Patent Application
20070165894
The present disclosure generally relates to speakers and speaker cabinets for use with musical instruments, and relates in particular to attenuation of a speaker.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Speakers and speaker cabinets, and guitar speaker cabinets in particular, have long suffered from a tendency to project frequencies unevenly to an audience, such as performers, listeners, and microphones positioned in front of the speakers. With reference to
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While response curve 500 extends from five-hundred Hertz to eight-thousand Hertz, it should be readily apparent to one skilled in the art that the range of human hearing extends from about twenty Hertz to about twenty-thousand Hertz. It should also be readily apparent that musical instruments, such as guitars, are typically only capable of playing notes in a range from about forty Hertz, in the case of a contra base guitar, to about one-thousand seven-hundred sixty Hertz, in the case of an alto guitar. However, musical instruments, and especially electric guitars, can produce higher frequencies as harmonic overtones, especially in the case of tube amp distortion for an electric guitar or use of artificial aural excitation for an electric/acoustic guitar. These harmonic overtones can easily range up to eight-thousand hertz. Thus, the presence of higher frequencies dramatically effects the tone of an amplified guitar signal.
Moreover, one skilled in the art will readily recognize that decibels are a logarithmic measure, and that perceived loudness of a sound is generally known to double with an increase of ten decibels. This perceived loudness does not directly relate to actual intensity or amplitude, which doubles with an increase of three decibels. Moreover, perceived loudness, which is an experimentally obtained psychoacoustic measure typically expressed in phons, does not directly correspond to decibels. Typically, a contouring filter, such as an A filter generally accepted for use in musical applications, can be applied to a rough conversion of decibels to phons, with the units expressed as dBA, dBB, or dBC, depending on the filter employed. Alternatively, a conversion table available in acoustics textbooks can be employed to achieve a more accurate conversion expressable as phons. However, the difference between decibels and phons or dBA is mostly significant for frequencies below one thousand Hertz and above eight thousand Hertz. For example, one skilled in the art will readily recognize that application of an A filter to curve 500 would leave points of the curve the same at one-thousand Hertz and five-thousand Hertz, while adjusting other frequencies between one-thousand and eight thousand Hertz by no more than about two decibels. Such application would, however, significantly reflect a decrease in the perceived loudness of lower frequencies below one-thousand Hertz. Accordingly, the difference between perceived loudness of the higher and lower frequencies is even more dramatic than might be otherwise reflected by curve 500.
The increased amplitude of the higher frequencies in the central beam region is generally referred to as “beaminess,” and has long been known to be an undesirable characteristic of speakers, and especially of guitar speaker cabinets, that causes various undesirable results. For example, audience members closer to the stage and positioned to receive the central beam experience “ice pick highs” or “sizzle” generally perceived as unpleasant. Also, recording professionals in the past have discovered that positioning a recording microphone in the central beam region produces undesirable results, and have learned to position the microphone in one of the outer beam regions. Similarly, live sound technicians, especially at larger venues, also need to mic one or more speakers of a guitar speaker cabinet for sound reinforcement through local PA systems. However, more often than not, these live sound technicians tend to place the microphone in the central beam region. As a result, the sound emanating from the PA system tends to be unbalanced, and the entire audience experiences the unpleasant “ice pick highs” or “sizzle.”
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Accordingly, the need remains for a way to reduce the unevenness, or “beaminess,” of a speaker without creating a perceptible “hole in the sound” in the central beam region. The present invention fulfills this need.
A speaker attenuation system includes an attenuating member comprised of suitable material and having a size and a shape capable of attenuating a speaker when positioned in a central beam region of the speaker. A positioning mechanism is capable of positioning the attenuating member predominantly in the central beam region of the speaker in such a manner that it is between the speaker and an audience in a performance setting. The suitable material, such as open cell foam (i.e., acoustic foam), preferably has a property that it is capable, at one or more thicknesses, of reducing amplitudes of a majority of frequencies between one-thousand and eight-thousand Hertz by at least six decibels without reducing amplitudes of any frequencies in that range by more than eighteen decibels. Accordingly, the “beaminess” of the speaker can be reduced without creating a “hole in the sound.”
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
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In accordance with the present teachings, an attenuating member 162 is positioned positioned predominantly in the central beam region of the cabinet speaker 152 when the cabinet 150 is being operated to produce sound in a performance setting. Preferably, the attenuating member is positioned proximate to the speaker in the performance, such as within a two or three feet of the speaker. For example, the attenuating member can be attached to one or more portions of the guitar speaker cabinet in such a manner that it is properly positioned when the cabinet is assembled for operation. In a presently preferred embodiment, the attenuating member 162 is disc-shaped and centered in front of the voice coil of the speaker 152. The attenuating member 162 also preferably includes one or more layers of open cell foam, also known as acoustic foam. A layer can be one inch thick. A layer can also be six inches in diameter, especially for a twelve inch guitar speaker. Thus, two or more layers can be combined to form the attenuating member 162 when the speaker 152 is relatively new and therefore more “beamy.” Then, as the speaker 152 ages and becomes less and less “beamy,” layers can be progressively removed to effect less and less attenuation of the higher frequencies in the central beam region.
The attenuating member 162 can, for example, be attached to an interior of the screen 158 in any suitable manner. The attachment of the attenuating member 162 can be accomplished using a bolt assembly through a center of the attenuating member that is received in a wooden strut of the screen 158. When layers are removed, a shorter bolt can be used. It should be readily understood that the attenuating member can alternatively or additionally be mounted to the exterior of the screen 158, to the baffle board 154, the housing 156, and/or to the speaker 152. Moreover, any number of attachment mechanisms, such as nails, rivets, screws, staples, glue, gum, thread, latches, straps, etc. can be employed. This list of potential attachment mechanisms is not meant to be limiting in any way. Further, the attenuating member does not have to be attached to the cabinet or any of its components, but can be positioned in the central beam region in any manner.
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It should be noted that open cell foam, while presently preferred as a material for the attenuating member, may be replaced with a future equivalent when it is discovered to have properties suitable for use as an attenuating member. Further, other shapes, sizes, and varieties of acoustic foam are available and may reveal different attenuation characteristics. In general, suitable properties for material used to form the attenuating member include the ability, at some uniform or non-uniform thickness, to reduce amplitude of a majority of frequencies between one-thousand and eight-thousand Hertz by at least six decibels without reducing amplitude of any frequencies in that range by more than eighteen decibels. It should be readily understood that the material need not be employed at a thickness to accomplish at least six decibels of attenuation for the majority of frequencies in the range. Rather, it is sufficient that the material be capable of so attenuating the frequencies at some thickness. More preferably, suitable properties for material used to form the attenuating member include the ability, at some uniform or non-uniform thickness, to reduce amplitude of a majority of frequencies between one-thousand and eight-thousand Hertz by at least eight decibels without reducing amplitude of any frequencies in that range by more than sixteen decibels. Moreover, it is envisioned that layers of different materials having different properties that are suitable when layered can be combined to form the attenuating member. In this case, the combination of materials has the suitable properties. One skilled in the art is reminded that the layers can be of different thicknesses, shapes, and sizes.
Various embodiments are possible according to suitable properties of material for forming the attenuating member. For example, in some embodiments, suitable properties will allow the material to reduce amplitudes of all frequencies between two and five thousand Hertz by at least four decibels without succeeding in reducing amplitudes of any of those frequencies by more than twelve decibels. In another additional or alternative embodiment, suitable properties will allow the material to reduce amplitudes of a majority of frequencies between two thousand and five thousand Hertz by at least four decibels without reducing amplitudes of any frequencies between one and five thousand Hertz by more than twelve decibels.
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As taught herein, the speaker attenuation method, system, and apparatus is capable of improving evenness of tone of a speaker by reducing “beaminess” of the speaker without creating a “hole in the sound.” As a result, audiences in large venues will be treated to a pleasing tone even when the sound technician places the microphone to the local PA system in the central beam region of the speaker. Moreover, audience members proximate to the speaker in the central beam region will also experience the pleasing tone, and not the “ice pick highs” or “sizzle” of an unattenuated speaker, or the “muddy” tone of a blocked speaker.
