I'm currently studying compression and I have it down packed I think minus one issue.

I am able to get the same gain reduction on a signal no matter how high or low my ratio is. If i want a gain reduction of lets say 5dB, I can get that gain reduction from every ratio be it 2:1 or 8:1 just by adjusting the threshold to be higher or lower on the audio signal. 

I'm sure you guys would say that what I am achieving by doing that is just affecting more or less of the signal. Granted.

I have a piano piece and the highest peak to the average volume of the piano is a 3db difference. I lower the threshold 3dB from the highest peaks so now my threshold line is just touching the average volume of the piano. I need a 3dB gain reduction but even with the compressor at a ratio of 100:1, it's not even giving me 2dB gain reduction.

What am I missing here?