Electrical audio signal processing systems and devices – Including frequency control – Having crossover filter
Reexamination Certificate
2000-12-20
2004-03-16
Ramakrishnaiah, Melur (Department: 2644)
Electrical audio signal processing systems and devices
Including frequency control
Having crossover filter
C381S117000
Reexamination Certificate
active
06707919
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to driver control circuits for controlling audio speakers. More particularly, the invention relates to a driver control circuit that optimally controls the frequencies of audio signals delivered to one or more speakers using a minimum number of components.
2. Description of the Prior Art
Driver control circuits divide audio signals into different frequency bands or ranges for controlling two or more speakers or “drivers” in a speaker system. Driver control circuits apportion the frequency spectrum in such a way that each speaker operates in its optimum frequency range and the entire speaker system reproduces sound with a minimum of distortion.
The frequency at which a driver control circuit separates one frequency band from an adjacent band is called the crossover frequency. A driver control circuit passes a selected frequency range or band of signals to each speaker and attenuates frequencies that are beyond the speakers' crossover frequency. In this way, each speaker reproduces audio signals only in its optimum frequency range and then “rolls off” beyond the crossover frequency.
The rate at which a driver control circuit attenuates frequencies delivered to a speaker beyond the crossover frequency is called the crossover slope. Crossover slopes are measured in dB of attenuation per octave and are categorized by their magnitude or “steepness”.
Driver control circuits with steep crossover slopes are desirable because they attenuate frequencies that are beyond a speaker's effective operating range more rapidly so that the speaker audibly reproduces only audio signals in its optimum frequency range, reducing distortion from signals outside the range. Steep crossover slopes are also desirable because they allow the operating ranges of the speakers to be extended and reduce or eliminate interference between speakers operating at adjacent frequency ranges.
In addition to constructing driver control circuits with steep crossover slopes, it is also often desirable to select or shape the frequency response of a driver control circuit above or below its crossover frequency. Such frequency shaping or selecting is especially desirable for audio speakers used in home theater systems where sound is reproduced by a plurality of different types of speakers including, for example, left and right main speakers, a center channel speaker, left and right surround speakers, and a low-frequency effects sub-woofer speaker. Because each speaker or speaker pair in a home theater system should optimally reproduce only certain frequencies of audio signals, it is important to carefully select the crossover frequencies of all of the speakers and to shape the frequency response of the speakers using the driver control circuits. It is often even desirable to adjust the frequency response of each type of speaker using the driver control circuits so that the sound from the different types of speakers match as perfectly as possible.
Applicant has discovered that home theater speaker operation can often be optimized if the frequency response of the driver control circuits for the speakers can be selectively shaped or adjusted above and below the speakers' crossover frequencies to match all the speakers. Such selective adjustment of the frequency response allows home theater system designers and installers to custom-configure home theater systems to achieve extremely high-quality sound.
Many solutions exist in the prior art to shape or select the frequency responses and crossover frequencies of driver control circuits. However, prior art solutions require the addition of a plurality of inductors, capacitors, and other electronic components to existing filter networks, thus significantly increasing the size and cost of the driver control circuits. In addition, in-wall units required in many home theater applications do not have space for such components.
SUMMARY OF THE INVENTION
The present invention solves the above-described problems and provides a distinct advance in the art of driver control circuits. More particularly, the present invention provides a driver control circuit that enhances a steep crossover slope while permitting selective shaping or adjusting of its in-band frequency response near its crossover frequency with a minimum number of components.
One embodiment of the driver control circuit of the present invention broadly includes a signal connector for connecting with a source of audio signals; a speaker connector for connecting with a speaker; and a frequency passing circuit coupled between the signal connector and the speaker connector for passing a selected range of frequencies of the audio signals to the speaker and for attenuating other frequencies. The frequency passing circuit includes components forming a traditional low-pass and/or high-pass filter network and a resistive component connected in parallel across the second series mounted component of the low-pass and/or high-pass filter network.
The resistive component increases the crossover slope of the driver control circuit and shapes its in-band frequency response near the crossover frequency. By selectively adjusting the resistance value of the resistive component, the frequency response and crossover frequencies of the driver control circuit can be optimally selected or adjusted for use in home theater systems and other applications requiring precise frequency shaping between multiple types of speakers.
These and other important aspects of the present invention are described more fully in the detailed description below.
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Combest Christopher E.
Koval John
Multi Service Corporation
Ramakrishnaiah Melur
Williams LLP Hovey
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