What is a High Pass Filter?
Solution: A High Pass filter is a filter that passes high frequencies and attenuates low 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 infinity down 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 infinity 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 down to zero (or near zero) is defined as the stopband of the filter. The amplitude of the filter at one tenth 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 lower frequencies, the amplitude continues to roll off in a linear fashion, where the slope of the line is -20
A high pass filter is a feature in many car audio systems that allows the user to keep low frequency sounds from playing through front or rear full-range speakers. This is especially nice when you want low frequencies to play through a subwoofer exclusively. If a stereo system does not include a subwoofer, a high pass filter can be used to direct higher frequencies through the front speakers, while leaving rear full range speakers to handle bassier frequencies. A user sets the high pass filter by choosing a cutoff frequency. Sounds above the cutoff will pass through the high pass filter, while those that fall below the cut off will be attenuated or filtered out. Generally, high-end frequencies are channeled towards the front of the sound environment in a car, while mid-range is shared by front and rear. The rear speakers also handle bass, unless a subwoofer is present, in which case it might handle all lower frequencies. While a high pass filter is a high-tech feature, it can be used t
