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How do you use subwoofer phase control ?

Recently obtained 1986 era Duntech Thor powered large bench-sized subwoofers with outboard crossover box. No instructions about dialing in the phase somewhere between 0 to 180 degrees. What does one do to choose an optimum setting? Is one sub adjusted separately, and then later the second if allocating one sub per channel? May simply be using one of the subs equidistant between stereo Duntech wall mounted speakers as room size dictates due to massive "coffin" appearance of each sub. These subs specifically designed to complement these wall mounted speakers. Quite a contrast from the modern micro-sized subwoofers such as a Carver.
listener57
listener57 OP
730 posts
 
Thanks to both responders for the explanation.
bigtee
803 posts
 
The best way is to take a SPL and set a level for the crossover region(like 80hz) Set the subs phase for maximum output at this level with the main speakers and it should be in closest phase. However, room anomalies can change this situation somewhat. I have found it is pretty easy to tell when they are in phase. Place your head between the mains and subs and listen. It shouldn't sound like there is a suckout.
eldartford
4,262 posts
 
I need help on this one too. I have three MG1.6 speakers with three wall-mounted JBL 15" drivers for subwoofers. Crossover at the moment is 70Hz, 24 Db.
I have no problem getting flat response down to 20 Hz.
To adjust the SW phase, I set the warble tone generator to 70 Hz, so that both speakers are putting out sound, and I measure the sound level using a meter, while I vary the SW phase from 0 to 180. NO CHANGE!! I can't explain this. Can you?.
bigtee
803 posts
 
Sounds like the crossover isn't where it is suppose to be. Try changing it up or down and see if you get a difference.
eldartford
4,262 posts
 
Bigtee..Thanks, but I know the X/O is at 70 Hz, and anyway the objective of having both speakers putting out sound is met even if the Hz isn't exactly 70 Hz.
I have one idea that I still need to try out. Perhaps the crossover (Audio Control Richter scale) is doing phase shift things around the X/O frequency. The test signal is a warble tone (range of frequencies) which is good for setting level but which may average out phase over the range of frequncy. I will drive both speakers full range, and see what happens when I diddle the SW phase. I will post results for your info.
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