Loudspeaker thermal management structure

Total thermal management accomplishes self-cooling from acoustic air movement in a light-weight loudspeaker system for professional sound applications: a cast aluminum front panel, forming the front baffle portion of a total enclosure, is configured to include on the front panel a horn opening, a woofer opening with a ring mount for a conventional woofer cone, a pair of bass reflex ports, and, extending rearwardly, a woofer frame with a mount for a conventional woofer driver, a horn structure with a threaded mount for a conventional horn driver, and an amplifier mounting shelf, all thermally combined by a pattern of generally vertical integral cooling vanes. The lower portions of the vanes are shaped to form structural legs of the woofer frame, and their upper portions are integrally attached to the horn. A shelf for mounting an amplifier in the speaker enclosure is formed by a transverse cooling vane. All of the heat-producing devices are thermally connected via good heat-conduction paths provided by the vanes attached integrally to densely-vaned cooling grilles forming the tuned reflex ports; thus, as the woofer is energized, air moves in and out of the grilles at high velocity particularly at low frequency resonance, acting like a fan on the grilles and thus enhancing their thermal dissipation with a cooling effect that increases as the woofer plays louder due to the increased velocity of the reciprocal air movement.

FIELD OF THE INVENTION 
The present invention relates to the field of acoustic loudspeakers and 
more particularly it relates to a total thermal management system for 
dissipating heat from a loudspeaker and associated components in an 
enclosure for professional sound systems in a manner that improves 
performance while reducing cost and weight by utilizing air movement 
produced by the loudspeaker for heat dissipation that increases in 
efficiency with the sound pressure level. 
BACKGROUND OF THE INVENTION 
Many components in loudspeaker systems create heat: these can include an 
amplifier, crossover components, low frequency driver, high frequency 
driver, and transformer, each of which are conventionally designed to 
dissipate heat in a different manner. Generally the heat generated in each 
of these components increases with the loudness level. 
DISCUSSION OF RELATED KNOWN ART 
U.S. Pat. No. 4,811,403 to Henricksen et al discloses mounting of one or 
more loudspeakers in thermal engagement with a load bearing member of good 
thermal conductivity which is in turn attached to rigid lightweight 
enclosure. 
U.S. Pat. No. 4,210,778 to Sakurai et al discloses a loudspeaker with a 
heat pipe having a lower end disposed in the drive means and an upper end 
disposed in a front panel exit opening in the reflex port, for removing 
heat from the drive means by gravity air flow through the heat pipe. 
U.S. Pat. No. 4,138593 to Hasselbach et al addresses improvements in heat 
removal from a loudspeaker by thermally engaging the driver means to 
portions of the speaker housing, either by the addition of internal heat 
removal structure, e.g. extending from the rear of the magnet to the rear 
housing panel and/or by constructing the speaker frame and sound panel in 
one piece of thermally conductive material. 
U.S. Pat. No. 3,991,286 to Henrickson discloses a loudspeaker having a 
voice coil, spider suspension and speaker frame all made of material 
having high thermal conductivity, including a horn type speaker embodiment 
with a thermally conductive horn element and a heat sink member attached 
on the rear. 
U.S. Pat. No. 4,757,547 to Danley discloses an electrical blower passing 
cooling air through a loudspeaker driver. 
U.S. Pat. No. 4,993,975 to Button, the present inventor, discloses a 
loudspeaker structure with means for conducting heat outwardly from the 
magnetic gap comprising a cylindrical collar confronting the voice coil 
former having radial vanes extending outwardly to a circular ring integral 
with the frame of the loudspeaker. 
Unlike the foregoing patents, the following patents are directed to 
amplifier cooling and fail to address loudspeaker cooling: 
U.S. Pat. No. 3,909,679 to Petri discloses a solid state amplifier 
utilizing a cast aluminum chassis mounted in an opening in the rear wall 
of an internally sealed cabinet with heat convecting fins of the chassis 
extending outwardly. 
U.S. Pat. No. 3,778,551 to Grodinsky discloses an air cooled audio 
amplifier assembly mounted onto an upper region of a speaker cabinet; air 
passages from the speaker cavity within the cabinet communicate with 
transistor heat sinks of the amplifier so that the speaker cone serves as 
a pump for cooling air that passes across the heat sinks. 
U.S. Pat. No. 3,462,553 to Spranger discloses a solid state amplifier and 
control panel assembly in a rectangular sheet metal enclosure cooperating 
with wood frame means to define a loudspeaker chamber, the sheet metal 
enclosure extending outwardly from the main body of the wooden loudspeaker 
chamber and having perforations on top and bottom panels above and below 
vaned heat sinks carrying transistors of the amplifier so as to provide 
upward cooling air flow past the heat sinks. 
A common approach in known art of thermal management in the design of high 
power professional loudspeakers consists of simply making the driver 
structure exceptionally massive in size and weight, accepting these 
excesses along with the resulting cost increase as disadvantages of a 
tradeoff perceived as unavoidable. 
OBJECTS OF THE INVENTION 
It is a primary object of the present invention to provide, for a 
professional sound system, a low cost light weight loudspeaker assembly 
containing heat-producing devices such as speaker drivers, amplifiers, 
crossover components, power supplies and the like, featuring a heat 
dissipation system that uses a unified mechanism to dissipate the heat 
that is generated by all of the devices. 
It is a further object for the heat dissipation mechanism to be enhanced by 
the operation of the speaker, such that the cooling effect increases as a 
function of loudness. 
SUMMARY OF THE INVENTION 
The abovementioned objects have been accomplished in a loudspeaker assembly 
comprising an enclosure of lightweight thermally conductive metal, e.g. 
die-cast aluminum, that is a single part which incorporates the following 
functions: front baffle portion of the speaker enclosure, woofer frame, 
woofer driver mount and heatsink, high frequency horn, compression horn 
driver mount and heatsink, amplifier mount and heatsink, and low frequency 
tuned port system. To provide the key heat dissipation mechanism, heat 
sink vanes are located in the low frequency port system, which in a 
preferred embodiment comprises a symmetrical pair of ports, so that as the 
speaker is energized by low frequency signals air moves in and out of the 
ports at high velocity across the vanes. This acts like a fan on the vaned 
heat sink, providing a substantial increase in the thermal dissipation 
characteristic of the vanes; the cooling effect increases as the woofer 
plays louder due to the increased velocity of the air movement. Another 
important feature of this total thermal management system is that all of 
the devices are connected by good heat conduction paths to the ports, 
located on the periphery inside the box. An amplifier or other 
heat-producing device can be mounted in the box in the vicinity of the 
port region with all devices funneling the heat into the ports which are 
then cooled by the low frequency air resonance.

DETAILED DESCRIPTION 
In FIG. 1, a front elevational view of a loudspeaker assembly 10 of the 
present invention wherein a front panel unit 12, preferably die-cast from 
aluminum, is formed integrally to act as a front baffle board and to 
provide a horn structure 12A, a pair of openings defining reflex ports 12B 
and 12C traversed by cooling vane grilles 12D and 12E, a round woofer 
opening defined by a peripheral edge ring 12F providing a mounting surface 
to which is attached a speaker cone 14 and voice coil of a permanent 
magnet woofer driver 16 of known art, shown in dashed outline. 
FIG. 1A is a cross-sectional view through axis 1A-1A' of the panel unit 12 
of FIG. 1, showing grilles 12D and 12E formed from arrays of vanes 12G 
extending across the regions of the reflex ports 12B and 12C. Typically 
the vanes 12G are configured in greater density in these grilles 12D and 
12E than elsewhere in order to obtain good heat exchange to the air. 
FIG. 1B is a bottom view of the panel unit 12 of FIG. 1, showing a woofer 
frame 12H formed mainly from vanes 12G formed perpendicular to the front 
plane of panel unit 12, as in FIG. 1A. 
FIG. 1C is a side elevational view of assembly 10 of FIG. 1, showing the 
profile of the woofer frame 12H, cone 14, a woofer driver 16, shown 
partially in dashed outline, secured structurally in a recessed mounting 
region formed as part of woofer frame 12H integral with vanes 12G which 
are seen to extend virtually the full panel height, from the bottom of the 
woofer frame 12H upwardly through the grilles in the port region and then 
joining the horn structure 12A and continuing to the top of panel unit 12. 
A compression horn driver 18 of known art is attached to horn structure 
12A by known threaded means. 
An amplifier mounting shelf 12J is formed just below the horn structure 12A 
and above the ports: the shelf 12J can support an amplifier 20 as shown in 
dashed outline, serving as a heat sink. 
A main enclosure 10A, shown in dashed outline, is attached around the edge 
of panel unit 12 in a substantially air tight manner by regular screw 
means. 
FIG. 2 is an enlarged rear view of panel unit 12 of assembly 10 (FIG. 1) 
showing the horn structure 12A and the woofer frame 12H formed integrally 
from vanes. Vane 12G is typical of the vanes, which extend from bottom to 
top and which are joined integrally to the rear of the panel unit 12 
wherever practicable. The vanes effectively span the ports 12D and 12E 
where they become part of the vane grilles 12D and 12E. The amplifier 
mounting shelf 12J is a transverse web vane extending across the top of 
vane grilles 12D and 12E which thus provide good thermal coupling to cool 
the amplifier along with the thermal coupling to the front plane of panel 
unit 12. The bottoms of the vane grilles 12D and 12E are defined by 
transverse web vanes 12K and 12L. Thus the grilles with top, bottom and 
side walls, define a ducted tuned bass reflex port. 
It is noted that additional vanes are provided in an interleaved manner in 
each of the vane grilles 12D and 12E: these effectively double the vane 
surface area in the regions in ports 12B and 12C so as to enhance the 
vane-to-air heat transfer. 
In woofer structure 12H the vanes are seen to extend downwardly in a single 
cluster to form a lower structural leg of the woofer frame 12H, and to 
divide into two clusters diverging upwardly to form two upper structural 
legs of woofer frame 12H. Because of good heat sinking thus provided by 
the woofer frame 12H, a small neodymium magnet structure can be used in 
the woofer driver 16. 
Above the grilles 12D and 12D the vanes join the horn structure 12A: the 
outline of horn driver 18 is shown as a dashed line only, in order to show 
how the vanes are webbed onto the horn mount throat region for effective 
heat transfer from driver 18. 
Some of the heat generated by the two speaker drivers and other 
heat-generating components located in the speaker enclosure is conducted 
to the die cast aluminum panel unit 12 via the vanes and thus will 
dissipate to the surrounding air directly from the outside of the panel 
unit 12; however, particularly when the woofer cone 14 is driven at high 
sound levels at low frequencies, air will be pumped back and forth past 
the vanes in the vane grilles 12D and 12E, thus providing a cooling effect 
that increases in effectiveness with the audio power level. 
A power transformer, e.g. associated with an amplifier, maybe be mounted on 
one of the vanes of the woofer frame structure 12H as shown in dotted 
outline 22. 
The principle of acoustic air-cooling of vanes extending across the bass 
reflex ports of a speaker enclosure can be applied to enhance heat removal 
from any additional heat-producing components located within the speaker 
enclosure by coupling such components thermally to the vane structure. 
In an alternative configuration of woofer frame structure 12H, instead of 
the single lower structural leg described above, the vanes in that region 
may be divided into two separate vane clusters diverging downwardly so as 
to form an X-shaped woofer frame structure. 
Although a two-way speaker system is shown in the illustrative embodiment, 
the self-cooling principle of the present invention can be beneficially 
applied as well to other speaker systems utilizing a single loudspeaker 
and to those utilizing more than two loudspeakers. 
The invention may be embodied and practiced in other specific forms without 
departing from the spirit and essential characteristics thereof. The 
present embodiments are therefore to be considered in all respects as 
illustrative and not restrictive, the scope of the invention being 
indicated by the appended claims rather than by the foregoing description; 
and all variations, substitutions and changes which come within the 
meaning and range of equivalency of the claims are therefore intended to 
be embraced therein.