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How much does speaker polarity matter?

Discussion in 'Electronic Repair' started by [email protected], Jan 2, 2008.

  1. Guest

    Hello all...

    I recently installed a radio and stereo speakers in my car. The
    speakers were a trashpicking find and they seem to work just fine. At
    the time I wired them up, I didn't know which terminals represented +
    and - on the speakers, so I took a guess and wired them both the same
    way. The speakers had no marking to indicate polarity, other than a
    "thin" spade lug for one terminal.

    Just the other night I found the box the speakers were in. It has a
    detailed wiring diagram on the side. According to the diagram I have
    reversed the + and - connections on both speakers.

    Over the years I've read a number of different views on the effect of
    wiring speakers with reversed polarity. I've heard everything from "it
    won't really matter if the speakers are both wired the same way" to
    "the sound won't be as good because the speaker cone will pull inward
    instead of being pushed out".

    It wouldn't be hard to fix, but should I bother correcting the
    polarity?

    William
     
  2. Arfa Daily

    Arfa Daily Guest

    I've never known it to matter, as long as they are both wired the same way
    round, as you say. Reverse wiring just one will result in a lack of bass and
    a 'woolly' stereo image, as I'm sure you are aware. If you think about it,
    any waveform driving them will have a pretty symmetrical count of positive
    and negative half cycles of largely similar amplitude, so there is no real
    reason why the speaker moving back, at a time when the diaphragm in the
    microphone that made the original recording was moving forward, should have
    any effect. The theory also assumes that the phase relationship was
    maintained throughout the entire recording process, and that there is no
    inversion taking place in amplifier stages in your player, that isn't
    reversed again, by the time the signal reaches the output terminals ...

    Arfa
     
  3. N Cook

    N Cook Guest

    Do you want fixed "image" stereo or musicians "wandering around in space"?
     
  4. jakdedert

    jakdedert Guest

    In a word, no. The only time that speaker polarity 'really' matters in
    non-critical situations is in cases where different speakers in a system
    are wired differently...leading to cancellation (one speaker is
    'pushing' air, while another is 'pulling'.)

    In your case, if those are the only two speakers in the car, absolute
    polarity is irrelevant.

    Next time, use a 9v battery to check. *Briefly* touch the battery
    terminals to the speaker terminals. The speaker polarity matches the
    battery polarity when doing so makes the speaker cone extend, as opposed
    to pulling in. IOW, when the cone comes out, the positive battery
    terminal is connected to the positive speaker terminal.

    jak
     
  5. I don't know whether there is any standard among audio equipment
    manufacturers that guarantees at the speaker output the same phase as
    the original signal, and this could be the real issue. If there were
    one, then I would suggest you correcting your polarity. Probably you
    will soon agree yourself if you think of the sound that comes from a
    bass drum vigorously hit by the pedal.
    Antonio - Italy
     
  6. Guest

    Hi!

    To everyone who has replied so far, thank you for your information.

    I would have normally used a nine volt battery to check the polarity,
    but I couldn't find one anywhere in the various messes I have. :)

    I think I'll go ahead and correct the speaker polarity so that it at
    least matches what the radio manufacturer and speaker manufacturers
    say it "should" be. This will not be difficult. There are only two
    speakers in the car (at this time...I may add two more later the car's
    design permits it) However, I do see the point that one poster made
    about which way the speaker cone will "fire" when a large signal comes
    its way. It would seem logical that the speaker cone can extend much
    further outward than it can inward (toward the speaker basket).

    Again, thanks for the info. I will keep checking into this posting if
    more information shows up.

    William
     
  7. Meat Plow

    Meat Plow Guest

    It would matter for impulses from the waveform say as in a drum beat?
    Wouldn't the beat of a kick drum cause the speaker cone to move inward if
    the polarity is reversed? This certainly wouldn't be suitable for a sound
    reinforcement system.
     
  8. hath wroth:
    It doesn't matter. The speaker audio has no DC component and neither
    is connected to the speaker frame. The AC component of the audio is
    generally symmetrical about the 0 volt axis. Whether you push or you
    pull doesn't really matter. However, you do have to get the phasing
    correct between the two speakers to avoid "ping pong" stereo. Try a
    test CD where a train or car goes from the left to right speakers. If
    it sounds "real", then you got it right. If it bounces back and forth
    between speakers, reverse ONE of the speaker polarities.

    I forgot to mail you the PS2 boards. I also found some Dallas clock
    blobs. Sorry. Still want them?
     
  9. hr(bob)

    hr(bob) Guest

    The speakers should move equally in and out if they are not to distort
    the sound.
     
  10. Some people believe that "absolute" polarity matters -- that is, a
    compression (rarefaction) in the original sound should be reproduced as a
    compression (rarefaction). I experimented with this 28 years ago, and never
    heard an effect from simply flopping the polarity of both channels. Even if
    it were audible, there are no industry standards for recording polarity.

    All that matters in practice is that both sides are wired identically. This
    gives maximum bass, and guarantees that mono components will be properly
    centered.
     
  11. Ron(UK)

    Ron(UK) Guest

    One might think that, but flipping the polarity on a kik drum mike has
    little if any effect on the sound through the PA. Sometimes I mike a
    bass drum from both sides, using a 'bassdrum' mike on the front head and
    a normal instrument mike on the batter head. Reversing the polarity of
    the batter head mike does make a difference in this instance.
    Ron(UK)
     
  12. Fleetie

    Fleetie Guest

    Basically (and I have some experience with audio and hi-fi, including an
    electroacoustics degree - but I am NOT an "expert"), I agree with Arfa that
    for MOST practical purposes, as long as both speakers are connected with
    the same polarity, then it'll be fine and you won't be able to distinguish
    one polarity from the other.

    If one speaker is wired in antiphase with the other, you'll lose bass to
    an extent that depends on room geometry and speaker positioning - but
    whatever happens, it won't be good.

    There has indeed been debate about whether people are sensitive to
    "absolute phase"; and I remember reading about higher-end DAC units for
    CDs that included a switch to flip phase on both channels. ISTR, an d
    I may be wrong, that back in the late 80s when I had a part-time job
    at a hi-fi shop, there was a Musical Fidelity outboard DAC unit that
    featured such a switch - but it was 20 years ago, so don't quote me.

    Personally I don't believe that people are sensitive to absolute phase, and
    anyone who claims they are needs to submit to a double-blind test, and
    maybe if they pass, go and have a word with James Randi, who while
    AFAIK he isn't offering a prize for absolute phase YET, may be interested
    in handing out a financial prize if they can repeat the souble-blind
    performance repeatably. He offers a prize to those claiming to be able to
    distinguish between interconnect cables (providing both sets are reasonably
    well-executed and one pair isn't made of wet string, for example!).

    As Meat Plow suggests, there COULD be an issue with high cone excursions,
    where on a bass kick, or similar, the cone former may hit the endstop
    on the way IN (away from the listener) with the speaker wired one way
    round, but not with it wired the other way round. However, that's a
    completely separate consideration unrelated to human sensitivity to
    "absolute phase". You just hear a nasty knocking sound when it happens and
    risk damaging your bass unit. If you're driving them that hard though, you
    may encounter problems regardless of polarity.

    Summary: Make sure both speakers are wired the same way round. That done,
    forget worrying about it. Unless you're maybe doing an acoustics PhD.


    Martin
     
  13. Guest

    Hi!
    I must have it right then. Both speakers are wired exactly the same
    way. I was careful to be sure of that and even used different colored
    wire. The "+" lead is red while the "-" is black. Stereo separation is
    excellent, and sounds that do move "across" from one speaker to the
    other do sound "real". In fact, it's quite surprising how good the
    sound really is. The speakers are small, so they don't have a whole
    lot of bass, but otherwise the sound is good, if a bit centered on the
    midrange.
    Yep. Dallas clock blobs (!!!) are also interesting. I have been
    reworking them...maybe I mentioned that.

    William
     
  14. Meat Plow

    Meat Plow Guest

    Hmmmmm I would think the pressure wave created from the bass drum head
    upon the mic element would be mimicked at the speaker. Not that I don't
    trust your years of experience but I just need to get a hands on with this
    one.
     
  15. Ron(UK)

    Ron(UK) Guest

    I`m sure it does, but the initial pulse from a bass drum hit is a lot
    higher in frequency than you might think.
    If you look at a trace of a drum hit it`s quite a complex waveform,
    although there`s a lot of low frequency energy, the main transient
    impulse is mid band where you shouldn't be getting a lot of cone
    excursion. Often this mid band impulse is accentuated by a sound
    engineer to get the bass drum to 'pop out' over the rest of the band.
    The bottom end is still there, but the punch comes from higher up.

    The low sound that you feel in your gut (63/80hz ish) is usually
    reproduced by different sub bass speaker cabinets (and amplifiers) that
    are easily capable of handling those kind of frequencies. Subs are
    generally crossed over around 80/100 cycles and can be driven with
    several kilowatts of amplifier power.

    If you think about it, the bass drum head itself doesn't move much when
    it`s hit by the beater, why should the speaker.

    Ron(UK)
     
  16. jakdedert

    jakdedert Guest

    Ron(UK) wrote:
    Actually, it does move quite a bit; but the operative dimension is not
    the excursion, but the size of the head vs. the size of the speaker. To
    move as much air as a 20-someodd inch bass drum head--moving x
    distance--the 6 to 18 inch woofer cone has to move correspondingly
    farther. I'm sure there's a mathematical relationship there that I
    don't have the chops to calculate....

    jak
     
  17. Ron(UK)

    Ron(UK) Guest

    The majority of the initial energy is outside the range of the
    subwoofer, also a bass drum (any drum in fact) is a tuned instrument.
    the 'x distance' excursion as you put it, is very small in relation to
    the sound output, maybe half an inch or so on a properly tuned bass
    drum. Don't go by the front head which is often far slacker than the
    batter head, sometimes it`s only there for show.

    IMO
    Ron(UK)
     
  18. Eeyore

    Eeyore Guest

    You presume that the recording-reproduction chain is polarity accurate. IME it's a
    lottery.

    Graham
     
  19. Meat Plow

    Meat Plow Guest

    Just so you know, I spent 2 decades gigging with several bands playing
    bass, rhythm, and drums. I well understand the dynamics of sound
    reinforcement having owned at one time a full tri-amped pa system
    consisting of 18s mids and horns, 24 channel board, snakes, mics, effects,
    compressors, gates, active crossovers and around 5K of power. I still have
    much of that equipment but got rid of a few amps and the separate
    cabinetes buying a pair of 3 way cabs with an 18" in a Theil designed
    enclosure, a 10" mid sitting in a large horn lens and piezo horn.

    Anyway back to the subject. I know the drum head doesn't move much. But
    to reproduce the bass drum enough to fill a big room with plenty
    of low end the speakers are going to move much more than the bass head. I
    do fully understand that the tap part of the bass drum is frequently
    desired to cut through and it does add emphasis on the bass drum but I for
    one am not partial to hearing a lot of it. The best subs are designed to
    utilize both the front and back of the speaker instead of just baffling
    it as in but not limited to a folded horn enclosure as you probably know.
    My cabinets are Thiel design which utilize a tuned enclosure and a slot
    to allow the pressure wave of the back of the speaker to unite in phase
    with the front.

    I suppose I'm going to go get my Yamaha sound reinforcement handbook and
    refresh my memory on all of this. That's a damn good book and it's been my
    bible for many years.
     
  20. Basically you're talking about so called 'absolute phase'. Which is total
    rubbish spouted by some self appointed 'experts'. If you think of a sine
    wave, moving your head relative to the source can reverse the phase at any
    one point in time.
    No reason to at all.
     
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