This invention relates to loudspeaker systems, and, more particularly, to a loudspeaker system which may be used in watercraft wherein a driver is mounted within a single-reflex band-pass box that is self-draining to protect the driver from exposure to standing water.
Loudspeaker systems are frequently utilized in applications such as watercraft where exposure to water and other elements can damage the system's driver(s). In sound systems for boats, the drivers are typically mounted in side bulkheads near the entertainment areas of the vessel to protect them from water damage and to direct acoustic output toward passengers seated in such areas. Smaller boats such as ski boats, bow riders, wakeboard boats and deck boats do not have a cabin or enclosed helm, and therefore essentially the entire deck area is open to the air. This allows acoustic energy from the drivers to dissipate quickly as it radiates into space, and it is particularly difficult for such systems to provide quality sound behind the boat such as to a skier being towed.
This invention is directed to a loudspeaker system including a driver mounted within the interior of a single-reflex band-pass box which is self-draining to protect the driver from exposure to standing water. The band-pass box may be mounted at the stern of the boat to direct acoustic energy to one being towed behind it.
In one presently preferred embodiment, the band-pass box is formed in two sections which are connected to one another to form a box interior. A driver is mounted to a plate within the box interior so that one side of the driver is located within a sealed volume of the band-pass box and its opposite side resides in a ported volume thereof. Acoustic output from the driver entering the ported volume is transmitted through a port to the outside of the box.
Several features of this invention are designed to reduce exposure of the driver to water entering the box interior through the port. The plate which mounts the driver positions it above where water that enters the box interior may pool. A number of drain tubes are mounted over holes formed in the bottom of the band-pass box through which water may drain to further prevent pooling in the box interior. In some embodiments, the bottom wall of the band-pass box may be oriented at an angle so as to direct water that enters the box interior toward the drain tubes and/or the port.
The loudspeaker system of this invention may be utilized in watercraft to direct acoustic output from the driver toward the rear of the vessel or within its entertainment area. In watercraft that include an engine compartment, such as inboard and inboard-outboard boats, the band-pass box of this invention may be mounted to a panel which covers such compartment and is movable between open and closed, positions. The drain tubes connected to the box interior are located within the engine compartment and preferably extend to the bilge where water from the box interior is directed.
The structure, operation and advantages of the presently preferred embodiment of this invention will become further apparent upon consideration of the following description, taken in conjunction with the accompanying drawings, wherein:
Referring initially to
With reference to
When the upper and lower sections 28, 30 are connected to one another, the band-pass box 26 depicted in
Calculations of the ported volume, sealed volume, port diameter and port length for a band-pass box are well known in the art, and the details of same form no part of this invention. For purposes of illustration, assuming the driver 38 is a Model 12TW3 subwoofer commercially available from JL Audio, Inc. of Miramar, Fla., the sealed volume 54 may be 0.60 cubic feet, the ported volume 56 may be 0.80 cubic feet, and, the port 44 may be 4.0 inches in diameter and 11.625 inches in length. These values result in tuning the band-pass box 26 to a resonant frequency of about 54 Hz.
An important aspect of this invention are features which allow the loudspeaker system 24 to be utilized in environments where water is present, such as in watercraft 10, while minimizing or eliminating damage to the driver 38. In the embodiment shown in
In order to prevent or at least reduce pooling of water within the box interior 52, a number of drain tubes 60 are connected to holes 62 formed in the bottom wall 46 of the lower section 30 of box 26. The drain tubes 60 extend from the box 26 to the bilge 14 of the watercraft 10 to remove water iron the box interior 52. The use of drain tubes 60 is important to ensure proper acoustic performance of the loudspeaker system 14 of this invention. If only the holes 62 in the bottom wall 46 were provided, without drain tubes 60, there would be a significant acoustic leak, i.e. wide bandwidth noise caused by high-velocity air flow created by pressure shifts within the box interior 52 resulting from operation of the driver 38. Such acoustic leakage would lower the efficiency of the loudspeaker system 24 and creates noise that could be bothersome to listeners.
The drain tubes 60 connected to the holes 62 are designed to only pass in-band signal airflow in a narrow frequency range well below the functional bandwidth of the loudspeaker system 24. In particular, the diameter and length of the drain tubes 60 are chosen so that they resonant at a specific low frequency. Due to the nature of acoustic resonance, there is only significant airflow through the drain tubes 60 in a small frequency range at which they are tuned and such tubes 60 are largely inert at other frequencies. In the particular example of the Model 12TW3 subwoofer, and assuming all of the parameters described above, a drain tube 60 having a 0.50 inch diameter and a length of about 60 inches is tuned to a resonant frequency of between 3 Hz and 5 Hz. Such frequencies are well below the tuned frequency of 54 Hz for the loudspeaker system 24.
In addition to reducing unwanted acoustic flow via resonance,the relatively long, about 60 inch drain tubes 60 having a 0.50 inch diameter create a relatively high resistance to airflow considering the surface area formed by their diameter and length. Air flowing into the drain tubes 60 engages their interior surfaces and inherently lowers the volume of air that can flow therethrough, thus highly damping the resonance of the tubes 60. This prevents “ringing” of the drain tubes 60 after excitation frequencies are removed. At the same time, however, the drain tubes 60 efficiently act as a static drain of water from the box interior 52.
Referring now to
The embodiment of
Further alternative embodiments of this invention are shown in
The band-pass box 64 of
In the embodiment of
While the invention has been described with reference to a preferred embodiment, it should be understood by those skilled in the art that various changes may be made and equivalents substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof.
The specific example of the loudspeaker systems 24 and 62 of this invention designed for use with a Model 12TW3 subwoofer are intended for illustration purposes only. Different sizes of subwoofers would require different parameters, including sealed volume, ported volume, port diameter, port length, drain tube diameter and drain tube length. The discussion given above is therefore not intended to be limited but merely indicative of the relationship between such parameters and the relative resonant frequencies of the ported volume of the band-pass box 26 and the drain tubes 60.
Additionally, the loudspeaker systems 24 and 62 are depicted as being mounted to the engine cover panel 22 of a watercraft 10 having an engine compartment 12 with a bilge 14. It is contemplated that the systems 24 or 62 could be mounted elsewhere on boats of this type, and/or be utilized with watercraft without an engine compartment such as those having outboard motors.
Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
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Number | Date | Country | |
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20180084334 A1 | Mar 2018 | US |
Number | Date | Country | |
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62482363 | Apr 2017 | US | |
62397597 | Sep 2016 | US |