Most simple DIY comb generators seem to run out of steam about 1 GHz ... One experiment to try might be to install a simple high-pass filter (with cutoff frequency about 500-1000 MHz) to equalize the ...

Then we moved the microphone 1 inch off center and ran another curve. In Figure 2, the green curve shows the next comb filter cancellation at 5.5 kHz. In Figure 3, the measurement microphone was moved ...