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Roll-off is also significant on audio loudspeaker crossover filters: here the need is not so much for a high roll-off but that the roll-offs of the high frequency and low-frequency sections are symmetrical and complementary. An interesting need for high roll-off arises in EEG machines. Here the filters mostly make do with a basic 20 dB/decade ...
Low frequency equaliser section with compensation for inductor resistance. The resistance r represents the stray resistance of the non-ideal inductor. The resistance r' is a real resistor calculated to compensate for r. Occasionally, a low-pass section is included to compensate for excessive line transformer roll-off at the low frequency end.
The filter does not attenuate all frequencies outside the desired frequency range completely; in particular, there is a region just outside the intended passband where frequencies are attenuated, but not rejected. This is known as the filter roll-off, and it is usually expressed in dB of attenuation per octave or decade of frequency. Generally ...
Quick roll-off around the cutoff frequency, which improves with increasing order; Considerable overshoot and ringing in step response, which worsens with increasing order; Slightly non-linear phase response; Group delay largely frequency-dependent; Here is an image showing the gain of a discrete-time Butterworth filter next to other common ...
Far from the cutoff frequency in the transition band, the rate of increase of attenuation with logarithm of frequency is asymptotic to a constant. For a first-order network, the roll-off is −20 dB per decade (approximately −6 dB per octave.)
Cutoff frequency is the frequency beyond which the filter will not pass signals. It is usually measured at a specific attenuation such as 3 dB. Roll-off is the rate at which attenuation increases beyond the cut-off frequency. Transition band, the (usually narrow) band of frequencies between a passband and stopband.
Modern systems have far wider potential bandwidth. An essential feature of all cutting amplifiers—including the Neumann cutting amplifiers—is a forcibly imposed high frequency roll-off above the audio band (>20 kHz). This implies two or more additional time constants to those defined by the RIAA curve.
The frequency response of a fifth-order type II Chebyshev low-pass filter with = Also known as inverse Chebyshev filters, the Type II Chebyshev filter type is less common because it does not roll off as fast as Type I, and requires more components.