Electrical audio signal processing systems and devices – Loudspeaker feedback
Patent
1998-06-09
2000-08-15
Chang, Vivian
Electrical audio signal processing systems and devices
Loudspeaker feedback
H04R 300
Patent
active
061048178
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates generally to audio speaker drivers.
BACKGROUND ART
Recent decades have seen numerous developments in high-fidelity sound reproduction. Electronic and mechanical components made available to amplifier manufacturers have permitted the design of amplifiers that have better linearity and frequency response and lower distortion. Such amplifiers are smaller in size, less fragile, and less expensive. The audio sources (e.g. multiplexed stereo FM, digital compact disk, and compact cassette tape) are greatly improved over those previously available, and are dropping in cost. The electrical signals provided to the terminals of the speakers of a stereo sound system are, in present-day times and at modest cost, of a quality and fidelity that would have been unavailable to the consumer of two decades ago, except at prohibitive cost.
Those skilled in the art will appreciate, however, that one aspect of a high-fidelity sound system has remained stubbornly resistant to these improvements, namely the technology whereby the electrical energy of a sound system is converted to accoustic (airborne) energy: the speakers.
FIG. 1 shows the impedance of a electromagnetic speaker driver. It consists of three components: R.sub.e is the voice coil dc resistance, L.sub.v is the voice coil inductance, and the parallel network of L.sub.m, C.sub.m and R.sub.m is the motor impedance. The inclusion of L.sub.m, C.sub.m and R.sub.m is a result of the energy conversion process between electric energy and mechanical energy in the electromagnetic speaker driver. To be more specific, the mass of the diaphragm causes C.sub.m to appear in the driver's impedance, the friction for R.sub.m, and the compliance of the diaphragm assembly for L.sub.m. There are known formulae to relate the values of C.sub.m, R.sub.m and L.sub.m to the mechanical parameters of the driver. If one puts a driver in a box, the measured impedance changes. There will be a network, which is related to the mechanical parameters of the box, appeared in parallel with the motor impedance. FIG. 2 show the added networks for closed-enclosure and bass-reflexive types of boxes.
The analysis of the frequency response in these systems under a voltage-source input signal can be done as in FIG. 3. Z.sub.b is the added impedance component from the speaker box. In the bass frequency region, the importance of L.sub.v is very minor and hence omitted in FIG. 3. There is an equivalent mechanical system for the electrical system described in FIG. 3b. Alternatively, the analysis can be done on the mechanical system and result will be the same. Note that the dc resistance of the voice coil acts as part of the mechanical friction in the driver as seen from FIG. 3b.
In general, the bass response of a electromagnetic (boxed) speaker system (that is, the system including a electromagnetic driver (or drivers) and an enclosure in which the driver(s) resides) depends on the mechanical parameters of both the enclosure and the driver itself, as well as the voice coil dc resistance. Examples of the parameters for enclosure are the box volume and port resonance frequency (if the enclosure is ported or vented). Examples of the driver parameters are compliance, mass, and the friction of the diaphragm assembly. These parameters have to be carefully chosen so that the combined system provides good bass response. Very often the design procedure starts with some known parameters in the driver or the enclosure, then calculates the required values for the rest parameters. There are at least two implications here.
First, when one parameter (say enclosure volume) is altered during the design procedure, the drivers need to be redesigned so that they exhibit the new set of required parameters. Second, after one fixes some parameters and then calculates the required values for other parameters, these values may becomes unrealistic to implement mechanically, or the efficiency of the speaker system becomes unacceptable.
Several apparatus have been proposed to address the above-mentio
REFERENCES:
patent: 4118600 (1978-10-01), Stahl
patent: 4276443 (1981-06-01), Meyers
patent: 4335274 (1982-06-01), Ayers
patent: 4573189 (1986-02-01), Hall
patent: 4980920 (1990-12-01), Noro et al.
patent: 5031221 (1991-07-01), Yokoyama
patent: 5086473 (1992-02-01), Erath
patent: 5206912 (1993-04-01), Noro
patent: 5537479 (1996-07-01), Kreisel et al.
patent: 5588065 (1996-12-01), Tanaka et al.
K.G. Stahl, "Synthesis of loudspeaker mechanical parameters by electrical means: a new method for controlling low-frequency loudspeaker behavior" in J. Audio Eng. Soc. vol. 29, No. 9, pp. 587-596 (1981).
P.G.L. Mills and M.O.J. Hawksford, "Distortion reduction in moving-coil loudspeaker systems using current-drive technology" in J. Audio Eng. Soc. vol. 37, No. 3, pp. 129-148 (1989).
P.G.L. Mills and M.O.J. Hawkford, "Transconductance power amplifier systems for current-driven loudspeaker" in J. Audio Eng. Soc. vol. 37, No. 10, pp. 809-822 (1989).
LandOfFree
Speaker and amplifier system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Speaker and amplifier system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Speaker and amplifier system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2016001