Current Issue

Jan/Feb 2012

Print Article     Email Article

  Page 1 of 3   >>

Audio Review: dbx Driverack PA+ Loudspeaker Management System

Unit is particularly useful for churches that set up and tear down each week

by John F. McJunkin

dbx is well known for its speaker management products, ranging from simple speaker processors like the DriveRack PX up to sophisticated system management solutions like the DriveRack 4800. Included in this array is the DriveRack PA+, the new revision of the DriveRack PA. Considering the list of features included with this device, its $749 list price is astonishingly low. The original version was powerful, and this revision adds welcome and useful new features that not only increase the functionality of the unit, but make its operation simpler for the benefit of users who do not have any formal education or much experience (i.e. volunteers.)

The new version of the DriveRack PA continues to feature all the functionality of the original, and quite a bit more. First, to address the original unit's attributes: it features compression and limiting, parametric equalization, advanced feedback suppression, the dbx120A subharmonic synthesizer, and a 2x6 crossover matrix, accommodating up to a stereo three-way system. Moreover, all parameters are stored as part of system presets, and the system has presets for a spate of different speakers. The compressors feature dbx's famous "over-easy" knee adjustment to smooth out the onset of compression, which can pretty radically alter the nature of the compression. The original unit offers graphic equalization before the crossover stage - specifically dual 28-band graphic EQs. I'm not super fond of the user interface mechanism for the graphic. You select a frequency and either boost or cut it - a little tedious, but it still works. The included advanced feedback suppression utilizes up to 12 filters under the control of an intelligent system that "listens" for feedback, isolates it, and suppresses it by reducing a small range of frequencies. I tested this by placing a sensitive omnidirectional condenser mic less than three feet directly in front of a speaker. Not only did the feedback suppression system work very effectively, but it did not mangle the signal, and indeed, this system is intended for wringing feedback from the mains, not the monitors.

The system's dbx 120A subharmonic synthesizer has been a tried-and-true mechanism for live sound engineers to add a little girth to the low end, and in this case, it works just as advertised. The crossovers allow for up to three-way operation, with Butterworth filters at 6, 12, 18, and 24 dB/octave slopes, and Linkwitz-Riley filters at 12 or 24 dB/octave. After the crossover section in the signal flow, parametric equalization is available with up to 12 dB of boost or cut in three bands with a Q ranging from 0.2 to 16. Compression and limiting follows next, and features control over threshold, ratio, gain, and "over-easy" which is dbx' vernacular for the softness of the knee. Hard-knee is at 1, and soft-knee is at 10, and this helps to make the compression more transparent. One minor critique: An inexperienced volunteer can easily wind up with obvious, pumping compression. This unit is intended to simplify for the untrained volunteer, and largely excels at that notion. But there is no "volunteer-proof" mechanism to help a neophyte avoid mangling the signal with too much compression. Otherwise, dbx' compressors sound great when they're configured properly, as does the system's limiter, which also has the over-easy capacity to soften the knee.

  Page 1 of 3   next page >>

John McJunkin is the CEO of Avalon Podcasting in Chandler, Arizona, which offers high quality podcast production and consultation services to a broad range of clients. He’s also the host of the Podcast Pro Tech & Tips Podcast at www.avalonpodcasting.com.