From Blue Cat Audio:
Blue Cat's Triple EQ is a 3 bands semi-parametric equalizer that can be controlled as a single filter with customizable shape. It includes a low shelf filter, a high shelf filter and a boost/cut peak filter. Its wide range of gain (+/-40 dB per band) and bandwidth (.01 to 5 Octave) makes it very versatile to create any filter shape. The three filters are linked together so that when you change the center frequency or the bandwidth, the parameters of the three filters are modified accordingly: you can control the entire equalizer characteristics with a single mouse click.
The graph shows the computed frequency response of the plug-in, so that you can exactly know how your signal is processed. The controls are now directly available on the filter graph, making the design of the filter shape even easier.