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Active vs. Passive
To operate passive monitors, you connect the line-level outputs of your mixer to a power amp and then run speaker wire to the monitor. Lots can go wrong in a passive system – and often does.

This new breed of active speaker system has numerous advantages over older passive systems:

Vastly improved damping.
You've probably heard speakers compared to electric motors - both turn power into motion. But a speaker is also a generator that converts return cone motion into electrical impulses which travel back to the amplifier. Called "back EMF" (electromotive force), this energy can be used by an amplifier to "brake" (damp) the cone's motion and reduce overshoot. However, tightly controlling a passive speaker cone via damping isn't easy. First, your external power amp has to deliver massive current to the loudspeaker – and sink the same amount of current coming back. Second, because speaker wire has its own capacitance and resistance, any significant length of even the most exotic cable compromises an amplifier's ability to damp back EMF. The active HR824's FR Series amplifiers have extraordinarily high damping factors and are just inches away from the transducers. Test their awesome damping by gently pressing on the low frequency transducer cone when the speaker is turned on. It "fights back" with a strong force of its own.

Eliminates cost and variability of external amps.
Because power amps vary widely in output ratings, damping factors and sound characteristics, they introduce an unwanted variable in the monitoring process. The HR824's internal amplifiers are low negative feedback, audiophile-quality designs which are specially tailored to the optimum power requirements of the transducers.

Improved overload protection.
Since passive monitors have no control over input power, they have to rely on some sort of crude "crowbar" circuit or fuse to keep the transducers' voice coils from toasting.

Wave guides for better treble dispersion.
Wave guides aren't a new concept, but they're next to impossible to use in a passive system because they also induce a frequency amplitude shift. An active system can electronically compensate, providing both wide dispersion and flat frequency response.
Servo loop woofer technology.
When a bass transducer can "talk back" to its amplifier, they can work together as a unit, achieving greater extension, more accurate damping and faster response. This is impossible in a passive system – or a "powered system" that merely consists of a single amp stuck on the back of the speaker.

Precise, distortion-free electronic crossover.
Passive crossovers are simply a network of inductors and capacitors. Typical iron- or air-core inductors can saturate and cause distortion at high power levels. Worse yet, extreme saturation causes them to stop being inductors, resulting in drastically altered crossover characteristics and possibly blown transducers.

Bi-amplification.
When a passive system's single amplifier must reproduce the whole audio spectrum, low frequencies rapidly "use up" the amp's headroom. As higher frequencies "ride along" on lower frequency waveforms, they can be chopped off or distorted even though the high frequencies themselves would not be clipping. Separating highs from lows via an active electronic crossover lets the HR824 use two different amplifiers. Each is free to drive just one transducer to its safe maximum limit without intermodulation distortion or other interaction between the two drivers.