Here you can find several measurements I made in the past. The measurements have been done solely using my own, proprietary tools. I will add some more in the future, if I find some time for it.
For my work on the VST plugin ‘HeadphoneMix’, I needed to evaluate the crosstalk from the left speaker to the right ear and vice versa. To find a more or less globally valid transfer function I averaged every single transfer function in my HRTF database (from about 50 different persons). The function represents the magnitude. It turned out to be naturally that smooth.
Comparison of an analogue C-Weight filter and its simple digital implementation using bilinear transformation
Lowpass filter comparison
Out of interest I once performed some measurements of the Behringer ‘Composer’. Here are some result plots: