The graphic nature of the Filter And EQ > FFT Filter effect makes it easy to draw curves or notches that reject or boost specific frequencies. FFT stands for Fast Fourier Transform, an algorithm that quickly analyzes frequency and amplitude.
This effect can produce broad high‑ or low‑pass filters (to maintain high or low frequencies), narrow band‑pass filters (to simulate the sound of a telephone call), or notch filters (to eliminate small, precise frequency bands).
Scale
Determines how frequencies are arranged along the horizontal x‑axis:
For finer control over low frequencies, select Logarithmic. A logarithmic scale more closely resembles how people hear sound.
For detailed, high‑frequency work with evenly spaced intervals in frequency, select Linear.
Spline Curves
Creates smoother, curved transitions between control points, rather than more abrupt, linear transitions. (See About spline curves for graphs.)
FFT Size
Specifies the Fast Fourier Transform size, determining the tradeoff between frequency and time accuracy. For steep, precise frequency filters, choose higher values. For reduced transient artifacts in percussive audio, choose lower values. Values between 1024 and 8192 work well for most material.
Window
Determines the Fast Fourier transform shape, with each option resulting in a different frequency response curve.
These functions are listed in order from narrowest to widest. Narrower functions include fewer surrounding, or sidelobe, frequencies but less precisely reflect center frequencies. Wider functions include more surrounding frequencies but more precisely reflect center frequencies. The Hamming and Blackman options provide excellent overall results.
The Filter And EQ > Graphic Equalizer effect boosts or cuts specific frequency bands and provides a visual representation of the resulting EQ curve. Unlike the Parametric Equalizer, the Graphic Equalizer uses preset frequency bands for quick and easy equalization.
You can space frequency bands at the following intervals:
Graphic equalizers with fewer bands provide quicker adjustment; more bands provide greater precision.
Range
Defines the range of the slider controls. Enter any value between 1.5 and 120 dB. (By comparison, standard hardware equalizers have a range of about 12 to 30 dB.)
Accuracy
Sets the accuracy level for equalization. Higher accuracy levels give better frequency response in the lower ranges, but they require more processing time. If you equalize only higher frequencies, you can use lower accuracy levels.
If you equalize extremely low frequencies, set Accuracy to between 500 and 5000 points.
Master Gain
Compensates for an overall volume level that is too soft or too loud after the EQ settings are adjusted. The default value of 0 dB represents no master gain adjustment.
Note:
The Graphic Equalizer is an FIR (Finite Impulse Response) filter. FIR filters better maintain phase accuracy but have slightly less frequency accuracy than IIR (Infinite Impulse Response) filters like the Parametric Equalizer.
The Filter And EQ > Parametric Equalizer effect provides maximum control over tonal equalization. Unlike the Graphic Equalizer, which provides a fixed number of frequencies and Q bandwidths, the Parametric Equalizer gives you total control over frequency, Q, and gain settings. For example, you can simultaneously reduce a small range of frequencies centered around 1000 Hz, boost a broad low‑frequency shelf centered around 80 Hz, and insert a 60 Hz notch filter.
The Parametric Equalizer uses second‑order IIR (Infinite Impulse Response) filters, which are very fast and provide very accurate frequency resolution. For example, you can precisely boost a range of 40 to 45 Hz. FIR (Finite Impulse Response) filters like the Graphic Equalizer provide slightly improved phase accuracy, however.
Master Gain
Compensates for an overall volume level that’s too loud or too soft after you adjust the EQ settings.
Graph
Shows frequency along the horizontal ruler (x‑axis) and amplitude along the vertical ruler (y‑axis). Frequencies in the graph range from lowest to highest in a logarithmic fashion (evenly spaced by octaves).
Identifying band-pass and shelving filters in the Parametric Equalizer:
A. High- and low-pass filters B. High and low shelving filters
Frequency
Sets the center frequency for bands 1-5, and the corner frequencies for the band-pass and shelving filters.
Use the low shelving filter to reduce low‑end rumble, hum, or other unwanted low‑frequency sounds. Use the high shelving filter to reduce hiss, amplifier noise, and the like.
Gain
Sets the boost or attenuation for frequency bands, and the per-octave slope of the band-pass filters.
Q / Width
Controls the width of the affected frequency band. Low Q values affect a larger range of frequencies. Very high Q values (close to 100) affect a very narrow band and are ideal for notch filters removing particular frequencies, like 60 Hz hum.
When a very narrow band is boosted, audio tends to ring or resonate at that frequency. Q values of 1-10 are best for general equalization.
Band
Enables up to five intermediate bands, as well as high-pass, low-pass, and shelving filters, giving you very fine control over the equalization curve. Click the band button to activate the corresponding settings above.
The low and high shelving filters provide slope buttons (
,
) that adjust the low and high shelves by 12 dB per octave, rather than the default 6 dB per octave.
To visually adjust enabled bands in the graph, drag the related control points.
Constant Q, Constant Width
Describes a frequency band’s width as either a Q value (which is a ratio of width to center frequency) or an absolute width value in Hz. Constant Q is the most common setting.
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