awkwardbydesign
Officially Awesome
Well, I used the wrong term too. So polarity it is, as per the original question. Still audible, whatever it's called.
Reverse polarity on speakers (not out of phase)
- Thread starter allthingsanalog
- Start date
awkwardbydesign
Officially Awesome
Strangely, I wasn't interested in the theory, just what I could hear. And the cure.
adamdea
You are not a sound quality evaluation device
yes they allow for changing the phase of the channels relative to each other. But why have the whole system on the "wrong" phase by default?
Their switchboard must be jammed with customers complaining about the deqx sounding wrong.
Yank
Bulbous Also Tapered
If you swap speaker leads you're inverting polarity. I don't know how the words "invert" and "phase" could relate to each other.
Ted-M
pfm Member
The manual (Bias Peak 6 waveform editor) states that the 'invert' function inverts the phase. So even they are confused...!?
Invert
The Invert function allows you to invert the phase of a selection or an entire audio document.
The Invert function allows you to invert the phase of a selection or an entire audio document.
Ted-M
pfm Member
I found this at ethanwinner.com, might be of interest:
Here is the link to the page if you want to hear the files:
http://ethanwiner.com/myths.html
Myth: Absolute microphone or speaker polarity makes an audible difference.
Fact: While nobody would seriously argue that it is okay to reverse the polarity of one signal in a stereo pair, I've never been able to determine that reversing the polarity of one signal - or both if stereo - ever makes an audible difference. Admittedly, it would seem that absolute polarity might make a difference in some cases, for example, when listening to a bass drum. But in practice, changing the absolute polarity has never been audible to me.
You can test this for yourself easily enough: If your console offers a polarity-reverse switch, listen to a steadily repeating bass drum hit and then flip the switch. It is not sufficient to have a drummer go into the studio and hit the drum while you listen in the control room, because every drum hit is slightly different. The only truly scientific way to compare absolute polarity is to audition a looped recording or drum sample, to guarantee that every hit is identical.
Important Update: Mike Rivers from Recording magazine sent me a test Wave file that shows absolute polarity can be audible in some circumstances. The polarity.wav file (87k) is a 20 Hz sawtooth waveform that reverses polarity in the middle. Although you can indeed hear a slight increase in the low end fullness after the transition point, I'm still not 100 percent certain what this proves. I suspect what's really being shown is a nonlinearity in the playback speaker, because with a 50 Hz sawtooth waveform there is no change in timbre. However, as Mike explained to me, it really doesn't matter why the tone changes, just that it does. And I cannot disagree with that.
More Update Info: After discussing this further with Mike in the rec.audio.pro newsgroup I created two test files you can download and audition yourself. The Kick Drum Wave file (324 KB) contains a kick drum pattern twice, with the second reversed. Play it in SoundForge or any audio editor that has a Loop mode, so you can play it continually to see if you hear a difference. The Voice Wave file (301 KB) is the same but with me speaking, because Mike says reversing polarity on a voice is surely audible. I don't hear any difference at all. However, I have very good loudspeakers in a room with proper acoustic treatment. As explained above, if your loudspeakers can't handle low frequencies properly that could account for any difference you might hear.
Fact: While nobody would seriously argue that it is okay to reverse the polarity of one signal in a stereo pair, I've never been able to determine that reversing the polarity of one signal - or both if stereo - ever makes an audible difference. Admittedly, it would seem that absolute polarity might make a difference in some cases, for example, when listening to a bass drum. But in practice, changing the absolute polarity has never been audible to me.
You can test this for yourself easily enough: If your console offers a polarity-reverse switch, listen to a steadily repeating bass drum hit and then flip the switch. It is not sufficient to have a drummer go into the studio and hit the drum while you listen in the control room, because every drum hit is slightly different. The only truly scientific way to compare absolute polarity is to audition a looped recording or drum sample, to guarantee that every hit is identical.
Important Update: Mike Rivers from Recording magazine sent me a test Wave file that shows absolute polarity can be audible in some circumstances. The polarity.wav file (87k) is a 20 Hz sawtooth waveform that reverses polarity in the middle. Although you can indeed hear a slight increase in the low end fullness after the transition point, I'm still not 100 percent certain what this proves. I suspect what's really being shown is a nonlinearity in the playback speaker, because with a 50 Hz sawtooth waveform there is no change in timbre. However, as Mike explained to me, it really doesn't matter why the tone changes, just that it does. And I cannot disagree with that.
More Update Info: After discussing this further with Mike in the rec.audio.pro newsgroup I created two test files you can download and audition yourself. The Kick Drum Wave file (324 KB) contains a kick drum pattern twice, with the second reversed. Play it in SoundForge or any audio editor that has a Loop mode, so you can play it continually to see if you hear a difference. The Voice Wave file (301 KB) is the same but with me speaking, because Mike says reversing polarity on a voice is surely audible. I don't hear any difference at all. However, I have very good loudspeakers in a room with proper acoustic treatment. As explained above, if your loudspeakers can't handle low frequencies properly that could account for any difference you might hear.
Here is the link to the page if you want to hear the files:
http://ethanwiner.com/myths.html
Can I just correct a bit of a misconception about phase and phase inverting when recording.
Absolute phase can be switched on a desk, but is also affected by the majority of EQ applied in a studio - the very act of shaping the frequency response will alter phase, and this shift will be frequency dependent.
In addition, any vaguely complicated instrument will typically be a combination of overhead mics and a close mic - drums for example. The different path lengths to the different microphones produces a relative phase shift, so even if the mics are all 'in phase' with each other, they will still produce some degree of comb filtering due to path length differences when mixed together. Overheads aren't panned hard left/right, but are mixed into the stereo image, so you have issues with comb filtering to deal with. Remember, a snare hit has energy right up into the 10Khz region, and that's what, 3cm as a wavelength? If the path to the overheads differs by 1.5cm they will be completely out of phase, but at 5Khz, they would be 90 degrees out, and a 2.5Khz, only 45 degrees out. See the problem?
BTW, it's quite common for the overheads to sway around whilst the drummer is working, and by more than a cm ;-)
So, add in different EQ, dynamics processors such as limiters, gates, compressors, EQ on the desk channels all adding frequency, and possibly amplitude dependent phase shifts (so the shift alters as the note decays), and try and explain how the engineer is going to give the correct absolute phase for both the snare, and the floor tom at the same time.
The phase invert is handy for close mics which are on opposite sides of a drum, or for example, on a kick drum (where it's placed opposite the hit side) unlike, say the snare (same side).
For extra points, consider where you would place a pair of mics to record a piano in phase across all of it's frequency range (20Hz to 4Khz).
Absolute phase can be switched on a desk, but is also affected by the majority of EQ applied in a studio - the very act of shaping the frequency response will alter phase, and this shift will be frequency dependent.
In addition, any vaguely complicated instrument will typically be a combination of overhead mics and a close mic - drums for example. The different path lengths to the different microphones produces a relative phase shift, so even if the mics are all 'in phase' with each other, they will still produce some degree of comb filtering due to path length differences when mixed together. Overheads aren't panned hard left/right, but are mixed into the stereo image, so you have issues with comb filtering to deal with. Remember, a snare hit has energy right up into the 10Khz region, and that's what, 3cm as a wavelength? If the path to the overheads differs by 1.5cm they will be completely out of phase, but at 5Khz, they would be 90 degrees out, and a 2.5Khz, only 45 degrees out. See the problem?
BTW, it's quite common for the overheads to sway around whilst the drummer is working, and by more than a cm ;-)
So, add in different EQ, dynamics processors such as limiters, gates, compressors, EQ on the desk channels all adding frequency, and possibly amplitude dependent phase shifts (so the shift alters as the note decays), and try and explain how the engineer is going to give the correct absolute phase for both the snare, and the floor tom at the same time.
The phase invert is handy for close mics which are on opposite sides of a drum, or for example, on a kick drum (where it's placed opposite the hit side) unlike, say the snare (same side).
For extra points, consider where you would place a pair of mics to record a piano in phase across all of it's frequency range (20Hz to 4Khz).
Absolute phase differences will not affect how music is perceived in the home when listening in stereo, (changing the polarity of each speaker so they remain the same ie swapping positive and neg on each).
Changing the polarity on one but not the other most certainly is audible and will change how the speakers sound! Relative phase is most certainly audible. That's why speaker designers such as myself go to such lengths with crossover design to ensure phase relationships between individual drivers handling overlapping bandwidth is as close as we can get it (although with all multidriver systems, overlapping drivers will only be in absolute phase at one or at most, several points within the audible overlapping frequency bands depending on the steepness of the acoustic roll off slopes).
It's a dead easy thing to demonstrate, and anyone who's used one of those Test lPs knows exactly how being out of relative phase can sound: where the speaker says "phase test...listen to your speakers...my voice should appear to be focussed and coming from in between the speakers. Out of phase test....my voice should not be focussed and difficult to place". Just try reversing polairty on one speaker but not the other and you'll soon pick it up.
Changing the polarity on one but not the other most certainly is audible and will change how the speakers sound! Relative phase is most certainly audible. That's why speaker designers such as myself go to such lengths with crossover design to ensure phase relationships between individual drivers handling overlapping bandwidth is as close as we can get it (although with all multidriver systems, overlapping drivers will only be in absolute phase at one or at most, several points within the audible overlapping frequency bands depending on the steepness of the acoustic roll off slopes).
It's a dead easy thing to demonstrate, and anyone who's used one of those Test lPs knows exactly how being out of relative phase can sound: where the speaker says "phase test...listen to your speakers...my voice should appear to be focussed and coming from in between the speakers. Out of phase test....my voice should not be focussed and difficult to place". Just try reversing polairty on one speaker but not the other and you'll soon pick it up.
RustyB
Registered Ginga
Also old JBL drivers; applying positive voltage to the + terminal kicks the cone backwards.
davidsrsb
pfm Member
This page has some explanation about microphone phase
http://www.johnvestman.com/polarity.html
Looking at some of my CDs, the kickdrum waveform is one way on one track and the the other on another
http://www.johnvestman.com/polarity.html
Looking at some of my CDs, the kickdrum waveform is one way on one track and the the other on another
OK just for fun below is a recording of a snare. It is the same hit repeated. One file is with normal phase, one file is inverted.
Download and see if you hear differences.
http://gofile.me/2vnEF/kKnV3UWz
Download and see if you hear differences.
http://gofile.me/2vnEF/kKnV3UWz
Rodney gold
Im just me...
Regardless of absolute phase *and i could hear the difference on my meridian speakers that allow you to change it , but the difference could be ascribed to the DSP that does it* the room problems are totally different issue.
you need either room treatment or something like a miniDSP2x4 for $105 that will cure this for you at listening position
You can try a freebie by just moving your listening position to be out of the node to cure the boom..
you need either room treatment or something like a miniDSP2x4 for $105 that will cure this for you at listening position
You can try a freebie by just moving your listening position to be out of the node to cure the boom..
With some JBLs, the terminal markings on some drivers are actually reversed (peculiar to JBL presumably to avoid confusion regarding phase when wiring them up). Positive voltage to positive terminal normally kicks a driver cone forwards, not backwards.
For Tannoys, because they are dual drivers being driven off what is electrically a second order crossover, one of the drivers has its polarity reversed, which in the case of vintage Tannoy drivers, is the bass driver. To check for correct polarity on a Tannoy, positive voltage applied to the woofer should make the cone go backwards.
That link is funny - there's a discussion about which way around is correct for a kick drum.
If you are the drummer, it's one way around, if you are standing looking at the kit, it's the other. Which way is 'correct'?
It seems that this is yet another case where hi-fi history is forgotten. An American named Clark Johnsen has written a book about the audibility, or not, of absolute phase/polarity reversal. The book is called The Wood Effect.
The consensus seems to be that a relatively small minority of listeners is polarity sensitive, the majority isn't.
The consensus seems to be that a relatively small minority of listeners is polarity sensitive, the majority isn't.
Michael J
pfm Member
I suppose it depends, special circumstances aside, on what you consider to be the purpose of the drum kit. Is it there to serve the band and audience, or is it an ego trip for the drummer? Imo, the "correct" way to record it is as heard by the paying listener, not the paid performer.
Acoustic guitarists never get to hear what they themselves "sound like" either, the instrument projects forwards and the player never hears the full tone. It makes no sense (excepting special circumstances) to place a microphone near the player's ears, it does make sense to place it somewhere in front of the soundboard.
Yank
Bulbous Also Tapered
A recording should be from the audience perspective.
Ted-M
pfm Member
Quote from the book:
"[polarity]Reproduced incorrectly, it becomes what I call "the muffling distortion," because our ears detect an inverted leading transient and suppress the impulse response. Thus the pluck on a guitar string, so striking in real life, becomes dull, muted, and inexpressive. A musician might say, "You cant hear the fingers, man."
Well I tried to reproduce this example (and various others) and I cannot hear any difference whatsoever. If there is any effect at all it is surely beyond tiny, and certainly not in the range of something "striking" becomes "dull". I'm still open minded but the evidence so far is not compelling...