suppose I want to design a low pass filter (for instance a Chebyshev filter) by using the low pass prototype method:
The upper circuit is the Low pass prototype filter, while the lower one is the real filter (which is obtained from the first one by using a frequency and impedance de-normalization).
As you can see, the "effect" of a filter on the input signal does not depend only on the filter (i.e. on its transfer function) but also on the source output resistance and on the load.
Now suppose I want to realize the same transfer function with an active filter, such as the Sallen - Key Low Pass filter:
As you can see in Wikipedia page, there are the following design equations which can be used to realize a second order low pass transfer function by choosing w0 and Q.
So, it seems to me that if we design a filter transfer function with the second method, it will be ok for any source output resistance and for any load. It seems quite strange to me and it seems in contrast with the fact that the filter realized with the first method depends on them.
Maybe the dependence on the source and load resistances is hidden and I do not see it.