Mackie M1200 Owner's Manual - Page 38

Biamplified and Triamplified Systems Most speaker systems in use today are of the two-way or three-way variety. Cone speakers are good at reproducing low and mid-range frequencies, but not high frequencies. Likewise, compression drivers are good at reproducing high frequencies, but definitely not low frequencies. This is why two-way, three-way and even four-way speaker systems were developed - to improve the efficiency of each individual driver by requiring it to reproduce only the frequencies that it reproduces best. One method of accomplishing this is through the use of a passive crossover network between the amplifier and the speaker(s). Often the passive crossover is built into the cabinet along with the various drivers. The crossover divides the high-level speaker signal into frequency bands, which are then directed to the appropriate driver. There are some drawbacks to this method, however. The passive crossover adds reactance to the load that the amplifier sees, which can affect the damping. Power is wasted as heat across the resistors in the crossover, reducing the amount of amplifier power available to the drivers themselves. FR SERIES POWER AMPLIFIER (STEREO MODE) FROM SIGNAL SOURCE CH 1 (MACKIE MIXING CONSOLE) IN FROM SIGNAL SOURCE CH 2 (MACKIE MIXING CONSOLE) IN CH 1 + OUT - CH 2 - OUT + Biamplified and triamplified systems use separate power amplifiers to power each individual low-frequency and high-frequency driver. An electronic crossover (a.k.a. active crossover) is located between the signal source and the power amplifier. The advantages of this method include 1) increased headroom available from each amplifier, since they're amplifying only a portion of the entire audio spectrum; 2) improved damping factor because the amplifier output is connected directly to the driver; 3) improved efficiency because there are no passive resistors to dissipate heat; and 4) flexibility to choose the optimum crossover frequency and crossover slope for the individual drivers in the system. TWO-WAY SPEAKER CABINET HIGH-LEVEL PASSIVE CROSSOVER HIGH FREQUENCIES TO TWEETER LOW FREQUENCIES TO WOOFER TWO-WAY SPEAKER CABINET HIGH-LEVEL PASSIVE CROSSOVER HIGH FREQUENCIES TO TWEETER Passive Crossover System LOW FREQUENCIES TO WOOFER FROM SIGNAL SOURCE (MACKIE MIXING CONSOLE) LOW-LEVEL 2-WAY ACTIVE CROSSOVER TO HIGH-FREQUENCY AMPLIFIER TO LOW-FREQUENCY AMPLIFIER FROM SIGNAL SOURCE (MACKIE MIXING CONSOLE) LOW-LEVEL 3-WAY ACTIVE CROSSOVER TO HIGH-FREQUENCY AMPLIFIER TO MID-FREQUENCY AMPLIFIER FR SERIES POWER AMPLIFIER (STEREO MODE) CH 1 INPUT CH 2 INPUT CH 1 + OUT - CH 2 - OUT + FR SERIES POWER AMPLIFIER (STEREO MODE) CH 1 INPUT CH 2 INPUT CH 1 + OUT - CH 2 - OUT + TWEET WOOF TO LOW-FREQUENCY AMPLIFIER FR SERIES POWER AMPLIFIER (BRIDGE MODE) CH 1 INPUT CH 1 + OUT - CH 2 - OUT + TWEET MID WOOF Biamplified System with Active Crossover 38 Triamplified System with Active Crossover