Amplification: Studio monitors may be "active" (including one or more internal power amplifier(s)), or passive (these require an external power amplifier). Active models are usually bi-amplified, which means that the input sound signal is divided into two parts by an active crossover for low and high frequency components. Both parts are amplified using separate low- and high-frequency amplifiers, and then the low-frequency part is routed to a woofer and the high-frequency part is routed to a tweeter or horn. Bi-amplification is done so that a cleaner overall sound reproduction can be obtained, since signals are easier to process before power amplification. Consumer loudspeakers may or may not have these various design goals.