Level change when changing stereo to mono

[Steven]

Hi,

I've noticed a level change when converting stereo files to mono files- an increase of 1.9dB measured using a -18dBFS reference tone. I noticed this because I used a VST DSP effect (a peak limiter) and its "ceiling" level, which I had set to -0.5dBFS was being exceeded into digital distortion. Am I correct in this conclusion or is something else at play? Obviously summing signals can lead to a level change (+6dB for phase coherent identical level signals) but software often compensates for this.

[Steven]

Re: Level change when changing stereo to mono

OK, a bit more forum searching found this post here where it says the channels are summed together. So.... why am I seeing only a 1.9dB increase in level? Any ideas?

[Spoon]

Re: Level change when changing stereo to mono

They are summed with slight gain, you can use a DSP effect Volume Normalize and set a fixed reduction before the summing (before Volume Normalize use the DSP effect Bit depth and set to floating point, then the last effect back to 16 bit).