Phase adjustment in Subs

K

kryolla

Enthusiast
Can someone please explain phase adjustment in subs and the reason for doing it. Thanks Drew
 
M

MDS

Audioholic Spartan
The phase setting is to help integrate the sub with the rest of the speakers. When it is at zero degrees, the subwoofer is 'in phase' with the other speakers; ie when the other speakers move inward, so does the sub. When the setting is at 180 degrees, the subwoofer is 180 degrees out of phase with respect to the other speakers; ie when the other speakers move inward, the sub moves outward. Some subwoofers have a continuously variable phase control that can be set anywhere between 0 and 180 degrees.

Sometimes a setting of 180 degrees works better when the sub is at the opposite end of the room than the other speakers. Sometimes you can't really tell any difference. The purpose of the control is to allow you to tailor the sound and deal with nulls caused by the phase of the sub being different than the other speakers. A null would be caused by two sound waves 180 degrees out of phase colliding (and to varying degrees any two waves that are out phase with respect to each other).

Without doing extensive measurements to determine if there is a problem, typically you just experiment with the sub phase control until you get the best sounding, non-boomy bass.
 
agarwalro

agarwalro

Audioholic Ninja
First and foremost, before you start tweeking the phase, make sure your mains and sub are level matched. I am assuming you have taken this step.

That phase knob setting can make the difference between high SPL base with good frequency repsponse or completely the opposite. Placement and distance difference between then mains and sub are what generate the need for this control. The aim is that when the acoustical wave from your mains reaches your ear, so does the acoustical wave from the sub. When set correctly, you will not be able to tell that the sub is outputting any sound since the ear has difficulty in directionalizing lower frequencies.

If the sub is located on the imagenary line joining the mains and between the two, its easy, the knob stays at "0". If not, then here is what you do.

Take any CD with good bass like in Jazz or Techno (if you are into Rock, from personal preference I recommend using "A Perfect Circle - Thirteenth Step") . Start with the phase knob on the "0" setting and start listening. keep moving the knob in small increments and re-listen to the selected passage. The setting at with you cannot tell that the sub is playing, the bass appears to come from the mains, is where you want to leave it. If you are not being able to decide, change what you are listening to.

The difference between the correct setting and incorrect setting is fairly apparent.
 
K

kryolla

Enthusiast
Thanks everyone, I have a better understanding of phase alignment. I just bought a BFD and will use that and REW to eq the bass.

Drew
 
Last edited:
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