Marcus had read one article about EQ in 2011 and had been applying the same technique ever since: high-pass filter at 100 Hz on every channel. Kick drum? HPF at 100. Bass guitar? HPF at 100. Floor tom? Believe it or not, HPF at 100. Subwoofer send? You guessed it.

His mixes were remarkably consistent. They all sounded exactly the same: thin, lifeless, and missing approximately everything below the second harmonic of most instruments. Vocalists loved working with Marcus because their voices were the only thing that survived his filtration philosophy.

When I asked him why he high-passed the subwoofer feed, he said, 'To keep it clean.' The subwoofer's response started at 30 Hz and rolled off naturally at 120 Hz. His 100 Hz high-pass filter was removing 80% of the subwoofer's usable output. People at his shows didn't feel bass — they inferred it, the way you might sense a distant earthquake through mild vibrations in your coffee.

The turning point came when a headlining band's front-of-house engineer arrived, looked at the system processor, and said five words that changed Marcus's life: 'Why is everything high-passed?'

The Moral: EQ is not a recipe — it's a response to measurement. What works on one source in one room means nothing on another. SonaVyx's AI diagnostic recommends EQ based on actual measured problems, not inherited habits from a single article read thirteen years ago.