Input & output impedances of filters will affect the resultant response, especially if they are low frequency LC ones.
Many years ago, I had to build a filter to prevent interference between a local transmitter & a distant one which was being used to provide backup programme material for the local one.
i happily designed an appropriate filter for this job, for 50 Ohms input & Output impedances, using design tables.
When built & tested, it was a disaster!
What I had neglected to account for was the resistance of the quite high value inductors, which approached the design impedance.
Too late, I found I should have designed it for much higher impedances, with matching sections at Input & Output.