I just started to explore the combination Teensy and Audio board and I'm stuck with a problem.
This is the diagram of the processing with the source code.

View attachment experiment_2_0a.ino
This is frequency response diagram that shows in red the frequency response of the Teensy Audio shield then output is connected directly to the input: i2s1 connected directly to i2s2 (aka DPS bypass). In blue the frequency response of the audio card I used for the measurements.

This below is the actual response of the filters. The blue line in the LPF output, the green line the HPF and the red line is the DSP bypass.
What worries me is the loss of high frequencies when the filter is introduced. The cut off frequency is set at 100Hz and the high frequency loss kicks in a 4kHz. At 10kHz is around -2dB and 15kHz -3.7dB.
For a digital filter is not a great frequency response. Did you notice anything similar before? Am I doing something wrong?

P.S. I enabled IMPROVE_HIGH_FREQUENCY_ACCURACY and IMPROVE_EXPONENTIAL_ACCURACY in filter_variable.cpp but it didn't make any visible difference.
This is the diagram of the processing with the source code.

View attachment experiment_2_0a.ino
This is frequency response diagram that shows in red the frequency response of the Teensy Audio shield then output is connected directly to the input: i2s1 connected directly to i2s2 (aka DPS bypass). In blue the frequency response of the audio card I used for the measurements.

This below is the actual response of the filters. The blue line in the LPF output, the green line the HPF and the red line is the DSP bypass.
What worries me is the loss of high frequencies when the filter is introduced. The cut off frequency is set at 100Hz and the high frequency loss kicks in a 4kHz. At 10kHz is around -2dB and 15kHz -3.7dB.
For a digital filter is not a great frequency response. Did you notice anything similar before? Am I doing something wrong?

P.S. I enabled IMPROVE_HIGH_FREQUENCY_ACCURACY and IMPROVE_EXPONENTIAL_ACCURACY in filter_variable.cpp but it didn't make any visible difference.