PA System EQ Guide: How to Tune Any Sound System

Every PA system interacts with the room it is installed in. A loudspeaker that measures flat in an anechoic chamber will not be flat in a real room. Room reflections add energy at some frequencies and cancel at others. The distance between speaker and listener causes high-frequency air absorption. Boundary effects boost low frequencies near walls and corners.

System EQ compensates for these acoustic effects to provide a consistent, predictable frequency response at the listening position. Without system EQ, the mix engineer is fighting the room with every channel, adjusting individual EQ settings to compensate for system deficiencies rather than shaping the artistic content.

Open SonaVyx and select Transfer Function mode. Position the measurement microphone at the primary mixing position, approximately ear height, facing the speakers. The reference signal (from the console output) provides the input to compare against the measured response.

For single-device measurement, SonaVyx generates pink noise internally and uses loopback to capture both the reference and measurement signals. For multi-device measurement, use the session pairing feature to link a phone at the mix position with a phone near the speakers.

Play pink noise through the system at a moderate level, approximately 85-90 dB SPL at the mix position. Allow the measurement to average for at least 10 seconds to produce a stable trace. This is your baseline response before any EQ adjustments.

Store this trace for comparison after tuning. Examine the coherence display. Frequencies with coherence above 0.8 are reliable and can be adjusted with EQ. Frequencies with low coherence (below 0.5) are dominated by noise or reflections and should not be aggressively equalized because the EQ adjustment will not produce predictable results.

Start with broad corrections using parametric EQ. Address the largest deviations first, typically low-frequency room modes causing 6-10 dB peaks between 60-200 Hz. Use wide bandwidth (low Q) cuts for broad spectral tilt corrections and narrow bandwidth (high Q) cuts for sharp resonances.

Work from low to high frequency. Low-frequency corrections often shift the overall spectral balance, making subsequent adjustments clearer. Apply high-shelf or low-shelf filters for overall tilt before using parametric bands for specific corrections.

Keep individual EQ adjustments to 6 dB maximum. If you need more than 6 dB of correction at any frequency, the problem is likely physical (speaker placement, room acoustics) rather than something EQ can solve effectively.

After applying EQ, capture a new measurement trace and overlay it with the baseline. SonaVyx before-after comparison shows the improvement visually and calculates the overall flatness improvement. Check coherence, which should remain high across the corrected frequency range.

Walk the room with the SPL meter to verify that the tuning is consistent across different seating areas. Variations of 3-6 dB between positions are normal. If specific areas show significantly different response, consider adding delay speakers or adjusting speaker aim rather than re-equalizing.

Do not chase every dip and peak in the frequency response. Narrow dips caused by comb filtering from reflections cannot be fixed with EQ because adding energy at the null frequency simply adds more energy to the reflection path. Only correct broad trends and clear resonances with high coherence.

Do not tune the system at a volume significantly different from the performance level. Frequency response changes with level due to speaker nonlinearities and room behavior. Tune at the expected performance SPL.

Do not EQ with the room empty. Audience absorption significantly changes the high-frequency response and RT60. If possible, tune during soundcheck when at least some audience is present, or apply a predictive correction based on expected audience absorption.