So digital eq is nothing more then delay networks. Reverb is a bunch of short delays as well. the human ear perceives very short delays as eq changes or frequency cancellations. Short as in the 1 to120 sample range @ say 96k sample rate. That would translate to fractions of a second, micro to mille but I don't have the equation in front of me to be exact. By using those small delay times he is creating reverb that is also shelving the high end as well. All eq's in the box work on this principal. extremely short delay's are heard as eq changes and the further out the delay time is increased we get to a point where it is perceived as early reflections. By cascading a bunch of delay's with very short delay times, as short as you can make them. This is called an FIR filter.