the best twenty quid you ever spend on acoustic treatment. As long as you don't mind working in imperial measurements, which do my fruit, hence the conversion to metric above. Quote Ian Savage: the lecturer in acoustics had leaned heavily on a book called 'The Master Handbook of Acoustics', by F. Alton Everest. I recommend it heartily, it'll be the best twenty quid you ever spend on acoustic treatment. Funny you should mention it-- I have the book right here! I bought it about two years ago on a trip back home, but haven't paid any attention to it until recently. (In a weird turn of dumb blind luck, I bought two then-unknown-to-me books on audio-- the other one was Bob Katz's book.) I put myself to sleep last night with the section on tuned traps and a couple glasses of red. Quote Ian Savage: I can't remember offhand exactly how putting rockwool or similar in the airspace affects the maths, but it obviously makes the thing more efficient. Here's the part that scares me-- both Everest's book and Paul White's article say that putting rockwool in the airspace lowers the resonant freqency "somewhat", but they're both vague on that point. (I see experimentation and material waste ahead... ) Quote Ian Savage: As long as you don't mind working in imperial measurements, which do my fruit, hence the conversion to metric above. No worries there and no need to translate for me! As a Canadian I was brought up with