PureData: Highpass and Bandpass bug report
I reported a bug to the PureData developers regarding the highpass [hip~] and bandpass [bp~] filter.  This error occurred in PureData-Extended (0.43.4).
As you can see in the forum thread  the highpass filter is showing some strange behaviour. Until 6kHz everything seems fine. Above 6kHz the filter does not filter the deep frequencies any more.
The bandpass filter gets stuck around 13kHz and does not go higher. Using the voltage-controlled filter it works fine anyway.
A workaround is to use the more up-to-date PureData-Vanilla (0.45.4). However, if you need some externals you have to import them into vanilla yourself.