Profit in the sense that I want to prevent blowing up woofers by inadvertantly driving them into over excursion under 40 cycles... Active - I would like to run this in the effects loop of my WT-800. I don't want to incur the in-efficiency of a passive filter if at all possible. The WT-800 is biamp ready and I intend to use that. Just gotta be able to set a protective lower limit ... Smaller is better. If I could cable this thing, power it and embed it in the rack, set and forget, never to be seen again - that would be sweet! So I'm thinking of a device along the lines a Francis Deck's hfp box but with some twists... Any suggestions ?