That is exactly what Martin replied to me to do in his "Lowther design" ( I think) and is exactly what others (Akhelish!) said would ruin the "magic" of the driver as a FRD ---I think it's still important to build and listen and thereby get the experience in what sounds like what---otherwise it tends to be a discussion with no conclusion-- These Martin "Lowther" Br box looks pretty easy and straightforward to build too----and it would allow me a good test --#1 build and run without the filter --test # 2--install the low end filter---might build it with a switch to be able to turn on and off the filter---Jim