Electrical audio signal processing systems and devices – Circuitry combined with specific type microphone or loudspeaker – With magnetic loudspeaker
Reexamination Certificate
1997-09-17
2001-06-05
Mei, Xu (Department: 2644)
Electrical audio signal processing systems and devices
Circuitry combined with specific type microphone or loudspeaker
With magnetic loudspeaker
C381S397000, C381S401000, C381S407000, C381S412000, C361S704000, C029S594000
Reexamination Certificate
active
06243472
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to loudspeakers, and in particular, to electro-acoustic devices of the voice coil variety with built in amplification.
The desire to build a single assembly containing a loudspeaker and an amplifier has existed since the birth of audio electronics. Early attempts focused on creating lighter weight portable combination chassis units that could be placed anywhere to provide amplified sound. This type of unit, in reality, was bulky and quite heavy due to then available technologies, and is exemplified by Michael in U.S. Pat. No. 2,812,382.
With the miniaturization of electronic components came the desire to mount an entire power amplifier and related circuitry on the frame of a speaker. One of many such types of implementation is disclosed by Johnson et. al., in U.S. Pat. No. 5,164,991. In the Johnson patent, the goal was to provide variable amplification so as to permit a number of different types of line level signals to be connected to the amplifier rather than addressing the miniaturization and compacting issues of design. Another example is outlined in U.S. Pat. No. 3,499,988, where the speaker frame provides an area for mounting an associated amplifier circuit. The resulting amplifier/speaker assembly is easily accessible for servicing while taking advantage of the speaker frame for heat sinking the miniature electronic components appropriately. However, the components are not self contained with in the loudspeaker itself, electromagnetic interference (EMI) radiating components cannot be easily shielded at low cost. In U.S. Pat. No. 4,625,328, Freadman provides a less fragile more bulky amplifier loudspeaker combination by enlarging the speaker frame and integrating a traditional adaptation of a thin type heat sink which relies on the motion of the diaphragm to generate airwaves to cool the heat sink/amplifier structure. However, once again there is no easy way to inherently shield EMI radiating components within the assembly provided.
Another similar but different approach was undertaken by Jordan in U.S. Pat. No. 5,097,513 where both the loudspeaker and amplifier, as well as the enclosure are placed at opposite ends of a reflex duct to improve cooling while increasing base response. But this and similar arrangements do not inherently provide a way of achieving near zero length wiring connections between the loudspeaker and the amplifier/driver circuitry, providing EMI shielding for any EMI radiating components or reducing manufacturing costs. More recently, assemblies have been built where one or more loudspeakers have been placed in an enclosure with amplification stages and in some cases include either an optical or wireless radio-frequency receiver. While the prior art addresses various combinations of known technical issues, none address, greatly reduce or actually eliminate the cost of building and manufacturing multiple assemblies, the cost associated with heat dissipating hardware, the need to shield electromagnetic radiating components, as well as, other related technical issues.
SUMMARY OF INVENTION
Amplified loudspeakers built according to the present invention are fully integrated assemblies wherein the amplifier is physically embedded into the loudspeaker's voice coil or magnetic housing assembly and is not externally visible. The first general way of practicing the current invention is to assemble the amplifier and any related circuit using thick or thin film hybrid techniques or miniature printed circuit board techniques and integrating the assembly as a part of the loudspeaker's voice coil. Using these techniques, the amplifier would directly drive the voice coil with little or no lead length. Power and line level audio signals would be brought to the cone of the loudspeaker according to the current invention using standard tinsel wire connections. In the case of wireless signal transmission, only power and ground would nominally need to be brought to the loudspeaker's cone. In the case of optical signal transmission, the voice coil assembly would also contain an optical sensor. In the case of Radio Frequency transmission, an antenna could be integrated into the cone of the loudspeaker. Further, the amplifier would be cooled by the turbulent air circulated within and without the voice coil assembly during the mechanical movements associated with the production of audible sound.
The second general way of practicing the current invention is to assemble the amplifier once again using miniature circuit assembly techniques and this time placing the assembly preferably within the internal magnetic cavity of the loudspeaker. Voice coil connection to the amplifier would now be internal using standard tinsel wire. Power and line level audio signal would be brought inside the housing of the loudspeaker to the amplifier using through-hole connections. In the case of wireless signal transmission, only power and ground would nominally need to be brought to the amplifier assembly. In the case of infrared signal transmission, a means would be provided for optical signals to be transferred to the amplifier assembly using an optical link. In the case of radio frequency signaling, a miniature antenna could be placed at the back of the magnetic assembly. In this case, the amplifier would be conduction cooled by attachment of the circuit assembly to the surface of the loudspeaker's magnetic assembly.
Depending on the type of amplifier circuit utilized in an embodiment of this invention, there can be further added advantages. For example, if a class D amplifier were to be used, this invention provides distinct and unique advantages. A primary advantage is the ability to integrate the output stage filter inductor or inductors into the voice coil assembly. A further advantage is the virtual absence of EMI due to the inherent shielded construction of the traditional loudspeaker assembly. An additional advantage that class D amplifiers provide is the much higher and more efficient (approximately 90 percent) output drive capability provided. Thus, higher audio output power can be integrated into the voice coil assembly given similar amount of thermal energy to be removed than is possible using traditional linear amplifiers such as a class B amplifier, etc. The present invention is ideally suited to class D for the above reason and the inherent EMI shielding provided which are a bane to the high fidelity industry at present requiring expensive passive filtering.
In embodiments of the present invention where a class D or other high power efficiency type amplifier circuit is utilized, the resulting amplified loudspeaker systems are ideally suited for automotive applications. In addition, the present invention also solves the age old automotive industry problems of finding space for placing and housing the amplifier circuitry, associated wiring issues, heat dissipation.
Regardless of the type of amplifier utilized in an embodiment of the present invention, a further advantage is that the amplifier does not have to drive a pair of variable length heavy gage speaker wires. This allows the amplifier to be optimized for near zero length speaker wires and matched to the loudspeaker voice coil dynamic characteristics.
In summary, the present invention has many advantages over the prior art. Among those advantages are:
(a) a lower cost electronic assembly;
(b) a very compact amplified loudspeaker system;
(c) inherent shielding and solving of EMI issues;
(d) elimination of most heat sinking associated costs;
(e) allowing for optimal matching of the amplifier/driver electronics to the characteristic of the loudspeaker's voice coil;
(f) allowing for easy addition of various electronic circuitry and amplification stages to improve the linearity of the entire amplified loudspeaker;
(g) the realization of a near zero length electronic voice coil connection; and
(h) the elimination of heavy gage speaker wires.
REFERENCES:
patent: 3499988 (1970-03-01), Watanabe et al.
patent: 3941932 (1976-03-01), D'Hoogh
patent: 41328
Bilan Frank Albert
Jelinek Jules Joseph
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