The bigger the cone..........
The heavier and slower it is. Therefore, up to 18in and no more! 21,s and 24,s and the old cerwin vega 32in woofers cant respond quickly enough to make good sounding bass!
An 18in woofer is really only used for sub bass, when do you see 18,s used for midbass and midrange?
Another problem you will encounter with really big woofers is sag! After time the cone will sag, even more than an 18!
Mr. Scott Fitlin