Modular horn loudspeaker

Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Having acoustic wave modifying structure

Reexamination Certificate

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Details

C381S342000, C381S343000, C381S397000, C181S159000, C181S177000

Reexamination Certificate

active

06516076

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to horn loudspeakers, and, more particularly, to compact horn loudspeakers suitable for paging or emergency signaling uses in harsh environments and confined spaces such as are found on emergency vehicles.
2. Discussion of the Prior Art
Emergency vehicles (e.g., ambulances) usually carry horn loaded siren loudspeakers for emergency signaling, and in the past it was customary to mount one or more siren loudspeakers on an overhead light bar or on a front bumper.
Traditional horn loaded siren loudspeakers are not well suited for use on some modern vehicles, however. In the past, when it was desired to aim the siren's sound forwardly, a siren loudspeaker was mounted on the front bumper, in front of the grille covering the radiator. On cars built in the 1980's, front bumpers projected forwardly four to six inches, providing an exterior surface with ample room for mounting a traditional horn loaded siren loudspeaker.
Many modern vehicles have integrally contoured and painted bumper surfaces and so do not have a front bumper surface well suited to mounting a siren loudspeaker. The siren loudspeaker can be mounted under the hood, behind the grill and in front of the radiator, but this mounting location presents a number of problems. There is very little room between the grille and the radiator, the radiator is often hot, and the siren loudspeaker is exposed to a damp, corrosive environment.
Other loudspeaker designers have sought to solve these problems by fashioning loudspeakers from stacks of metal, planar, plate-like members defining folded or reentrant horns. For example, U.S. Pat. No. 5,970,158, to Beltran, discloses a compact horn loudspeaker intended for use behind the grille of an emergency vehicle or the like. The Beltran horn loudspeaker does achieve a small front to back thickness dimension, but is expensively fabricated from a plurality of planar plate-like aluminum pieces joined in a stack with vulnerable, exposed seams running around the periphery of the horn.
Another problem is that the small space available behind the grille may not be suitable for mounting a siren loudspeaker of sufficient power; there are applications requiring more acoustic output than one compact siren driver can produce. For example, when using the Beltran siren, installers may not be able to find sufficient space to mount two or more of Beltrans' siren housings. Airflow does have to reach the radiator, after all; one cannot simply cover the interior of the grille with sirens. Another problem with requiring the siren installers to mount two separate sirens is that separate wiring connections have to be made, thus increasing the cost of installation and the opportunity for incorrect wiring. If the siren loudspeakers are wired in parallel, impedance is halved, and if wired in series, impedance is doubled, as compared to a single siren driver. Incorrect wiring can lead to poor acoustic performance or equipment failure due to an overcurrent condition.
Turning to a more general view, the prior art includes a number of compact folded or reentrant horn loudspeakers for use in a variety of settings. For example, the
Handbook for Sound Engineers
2
d. Edition,
pp 545-558, Glen M. Ballou, Editor, 1991, describes a number of “folded horns” folded to make “compact” products. In the examples cited, the sound path makes one or two 180 degree turns, effectively reversing or folding the sound path back on itself.
U.S. Pat. No. 1,767,812, to W. J. Polydoroff, discloses an “acoustical horn” including a compression driver and a “body” including a continuous winding sound channel having a flared terminal portion constituting the mouth of the horn. The body is, preferably, made in two or three “matched discs or sections” independently molded, machined or die pressed and then glued, cemented or fastened together in a stack.
U.S. Pat. No. 1,832,763, to W. M. Campbell, discloses a horn-loaded loudspeaker including what is called an “acoustic chamber” intended to reflect or deflect sound waves to redirect sound received in a throat tube
9
, directing the sound towards exit slots
7
.
In 1928 H. C. Harrison invented an acoustic horn which became the subject of U.S. Pat. No. 1,747,830. Harrison's acoustic horn was given a “compact form” obtained by “providing a reentrant horn in which the sound waves traverse the space within the enclosing walls a plurality of times and expand progressively at a suitable rate in their passage therethrough.”
U.S. Pat. No. 2,160,166 issued to H. R. Pausin in 1939 and includes a horn for a loudspeaker cast in metal, preferably aluminum, in two parts. The horn is formed of a lower section separably attached to an upper section. The lower section includes the mount for a compression driver and a horn mouth; the upper section is a single casting providing a folded horn throat arcing through 180 degrees and connected to the horn mouth for coupling an acoustic wave to external air.
U.S. Pat. No. 2,957,054, to Levy et al, discloses a transducer or horn-loaded loudspeaker having a driver assembled into an inner compartment of a mechanical acoustic body formed as a horn throat member received within a flared body which forms the horn mouth. Levy's loudspeaker is characterized as a “reflex horn speaker” having “acoustic ducts” fabricated within two complimentary dieformed members.
U.S. Pat. No. 2,301,459, to A. J. Sanial, disclosing a loudspeaker called an “electric megaphone” wherein a loudspeaker driver projects an acoustic wave into a tubular extension projecting forwardly which is in communication with a rearward or reentrant annular space characterized as a reversely extending annular passage for communication with a horn mouth. An outer cylindrical housing is closed at the rear end and the soundwave from the annular passage reflects at a solid rear wall and is reflected forwardly to project out and be coupled to the external air by a flared end or horn mouth.
U.S. Pat. No. 5,804,774, to Ford et al, discloses a ported reflex horn. The background section of this patent discusses “re-entrant” horns having horn sections which “fold back” on one another, offering a compact alternative to straight horns.
These background references illustrate the many approaches taken in fashioning compact horn-loaded loudspeakers. None of the designs illustrated therein address all of the problems identified by the applicant, as discussed above. In particular, the prior art does not teach or suggest an optimum structure for a compact siren loudspeaker which impervious to the environment, is easy and inexpensive to manufacture, and is easy to install. The prior art is also silent on how one may fashion a siren loudspeaker in a modular configuration, permitting the installer to select a siren having an optimum output power rating for installation under the hood of an emergency vehicle, or the like.
There is a need, therefore, for a modular compact siren assembly adapted for use in small spaces and harsh environments, such as under the hood of an emergency vehicle.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to overcome the above mentioned difficulties by providing a modular, compact siren assembly adapted for use in small spaces and harsh environments, such as under the hood of an emergency vehicle.
Another object of the present invention is to provide a modular system of loudspeaker elements adapted for economical manufacture and ease of assembly.
Yet another object of the present invention is to provide a modular loudspeaker which is easily installed under the hood of a vehicle in the confined space between the grille and the radiator.
The aforesaid objects are achieved individually and in combination, and it is not intended that the present invention be construed as requiring two or more of the objects to be combined unless expressly required by the claims attached hereto.
A modular horn loudspeaker principally intended for use on emergency vehicles con

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