Identifying correct Subwoofer phase

Is there a definitive way to ensure that a subwoofer is in phase with the main speakers? Mine has a 0/180 deg. Phase switch and while I can tell a difference I’m still not sure which position is in phase with my speakers…

is there a test track to try to set it with?

 

I am not a sub person, but my understanding is that you try and set a crossover point where the mains drop off and sub takes over. I would record a tone or create a limited frequency pink noise track that covers the crossover area. Then I'd mic the sitting position and adjust the phase angle for max volume. Essentially, if it is out of phase you'll get some cancellation, so in-phase would suggest minimum cancellation. My two cents.

 

REL recommends track 4 (IIRC) of the soundtrack CD of the movie Sneakers. With that track, whichever position of the switch lets you hear more true low bass at your listening position is the right one.

That said, my experience is somewhat different. (Not in contradiction of REL's advice, just different.) My experience is, if the crossover and volume settings are about right, the phase position that sounds the best to you over a variety of material is the correct one for you.

 

Play any track with solid, deep bass and listen. The setting with the deeper bass is correct; it's always been obvious to me.

 

Yes I understand doing this but I guess my question is, although it may sound better/deeper from the listening position, does that guarantee the phase is correct? I would think that there are bass phase shifts all over the room regardless of the position of the phase switch.

 

the goal for subwoofer integration is a smooth frequncy response at your listening position from 20hz through the bass and midbass region, e.g. 250 hz.
smooth means no peaks or valleys as measured at your listening position.
a phase switch is one tool / control to help you achieve that goal
other tools include position of the sub, (especially relative to wall boundaries) and crossover frequency.
the only way i have been able to understand if i have smooth response is to measure it.
there are various ways to do this.
for example in my room when both subs are 180 out of phase the deep bass measures very high but there is a phase cancellation above 60 hz that lowers the response of the bass and midbass.
phase at zero gives me the smoothes response but not as deep, sounds the best but created peaks.
to reduce the peaks i had to lower the crossover and pull the subs away from the wall.
my subs sound perfect.
if you want the best sound out of your sub measuring is the only way in my opinion.

 

Phase is usually set when two subs are used.

 

Wouldn’t you want to set phase with a single sub so that it doesn’t cancel out your mains (assuming you crossover with them)?

 

No, the phase setting will be most evident when subs are synced. Don't confuse crossover frequency with phase, two totally different things.

 

Measure with test tones..spotify has bass test tones

 

Here's what I have done. You'll need some sort of SPL meter. Several phone apps out there that should work. I use my trusty Radio Shack meter. Start out by making sure your mains and sub are both level matched. Then Google for a .wav/.mp3 download of test tones. Play the test tone that corresponds to your crossover setting, i.e. if your XOVER is 80Hz, play an 80Hz test tone. Take a reading of the SPL at each phase setting. The highest reading is the right setting.

 

Get an FFT app
Get a test tone sweep file that spans your xover range, say 30-200 Hz Custom Chirp and Sweep Tones | Audio Test File Generator

Use the peak hold function on the app
At you listening position
Run the sweep at 0 and then 180 degrees
Whichever is flatter and higher is the correct setting

 

even with a single sub, depending on sub and speaker locations, there will be a best sounding, smoothest setting for phase 0 or 180 as i have found in my sub "trials".

 

individual test tones do not give nearly as accurate of a result as playing full bandwidth pink noise (track 44 on the linked test disk)
you need full spectrum in order to see the summed peaks and cancellations. individual tones do not work for that.


https://www.amazon.com/Sheffield-A2TB-Test-Disc-My/dp/B000V93NKY

 

that link is not a tone
It is a sweep, when run out of phase on mine, almost 10 dB attenuation difference.
I think I posted it here somewhere.
I have pinknoise, it was not as clearly defined

 

I set my Sunfire sub by ear. Bob Carver wrote in the manual for it to adjust by ear.

 

not supposed to be a tone, full spectrum 20 to 20khz uncorrelated stereo pink noise.

 

This is a tone sweep
30-120
Correct phase is obvious
How loud do you normally listen to your music?

 

I've always thought I only needed to be concerned with the phase at the crossover frequency between the mains and sub, but I think I see what you're saying. There could be more significant peaks/nulls elsewhere within the crossover slope where the mains and sub overlap. Is that right?

 

How To Tell If Your Subwoofer Is Out of Phase | BoomSpeaker

Setting Subwoofer Phase the Easy Way

always 0 here

 

That's pretty much the process I've always used (and what I described above.) In fact, that article may be where I first read about it.

 

absolutely. when i get a chance i am going to take some screen shots of my system frequency response at 0 and 180 for the subwoofers. huge difference through the entire 20 to 250hz. region

 

Yeah, if all you have is a 0/180 switch, there’s no use overthinking this. Try both, use the one that sounds deeper. It’s probable neither will be exactly in phase with the speakers, so there’s no point in worrying about that. If it sounds good, it’s good.

 

0 degree


180 degrees, -10 dB at 63 Hz, ~ xover region

 

below doesn't really matter
Above may depending on setting and roll off.
If concerned raise the sweep to a 1000 Hz.
Above your speakers lows to high crossover.

My sub is down 30 dB at 200 Hz
If speaker is flat at 200, say 80 dB
Sub is 50
Adding those 2 sum to 80.0004 dB

The reason I like a tone the pure fundamental cancels or adds more cleanly
Constructive or destructive interference

here's some alternate methods
A single tone and the NIOSH app
Setting Subwoofer Phase the Easy Way