Patent Application
20130047819
The present disclosure relates generally to keyboard percussion instruments, and, more particularly, to an adjustable stop for a resonator associated with a tone bar of a keyboard percussion instrument.
Keyboard percussion instruments, such as vibraphones and marimbas, are musical instruments that have tone bars and are played upon by musicians with mallets. Keyboard percussion instruments of the type played on by hand-held mallets fall into two distinct categories: non-resonator instruments such as the glockenspiel (orchestra bells) and chimes (tubular bells); and resonated instruments such as the marimba, xylophone and vibraphone (“vibes”).
Resonated instruments such as the vibraphone have resonating air chambers, e.g. resonators, acoustically coupled with associated vibrating tone bars located above. The resonators of keyboard percussion instruments serve to amplify the sound of the tone bar resting above. In order to achieve the optimal relationship between each tone bar and resonator, it is desirable to have the resonator respond sympathetically, or be tuned to, a certain pitch with respect to its associated tone bar. When a resonator is tuned very closely to the pitch of its associated tone bar, the resulting tone when the bar is struck is loud, but relatively short in duration. With a slight amount of de-tuning of the resonator, the resulting tone is not so loud, but persists longer. The degree of de-tuning and whether the de-tuning is above or below the pitch of the tone bar has a significant effect on the quality of the resultant tone. Different musical selections call for different tonal responses. Therefore, it is desirable for the performing artist to be able to select or adjust the response of his instrument to achieve the tonal response for the musical selection to be performed.
Keyboard percussion instruments can be particularly cumbersome in terms of tuning and tone quality. These types of instruments may go out of tune in a variety of environmental conditions. In warm temperature and high humidity, for example, the tone bars may go flat and the resonators may go sharp. In cool and dry weather, the opposite condition may result. These varying conditions have an adverse effect, not only on the pitch of the instrument, but also on the tone quality. Due to the fact that these types of instruments rely on sympathetic resonance of the resonator tube to the tone bar, unmusical results may occur if the two vibrating systems are not in tune.
Despite these problems with varying environmental conditions as well as tuning, keyboard percussion instruments are usually sold with non-movable force-fit metal stops in the resonator tubes. A forced-fit, domed metal stop produces a strong, long-ringing (lossless), brightly toned, reflective surface. The resonator, usually made from aluminum or brass tubing, has no air leakage or energy losses because the metal plug is forced into the tube (e.g., with a hydraulic press), producing a perfect air seal around the circumference between the outer diameter surface of the stop and the inner wall of the resonator tube.
Many instruments of this type are supplied with one end of the resonator tube (the end furthest from the tone bar), permanently sealed at a distance that produces a resonant frequency equal to the associated tone bar above. When the resonator is associated with a tone bar tuned to, for example, A=440, the manufacturer sets the stop in the tube to produce a resonant frequency as close to A=440 as possible. Positioning the stop slightly sharp or flat to A=440 produces different results, such as altered ring times, volume and timbre. These permanent stops are prepositioned at the factory to resonate the above-suspended bar at a particular temperature and humidity level.
The position of these plugs is determined not only by the temperature and weather conditions at the point of manufacture but also by the taste of the designer and accidents and/or inconsistencies of manufacturing. When the instrument is played in an environment that exactly duplicates that for which it was tuned (e.g., about 50% humidity and 72° F.), these resonators should perform well. A reduction of the ambient air temperature by as little as 4° F., however, substantially reduces the volume potential of the instrument while increasing the apparent ring-time of the bar, adversely influencing the tone character of the combined bar/resonator system. Conversely, an increase of 4° F. in the ambient temperature reduces the apparent ring-time of the bar/resonator system to a level that even a lay person can hear easily.
Until recently, musicians have generally had to endure these shortcomings in performance. Even if the musician could take along all the wood-working or metal-working equipment to tune the tone bars at the performance site, this would not be a viable method to compensate for transitory weather conditions because tuning the tone bar requires removing material from the bar. After a few tunings by removing material, permanent loss of mass begins to be audible as loss of tone quality. Thus, a better way to bring these two sympathetically-vibrating systems into musical resonance is to change the effective length of the resonator tube.
Several movable/tunable stop systems have been introduced. Although some of them offer tuning and volume advantages over the permanently installed metal stops used by the vast majority of manufacturers, each has one or more significant drawbacks. For instance, some versions of movable stops merely squeeze a flexible rubber membrane between two rigid plastic disks or plates. While this system is functional and produces an air-tight seal, it does not produce good musical or ergonomic results. One drawback with this type of stop is that it is very slow to tighten and/or loosen the clamping device sufficiently to allow movement. Additionally, the assembly can easily camber out of 90-degrees square to the inside wall of the tube as it is being loosened or adjusted. It can also be incorrectly tightened in an out-of-square, cambered position. Any of the out of square cambered conditions produces unacceptable “out of focus” timbre and false harmonics. Also, the system is never completely rigid after tightening the two plates together, because the rubber membrane sealing against the inside diameter of the tube is by soft and flexible. Lastly, a significant cross-section of the soft, flexible material is exposed to the vibrating air column in the resonator.
Other versions of movable/tunable stop systems use an O-ring around a disk. While this system is functional and produces an air-tight seal, it does not produce good musical or ergonomic results. When the stop is moved against the friction of the O-ring, the O-ring alternately drags and then rolls, so that only certain positions of the stop can be selected. Additionally, the cleanliness or “focus” of the pitch and harmonicity of the overtones are degraded by the pitch conflict produced by the space between the flat top plate and the actual seal, which is a bit further from the open end of the tube. Other hybrid designs, such as squeezing the O-ring between two disks or plates also share many of these same shortcomings.
Features and advantages of the claimed subject matter will be apparent from the following detailed description of embodiments consistent therewith, which description should be considered with reference to the accompanying drawings, wherein:
The present disclosure is generally directed to an adjustable resonator stop configured for use with resonators of keyboard percussion instruments. The adjustable resonator stop may include a resonator engaging body defining a cavity, a resonator end member disposed within the cavity of the resonator engaging body, and a tightening member coupled to at least a portion of the resonator end member. The tightening member moves the resonator end member from a disengaged position, wherein the resonator stop may be freely adjusted within a resonator, to an engaged position, wherein the resonator stop is securely engaged with an interior surface of the resonator. An adjustable resonator stop consistent with the present disclosure may be configured to provide the same or better performance characteristics as a permanently installed metal stop including a smooth, metallic, bi-polar vibrating surface with exposure to air on either side, while also providing quick adjustability at little or no cost when compared to other adjustable stops.
The embodiments disclosed herein may be used in conjunction with resonators for a variety of different keyboard percussion instruments. As used herein, “keyboard percussion instrument” refers to an instrument including resonators acoustically coupled to associated tone bars. The tone bars, which may be made of wood, metal, steel, fiberglass or other acceptable materials, are struck with mallets to produce musical tones. Non-limiting examples of keyboard percussion instruments include marimbas, vibraphones, and xylophones.
Referring to
As shown in greater detail in
In the illustrated embodiment, an adjustable resonator stop 218 may be shaped and/or sized to fit within the hollow body 208 of the resonator 106 proximate the distal end 212 of the resonator 106. In particular, at least a portion of the adjustable resonator stop 218 may define an outer diameter D2 that is less than the inner diameter D1 defined by the interior surface 214 of the resonator 106. The adjustable resonator stop 218 may be moved within the interior volume 216 defined by the resonator 106 and fixed at different locations to define vibrating air columns of different lengths.
As shown in greater detail in
The adjustable resonator stop 218 may further include a tightening member 332 configured to be coupled to at least a portion of the resonator end member 328 and to move the resonator end member 328 relative to the resonator engaging body 320 from a disengaged position to an engaged position. In the disengaged position, the resonator end member 328 is disengaged from the resonator engaging body 320 allowing the resonator engaging body 320 to move freely within a resonator 106. In the engaged position, the resonator end member 328 engages the resonator engaging body 320 causing the resonator engaging body 320 to engage the resonator 106 at a fixed location. As shown, the tightening member 332 includes a first end 334 configured to be coupled to at least a portion of the resonator end member 328 and a second end 336 for providing a user with leverage for adjusting the resonator end member 328 from the disengaged position to the engaged position.
As shown in further detail in
The attachment member 440 may be formed as one piece with the resonator end member 328, for example, by turning a single bar stock of material (e.g., aluminum). In other embodiments, the attachment member 440 may be formed as a separate piece (e.g., a threaded female stud) that is attached to the surface 438 of the resonator end member 328, for example, with adhesive if aluminum is used or by spot welding if stainless steel is used. Although the attachment member 440 is shown as a threaded female stud, the attachment member 440 may be a male threaded stud and the tightening member 332 may be a standard wing nut.
As understood by one skilled in the art, the first end 334 of the tightening member 332 may be coupled to at least the bottom surface 438 of the resonator end member 328 by other means. Other mechanisms may also be used to move the resonator end member 328 into engagement with the resonator engaging body 320. For example, a tightening member may include a biasing member coupled to an attachment member defined on the bottom surface of the resonator end member, wherein the biasing member may translate from a disengaged position, wherein the resonator end member is disengaged from the resonator engaging body, to an engaged position, wherein the biasing member pulls the resonator end member into the resonator engaging body.
As shown, the resonator end member 328 may define a peripheral edge 446 shaped and/or sized to fit within the cavity 326 of the resonator engaging body 320 and to engage a portion of the open second end 324 of the resonator engaging body 320. The resonator end member 328 may include a durable and substantially rigid material capable of vibrating and/or reflecting high frequency sound. The material may include a metal such as, but not limited to, brass, aluminum, and/or combinations thereof.
As shown in greater detail in
As shown, the end wall 548 may include an aperture 558 shaped and/or sized to receive at least a portion of the first end 334 of the tightening member 332 and to allow at least a portion of the first end 334 to be disposed within the cavity 326 and be coupled to a portion of the resonator end member 328. As shown, the end wall 548 may further include at least one venting aperture 560 for venting air through the resonator engaging body 320 to the resonator end member 328. Although the end wall 548 defines two venting apertures 560 in the illustrated embodiment, the end wall 548 may define more or fewer venting apertures having a variety of dimensions and/or configurations, as well as placement on the end wall.
When the adjustable resonator stop 218 is assembled and the resonator end member 328 is in the engaged position, the venting aperture(s) 560 may be configured to effectively vent the cavity 326 and at least the bottom surface 438 of the resonator end member 340 to any surrounding air 562 located outside of the resonator engaging body 320 and/or resonator 106. The venting aperture(s) thus 560 allows bi-polar vibration of the resonator end member 328, wherein both the top surface 330 and/or bottom surface 438 of the resonator end member 328 may vibrate more freely when exposed to a vibrating air column when a tone bar 102 is struck. In other words, the bottom surface 438 of the resonator end member 328 may be exposed to air so that any vibration of the resonator end member 328 has the advantage of a bi-polar contribution to the surrounding air. The resonator end member 328 may be configured to act as a type of “drum head” in that the resultant sound is different than a solid plastic or metal stop. Similar to the venting of a snare drum or tom-tom, the resonator end member 328 may vibrate more freely because the bottom surface 438 of the resonator end member 328 encounters less back-pressure created in the cavity 326 of the resonator engaging body 320 due to the venting aperture(s) 560.
In other embodiments, the end wall 548 may be solid, except for aperture 558, and such that the top surface 330 of the resonator end member 328 is configured to vibrate into the interior volume 216 of the resonator 106 and/or into the cavity 326 of the resonator engaging body 320. The bottom surface 438 in these embodiments, however, may encounter back pressure within the cavity 326.
The resonator engaging body 320 may include a resilient and durable material capable of elastic expansion, particularly at the radially expandable lip 552, when a force is applied thereto and capable of elastic recovery when the force is removed therefrom. The material may include, but is not limited to, either natural or synthetic materials such as polymers and/or co-polymers. Examples may include polyurethane, latex, natural rubber, nylon (polyamides), polyester, polyethylene, polypropylene, PVC, fluoroplastics, block copolymers, polyethers and composites thereof. In one embodiment, the resonator engaging body 320 may include a low-density polyethylene (LDPE) material.
In the illustrated embodiment, the interior surface 556 of the side wall 550 may include an angularly disposed interior tapered surface 664 gradually tapering from a first interior portion 666 to a second interior portion 668 terminating at the lip 552 of the side wall 550. The resonator engaging body 320 may include a first interior diameter D3 measured at the second interior portion 668 and a second interior diameter D4 measured at the first interior portion 666. Additionally, the interior tapered surface 664 of the side wall 550 may be oriented at an angle θ of less than 90 degrees relative to the interior surface 556 at the second interior diameter D4.
As shown, at least a portion of the resonator end member 328 is shaped and/or sized to fit within at least a portion of the resonator engaging body 320. In particular, the resonator end member 328 has an outer diameter D5 measured at the peripheral edge 446 of the resonator end member 328, which is less than the first interior diameter D3 of the resonator engaging body 320. As shown, the resonator end member 328 includes an angularly disposed tapered surface 670 extending along a periphery of the resonator end member 328. The tapered surface 670 gradually tapers in width from at least the peripheral edge 446 to the bottom surface 438 of the resonator end member 328. The tapered surface 670 may be shaped and/or sized to form a complementary engagement with at least the interior tapered surface 664 of the side wall 550 of the resonator engaging body 320 when the resonator end member 328 moves from the disengaged position to the engaged position. As shown, for example, the tapered surface 670 of the resonator end member 328 may correspond to the tapered surface 664 on the side wall 550.
In other embodiments, the peripheral edge 446 of the resonator end member 328 may include other dimensions and/or configurations, e.g. a rounded surface or any shape capable of engaging the interior tapered surface 664 of the side wall 550 of the resonator engaging body 320.
As shown, the first end 334 of the tightening member 332 passes through the aperture 558 of the resonator engaging body 320 and is threadably coupled to the attachment member 440 of the resonator end member 328. In the illustrated embodiment, turning or rotating the tightening member 332 in a direction as indicated by arrows 772 causes the resonator end member 328 to be moved in a direction towards the resonator engaging body 320 as indicated by arrow 774. Turning or rotating the tightening member 332 in a direction opposite the direction indicated by arrows 772 causes the resonator end member 328 to be moved in a direction away from the resonator engaging body 320 as indicated by arrow 776.
When in the disengaged position, as shown in
When in the engaged position, as shown in
As shown in even greater detail in
The lip 552 may provide a generally air-tight seal with the interior surface 214 of the resonator 106 such that the interior volume 216, i.e. air column, of the resonator 106 is mostly exposed to the resonator end member 328. The original size and/or shape of the resonator engaging body 320 (i.e. outer diameter D2 of the resonator engaging body 320 when resonator end member 328 is in the engaged position) is configured to provide an adequate slip fit within the resonator 106 such that, in order to securely fix the resonator engaging body 320 to the interior dimension of the resonator 106, the lip 552 need only radially expand a few thousandths of an inch. Thus, the seal may be air-tight and rigid, while minimizing the amount of resonator engaging body 320 exposed to the vibrating air column. In one embodiment, for example, the amount of resonator engaging body 320 exposed to the interior volume 216, i.e. air column of the resonator 106 is less than 5% when the resonator end member 328 is in the engaged position and the resonator stop 218 is securely fixed within the resonator 106. Thus, the resonator end member 328 covers at least about 95% of the air column in the resonator 106. In other embodiments, the amount of the resonator engaging body 320 exposed to the interior volume 216 of the resonator 106 may be as low as 2% or 1% or less when the resonator end member 328 is in the engaged position.
To tune the resonator, therefore, the user loosens the tightening member 332 such that the resonator end member 328 is drawn in a direction away from the resonator engaging body 320, as indicated by arrow 776 (
Referring to
As illustrated, a tightening member (e.g., a threaded bolt 940) passes through an aperture 934 in the second plate 930 and engages the first plate 920 (e.g., an internally threaded member 922 coupled to the first plate 920). The threaded member 922 may be an aluminum nut spot welded to the center of the first plate 920 or may be formed as one-piece with the first plate 922. Other tightening or engaging mechanisms may also be used.
In operation, the tightening member or threaded bolt 940 causes both plates 920, 930 to be pulled together during tightening to expand the tapered ends 915, 916 of the side wall 914 of the resonator engaging body 910 against a resonator tube. Because the resonator engaging body 910 expands at both ends 915, 916, the tolerances for slip fit may be less critical. A 1.75 in. diameter engaging body 910, for example, may expand about 0.040 in. This embodiment may also produce an even more secure seal against the inside of a resonator tube because it seals at both ends 915, 916 (e.g., top and bottom) of the resonator engaging body 910 and with the same acoustic performance.
An adjustable resonator stop consistent with the present disclosure may be configured to provide substantially the same or better performance characteristics as a permanently installed metal stop including a smooth, metallic, bi-polar vibrating surface with exposure to air on either side, while also providing quick adjustability at little or no cost when compared to other adjustable stops in the industry.
Consistent with one embodiment, an adjustable resonator stop includes a resonator end member configured to be disposed within an interior dimension of a resonator of a keyboard percussion instrument to form a closed end of an air column defined by the resonator and a resonator engaging body configured to be disposed within the interior dimension of the resonator and to engage inner walls of the resonator. The resonator engaging body has a first end and an open second end defining a cavity configured to receive the resonator end member. The adjustable resonator stop also includes a tightening member configured to be coupled to at least a portion of the resonator end member. The tightening member is configured to move the resonator end member relative to the resonator engaging body from a disengaged position to an engaged position with the resonator end member engaging the resonator engaging body and being disposed at least partially within the cavity of the resonator engaging body. The resonator engaging body is disengaged from the resonator in the disengaged position such that the resonator stop is able to traverse within the resonator. The resonator engaging body engages the resonator in the engaged position such that the resonator stop is fixed within the interior dimension of the resonator.
Consistent with another embodiment, a keyboard percussion instrument includes a plurality of tone bars, a plurality of resonators associated with the tone bars, respectively, and acoustically coupled to the tone bars, and at least one adjustable resonator stop configured to be adjustably positioned in at least one of the resonators.
While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.
