Axiom Home Page Forums General Discussion Technical Questions Phase switch on subs

The typical sub has a phase switch-normal/reverse-0/180*. I have played with the switch before but really can't tell any difference although I'm sure with meters, etc. there are differences. My new SVS PB-12 (not Ultra so no comments!! :-)) is being delivered tomorrow (hurry! hurry!). Is there a simple method of setting the phase switch? Is this a key setting for the sub? How often do people set it at some in between setting and how do you measure that?

The usual short approach is to set it to the position that gives you the higher output when at your primary listening position. It might be helpful to have someone else flip the switch for you so you don't have to get up in-between.

The idea is that you don't want the woofers of some speakers "pushing" while others are "pulling" or they can cancel each other out to some degree. You want them all "pushing" at the same time.

Sometimes the difference is very subtle. In other cases, it can be dramatic.

If the sub is inline with the mains, you want it at 0 phase, other than that play it by ear...not sure if there is a meter method of calibrating the phase.

That's a bit misleading. If it's inline and close, yeah. But if it's a few feet to the side, having it set to 180 could be advantageous.

The phase setting on your new SVS is a dial not a switch...

Don't have the disk in front of me (at work) but I believe that AVIA has some tests specifically designed for setting of phase...you do need a helper though in any case...one to turn the dial, the other to listen or read a meter.



Are you getting the PB12-ISD or the PB12-Plus?

I believe that I have some additional tweaking to do in my room when it comes to phase...I have the PB12-Plus/2 for my great room.

You will love it!

WhatFurrer

The alternative, if you don't have a meter or enthusiastic assistant is to twirl the phase dial a bit at a time, take notes and wait til tomorrow

Takes lots of patience that way

But after a few days(or weeks)it'll all come together

Really

Funds and budget would only allow the standard PB-12 at this time but it will be more than enough for my room. Just thought of another question. Does setting the receiver setting on setup to sub phase "normal" or "reverse" cancel out any setting on the phase dial on the back of the sub? Are these settings related or separate? Sorry for all the questions, but I love to tweak and want every ounce of energy and production possible from this system.

It was my understanding from somthing Alan mentioned once, is if the sub is inline, so the woofers are on the same plane, you want them moving in/out the same. So I guess I don't see how having them in the center of the mains, or off to the side of one of the mains would make any difference. Now along the side wall or back of the room may be a different story. But then again, I'm still learning about Sub calibration..

>>Does setting the receiver setting on setup to sub phase "normal" or "reverse" cancel out any setting on the phase dial on the back of the sub? Are these settings related or separate?

Interesting -- I haven't seen a phase setting in the receiver myself but I expect they would do the same thing, ie would cancel each other out like three way light switches. You could flip phase at either point, but if you flipped it at both points the result would be 0 again.

John,
Yamahas have a setting in the speaker setup for sub phase-normal or reverse. So I was wondering about the effects. Sorta like the effect of the receiver crossover and the sub crossover. My RX-V657 has it and I set it to normal and the sub phase to "0" but I don't know if or how these settings impact each other.

Sirquack,

I can see why the comment is confusing you. Let me try to explain. The ideal speaker setup -- as far as phase is concerned -- is to have all the speakers the same distance from your head. In this way, the sound from all speakers arrives at your ears at the same time and in phase. If your mains and your subwoofer are arranged inline, then at least one of those speakers is closer or further from your ears than the others.

Here is what the EP600/EP500 manual has to say about phase. Coincidentally, I JUST HAPPENED to be perusing the manual today.

0 & 180 PHASE: This synchronizes the in/out movement of the subwoofer
cone driver with the other speakers in your system. Once you have
chosen the best location for your subwoofer, try flipping the phase switch
between 0 and 180 to see if one or the other setting produces deeper and
smoother bass output in your room. Leave the switch at the setting that
results in the smoothest and deepest bass at several listening locations
in the room. If you hear no difference, leave the switch at the 0 position.
Quite often the phase switch makes no difference, but it’s dependent on
your room and subwoofer location."

(bold emphasis is mine.)

My understanding (and observations in my room confirm it) is that if all your speakers are set to "small" the bass is only coming through the sub. In this case there will be VERY little if any difference from changing the phase on the sub as ths sub and other speakers are not outputting same tones.

If however the speakers are set to "large" then they and the sub are outputting same bass tones and the phase will matter. Depending on the sitting position and the speakers placement the same tone may be coming to your ears out of phase from the mains and from the sub cancelling each other. If you find this is the case flip the phase switch.

In general setting the speakers to "small" seems to be consensus, probably in part because blending with the sub becomes a much easier thing across the sitting positions and even with sub-optimal speaker placement.