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For Butterworth filters no value can be entered and any value displayed is ignored.

"1" - first-order filters - have the most gradual cutoff slope Highpass: The filter passes high frequencies and attenuates low frequencies.Ĭhoose a value between 1 and 10.Lowpass: The filter passes low frequencies and attenuates high frequencies.

(Here it is common to use a ripple value of 20, 30 or more dB).įor details about these filters see the Wikipedia pages on Butterworth filters and see Chebyshev filters. Chebyshev Type II: Chebyshev Type II filters are similar to Butterworth, including the flat passband response, except that a) at the cutoff frequency the magnitude response is equal to the ripple value, b) above (below for highpass) the cutoff frequency, the stopband attenuation increases more rapidly, for a given filter order, than Butterworth, and c) the stopband attenuation varies from infinite to the ripple value.Chebyshev Type I: Chebyshev Type I filters are similar to Butterworth filters, except that a) the magnitude response of the passband has "ripples" in it (usually small), b) at the cutoff frequency the magnitude response is equal to the ripple value, and c) above (below for highpass) the cutoff frequency, the stopband attenuation increases more rapidly, for a given filter order, than Butterworth.no ripples), the magnitude response at the cutoff frequency is -3 dB, and above (for lowpass) or below (for highpass) the cutoff frequency, the attenuation increases at approximately 6 dB per octave times the filter order (so for example 60 dB per octave for 10th order). Butterworth: An analog Butterworth filter provides a "maximally flat" passband (ie.Note that moving either slider may change the horizontal position of the 0 dB line. Vertical scale sliders: By default the vertical scale reads from 0 dB to -10 dB, but these two sliders to left of the scale let you adjust the upper and lower dB values so as to change the visible range on the graph.Dragging the Classic Filters window wider displays some additional points on the scale. Horizontal Scale: This shows the frequencies in Hz to which volume adjustments will be applied.