Comb Filtering

The effect (on comb filtering) of adding a 30ms delay to one speaker in a stereo pair.
Caveats: room reflections are not considered here. Assumption is a mono sound source reproduced in both speakers. Speakers are 10m apart. 200Hz and above assumes a 60-degree directional driver. This assumes that single frequencies are being played for a significant length of time (much greater than 30ms, for example).

Note: 30ms diagrams assume speaker #1 has a 0 ms delay and speaker #2 has a 30ms delay.

40Hz, 0ms

40 Hz 30 ms.

50 Hz 0 ms

50 Hz 30 ms

60 Hz 0 ms

60 Hz 30 ms

70 Hz 0 ms

70 Hz 30 ms

80 Hz 0 ms

80 Hz 30 ms

Note: As we go to 200 Hz, a single wavelength is 5 ms. So a 30ms delay is six full cycles at 200 Hz, so there really won't be any difference in the patterns for the nulls and lobes. Any multiple of 200 Hz (400, 800, 1000, 2000, 4000, 8000, etc.) will exhibit this same behavior. For this reason I've included some additional frequencies at random points to avoid this problem.

200 Hz 0 ms Wavelength = approx 5.6'