I have been doing a lot of research lately in creating my own speakers with quality parts to meet my musical tastes. Since most speaker manufactures are aimed at customers that want smaller speakers and the look of an art piece, I figured I would have to step up and build them myself. I am very surprised in my research that I haven't found someone else in this pursuit of the perfect heavy metal, classic rock speaker and has created their own.@lizzardkingseattle The reason is you can't build a speaker that favors any kind of music. The properties that make a speaker good for metal will also make it good for classical or jazz. FWIW I play both on my system. IMO/IME the speaker you would want is one that is fairly efficient- since there is no good reason to make any amplifier work hard, since that just results in more distortion. You don't want distortion even though the guitar amps are making quite a lot- you just want to get the recording to sound the way it was made.
I still have the Classic Audio Loudspeakers I mentioned several years ago in this thread and they excel at metal and any other form of music. They are 98 db, 16 ohms (so easy to drive) and go down to 20Hz. The midrange driver has its first breakup at 35KHz, so it sounds very fast, detailed and very smooth.