What is a Low Pass Filter?
Solution: A Low Pass filter is a filter that passes low frequencies and attenuates high frequencies. The Knowledgebase discusses Single Pole and Two Pole filters. For filters with more poles, please contact Texas Instruments Applications. The amplitude response of a low pass filter is flat from DC or near DC to a point where it begins to roll off. A standard reference point for this roll-off is the point where the amplitude has decreased by 3 dB, to 70.7% of its original amplitude. The region from at or near DC to the point where the amplitude is down 3 dB is defined as the passband of the filter. The range of frequencies from the 3 dB point to infinity is defined as the stopband of the filter. The amplitude of the filter at ten times the 3 dB frequency is attenuated a total of 20 dB for a one pole filter, and a total of 40 dB for a two pole Butterworth filter. At higher frequencies, the amplitude continues to roll off in a linear fashion, where the slope of the line is -20 dB per deca
A low pass filter, a feature found in many of today’s car audio systems, allows the user to exclusively designate lower frequencies to a subwoofer. In the absence of a subwoofer, the low pass filter can do the same for rear, full range speakers. Once the low pass filter is set by the user at a specific cutoff point, all frequencies lower than the cutoff will be passed along, while higher frequencies will be muted or filtered out. Used in conjunction with a high pass filter, one can “place frequencies” to the proper speakers, creating a total sound environment. Generally, low frequencies like bass guitar and bass drum are poorly reproduced through small-coned speakers. While high-end smaller speakers might do a satisfactory job for some, for heart-pounding, chest-thumping bass, many audiophiles will want a speaker made for the job: a subwoofer. A subwoofer is designed to handle lower frequencies, delivering an astounding fullness and depth to any music that leans heavily on low-end freq
