Author Topic: How Does Incorrect Subwoofer Phase Manifest Itself?  (Read 62 times)

Offline James Edward

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How Does Incorrect Subwoofer Phase Manifest Itself?
« on: June 21, 2022, 03:03:55 PM »
As you can see from my equipment list, I use a sub…
As I can’t help but mess with things, I went looking for something, anything, to mess with today. I thought my initial setting of 180 degrees was right. This was even though the sub is up front behind my left speaker, which common thinking would indicate 0 degrees.
I switched it to 0 degrees, and I am hard-pressed to hear a difference.
Is there a definitive test for this? I think I remember reading that recordings vary in phase, so it may not be definitive from recording to recording. Or was that polarity?
Talk me down.
Thanks,
Jim
Luxman L- 590 AX MK2
Esoteric K-07X
Pro-Ject Debut Carbon Esprit SB
Audience Au24SE
PI Cat6
Spatial Audio M3 Turbo S
Hsu ULS-15 Mk2

Supra Classic 6.0

Offline _Scotty_

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Re: How Does Incorrect Subwoofer Phase Manifest Itself?
« Reply #1 on: June 21, 2022, 03:56:04 PM »
James your Spatial Audio M3 Turbo S are dipole loudspeakers, which means that the rear output is out of phase
with the radiation from the front. If the main loudspeaker produces any low frequencies, those emitted from rear of the speaker are out of phase with sub if it is at zero phase.  If the sub is set at 180 degrees, then the subs' output and the rear wave from the main are out of phase with the front and both are working together to cancel out the bass output from the front of the loudspeaker.  You can chose which side of the main speakers bass output you wish to try to reinforce with the sub.
 Every set up and room are different from each other, there may be no perfect setting between the subs phase and the main speaker.
All you can do is chose the one that you find most satisfying. If you can experiment with how far the mains are placed away from the rear wall and how far the sub-woofer is behind the plane the main loudspeakers you may
find a happy medium.

Offline steve

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Re: How Does Incorrect Subwoofer Phase Manifest Itself?
« Reply #2 on: June 23, 2022, 07:51:37 PM »
Hi James,

As a suggestion, I would play different musical selections along with different placements of the speaker for
the best midrange/highs. Once that is accomplished, I would connect the sub(s).

I would also include signal sweeps, say 500hz to 20hz, and see how each sub position and polarity reacts.
I would think that there might be larger bass mode(s) with one polarity than the other, or you might perceive
a dis-jointed quality with the "wrong" polarity. I am particularly wondering around the speaker to sub crossover
frequency. Maybe a double peak/dip.

I think the key is speaker position first, then work with the sub position and polarity.

Just a thought that might help James.

steve
« Last Edit: June 23, 2022, 07:57:09 PM by steve »
Steve Sammet (Owner, Designer, Electron Eng, SAS Audio Labs, Ret)
SAS "V" 39pf/m 6N copper ICs,
SAS Test Phono Stage
Accutex 320 iii STR Mov Iron Cart
SAS 11A Ref Tube Preamp
SAS 25 W Reference Triode/UL Monoblocks
2 way Floor standing Test Speaker

Offline steve

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Re: How Does Incorrect Subwoofer Phase Manifest Itself?
« Reply #3 on: June 23, 2022, 07:58:47 PM »
Hi James,

As a suggestion, I would play different musical selections along with different placements of the speaker for
the best midrange/highs. Once that is accomplished, I would connect the sub(s).

I would also include signal sweeps, say 500hz to 20hz, and see how each sub position and polarity reacts.
I would think that there might be larger bass mode(s) with one polarity than the other, or you might perceive
a dis-jointed quality with the "wrong" polarity. I am particularly wondering around the speaker to sub crossover
frequency. Maybe a double peak/dip.

I think the key is speaker position first, then work with the sub position and polarity.

Just a thought that might help James.

steve
Steve Sammet (Owner, Designer, Electron Eng, SAS Audio Labs, Ret)
SAS "V" 39pf/m 6N copper ICs,
SAS Test Phono Stage
Accutex 320 iii STR Mov Iron Cart
SAS 11A Ref Tube Preamp
SAS 25 W Reference Triode/UL Monoblocks
2 way Floor standing Test Speaker