The Geometry of Clarity: Coaxial Physics in the Electro-Voice PXM-12MP

The stage is an acoustic battlefield. Between the crash of cymbals, the rumble of bass amps, and the slap-back from the back wall, clarity is the first casualty. For the musician, the traditional solution has been “more volume.” But turning up the monitor often leads to a muddy mess or, worse, ear-piercing feedback.

The problem isn’t usually loudness; it is Phase. Traditional “wedge” monitors separate the woofer (lows) and the tweeter (highs) by a few inches. This physical distance creates a time delay between frequencies reaching your ear, resulting in Comb Filtering—a phenomenon where certain notes are cancelled out while others are boosted artificially.

The Electro-Voice PXM-12MP attacks this problem not with more power, but with better geometry. By utilizing a Coaxial Driver architecture, it aligns the physics of sound projection to create a “Point Source.” To understand why this matters, we must look at the behavior of sound waves in the near-field environment of a stage.

The Coaxial Advantage: Solving the Time Domain

In a standard 2-way speaker, the sound comes from two distinct sources.
As you move your head left or right, the distance to each source changes, shifting the phase relationship. This creates “lobing,” where the sound changes character drastically with movement.

The PXM-12MP mounts the 1.75” titanium compression driver (tweeter) inside the center of the 12” woofer. * Point Source Topology: All frequencies emanate from the exact same point in space. * Time Alignment: The high and low frequencies travel the same distance to reach your ear, arriving simultaneously.

This eliminates the “sweet spot” limitation. Whether you are standing directly over the monitor or stepping back to take a solo, the Phase Coherency ensures the tone remains consistent. You hear exactly what you are playing, without the “hollow” spots caused by phase cancellation.

The Feedback Equation: Gain Before Pain

One of the most practical benefits of a coherent wavefront is Feedback Rejection. Feedback loops occur when a microphone picks up specific frequencies from the monitor and re-amplifies them.

Because coaxial drivers produce a uniform 90° x 90° dispersion pattern without the erratic frequency spikes caused by lobing, the response is smoother. A smoother frequency response means fewer “rogue” frequencies sticking out to trigger feedback. * Tunable Notch Filter: For difficult rooms, the PXM-12MP’s internal DSP includes a high-Q notch filter. This acts as a surgical scalpel, allowing the engineer to cut the precise frequency that is ringing without destroying the overall tone of the mix.

Amplification and Angle: The 55° Solution

The physical geometry of the wedge is as important as the acoustic geometry. The PXM-12MP is angled at 55 degrees.

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(Note: A diagram showing coverage angle relative to standing/sitting performer would be ideal here).
This steeper angle is optimized for the “Near-Field.” It aims the “Point Source” directly at the ears of a performer standing 3-6 feet away, reducing the amount of sound splashing onto the floor or rear wall, which contributes to stage mud.

Powering this is a 700W Class-D Amplifier. Unlike Class-AB amps that generate significant heat (energy loss), Class-D operates with high thermal efficiency. This allows the monitor to run cool even at high SPLs (up to 129dB), ensuring reliability during long sets under hot stage lights.

DSP as a Utility: Beyond EQ

The onboard Digital Signal Processor (DSP) is not just for feedback. It offers presets like “Guitar Cab,” which emulates the frequency roll-off of a 12” guitar speaker. This allows guitarists using modelers (like Kemper or Fractal) to use the PXM-12MP as a FRFR (Full Range Flat Response) cabinet that still “feels” like a guitar amp on stage.

Conclusion: The End of the “Sweet Spot”

The Electro-Voice PXM-12MP represents a maturity in stage sound. It acknowledges that a monitor’s job is not just to be loud, but to be accurate. By solving the physics of phase through coaxial design, it removes the variability from the stage. It gives the musician a reliable acoustic reference, allowing them to stop worrying about the mix and start focusing on the performance.