Your track sounds dull after mastering? The cause is input level

A familiar story: you send a finished mix off for mastering and get back something dense, dull and oddly distant. The vocal has stepped two paces back, the bass lost its definition, and the stereo image breathes gently from side to side. Technically nothing is wrong — loudness is on target, peaks are safe. It just sounds worse than what you sent.

The cause is almost always the same, and it is not the algorithms. It is the signal level going in.

Compressor thresholds are absolute numbers

A mastering chain is a sequence of processors, and the central one — the multiband compressor — has thresholds. They are set in absolute units: say, −18 dBFS for the low mids and −16 dBFS for the mids. Anything above the threshold gets compressed, and the further above it sits, the deeper the compression.

Those thresholds are chosen for material at a normal level: a mix with peak headroom. Which is where the trap opens.

If the incoming track is already loud — exported with a limiter on the master bus, or pulled from an AI generator like Suno or Udio where everything arrives pinned to the ceiling — the signal exceeds those thresholds almost continuously and by a wide margin. The compressor does exactly what it was asked to do. It just does far more of it than anyone intended.

What that sounds like

Excess compression rarely reads as "distortion". It reads as a change of character:

The midrange collapses. Most musical energy sits between 300 and 2000 Hz — vocals, guitars, keys, the body of the snare. That band goes under compression first and hardest. The spectrum dips in the middle, and the brain interprets a scooped middle as distance. Hence the box, the tube, the well.

The top turns harsh. With the mids held down and the highs untouched, the ratio shifts and high frequencies move forward. Resonances that were unremarkable in the mix start poking out. People usually describe this as a metallic edge.

The low end loses its footing. Bass compresses along with everything else, but you hear it differently: the gap between attack and sustain closes, and bass becomes an even drone with no movement.

The stereo image starts to wander. When channels are processed independently, deep compression means left and right receive different gain reduction at any given instant. While compression is gentle, the difference is inaudible. Once it becomes excessive, the image shifts — the sensation of sound sliding from ear to ear.

None of this is a malfunction. It is the predictable result of a chain running outside the range it was designed for.

Gain staging: a boring fix for a boring problem

Studio practice has a fundamental principle — gain staging: make sure every processor receives signal in the range its parameters were tuned for. No hotter, no quieter.

For mastering this means one specific thing: level should be brought to the working range before compression, not after. Thresholds then engage as designed, compression stays moderate, the midrange holds, and the stereo image stays put.

The difference is measurable. On a dense mix crushed to a brickwall (−8 LUFS at the input), processing without level staging pulled the midrange down by 3.3 dB — the "well" effect exactly. With level brought to the working range before compression, the shift was 0.8 dB, meaning the source tonality survived essentially intact. Stereo balance spread dropped by roughly a quarter at the same time.

One detail matters: quiet and normal-level tracks are not affected at all. Staging only attenuates. If the source already sits in the right range, nothing touches it.

What you should do

Preparing a track for mastering, by hand or through a service, comes down to a few rules:

Take the limiter and maximiser off your master bus. This is the big one. Whatever loudness you won at the mixing stage, mastering has to work around.

Leave peak headroom. Peaks around −6 to −3 dBFS are a comfortable target. The exact number matters far less than the fact that headroom exists.

Do not normalise "just in case." Level matching is the processor's job, not yours.

Check your crest factor. Less than 8 dB between peak and average loudness means the material is already heavily compressed. A track like that does not need mastering in the usual sense — it needs dynamics restoration.

How Magic Master handles it

We dug into this class of problem after a specific complaint. A user sent detailed feedback: a boxy, in-a-well character, stereo drifting from ear to ear, the track objectively worse than before. His source was loud on input, and the chain behaved exactly as described above.

Level is now brought to the working range before compression: a hot source is gently attenuated, a quiet one is left alone. Tonal balance of loud tracks is preserved and the stereo image is steadier.

If your source is genuinely brickwalled, there is a dedicated tool for it: the AI Unlimiter preset does not compress the material further — it restores dynamics by lifting the crest factor. More on that in our piece on the loudness war and on the dynamics restoration page.

Upload a track and hear the difference in the app — analysis is free and shows your loudness, True Peak and crest factor before any processing.