I have a hardware De-esser, a dbx 263x. Instead of having a specific threshold it has two rms detection circuits, one for measuring the overall level and one for measuring the high frequency volume based on the frequency knob. It has three simple controls, a broadband or split toggle, frequency knob and a slider to adjust how the high frequency is processed vs the rest of the signal. This works very well in dynamic situations where you would normally have to adjust the threshold of a de-esser to adjust for changes in overall volume. Does waves have any plugins that do something similar or could you look at emulation something like this?