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Topic: Question about speaker phasing within a group/band context |
Eric Philippsen
From:
Central Florida USA
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Posted 9 May 2016 11:11 am |
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I understand about speaker phasing. That is, in an amp with multiple speakers, all of them must be "in-phase." Or, in simple terminology, their cones should travel "in" or "out" together when a signal or note is applied. Otherwise, you'll get a noticeable tone loss. I've heard it and it ain't pretty.
My question is doesn't the same physics or principle apply to when different amps are on stage?
For example, let's say you and the guitar player are playing unison lines. But your amps are "out of phase" - his amp's speaker is traveling "out" for those unison notes while yours is going "in" for the very same ones. Wouldn't there be phase cancellation in that situation, too? |
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Lane Gray
From:
Topeka, KS
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Posted 9 May 2016 11:27 am
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If we put out fundamental only, maybe. But since there's overtones at play, and waves propagating in different directions, and each note has markedly different wavelengths, and at least 7 other variables that aren't on my mind at the moment, the answer is pretty much "naah, don't worry about it."
Besides, if you're only a couple cents out, there's gonna beat frequencies roaming all around (which there are.)
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects |
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Jeff Bollettino
From:
Virginia, USA
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Posted 9 May 2016 2:51 pm
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Theoretically yes, but practically speaking no. The phase cancellation is audible for two or more speakers in one cabinet (if they're mis-wired) because it's the same exact signal coming from the nearly same point (speakers a few inches apart) so the direct wave from the speaker cabinet is out of phase for nearly every listening position in the venue. When you start to consider different musicians with signals that aren't identical (even if playing in unison) with speaker cabinets that have some significant distance apart (compared to the wavelength of sound) the cancellation is much, much less likely to be audible. In a studio environment, with parts played in unison, and the sound being picked up from a specific point due to the microphone placement, you might get come cancellation that can be heard. Someone with more studio experience might know if that's common or just possible.
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Pig Hog Cables |
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Lane Gray
From:
Topeka, KS
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Posted 9 May 2016 2:59 pm
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It just occurred to me: if you and the guitar player play the same A440 through equipment perfectly in phase with each other AND perfectly in tune with each other, if one of you strikes the string 1, 3, 5, or 7(et cetera)/800ths of a second earlier or later than the other, you'll STILL be 180° out of phase.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects |
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Georg Sørtun
From:
Mandal, Agder, Norway
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Posted 9 May 2016 3:28 pm
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...more chance for cancelation-effects for those in the audience that turn their heads for whatever reasons... 
On stage speaker-phasing only matters for each instrument on its own. No two speaker-cabs are perfectly in-phase in more than one listening position anyway, no matter how close they are to each other. |
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Eric Philippsen
From:
Central Florida USA
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Posted 10 May 2016 3:03 am
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Thanks from all of you for the great, informative answers. Two more questions, please, from my less-than-knowledgeable understanding of this?
When I'm playing through a stereo, dual NV400 (say) setup, isn't it optimal
that the single speakers in the two cabinets be in-phase with each other? After all, I'm thinking (hearing?), each of them are receiving the same signal, although, yes, one side is "clean" and the other "effected". However, the fundamental signal or note each "receives" is the same. Is it important or optimum that they be in phase?
Second, I heard or read somewhere that lower frequencies' phasing is much more important. I'm presuming that's because their waveforms are longer and, consequently, within a listening environment (i.e. arena, theatre, or Joe's bar on a Saturday night) is more, umm, what? It seems live-sound engineers are concerned about that aspect and you sometimes hear them worry and talk about bass bins being in-phase.
I'm guessing I'm not using all my audio terms correctly in my questions but hoping you get my meaning anyway. Thanks. |
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Georg Sørtun
From:
Mandal, Agder, Norway
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Posted 10 May 2016 3:49 am
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With one source - one instrument in your case - the two (or more) speaker cabinets should ideally be in-phase and lined up, for a normal, balanced, sound from that single source reaching the majority of the audience in front of the stage.
Out-of-phase speaker cabs fed by one source can, and sometimes are, used to create a "wide or stereo-like" effect. Other phasing effects - flangers, various reverb and/or delay units, etc, can also be inserted to create various "stereo-like" effects. Used properly various out-of-phase techniques can be set up to sound just fine, but "a little too much of a good thing" often ends up sounding chaotic.
As old stage technician / sound man I have often played with "stereo expansion" on PA systems, where amps and speaker cabs were in-phase but where a tiny bit of the signal sent to left side amps/speaker cabs was eq'ed and fed 180 degrees out-of-phase to the right side speaker cabs, and visa versa. Balanced well this gives a wider spread in front of the stage, and ensures that all instruments can be heard well by the entire audience.
(I used the same "stereo expansion" effects successfully on local radio stations - just enough of the effect to "widen the picture" on stereo receivers, without being noticed by those who listened in mono.)
But, such stereo expansion on stage only makes sense when several instruments are panned between the two channels in a well set-up full PA system. It rarely ever makes sense when you have only one source/instrument distributed via two regular combos on stage. |
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Bob Hoffnar
From:
Austin, Tx
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Posted 10 May 2016 4:42 am
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Sound waves phasing on stage is not a problem.
People playing too loud or poorly is a problem.
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Bob |
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Carl Mesrobian
From:
Salem, Massachusetts, USA
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Posted 10 May 2016 5:53 am
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That's great news! We don't have to talk about time alignment 
_________________
--carl
"The better it gets, the fewer of us know it." Ray Brown |
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Dave Grafe
From:
Hudson River Valley NY
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Posted 11 May 2016 11:11 am
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| Phase interference is only an issue when two or more speakers are reproducing THE SAME IDENTICAL SIGNAL. If the signals are not the same there is no "phase" to be out. |
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Carl Mesrobian
From:
Salem, Massachusetts, USA
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Posted 11 May 2016 12:51 pm
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I learned speaker phasing when I was about 15-16 from my older brother. When we got new stereo speakers, we'd wire them up (the ones we had weren't marked for polarity 50 years ago ). put them together and see how loud the sound was, then we'd reverse one speaker's leads, and compare to the first connection. Similar to this direct quote from a Bose manual
http://worldwide.bose.com/productsupport/assets/pdf/guides/speakers/101_series2/en/owg_en_101_series2_.pdf
"...
Phasing Test
To make sure that your speakers are connected to your receiver in phase (positive
to positive and negative to negative) perform this simple test:
1. Set your receiver or amplifier to MONO if that is an option. Set the balance
control to the middle (normal) position.
2. Temporarily place the loudspeakers so they are facing each other at close
range.
3. Play some deep bass passages of music through the speakers. The sound
should seem to come from a point directly between the speakers, with full, rich
bass.
4. If the music seems to be lacking in deep bass, reverse the + and – connections on one speaker and repeat the test. Use the connection which produces the
most powerful bass
..."
This reiterates David Grafe's point about the same signal 
_________________
--carl
"The better it gets, the fewer of us know it." Ray Brown |
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John Bresler R.I.P.
From:
Thornton, Colorado
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Posted 12 May 2016 6:27 am
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I doubt if Buddy charlton (spelling?) and Leon Rhodes even thought about speaker phasing but in phase or out of phase they sure sounded great!!
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Carl Mesrobian
From:
Salem, Massachusetts, USA
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Posted 12 May 2016 7:20 am
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IMO, another one of those "forget about phasing - go play" moments.
_________________
--carl
"The better it gets, the fewer of us know it." Ray Brown |
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b0b
From:
Cloverdale, CA, USA
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Posted 12 May 2016 8:15 am Re: Question about speaker phasing within a group/band conte
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| Eric Philippsen wrote: |
| For example, let's say you and the guitar player are playing unison lines. But your amps are "out of phase" - his amp's speaker is traveling "out" for those unison notes while yours is going "in" for the very same ones. Wouldn't there be phase cancellation in that situation, too? |
It's virtually impossible for two instrumentalists to create the exact same waveform, let alone create it in phase. Your timing, tuning and timbre would all have to be exactly the same.
as Dave Grafe said: "Phase interference is only an issue when two or more speakers are reproducing THE SAME IDENTICAL SIGNAL. If the signals are not the same there is no "phase" to be out."
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-𝕓𝕆𝕓- (admin) - Robert P. Lee - Recordings - Breathe - D6th - Video |
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