Multi-Band Compressor

I'm trying to use the M. Band Comp effect to do some frequency-specific compression and am having trouble figuring out how the thing works. Whenever I set the ratio to something greater than 1:1 (say 4:1), as I lower the threshold on a band it is increasing the volume in that band even when the input signal is way less than the threshold. It's looks like it's acting like an expander, but I can't quite figure it out. Has anyone used this effect? Can you give me some tips?

I want it to behave like a normal compressor that leaves the input signal untouched until the threshold is reached.

Thanks!

For the benefit of others, I contacted Yamaha and here's what I got:

Here is how Multi-band Dynamics/Comp works:

It amplifies the gain so that the input signal @0dB is calculated based on Threshold and Ratio, automatically being made up to 0dB output.
For instance, a Threshold=-6dB, Ratio=2:1 signal will simply be gained by 3dB.

When I am talking about "auto makeup", output gain (how much it is compensated) is always calculated based on the Threshold/Ratio relationship, no matter if the input signal is reduced or not, which means it works most efficiently when the input signal is @ 0dB.

I've requested the ability to turn off the automatic make-up gain functionality, but at least they say that the make-up gain is strictly a function of the threshold and ratio settings and is not dependent on the input level. I've confirmed this (as much as possible doing a very brief test) by playing with it.

So, to have no effect on the signal when it's below the threshold, you need to set the gain to: gain=threshold-(threshold/ratio). For example, if the threshold is -20dB and the ratio is 3.5:1, the gain should be (-20-(-20/3.5)) = -14.3 dB. Then it seems to work as expected.

Here's the corresponding topic on the ProSoundWeb forum where there's been some discussion: Topic on ProSoundWeb