Calculating the delay required

1. First determine crossover point. In this example: 80 Hz

2. Next you need the phase shift of your main speaker relative to your subwoofer. In this example we will use the phase shift shown in Figure 4 below for the main speaker of 135 degrees. The subwoofer is -180 degrees at this point. This means we need to add a phase shift of -45 degrees to the subwoofer to get phase aligned with the front speakers. 45 degrees is one eighth of a cycle.

3. Calculate the distance of one wavelength at the crossover point by the following formula:

wavelength = 344 / frequency (metres)

wavelength = 344 / 80

wavelength = 4.3m

4. Now convert phase shift into cycles

cycles = phase shift / 360

cycles = -45 /360

cycles = -0.125

5. Now multiply the number of cycles by the wavelength

In this case the distance compensation is -0.125 x 4.3 = -0.5m

In other words, the distance setting on the subwoofer should be adjusted so that we add this number to the physical distance. If your subwoofer is placed 4 metres from your listening position, then you should enter 3.5 m. The sign of distance adjustment is very important.

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