1. Parametric and Graphic Equalizers
Parametric equalizers are extremely useful, versatile tools in both live sound and recording applications. They can enable a wide variety of tasks, from gentle contouring and audio sweetening in the studio, to room equalization and feedback notching in sound reinforcement. The most advanced form of equalization system available, the parametric equalizer allows adjustment of all three parameters required for complete con- trol of equalization: bandwidth, frequency and amplitude boost/cut. While graphic equalizers only provide a series of adjacent bands for control of a specific frequency, parametric equalizers allow for selecting a specific frequency directly. Thus, they can be used to realize complex frequency curves with highest precision. Since the acoustic results obtained with parametric equalizers are not as predictable as those of graphic equalizers, it is necessary to work with parametric equalizers for a while to get a feeling for the functions and the results they can achieve.
2. Basic Operation of the PEQ-5B Parametric EQ
The Nady PEQ-5B provides all the advantages of both para- metric equalizers and narrow-band notch filters. Its advanced design and high performance enable equalization flexibility limited only by the imagination. With a variable bandwidth ranging from 0.03 to 2 octaves, the PEQ-5B is the most flexi- ble equalizer available. It is totally superior to graphic equal- izers in all ways, and for almost all applications, from post- production in audio, video and broadcast studios to on stage use.
Each of the PEQ-5B's 5 bands can be adjusted from extreme- ly narrow to broadband. Its additional low and high-cut filters have a slope of 6 dB/octave and can be varied over a wide frequency range and enable control of the entire frequency response for your specific application. With all this equaliza- tion available, it is easy to modify the entire spectrum of the signal being processed at once. The added filters allow both high and low broadband corrections, while the parametric fil- ters process hum, feedback, and other narrow frequency band problems.
The PEQ-5B utilizes Constant -Q filters which prevent the parameters frequency, bandwidth and amplitude from affect- ing each other. Such independence allows more clearly defined and repeatable filter settings. When several filters are used simultaneously, the resulting overall filter curve can be calculated by adding/subtracting the single band-specific fil- ter curves.
Conventional parametric equalizers typically employ series filters, which can introduce noticeable phase shifts and delays. The advanced-design PEQ-5B features parallel filters, which are a marked improvement and provide optimized audio free of such undesirable artifacts. Parallel filter design thus allows for more "musicality" in the audio processing.
It should be noted, however, that while extreme boost/cut of frequencies can be realized by overlapping the frequencies of individual bands, this technique must be exercised with care when using the PEQ-5B so that the "musicality" of the final sound image is retained.
The PEQ-5B enables both notching/peaking and rolling-off frequency bands. Notching and peaking refer to specific attenuation or boosting respectively of single frequencies or bands. Peaking is achieved by band-pass filters and notching by notch filters. Although similar in concept, these two filter types achieve the exact opposite effect. Rolling off is done by either high or low pass filters. In the PEQ-5B, these filters have a slope of 6 dB/octave and can be varied within a wide frequency range.
amplitude | | | | |
+15 dBu | | BW=.03 | BW=2 | |
| | | |
0 | | | | |
-15 dBu | | | | |
BW=.03 | BW=2 | | | |
f1 | f2 | f3 | f4 | frequency |
Fig. 1: Narrow (BW=.03) and Wide (BW=2)
Fig. 1: Narrown tch (BW=f1, f2) and.03)peak and(f3, f4) Widefilters (BW=2) notch (f1, f2) and peak (f3, f4) filters
amplitude | | |
0 dBu | | |
-15 dBu | | |
f l o w | f h i g h | frequency |
Fig. 2: Roll-off function
Fig. 2: Roll-off function
