Does reversing polarity change music?

[Erukian]

I could swear that it's changing the timbre and imaging of the music, but I'm no engineer or have ever been, so I can't be sure if it's just all in my head.

-Joe

[mike stehr]

It will gyp you out of bass response.....

[LarryC]

Do you mean change both sides at once, so that the two sides remain in phase but the drivers push where they used to pull & vice versa? Some say yes, some say no. I think I hear a difference. That type of "phase" is said to differ from recording to recording as well as component to component, so it's difficult to make it consistent. Some preamps have had polarity switches to make it possible to switch while listening.

Yes, you lose bass if you do only one side, thus making the two sides out of phase.

Larry

[Daddy Dee]

There is a real interesting thread that was started by Mark Deneen a year or two ago. He mentioned that he'd flipped over the two prong plug A/C plug and realized it had been plugged in the wall the wrong way. Those really old cords have the same size prongs and can go in either way. I turned over the plug on my HF-81 and marked it for correct use. You definitely want the drivers to excurse on the right impulse. Otherwise, it does sound bad, just off. Having the polarity right can make a significant difference in the sound of an amp.

[Duke Spinner]

plays backward with the right CD

[Duke Spinner]

remember, we are talkin' DC polarity, when +/-

music is a waveform, AC if you will ....

[WMcD]

You should find quite a bit about absolute polarity. I understand there are some studies showing that it is audible on some special waveforms.

I believe this is what you're talking about.

The theory is that, say at the microphone, there is a polarity that is correct. There is a long string of amplifiers, storage devices, transmission devices, etc., all along the way to your speaker. Polarity can be inadvertently reversed.

Some of the theory is based on the observation that the waveform of some elements of music is not symetric. E.g. the initial ramp up of a percusive hit on a drum or a piano string. (Maybe it is a ramp down if the drum head moves away from the mike. Smile.)

Longer term oscillations, though, tend to be symetric about zero; i.e. the top half and the bottom halfs of the signal are identical. My recall is that some reed instruments send out an asymetric wav, even in sustained notes.

It is my understanding that at best the audible effects are subtile on the waveforms where audibilty has been found.

- - -

The subject becomes fairly hopeless in some crossover designs. The H.F. gets shifted 90 degrees on way and the L.F. gets shifted 90 degrees the other (at least at cross over frequency). So the only way to make them sum correctly is to reverse the polarity of one.

When I made some of these type crossovers I decided to live with the dip caused by lack of inversion. It gave me the engineering hebbie jebbies to have half the drivers reversed.

Gil

[Daddy Dee]

http://forums.klipsch.com/idealbb/view.asp?topicID=47949&forumID=68&catID=19&search=1&searchstring=&sessionID={68E68D00-9D61-4828-AE5D-6CEF39DEC932}

This thread has some good info, including some drawings of waveforms relative to polarity.

[Deang]

Sure it sounds different, but how do you determine which way is right?

[Daddy Dee]

Mark,

That's interesting. I might have dreamed it. But I do have a mark indicating correct polarity on the top side of the A/C plug for my HF-81. In all seriousness, it certainly could have been another context.

Would switching the A/C also change polarity?

Dean,

Which one is right? The one that sounds "better" of course.

[fini]

When you factor in the Earth's changing magnetic field (a regular flip-flop recorded on the ocean floors), we're all screwed...

[djk]

Absolute polarity is what you are referring to.

Yes, it will change how the music sounds.

It is most noteable on minimalist mic'd recordings and with speakers with larger amounts of second harmonic distortion.

Some recordings can sound very strange if the absolute polarity is wrong.

A piano is generally mic'd with three mics, the one on the opposite side is reverse phase. Because of the highly asymetrical waveform of the piano the timbre can really change if the phase of one of the mics is wrong, or the absolute phase of the combo is wrong.

A solo clarinet is another one that can sound very different.

If you want to hear something real wild try this:

Listen to an SET driving a full range speaker like a Fostex. Reverse the absolute polarity. Reverse the absolute polarity again at the source (restoring absolute polarity). This will change the sound so much you won't believe it.

Prize to the person that can explain why.

[dodger]

----------------

On 7/17/2005 8:30:18 AM Daddy Dee wrote:

Mark,

That's interesting. I might have dreamed it. But I do have a mark indicating correct polarity on the top side of the A/C plug for my HF-81. In all seriousness, it certainly could have been another context.

Would switching the A/C also change polarity?

Dean,

Which one is right? The one that sounds "better" of course.

----------------

In theory changing the old style A/C plugs changes polarity. That's the reason for the dedicated larger sized prong now. That also can be shown with one of the test lights you plug in to see if an outlet is wired correctly.

BUT, then after the recording, you have the mixdown, Master Tape or Master CD and how they are all plugged in. Then the Power Company supplying our homes.

But if followed properly, yes a change in both can be heard. It seems that most notice it in bass, but the highs can also be affected.

Which is correct? As Daddy Dee said, the one that sounds better if you know the instruments.

[PrestonTom]

The issue of absolute polarity comes up every few years or so. Some manufacturers have capitalized on this confusion and made some money.

There are a couple of comments (which Gil mentioned also). Recording and reproduction is a very long chain of events. It is quite improbable that the absolute polarity was maintained throughout. Second, there may be some subtle differences using some very specific waveforms - one of these is referred to as as the "Wood effect" (I would have to dig up a reference on that).

Unfortunately, the discussion on polarity effects gets smeared because folks confuse left & right channel polarity (a big effect) and phase or polarity reversals between sections of a crossover (sometimes necessary and it may or may not be a problem).

Although I am fairly negative about whether absolute polarity has an effect, I do sometimes wonder in a mechanical transducer (either a mic or speaker), would the distortion differ (either in degree or type) with regards to whether it was moving inwards or outwards. Again, if the transducer were in its linear range there would be no problem; however; since there is a mechanical suspension etc, the direction might make a difference. This of course it simply speculation. The real question is whether a listener can actually discriminate between the two in an AB comparision.

-Tom

[Klewless]

Sometimes I wish I had one of those "BS Buttons" to display as a response.

I once wrote PWK a letter asking about phase reversal from the amp to the speaker and he wrote back suggesting that I make a reversing switch and then "proceed to frustrate yourself".

AC is AC, the electrons don't know if they are coming or going. As far as the Power Line AC to your house goes, I doubt that the utility company has gone to any effort to insure that your particular leg off their dropdown transformers are perfectly balanced and are without any phase lags with the voltage/current.

I do understand improvements if the source happens to have a problem solvable by a simple phase reversal (maybe one percent of the time if you are really in luck). I used to see this when I had equipment with the scope and could determine if one channel AT THE SOURCE was out of phase.

But when it is truely random I could never hear any difference one way or the other. I remember that one radio station was consistently out of phase on one channel, which I could clearly determine from the scope. Couldn't tell which channel but that didn't matter since OUT is OUT.

[dodger]

My response was not indicated to make money.

But in live sound you can, if you have good ears and a good scope, notice a change with the AC polarity. That's one of the reasons for the polarized plugs - note one.

The current alternates. The easiest way to determine any effect is to check with a Master Electrician who also did Pro sound for years and also recording.

Take a Reel to Reel, record an instrument, reverse the plug, list for any change.

Noting a switch between an amp and a speaker, quite a number have them. Som make the mistake of reversing the left and right of BOTH speakers when switched the result still one out of phase.

All one needs is to reverse one speaker.

[Erukian]

My friend abx'd reversing polarity.

He compared two songs, blindly, using a computer program called Foobar2000 with an ABX testing plugin and a home-made plugin for reversing the polarity.

He did this about 50 times and his 'margin of guessing' was about .5%

Keep in mind though, these are high end headphones (costing about $300) which give him bass response we could only dream of in a speaker system (because of room acoustics/dimensions/etc)

So it's definately audible, no queston about it.

-Joe

[DrWho]

----------------

On 7/17/2005 10:01:11 AM PrestonTom wrote:

I do sometimes wonder in a mechanical transducer (either a mic or speaker), would the distortion differ (either in degree or type) with regards to whether it was moving inwards or outwards. Again, if the transducer were in its linear range there would be no problem; however; since there is a mechanical suspension etc, the direction might make a difference. This of course it simply speculation.

----------------

Well no need for it to be speculation, the distortion patterns ARE different depending on the motion of the cone...it might not be different for a straight up tone, but once you start introducing multiple tones you get "doppler distortion" and then the direction starts to matter real fast...that's why those Foxtex full range drivers really sound way different when you change the polarity. They simply have lots of frequency modulation distortion. To visualize it, picture what the driver would be doing if you had a kick drum flute duet...with absolute polarity, the kick drum moves the driver forward while you have the flute signal riding on top. If you reverse the polarity, now the driver moves backwards while playing a very similar flute signal. However, we all know that sounds moving towards the listening increase in frequency and decrease when they move away (think of how a train sounds when it drives by). You basically end up changing the pitch of the flute when you do this with full range drivers because the cone motion is so drastically different beween the kick drum and flute frequencies. Is that along the lines of what you were thinking djk?

Another interesting concept is that we don't just listen to sound with our ears...we feel it in our chest too. If you get the polarity backwards on a kick drum it starts to sound wierd because you're expecting a compression wave to hit you first, not a trough followed by a smaller compression. Put your hand in front of the speaker and feel the air move by when the kick hits...then reverse the polarity and notice how much it changes. You practically don't feel it when the woofer moves away from you at first.

Btw, it doesn't matter if absolute polarity was maintained throughout the entire signal chain (studio/mastering facility etc etc) because the relative polarity of everything in the mix will be the same throughout the chain. It's then up to the listener to determine when the polarity should be switched, but I can't think of any recordings that I own though that might require this.

[Colin]

my CAL Gamma DAC has an "inverse" button, which some times makes a difference...

[colterphoto1]

If you invert the polarity, Ritchie comes out of the right speaker and Jon the left, contrary to stage presence.

LOL just kidding.

Michael