Pro Audio Review - June 2008 - (Page 28) STUDIO | Feature by Heather Johnson Powering Studio Monitors ith such a wide array of excellent studio monitors on the market, it’s becoming even more difficult to choose the ideal components for a particular room and budget. Both active monitors and passive designs with separate amplifiers bear strong arguments in their favor. In an attempt to weigh the pros and cons of this debate, and perhaps ease the decision-making process, we enlisted a few expert witnesses: Peter Chaikin, JBL Professional’s director of recording and broadcast marketing, and Bill Bush, director of engineering for KRK, offer a wealth of insight regarding active studio monitor advances. Nelson Pass, audio designer and founder of Pass Labs, and Richard Rose, president of Hot House Professional Audio, discuss the flexibility and fidelity behind passive monitors and control room amplifiers. PAR: What advantages do active and/or powered monitors offer over passive monitors with separate amps? PETER CHAIKIN: Powered speakers offer convenience for the end-user. The system is self-contained, nothing needs to be connected externally, and the amp and the transducers work together as a matched system. That’s not to say that passive speakers can’t be excellent speakers. But from a design perspective, d o l l a r - f o r - d o l l a r, including amplification, we can deliver better performance from a powered studio monitor. The job of the crossover in the speaker system is to provide the right amount of power and EQ to each transducJBL LSR 4328 er—the woofer, tweeter, and midrange transducers. A passive speaker employs a passive crossover, which sees very high power from an external power amplifier and divides and delivers that power to each of the transducers. To handle very high level signals, the cost of the tighttolerance components for a passive crossover can be very high. In a powered speaker, by putting the crossover in front of the amplifiers, and assigning a separate amplifier to each driver, we can optimize performance and compensate for response anomalies using equalization. Passive speakers are EQ’d as well, we just don’t have the same flexibility in a passive network as we do in an active network. Using an active crossover in a powered system, we can tailor the output for each driver to optimize system performance. The end result is a much more accurate speaker dollar for dollar than can be achieved with a passive system. BILL BUSH: Active monitors can have the drivers and the amplifiers optimized to work together as a system, making the best use of each and not having to design around possible mismatches that can be encountered with passive systems and separate external amplifiers. Active systems are biamped (or tri-amped for three-way systems) allowing each amplifier to be optimized (sensitivity/gain/et cetera) for the driver that it is powering. Active speakers can be tuned to provide increased low frequency extension and output without overdriving the system below resonance. This gives powered monitors more low frequency extension without overdriving them by rolling off the extreme low frequency. This also allows an active speaker to have a more linear woofer suspension because you can’t have the problem of putting in too low frequency of a signal at too high a level causing either bad distortion or speaker damage. Passive systems need to have a nonlinear suspension (added distortion) to protect them from being overpowered. Active monitors have more consistent frequency response because active crossover frequency response is not a function of speaker driver temperature (level) or minor variations of driver manufacturing. A passive crossover changes frequency response with increased voice coil temperature and with minor primary resonance deviations in the drivers. That is to say that passive speakers sound different at different volume levels and operating temperatures where active systems have dramatically lower changes with different levels. An active speaker can easily give frequency response adjustments with the flip of a switch, whereas it is difficult to do this with passive systems because changing the output level changes the impedance load the crossover sees, thus it changes the crossover frequency and shape. The lower impedKRK E8B ance fixed length of speaker wire in an active system has significantly lower power loss to the driver than does a long length of speaker wire and a passive crossover to the driver. Also, the lower fixed length of speaker wire inside the enclosure provides more consistent and increased damping of the drivers than passing the speaker level signal through a long length of speaker wire and passive crossover. PAR: And would this same argument apply when discussing a more “affordable” line of monitors? I understand there’s a greater risk of problems at this level. PETER CHAIKIN: Powered speakers are pretty reliable these days. It’s true that from MONITORS continues on page 30 ➤ 28 | ProAudio Review | June 2008 Subscribe to the Digital Edition of Pro Audio Review http://www.myparmag.com www.proaudioreview.com Davis White http://www.proaudioreview.com http://www.myparmag.com
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