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Audio Review: dbx Professional Products DriveRack PX

Nov 1, 2008 12:00 PM, By John McJunkin

A welcome optimizer for powered loudspeakers.

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Review Drive Rack PX

Using internally bi- and tri-amplified loudspeaker solutions has raised the bar on audio fidelity for contractors, and the simplicity of rolling up on scene with a pair or two of such loudspeakers is vastly preferable to packing loudspeakers, crossovers, and amps separately. But for many (myself notwithstanding), a slightly greater degree of control and quality is desired. In spite of the truly excellent quality of the three-way self-powered loudspeakers I'm known to use quite frequently, I've been known to employ supplementary processing to deliver more consistent levels, tune up the system for the room, and to avoid loudspeaker damage. I've always thought it would be nice to have a one-box solution to handle room-tuning, dynamics, feedback suppression, and crossover duties for subwoofer applications, rather than lugging a rack full of gear to get the job done. Dbx Professional Products has introduced the DriveRack PX powered loudspeaker optimizer. I was truly excited to hear about this development. Anything that can move the quality of powered loudspeakers toward a professionally tuned multi-amped system is welcome in my book.

The DriveRack PX is a 1RU box, and that small size is part of its raison d'être: to avoid taking up a lot of rack real estate. From left to right across the front panel, you'll find the XLR input for the unit's RTA mic. This is followed by an RTA input switch, which engages the RTA mic and launches the unit's Auto-EQ wizard. Next up is the LCD display, followed by a data-entry wheel. A 3×3 matrix of pushbuttons is up next, granting control of the unit. Among these, you'll find the obligatory navigation keys as well as comp/limiter and sub-harmonic synthesizer menu-access buttons. There are also three wizard-launcher buttons for setup, EQ, and advanced feedback suppression (AFS). To the right of the control buttons are the unit's meters: six-segment LED stereo pairs for input, output, and sub outputs. All four output meters have an LED to indicate engagement of limiters.

The rear panel is very straightforward, with balanced XLR I/O across the board. There is a stereo input pair, a stereo output pair, and stereo sub output pair. Literally, the only other feature of the rear panel is the unit's IEC power input. Like their corresponding meters on the front panel, the principal stereo outputs represent full bandwidth if no subs are employed and the LPF output if subs are employed.

The unit brings together a broad spate of processors that are generally useful in live sound and expressly useful to optimize powered loudspeakers. Specifically, the box provides stereo feedback elimination with 12 feedback notch filters, a stereo 28-band graphic EQ, a classic dbx (OverEasy) compressor, and the classic dbx 120A subharmonic synthesizer to fill in the low end. There are also a stereo three-band parametric EQ, stereo limiters, and a pink-noise generator for room tuning — which can be accomplished automatically with the system's auto EQ that is based on 28-band RTA. A dbx M2 measurement mic is included for this process; it's a small test mic in the traditional nuclear-missile shape you'd expect. Conversion is an issue because all internal processes are digital, and the resolution is 24-bit/48kHz. Dbx's Type IV conversion is employed, and it sounds very good.

Twenty-five user programs can be stored in the system, and it ships with 25 factory presets, including nearly every imaginable permutation of JBL's powered loudspeakers and subwoofers. The unit also provides support for powered loudspeakers from dB Technologies, Mackie, Peavey, QSC Audio Products, RCF, Samson, Yamaha, Yorkville, and HK Audio. The system's menus are easily navigated with the matrix of buttons and data wheel. One minor exception: You must literally press a button each time you wish to proceed on to the next of the graphic EQ's 28 bands. This is a bit unwieldy, but navigation is otherwise easy. The wizards are also a nice touch, facilitating simplified and quick setup, which is very useful for portable DJs and contractors alike.

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