Out of phase speakers...

Discussion in 'Amp Central Station' started by schmee, Sep 7, 2019.

  1. schmee

    schmee Poster Extraordinaire

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    I was thinking the other day while testing a guitar amp extension speaker I use for outdoor gigs to help the Bassist, Does in or out of phase really matter if the speakers are not near each other? Does anyone ever test their PA monitors and mains etc for correct phasing?
     
  2. Paul in Colorado

    Paul in Colorado Telefied Ad Free Member

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    Only when I replaced drivers in my PA cabinets I made sure they were all in phase. Other then that, I don't really know. I guess you could set 'em up and make a cable that has the polarity reversed and see what happens.
     
  3. TeleTucson

    TeleTucson Tele-Afflicted Ad Free Member

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    For bass especially, I'd say yes. The wavelength of the low E on the bass is about 27 ft. So unless the speakers are much further apart than that, it will matter quite a bit.

    It's not that hard to calculate where you get nulls in the sound field in front of two speakers when they are in phase and out of phase, but it all scales with the frequency of the note and the separation of the two speakers.
     
  4. summer_69

    summer_69 Tele-Meister

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    Yes, PA speakers should be phased correct.

    Don't know, but if internal wiring in speakers and the cables connecting them to the amplifier is correctly done everything should be fine.

    Phasing is only important if some signal is shared between the two speakers.
     
    Last edited: Sep 7, 2019
  5. schmee

    schmee Poster Extraordinaire

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    Let's go further; What if the bassist's amp produces "in" on the speaker and the guitarist's amp produces "out" on the speaker? Or guitarist #2?
    Also, is there an international standard for factory setup?
     
  6. TeleTucson

    TeleTucson Tele-Afflicted Ad Free Member

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    You started out asking about phasing of an extension speaker, and it sounded like it was for a single source. Now you've got two amps, a guitar and a bass, and maybe even two guitars?

    Forget about phasing from the different instruments.

    As was stated above, the situation where it matters is two speakers projecting the same signal, and there it is prudent to get the phasing correct.
     
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  7. codamedia

    codamedia Friend of Leo's

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    If you are never going to hear the other speaker then you may not notice, but as soon as you stand in a position to hear both speakers... it matters.

    They will come from the factory in phase... if you ever replace a speaker, you should make sure it's in phase.
     
  8. schmee

    schmee Poster Extraordinaire

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    You think so, even different brands?
     
  9. schmee

    schmee Poster Extraordinaire

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    No, I started out asking about an extension speaker, PA and monitors.
     
  10. TeleTucson

    TeleTucson Tele-Afflicted Ad Free Member

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    I'm just trying to give you useful answers to your questions, with some clarifications. But I do learn, and therefore won't keep trying. :)
     
  11. codamedia

    codamedia Friend of Leo's

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    IME...the industry standard is to "PUSH" the signal. JBL was the only company I was familiar with that tried to buck that trend and "PULL" the signal, but even they have conformed to the standards over the years.

    If I bought a MIX/MATCH PA system, I would check each connection to make sure it was set to PUSH the signal. I would trust a NEW system of NAME BRAND to be wired correctly/uniformly from the factory, but if I were buying used I would definitely check to make sure it's wired uniformly.

    NOTE: There really is no right or wrong... as long as all are equal, this is very important with the PA/FOH system. Even though it won't nessessarily be problematic with monitors, I would still make sure they were the same... just in case a front man wanted TWO pointed at his head.


    +1.....
     
  12. rangercaster

    rangercaster Friend of Leo's

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    This would be a good subject to research ... I recall an article that stated that proper phase in recording applications is critical ... The author gave examples ...
     
  13. BobbyZ

    BobbyZ Doctor of Teleocity

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    I know of you get um out of phase in a Twin Reverb you'll notice it.

    Just don't ask how I know. ;)
     
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  14. schmee

    schmee Poster Extraordinaire

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    For sure, I've made that mistake in amps before! "Why does this sound so crappy?" Just not what it should be ... then the light bulb goes on in the brain!
     
  15. gusfinley

    gusfinley Tele-Holic

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    Phasing always comes into effect when there are two sources producing similar sounds. Distance and the phase relationship between the speakers are major factors in what effects are observed.

    Two speakers close together of opposite phase will create destructive interference as frequencies cancel each other out.

    Two speakers separated by a larger distance of the same phase can produce out of phase effects depending on the distance from each speaker to the listener. They can produce destructive or constructive interference depending on the varied distances.

    Environmental effects such as reflections, etc can also affect the phasing of the speakers.

    When recording stereo sources, I like to flip the phase of one channel and listen to it, to see if I like the sound better. Sometimes it helps, sometimes it doesn't.

    So, the short answer is "it depends."

    If you can change the polarity of a signal ( there are some in-line devices that can do this ) change it back and forth to see how it affects the sound. You might just like it!
     
  16. gusfinley

    gusfinley Tele-Holic

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    As an example of the above:

    I was once given an audio recording to "clean up" as a volunteer effort. I placed the CD I was given in the CD player to give it an initial listen. I first noticed a distinctive Hummmmmmmmm in the recording and when I walked around the room I found one spot where the hum was VERY LOUD and I found one spot where the Hum was almost non-existent.

    I promptly grabbed my flatmates and had them listen from these two positions in the room and they were amazed that the Humm could just disappear like that.

    I was able to clean up the recording rather well in the end.
     
  17. gusfinley

    gusfinley Tele-Holic

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    Oh, another example of phasing effects:

    I was moved to a new cubical at work. The new room I was moved into was between two sections of a building and must have been fed by two different HVAC systems (or pehaps varying lenghts of ducting ).

    As I was sitting at my desk and the AC came on, I could feel the beating of the two vents- heard a kind of low-pitched woof, woof, woof. It drove me crazy enough that I had to to go to the conference table a few feet away to get away from it sometimes. The people near my cube thought I was crazy.

    One day I decided to bring in my measurement microphone, preamp and installed TruRTA on the PC. I showed the TrueRTA output to my boss - who had got a master degree in acoustics - and he agreed that he could see in the RTA response what I had described to him.

    Apparently, not one else could hear it!
     
  18. JRapp

    JRapp NEW MEMBER!

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    I knew a guy who got a very minty '58 Bassman from his uncle who said it never sounded right. The poor guy spent $$$ on EQ pedals, boost pedals, anything to get some low end out of the amp. Turns out they had wired half the speakers out of phase at the Fender factory back in '58...
     
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