Vented rear chamber horn subwoofer

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Bill Fitzmaurice
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Re: Vented rear chamber horn subwoofer

#16 Post by Bill Fitzmaurice » Tue Dec 29, 2020 3:20 pm

shrub0 wrote:
Thu Feb 06, 2020 10:43 pm
from my approximate of the table tuba in hornresponse I see a phase change of 26 degrees for the difference between 60hz and 120hz.
Sorry, I didn't notice this question earlier. The answer is that it doesn't matter, you can't hear phase when there's only one source. Phase interactions from more than one source can be heard when the combined shift approaches 180 degrees. Where time delay is concerned you can't hear that in the subwoofer pass band either until it's in the vicinity of 30ms or so.

Grant Bunter
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Re: Vented rear chamber horn subwoofer

#17 Post by Grant Bunter » Tue Dec 29, 2020 3:59 pm

Do some study on phase response.
I have certainly found it quite difficult to understand at times too.

Here's some things that may help:

Phase is frequency dependant. So you would expect phase response at two different frequencies (even in the one cab) to be different, and normal.

The most important thing in setting up PA is that subs and mains/tops are in phase at the crossover frequency. As Bill said above, not a problem with one source, but can cause cancellations with 2 sources (eg source 1 is subs, source 2 is tops).

EQ alters phase. EQ before the crossover. If you EQ on the outputs of DSP post crossover, check phase at the crossover point again.

Delay alters phase, see just above.
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
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