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Ask Jonah: Clearing Up Console Matrix Functions & Processor Compatibility

A matrix is actually not any more complicated than an auxiliary bus, so if you understand auxes, you can understand a matrix. Here's the scoop.

Dear Jonah:
Thanks for the explanation of subgroups and VCAs (here). Perhaps you could tell us how a matrix functions in a mixing console. – Steve Bullock

Thanks for your question, Steve. A matrix (plural: matrices) is actually not any more complicated than an auxiliary bus, so if you understand auxes, you can understand matrices.

Here’s the scoop: Inputs are mixed into buses, and buses are mixed into matrices. That’s it! As a “bus for buses,” a matrix can be a very effective tool to solve several audio routing challenges.

Some examples include:

● Let’s say you want your front fills to be a mono sum of the stereo left-right (LR) mix. Simply route the stereo mix to a mono matrix, and route that matrix to the front fills.

● How about if you want the front fill to be the main mix plus a little extra vocals? Same idea: route main LR to a matrix, mix in a bit of the vocal subgroup, and route that matrix to the front fills.

● Board recordings tend to be a bit on the dry side. By routing the main mix through a matrix and then to the recorder, you can sprinkle in a bit of reverb for a more natural sound, without messing up the house mix.

● In fact, instead of pulling the board mix from the main LR bus, create a more balanced recording by routing the appropriate amounts of each subgroup into a matrix, and send the matrix to the recorder.

● In a large-venue public address situation, we might choose to deploy various models of loudspeaker to cover different seating areas. By assigning a matrix to each zone and driving all of the matrices from the main LR mix, we can apply individualized level and EQ as needed while still maintaining control over the entire system with a single master fader.

● I know a few monitor engineers who, rather than drive their own cue monitors directly from the console’s solo bus, use a matrix signal consisting of the solo bus plus the talkback and comms mixed in, so they can be sure they’re not missing anything important while cueing up a mix.

Hopefully that’s enough to get you started. If you want to dig a little deeper, I recommend the fine article “Mixer Inside The Mixer” by Craig Leerman on ProSoundWeb.

Dear Jonah:
Can a dbx powered loudspeaker optimizer work with non-powered loudspeakers, and if so, does it work the same or what adjustments/changes need to occur? – Lead Worshipper

The (now discontinued) dbx DriveRack PX powered loudspeaker optimizer has many of the same DSP functions as the other members of the DriveRack line, so at first glance it certainly appears to be interchangeable with its siblings, and with other system processors in general.

The distinction is all about frequency: since each driver within a sound system is designed to reproduce a certain range of frequencies (lows for the woofer, highs for the tweeter, etc.), there needs to be some sort of filtering system, called a spectral divider or a crossover, to make sure each driver is receiving only the appropriate frequency range.

For passive loudspeakers – powered by an external amplifier – there are two choices: active and passive crossovers.

A passive crossover consists of circuitry built inside the loudspeaker enclosure, with a single amplifier channel feeding a full-range signal to the loudspeaker and the filtering happens internally. The other option is biamplification (or triamplification in a 3-way system), where an electronic crossover splits the line-level signal into frequency bands, which are then amplified independently and fed to the appropriate driver.

With powered loudspeakers, all of the crossover filtering and processing happens internally as decided by the manufacturer during the design process. As end users, all we need to do is connect a full-range line-level signal (like the one leaving the mixing console) and let the loudspeaker handle the rest. That’s why the DriveRack PX unit only has rear-panel outputs for mains and subwoofers while the DriveRack PA2 has enough outputs to accommodate a stereo 3-way system.

So the full crossover functionality is missing from the PX simply because it’s not needed when using active loudspeakers. The rest of the functions – such as graphic and parametric EQ, limiting, and feedback elimination – are still there, though, so if you’re using the unit for those purposes, I’d say you’re good to go.

Send your questions to [email protected].

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