Subwoofer in Phase test?

[johngalt47]

Is there a way to do an objective test to determine if the sub is in phase with the mains?

I have an O-Audio sub amp so I can adjust the phase as necessary.

[1100xxben]

The simplest way would be to adjust the phase until the output at the crossover frequency is the loudest at the listening position. When the sub and mains are in phase, the output will be additive and have the greatest output. When they are 180 out of phase, they have destructive output and cancel each other, creating a null at the crossover frequency.

[Wolf]

Yes, but his is continuously variable.

I find that you should find out which (0/180) sounds closer first. Then it could be a few degrees back to get it to line up just right.

For me- the bass/drum of the song 'You and I' from Scorpions is my test. If the drum is not on the beat of the tune, it's off. It's so precise that I can tell if it lags behind or is in front of the rest of the music.

Later,
Wolf

[johngalt47]

A-ha!

While checking something else in my pre-amp's setup, I discovered that the sub signal was being inverted.

[454Casull]

The simplest way would be to adjust the phase until the output at the crossover frequency is the loudest at the listening position. When the sub and mains are in phase, the output will be additive and have the greatest output. When they are 180 out of phase, they have destructive output and cancel each other, creating a null at the crossover frequency.

Technically, this could happen every 360 degrees. At high crossover frequencies and in large enough rooms, it might be possible to actually experience that phenomenon.

*WARNING* did not do math to check above statements

[dthomas]

Is there a way to do an objective test to determine if the sub is in phase with the mains?

I have an O-Audio sub amp so I can adjust the phase as necessary.

Easy way is to find some low frequency test signals, see below. Find a test signal that is close to your crossover frequency. Adjust phase for the loudest output.

Here is a link to test tones:

http://web.archive.org/web/200504180....ws/sinewaves/