Patent Application
20090226019
The present invention relates to audio speakers. A speaker is an electromechanical device that produces acoustic signals across a frequency range depending, at least in part, on one or more types of drivers used in the speaker. The term speaker can refer to a device with a single driver, multiple drivers, or a device that includes one or more drivers, an enclosure, and additional components such as a crossover circuit. It is often desirable for a speaker to produce an acoustic output across the band of frequencies that are audible to a human. Sometimes, a “flat” output from about 20 Hz to about 20 kHz is viewed as an ideal characteristic for a speaker to possess. However, in practice, the acoustic output of a speaker is often attenuated at one or more frequencies or across one or more bands of frequencies.
While various ideal performance characteristics for speakers are known and have been postulated, achieving them is practice is not always possible, particularly in light of cost and other constraints.
In one embodiment, the invention provides a speaker with an improved frequency response that is achieved at little or no increased expense. The speaker includes an enclosure. The enclosure includes a first side positioned at an angle with respect to a horizontal axis or plane. The first side includes an upper portion and a lower portion. The upper portion and the lower portion are offset from one another by a first offset in a first direction and a second offset in a second direction. The first offset in the first direction and the second offset in the second direction defining a vent extending across a width of the first side. The vent is positioned above a low-frequency transducer and below a high-frequency transducer. The low-frequency transducer is mounted to the lower portion and is configured to generate a first acoustic signal within a first frequency range. The high-frequency transducer is mounted to the upper portion and is configured to generate a second acoustic signal within a second frequency range. The low-frequency transducer and the high-frequency transducer are displaced by the first offset in the first direction and the second offset in the second direction to adjust a low-frequency transducer acoustic origin position and a high-frequency transducer acoustic origin position. The upper portion and the lower portion are configured such that a first acoustic signal arrival time and a second acoustic signal arrival time are synchronized in a listening area.
In another embodiment, the invention provides a floor monitor speaker that includes an enclosure. The enclosure includes a lower baffle at a first angle with respect to a horizontal axis and an upper baffle positioned at a second angle with respect to the horizontal axis. The lower baffle and the upper baffle are offset from one another by a first offset in a first direction and a second offset in a second direction. The first offset and the second offset define a vent extending across a width of the first side. The vent is positioned above a woofer and below a horn. The woofer is mounted to the lower baffle and is configured to generate a first acoustic signal within a first frequency range. The horn is mounted to the upper baffle and is configured to generate a second acoustic signal within a second frequency range. The woofer and the horn are displaced by the first offset in the first direction and the second offset in the second direction to adjust a woofer acoustic origin position and a horn acoustic origin position. The woofer acoustic origin position and the horn acoustic origin position are adjusted such that a first acoustic signal arrival time and a second acoustic signal arrival time are synchronized in a listening area.
In another embodiment, the invention provides a method of synchronizing at least two acoustic signals at respective acoustic origins. The method includes positioning a lower baffle at a first angle with respect to a horizontal axis, positioning an upper baffle at a second angle with respect to the horizontal axis, mounting a woofer to the lower baffle, and mounting a horn to the upper baffle. The method includes adjusting a woofer acoustic origin position and a horn acoustic origin position by displacing the lower baffle and the upper baffle by a first offset in a first direction and a second offset in a second direction. The method also includes positioning the upper baffle and the lower baffle such that there is a vent between the two. The method further includes generating, at the woofer, a first acoustic signal within a first frequency range, generating, at the horn, a second acoustic signal at a second frequency range, and synchronizing a first acoustic signal arrival time and a second acoustic signal arrival time in a listening area.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
In some embodiments of the invention, the enclosure 20 includes a speaker grille 15. The speaker grille 15 is, for example, a hard or soft grille mounted over the speaker driver (i.e. woofer, tweeter, etc.) or other components of the speaker 10. The speaker grille 15 can be covered with a fabric that allows sound to pass while protecting the speaker drivers and other components of the speaker 10 from dust, dirt, and physical damage. In one embodiment, the speaker grille 15 is made of metal (or a similar, relatively stiff and hard material) and includes a rib 16. The rib 16 provides additional strength and stiffness to the speaker grille 15. The rib 16 also reduces flexing of, and vibration in the speaker grille 15. In some embodiments, the rib 16 eliminates the need for a central brace which is, in many instances, required to provide necessary support and strength to a speaker grille. Without the need for additional bracing, the depth of the enclosure 20 is reduced and manufacturing time is decreased. The rib 16 can take many forms beside the also aesthetically pleasing one shown in
The speaker 10 also includes a vein line 18. The vein line 18 runs around the enclosure 20 from front to back, as opposed to being inset on a side panel. In some embodiments, the speaker enclosure 20 does not include the speaker grille 15.
Before continuing to describe the speaker 10, note that the term “signal,” as used herein, describes a signal that includes a single frequency or a signal that includes a plurality of frequencies. For example, for ease of writing, transducers are sometimes described herein as producing “an acoustic signal.” However, in actuality, the transducer might produce multiple acoustic signals; for example, all or a portion of the acoustic frequencies necessary to reproduce music. Thus, references to “a signal” or similar terms should not, necessarily, be interpreted as being limited to a signal composed of just one frequency, for example, a tone at 400 Hz. Instead, the term signal should be recognized as potentially including components at multiple frequencies. So for example, the acoustic signal or output of a woofer might include frequencies between about 50 Hz and about 1.8 kHz.
As illustrated in
In addition to the components described above, the speaker enclosure 20 also includes a crossover circuit 80, as illustrated in
The crossover circuit 80 can be a passive crossover circuit or an active crossover circuit. A passive crossover circuit is constructed from passive components such as resistors, inductors, and capacitors to create one or more passive filters. An active crossover circuit is constructed with active components such as, for example, operational amplifiers or components that require a source of power. An active crossover circuit requires, in many instances, a power amplifier for each output frequency band. For example, if the speaker 10 includes a low-frequency transducer 50 and a high-frequency transducer 45, a power amplifier is included for both the high-frequency band and the low-frequency band outputs of the crossover circuit 80. The power amplifiers are positioned between the crossover circuit 80 and the high and low-frequency transducers 45 and 50. In other embodiments, other types of crossovers circuits are used.
In the embodiment shown, the lower baffle 40 is supported by and extends beyond a beam 85. The beam 85 spans the width of the first side 30 and provides structural support for the enclosure 20. The lower baffle 40 is contoured so that is fits around a portion of the high-frequency transducer 45. In the illustrated embodiment, the lower baffle 40 includes a U-shaped contour or upper edge. In other embodiments, the lower baffle 40 can be contoured in a different fashion. Alternatively, the lower baffle 40 can be dimensioned so that it does not extend beyond the beam 85 and has a straight upper edge. The dimensioning and contouring of the lower baffle affects the size and shape of the vent 55. The vent 55 allows acoustic signals to pass out of the enclosure 20 and enhances a low-frequency response of the speaker 10. Different configurations of the baffle 40 and baffle 35 can be used to change the shape and size of the vent 55.
The lower baffle 40 and the upper baffle 35 are offset both vertically and in depth. For example, the lower baffle 40 and the upper baffle 35 are offset in a direction perpendicular to the angle A 90 by a first distance 115 with the upper baffle 35 being forward of the lower baffle 40. The lower baffle 40 and the upper baffle 35 are also offset in a direction parallel to the angle A 90 by a second distance 120. As a consequence, the lower baffle 40 and the upper baffle 35 are offset both vertically and in depth. The high-frequency transducer central axis 110 and the low-frequency transducer central axis 105 are then closer to one another than if the upper and lower baffles 35 and 40 were coplanar.
A low-frequency transducer acoustic origin 125 and a high-frequency transducer acoustic origin 130 are points at which sound waves appear to originate from the low-frequency transducer 50 and the high-frequency transducer 45, respectively. In some embodiments of the invention, the low-frequency transducer acoustic origin 125 and the high-frequency transducer acoustic origin 130 are not coplanar. In other embodiments, the low-frequency transducer acoustic origin 125 and the high-frequency transducer acoustic origin 130 are coplanar. A low-frequency transducer acoustic origin position and a high-frequency transducer acoustic origin position are adjusted using the upper baffle 35 and the lower baffle 40 to synchronize a low-frequency transducer acoustic signal arrival time and a high-frequency transducer acoustic signal arrival time in a listening area, for example, a location on a stage, a location in a room, or a location in a concert hall. A time-domain measurement of acoustic signal arrival times in a far field or the listening area is used to verify that the low-frequency transducer acoustic signal arrival time and the high-frequency transducer acoustic signal arrival time are synchronized.
The first and second offsets 115 and 120 also define the vent 55 between the lower baffle 40 and the upper baffle 35. As described above, the vent 55 extends across the width of the first side 30. The vent 55, first offset 115, and second offset 120 can be designed to synchronize acoustic signal arrival times of different combinations of transducers and to tune a Helmholtz frequency of the enclosure. In the described embodiment, the vent 55, first offset 115, and second offset 120 are designed for a woofer (low-frequency transducer) 50 and a horn (high-frequency transducer) 45. In other embodiments, different transducers are used.
Thus, the invention provides, among other things, a speaker with offset upper and lower baffles for synchronizing the arrival times of acoustic signals from a low-frequency transducer and a high-frequency transducer. Various features and advantages of the invention are set forth in the following claims.
