[Wayner]

Yes, but those components have been reduced to near zero. In the recording process, some are lost and in the playback process, even more subtleties are lost to distortion and speaker phasing caused by the cross-over, front baffle, room acoustics.

Good discussion, anywho.

[konut]

OK, what musical instrument sucks 

 Wayner

An accordion. And it doesn't even depend on who's' playing it.  

[Wayner]

Impressive! Any Lawerence Welk.............anyone............and now the lovely Lenon sisters.....

Good God....

[clarkjohnsen]

A really loud sound still consists of alternating compressions and rarefactions, there is no near-"DC" pressure component to worry about in music

Quite right. And the initial attack, the transient, can sometimes be a rarefaction, depending on the instrument -- or, with an organ, the particular stop selected.

 

All of the incident waves modulate the diaphragm at different frequencies and different intensities.  Whether or not you can detect one or the other depends on the dynamic range of the system, and the linearity of the microphone.

And a whole lot more!

However, polarity was discovered as a "MPE", or Monaural Phase Effect. Simplicity is the key to its detection. On the heavily-mixed pop recordings so many people talk about, played over speakers with crazee crossovers, it's hardly surprising that folks are in denial about this MPE.

[opaqueice]

Quite so, but that does NOT obviate the need for whichever way it's hit, to be reproduced the same way out of the loudspeaker(s).

Well, I agree that for a given instrument producing a given note listened to at a particular position in the room, there is a particular polarity to the leading edge.  But at a different position, or on a different note struck the other way, that polarity could be reversed.  So it's not accurate to say there's an absolute polarity of the leading edge, even for a given instrument.

And since almost all recordings are made with multiple mics in different positions and played back through speakers with multiple drivers, often in relative inverted polarity, it's really a mess.   Moreover, my own experiments lead me to believe that even when all of this is taken into account, the difference is very small unless it's amplified by large asymmetric non-linearities (in which case the problem is with the playback system, not the polarity).

[opaqueice]

That doesn't prove a thing except that the microphone has probably has a cardioid type pickup pattern.

It's got nothing to do with the pickup pattern of the mic - I wasn't moving the sound source relative to the mic, I was just changing the direction from which I flicked the pen.  When you flick towards the mic you create a wave with a leading compression edge propagating towards the mic, and when you flick away you create a wave with a leading rarefaction edge propagating towards it (and a compression edge propagating away).  Think about how the air molecules are going to react to the first motion of the vibrating object and you'll see why.

As for which instruments "suck" - all of them  !  All sounds are series of compressions and rarefactions, and the rarefactions are created when the instrument is moving away from the mic/ear and leaving a partial vacuum behind it.  The question was whether a rarefaction can be the first thing that arrives at the mic, and the answer is that it often is, depending on how the instrument is struck/bowed and where the mic is.

If you don't believe me, download a copy of audacity and check for yourself.  It's REALLY easy to, and it's interesting to see what kinds of crazy waveforms you get from tapping things like sheets of paper  .

[konut]

Since there are some really smart people following this thread, I pose this question. Since what we are talking about is the origin of the first impulse striking the element in the microphone, does it not follow that it will always be the leading edge which impinges on that element, and the rarefaction that follows returns the element to its original position, OR does the element move back AND FORTH, and is it then possible for the rarefaction to be the initial impulse? By extension, if the first impulse is indeed a leading edge, moving the element away from its initial position, then does it not follow that the corresponding speaker movement should be in, not out?

[opaqueice]

Since there are some really smart people following this thread, I pose this question. Since what we are talking about is the origin of the first impulse striking the element in the microphone, does it not follow that it will always be the leading edge which impinges on that element, and the rarefaction that follows returns the element to its original position, OR does the element move back AND FORTH, and is it then possible for the rarefaction to be the initial impulse?

If I understand what you're asking - yes.  For example, when I tap the pen in such a way that its first motion is away from the mic, the first thing the mic will record a moment later when the sound starts to arrive is lower pressure (i.e. the leading edge of the sound wave moving towards the mic is a rarefaction).

By extension, if the first impulse is indeed a leading edge, moving the element away from its initial position, then does it not follow that the corresponding speaker movement should be in, not out?

Sure - if you want to reproduce a sound as accurately as possible, you want the speaker cone to move in the same direction as the object that produced the original sound did towards the audience.  But the point I've been trying to make in this thread is that that is often impossible.  For example, what if the object moved vertically?  Not many speakers can do that   .  What if a drum head was moving towards the audience at the same time as a nearby guitar string was vibrating away and a cymbal was moving down??

What I think is a little more realistic is to remember that many instruments (brass, for example) produce truly asymmetric waveforms.  In other words it's not just the leading edge that matters - the whole waveform produces different compressions than it does rarefactions.  Such a sound does have a true absolute polarity, one which might even be independent of the listener's position and the manner it's played.  But, in my experience the difference between true and inverted polarity in these cases are so subtle as to be essentially inaudible, unless something in the playback system is adding non-linear even order distortion and artificially emphasizing it.

[PMAT]

It's my anniversary and I'm hopin' for some wood effect. Coupling is best out of phase, especially at higher frequencies.  aa

[clarkjohnsen]

Well, I agree that for a given instrument producing a given note listened to at a particular position in the room, there is a particular polarity to the leading edge.  But at a different position, or on a different note struck the other way, that polarity could be reversed. 

We are still missing the point, that whichever way it sounds polarity-wise should be reproduced that way.

So it's not accurate to say there's an absolute polarity of the leading edge, even for a given instrument.

Quite right, and I for one never did. All the original sound has, is a polarity, period.

And since almost all recordings are made with multiple mics in different positions and played back through speakers with multiple drivers, often in relative inverted polarity, it's really a mess.   Moreover, my own experiments lead me to believe that even when all of this is taken into account, the difference is very small unless it's amplified by large asymmetric non-linearities (in which case the problem is with the playback system, not the polarity).

Yet the experiments of others (Stodolsky, Heyser, Lipshitz, Meyer, Johnsen et al.) located major differences, many at the vaunted 99% confidence level.

Also there are many of us who never listen to, or even care about, recordings "made with multiple mics in different positions". 

[clarkjohnsen]

Since there are some really smart people following this thread, I pose this question. Since what we are talking about is the origin of the first impulse striking the element in the microphone, does it not follow that it will always be the leading edge which impinges on that element, and the rarefaction that follows returns the element to its original position?

We have a false premise here, that the initial impingement will necessarily be a compression wave.

OR does the element move back AND FORTH, and is it then possible for the rarefaction to be the initial impulse?

Whether the initial impulse is one or the other, depends solely upon the instrument and its player. Any mic can go either way.

By extension, if the first impulse is indeed a leading edge, moving the element away from its initial position, then does it not follow that the corresponding speaker movement should be in, not out?

Just the opposite! Imagine it from the P.O.V. of the performer, who then is replaced by the loudspeaker.

[opaqueice]

Quite right, and I for one never did. All the original sound has, is a polarity, period.

The original sound at a particular time and heard from a particular place, yes.

Yet the experiments of others (Stodolsky, Heyser, Lipshitz, Meyer, Johnsen et al.) located major differences, many at the vaunted 99% confidence level.

The one published article on this I've read is by Grenier and Melton, from the Journal of the Acoustic Engineering Society - they find that polarity inversion is almost impossible to hear for natural sounds, and impossible on music.

Also there are many of us who never listen to, or even care about, recordings "made with multiple mics in different positions". 

Well, OK - that rules out probably 99.9% of all recorded music.  Speaking personally I would hate to be so obsessed with sound quality that I could only listen to a tiny fraction of all the great stuff out there.  For me, the music is ultimately much more important than the sound quality.  And anyway, even just with regard to SQ there are many other factors out there which in my experience are far more important than polarity (like harmonic balance, room effects, distortion, noise, etc.)

[clarkjohnsen]

Quite right, and I for one never did. All the original sound has, is a polarity, period.

The original sound at a particular time and heard from a particular place, yes.

Geez Luiz. What else do you think we were discussing?

Yet the experiments of others (Stodolsky, Heyser, Lipshitz, Meyer, Johnsen et al.) located major differences, many at the vaunted 99% confidence level.

The one published article on this I've read is by Grenier and Melton, from the Journal of the Acoustic Engineering Society - they find that polarity inversion is almost impossible to hear for natural sounds, and impossible on music.

That article was highly flawed, and I have analyzed it elsewhere. G&M also would never reveal what loudspeakers they used, although I was told off-the-record by an associate of theirs that they were not useful for revealing polarity. Nor would G&M reveal how they switched polarity; I myself do not like any switch in any gear I've heard.

I note you don't seem to have read the other authors. Stoldolsky, for one, found wrong polarity (in DBTs) to be equal to 11.5% IM distortion. Heyser called for immediate implementation of a Polarity Convention, citing it as the single most important step the audio world could take, to improve sound reproduction.

Also there are many of us who never listen to, or even care about, recordings "made with multiple mics in different positions". 

Well, OK - that rules out probably 99.9% of all recorded music. 

Nice try. But taking it from the dawn of the electrical era, I'm going to counter-assert that over 90% has been simply recorded.

 

Speaking personally I would hate to be so obsessed with sound quality that I could only listen to a tiny fraction of all the great stuff out there.

 

Dude! "Obsessed"?! When we're talking about just making a simple switch?

 

For me, the music is ultimately much more important than the sound quality. 

Ah! Taking refuge I see. Then what, pray, are you doing in Audio Circle? Or for that matter, in audio?

 

And anyway, even just with regard to SQ there are many other factors out there which in my experience are far more important than polarity (like harmonic balance, room effects, distortion, noise, etc.)

There are those too, but your experience seems not to have included adequate exposure to Absolute Polarity, else you'd be standing with Dr. Heyser.

[Russell Dawkins]

Clark, your patience is a credit to you, given the many years you have had to support this seemingly unpopular notion.

I bought your book, The Wood Effect, 15 years ago, a first edition. Have there been other editions since and, if so, were there any significant changes?

[opaqueice]

]
Geez Luiz. What else do you think we were discussing?

Good - I'm glad you agree.  You might benefit from better precision in the future so as to avoid this kind of distraction.

That article was highly flawed, and I have analyzed it elsewhere. G&M also would never reveal what loudspeakers they used, although I was told off-the-record by an associate of theirs that they were not useful for revealing polarity. Nor would G&M reveal how they switched polarity; I myself do not like any switch in any gear I've heard.

The article looks pretty solid to me, and JAES is a well-respected peer-reviewed journal.  Flipping through it just now I found this tidbit in the bibliography:

"R.C. Johnsen, The Wood Effect (privately published monograph, 1989, 98 pp.).  This monograph uses quotes and paraphrases of anecdotal accounts of the audibility of polarity.  It also gives strong and personal observations of the author about audio reproduction which are highly controversial.  There is no bibliography."

Ouch!

Nice try. But taking it from the dawn of the electrical era, I'm going to counter-assert that over 90% has been simply recorded.

Touche.  Still, I occasionally enjoy listening to music recorded post the invention of the transistor.

 

Ah! Taking refuge I see. Then what, pray, are you doing in Audio Circle? Or for that matter, in audio?

You can't be serious.

 

There are those too, but your experience seems not to have included adequate exposure to Absolute Polarity, else you'd be standing with Dr. Heyser.

I think I'll continue to trust my own experience and experiments, plus the peer-reviewed article I have in front of me.  If you can provide a reference to this Heyser article I'll take a look.

[clarkjohnsen]

Clark, your patience is a credit to you, given the many years you have had to support this seemingly unpopular notion.

I bought your book, The Wood Effect, 15 years ago, a first edition. Have there been other editions since and, if so, were there any significant changes?

First, you are very kind. Yes, it's been a grind. I've never understood the ardent opposition to such an obvious physical principle. Also, their opposition belies such people's loud demands for double-blind tests, because here we've had 'em but they won't believe 'em!

There was a second printing of another 2000, but only a few dozen are left. I once planned a true second edition with all the more recent research included, and even wrote a new intro, but couldn't see putting the time and money into it. Now, with Amazon offering printing services (as it were), I may go ahead.

Or I may not!

For those of you interested, The Wood Effect cites some eighty references to absolute polarity in "the literatrure" of audio and acoustics, 1952 - 1988, and all but one are positive.

[clarkjohnsen]

I think I'll continue to trust my own experience and experiments, plus the peer-reviewed article I have in front of me.  If you can provide a reference to this Heyser article I'll take a look.

Sir, you are both oblivious to reality, and rather rude. You'll find the Heyser reference (and 78 others) in The Wood Effect; $20 + 2, should you care to learn the truth.

[Wayner]

I have to debate the existence of "Absoulte Polarity" as there is no sound that is of a singular frequency. Even middle C which I believe is 440 cycles, is not pure. It has complex harmonic structure (more or less due to musical instrument design/type) and we know that higher frequencies accelerate as compared to their counterpart lesser harmonics.

Therefore, any note struck on any instrument will have multiple arrival times by is harmonic counterparts, which in itself smears the purity of the note and thus the absolute polarity of the note. To Further the degradation of the absolute polarity is the other factor of distance, reflections (and reflective material), temperature and so on. Also, the human element (the ear) cannot react to a higher frequency as easily as a lower frequency because of the pure speed involved. That is why speaker manufacturers can put a tweeter out of phase (to conmpensate for x-over network design) because the frequency is too fast for the ear to benchmark an in or out of phase condition. The ear could more easily detect it at lower frequencies, but not with out the help of another low frequency driver that is out of phase with the first.

[*Scotty*]

Wayner.The speed of sound,it not just a good idea,it's the law. The propagation velocity of a sound wave is independent of it's frequency. See this link for the mathematical formula.
http://hyperphysics.phy-astr.gsu.edu/hbase/wavrel.html#c1
There are also online physics courses for those who are interested.
Scotty

[Wayner]

That is exactly what I'm taking about. the sounds we hear is not a simple wave form. The example scotty gives is from a simplistic world where one analyzes one wave form. The music we listen to is extremely complicated and the explanation of the this is not what we are talking about.

Sorry Scott but this ain't it. The absolute phase is bull shit. Music has an extreme texture and complexity. There is not one absolute phase to it at all. It is a complex language of in and out of phase deliveries that the microphone...or our ears hear. This is what gives the violin string it's texture, or sophistication. It's complex. It's like drinking a fine scotch whiskey that's been aged for years. It has many tastes, all at once.

I've been recording and listening to music for too many years to buy into this notion and there isn't one yet that has presented even one close argument of the physics. I don't care if you have written a book or not. It just isn't so.