Electrical audio signal processing systems and devices – Including frequency control – Having automatic equalizer circuit
Reexamination Certificate
1997-12-23
2004-01-06
Harvey, Minsun Oh (Department: 2644)
Electrical audio signal processing systems and devices
Including frequency control
Having automatic equalizer circuit
C381S098000, C381S059000, C381S099000
Reexamination Certificate
active
06674864
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to computer based audio control systems and more particularly to computer based audio control systems utilizing adaptive speaker compensation, such as in multimedia computers.
With the increased video and audio applications in multimedia personal computers, audio sound systems are becoming an increasingly important component of computer based systems. Computer users often upgrade their systems with new multimedia computer applications and may wish to add additional speakers or upgrade to higher performance speakers to take advantage of more sophisticated video and audio applications. Speaker response characteristics affect the quality of the audio systems. Speaker response characteristics depend upon many factors including overall speaker design, speaker material, manufacturing variations and other factors. An input audio signal to speakers can be distorted by the speaker due to the non-linear speaker response characteristics. Lower cost speakers typically have larger non-linear response characteristics and thus have more distortion. More expensive speakers typically have fixed built-in circuitry in the speaker cabinet to attempt to compensate for such non-linear response characteristics.
Some speakers use multiple speakers (speaker cones) within the same speaker box such as a mid range speaker, a bass speaker and a treble speaker. Many speaker manufacturers attempt to compensate for the non-linear speaker response characteristics by incorporating crossover filters directly into the speaker cabinet. Generally, crossover filters separate frequency ranges for each speaker of a cone within a multi speaker arrangement in an attempt to compensate for the non-linear response characteristics of each speaker. Such circuitry can become very complex and costly and adds to the expense of the speakers. Other filtering circuits are also typically incorporated into the speaker cabinet to ensure proper signal phase adjustment to avoid signal cancellation when multiple speakers are in the same cabinet. Where the level of compensation offers a higher quality sound, such built-in compensation circuitry can add substantial cost to the speaker and hence to the audio system.
Even less expensive speakers, such as headphone speakers, may have simple low frequency amplifiers built into the headphones. Such amplifiers typically boost bass frequencies, or other frequency ranges in an attempt to compensate for the non-linear characteristics of the headphone speakers. Although some compensation is provided, the level of compensation is often low due to the relatively simple compensation provided.
A problem arises with using such conventional speaker compensation systems because the old speakers must be replaced with new more expensive higher quality models. Also, adding new speakers with high cost built-in compensation can significantly increase the cost of the audio system.
Some high end home entertainment systems have multichannel audio systems, such as surround sound systems with three or more channels to provide theater sound effects. The surround sound channels are often presented at a lower volume level than front channels since movies contain most of the audio information in the front channels and use the surround channels sparingly as effects channels. A typical surround multichannel system may include six channels. These channels typically consist of a left, right and center front channel, a left and right surround channel and a subwoofer channel. Differing prerecorded equalization settings among surround channel recordings or among various formats can sound different on the same speakers and different on other speakers not having crossover filtering or only having limited bandpass filtering.
However such systems typically require the purchase of new speakers with built-in compensation. In addition, the cost of high quality speakers containing non-linear response compensation can limit the market for such speakers due to the high manufacturing cost and high overall product cost. With the market demand of maintaining a cost competitive computer audio system, a need exists for a computer based speaker compensation system that affords high performance at a relatively low cost and one that provides increased flexibility to allow adaptive compensation when interchanging or adding speakers within a system. Such a method and system should provide adaptive crossover filtering and compensate for non-linear speaker characteristics for speakers with single or multiple speakers in a cabinet, if needed. Such a system should provide adaptive speaker compensation such that the system may automatically provide differing filters on a per speaker basis in a relatively simple and cost effective manner.
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ATI Technologies
Grier Laura A.
Harvey Minsun Oh
Vedder Price Kaufman & Kammholz P.C.
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