheet material is secured to the inside surface of the front face of said cabinet in the area below said first driver. 18. The loudspeaker system of claim 7 or 8, where said gnill cloth material 32 is also stretched over the sides and top of said cabinet. 19. The loudspeaker system of claim 16, where there is a crossover frequency of about 3.5 kHz, and said second driver 16 is a compression tweeter having a dome. 20. The loudspeaker system of claim 1 or 3, where said cabinet has a height of about twenty inches. 21. The loudspeaker system of claim 6, where the bevel 3 in said sound absorbing material 24 in the area of said second driver 16 is such that there is an inimpeded forward radiation path from said tweeter of at least plus or minus 45 degrees from the axis thereof.

Inventors: WRIGHT WILLIAM MICHAEL DAYTON, WRIGHT, WILLIAM, MICHAEL, DAYTON
Applicants: ASQUITH ANTHONY, WRIGHT WILLIAM MICHAEL DAYTON, ASQUITH, ANTHONY, WRIGHT, WILLIAM, MICHAEL, DAYTON
Application year: 1984
Main classification: H04R1
IPC codes: H04R1, H04R3