What is the best HEAVY METAL speaker?

I do not know your Budget, however, you asked what speaker would do what you ask the best, first off, the sensativity needs to be good, and you need alot of air movement for woofer size, here is a speaker that has fast woofers and a 96 sensativity rating, you like double bass, well then here you go, The JBL DD-Everest 67000 speakers, they have 2 15" woofers, do 28hz to 50 khz, they are horn speakers, so you get the the impact of metal music the way it was meant to sound like, ever seen dynamic speakers on stage at a live concert?, of course not!, the metal bands use horn speakers for many reasons, the 2 15" woofers here will provide the seperation of 2 bass drums quite well, this JBL speaker should take you where you want to go, A royal Flush so to speak of, Enjoy fellow metal head, long live Rock-n-Roll!

Lizzard-

you cn do this in 1 of 2 ways;
older speakers - Infinity Crescendo Series (early 1990's).
new speakers - Thiel CS 2.7 or 3.7 depending on your room/space size.

I,too, enjoy Hard Rock/Metal and you are correct, most is very poorly produced/mixed- a real challenge for today's electronics and loudspeakers. Keep me posted & happy headbanging!

Legacy are alright, but not as good as Klipsch Heritage and JBL Synthesis, imo. I heard those old Polks back in '86 playing Deep Purple, I was not impressed. AS far as B&W, I would go with an old pair of 801 Matrixes series 2 or 3. Or the ever elusive 801Ds. There's a guy on you tube called audiophilemetallian with the 801Ds. Check out his videos, the 801Ds really rock!

Something that has a smooth, grain free top end and a warm midbass...vintage Infinity...also Klipsch have that boogie factor if one can deal with a more forward sound.

Altec a4