ABSTRACT
This chapter introduces the use of time delays in systems to create spectral processors. These audio effects include various types of filters for equalizers. Spectral processors change the characteristics of a signal in a frequency-dependent manner. Spectral processors are described based on how the amplitude of a signal is changed in a frequency dependent manner. The fundamental approach to creating a spectral processor is based on combining a signal with time-delayed versions of the signal. As a foundation for more complex processors, a basic low-pass filter (LPF) and high-pass filter (HPF) are initially considered. The chapter presents filters using a feedforward design. A LPF is a spectral processor that attenuates the amplitude of high frequencies while letting low frequencies pass through. A comb filter is a spectral processor that attenuates one or more frequencies within the bandwidth of a system. When visualizing the magnitude response of the system, notches occur spaced across the spectrum.
