Stereo image fix after applying analogue processing

Running stereo buses or full mixes through analogue devices like compressors, equalizers, summing boxes etc. is fun. They can add that magical touch to your track – a bit of stardust, the so-called 3D effect, punch, fullness and all sorts of adorable favours. But many times you face a problem even with high-end devices: the stereo image shifts…

I was mastering a track recently which has been run through a very expensive channel strip unit to add some shine to the mix. Sounded gorgeous except for that the mix – most noticeably the bass and the vocals – slightly shifted to the left, which was kind of annoying.

I asked my client to send me the mix without the channel strip processor applied on it. Then I measured the RMS levels for the left and right channels on both versions of the song (you can use Voxengo SPAN for such tasks). It looked like this:

Original (in the box) mix: Left: -18.2 dB, Right: -18.3 dB
Mix run through the channel strip: Left: -19.4 dB, Right: -20.4

You can see that the right channel has become 0.9 dB quieter compared to the relative levels of the original mix. To compensate for this I used the free Stereo Tool VST plugin from Flux where you can adjust the levels of the left and right channels independently (besides many other options). I increased the level of the right channel by 0.9 dB: now the vocals and the bass came back to the center. Problem solved!

Just a final note. Always check the mix with your ears too because RMS values are sometimes misleading. So don’t compensate for the stereo image shift in the mix blindly.

Stereo image fix after applying analogue processing