FIR Filters Help Improve Audio Quality in Consumer Electronics
By Tony Valentino, Quickfilter Technologies, Inc.
Audio quality in consumer electronics is often sacrificed for cost reasons. However, as the markets for these electronic products mature, audio quality will become an important product differentiator. The compromise in audio quality is often reflected by the manufacturers’ choice of speakers.
Tony Valentino, Quickfilter Technologies, Inc.
By Tony Valentino, Quickfilter Technologies, Inc.
Audio quality in consumer electronics is often sacrificed for cost reasons. However, as the markets for these electronic products mature, audio quality will become an important product differentiator. The compromise in audio quality is often reflected by the manufacturers’ choice of speakers.
The speakers chosen by these manufacturers are not only constrained by their cost, but also by the physical size of the equipment, and the manufacturing process in mounting the speakers. In making the design and cost tradeoffs, little attention is given to the speaker response over the audible frequency range (speaker transfer function) because it is thought that the equalizers in the audio processors will compensate for shortcomings in theselower-cost speakers. However, this rarely happens. Listen to the soundtrack of a DVD played through a $3000 HDTV and the same soundtrack played through a good quality sound system. The difference is very noticeable. With some minor changes, however, manufacturers can approach the audio quality of a high end sound system with very little to no incremental cost.
Many manufacturers believe that good audio quality is synonymous with maximum bass; however, audio quality is really the ability to reproduce the sound track exactly as it was recorded. To achieve this, the speaker response needs to be flat across the audible spectrum. Manufacturers of high-end stereo equipment have recognized — and achieved — this requirement. Surprisingly, in many cases, these manufacturers ship their equipment with no bass or treble adjustments. Manufacturers of consumer electronics equipment can achieve this same performance of high-end stereo equipment by using Finite Impulse Response (FIR) filters that are low in cost but high in performance. Typical audio devices which will benefit from the use of FIR filters include televisions, especially high definition TVs, docking stations, mid to low end stereo systems, portable stereo systems (e.g. Boom Boxes), wired and wireless Headsets,and personal computer audio equipment.
An ideal speaker would be capable of reproducing all the audible frequencies at the same volume at which they were recorded. Rarely in life are things ideal, so the generally accepted standard is a variation of +/-3dB around a centerline. The 3dB point is considered to be the point at which volume changes are barely perceptible. Even if a speaker transducer were to possess this characteristic, the process of mounting that speaker into a cabinet will change its response characteristics, so compensation will still need to be applied after the speaker is mounted in its final enclosure. The use of an FIR filter will simplify this compensation. The speaker response graphs below were taken from a high definition LCD TV manufactured by one of the world’s leading consumer electronics. manufacturers.
The difference in audio quality is startling. In the original response curve, the overemphasis of the low frequencies tends to wash out the midrange frequencies and the drop of in the midrange affects the intelligibility of the dialog. With the filters, the audio is heard exactly as it was recorded with neither over nor under emphasis. Utilizing Quickfilter Technologies SavFIRe (Simple and versatile FIR engine) products, manufacturers can now bring higher performance to their products at lower costs.
For more information on Quickfilter products, please visit Quickfilter.
About the author
Tony Valentino is Chief Operating Officer for Quickfilter Technologies. During the past 32 years, he has held executive and management positions in sales, marketing, operations and general management for companies in the electronics industry, including Texas Instruments, VLSI Technologies, Rohm Electronics, Alcatel Microelectronics and Acoustic Technologies. Mr. Valentino has served as the general manager for silicon products at Acoustic Technologies as well as the senior director for strategic accounts and national sales manager for Alcatel Microelectronics. In 1969, Mr. Valentino graduated from the University of Michigan with a Bachelor of Science degree in Electrical Engineering. In 1973, he received a Masters Degree in Business Administration from the University of Missouri.Tony Valentino can be reached at tvalentino@quickfilter.net.
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