Psychoacoustic effects of front and back reflections?

[Cosmik]

Just one to start with. Heard a Bahrain?

No! Is it an animal..?

Edit: has your computer autocorrected 'Bodhran' to the above word?! If so, I agree you could classify it as dipolar, but aren't we talking about situations in the natural world that human hearing may have evolved to interpret?

 

[Cosmik]

Point source dispersion which is not out of phase in any direction seems more "logical" to me, given that reflections will be more naturally related to the direct sound that way. In theory, I would expect it to work better. Having said that, I've heard several dipole setups that I've really liked, and which didn't sound "unnatural" at all. But it's difficult to assess unless one does A/B comparisons, because our ear/brain seems to adapt to almost anything (nobody would use turntables otherwise).

Yes, what seems to be being said is that you could take a bipolar speaker with wide enclosure (i.e. one with drivers facing front and back) in proximity to a front wall, and switch the polarity of the rear one without hearing any lasting difference - or at least nothing detrimental.

In the steady state frequency domain view of audio where phase is inaudible, the room represents 'chaos' on the laptop screen, so it's just a different chaos. In the heretical transient time domain view of audio, the inverted reflections represent something weird and unusual, possibly a new source of sound competing with the frontwards driver.

 

[RayDunzl]

but aren't we talking about situations in the natural world that human hearing may have evolved to interpret?

How much evolution did we have to undergo to appreciate the kick-drum?

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The phase of the reflection of any specific frequency relative to the phase of the source is dependent upon the distance (in wavelengths) to the wall.

Dipole or bipole will be measurably different, yes. Move the wall or the source a little, and there will be another set of differences.

I think we are already able to handle it without further evolution.

I think they probably "sound the same".

I'm not equipped to prove it in any way, other than some demonstration like comb filtering at the listening position.

 

[RayDunzl]

In the steady state frequency domain view of audio where phase is inaudible, the room represents 'chaos' on the laptop screen, so it's just a different chaos. In the heretical transient time domain view of audio, the inverted reflections represent something weird and unusual, possibly a new source of sound competing with the frontwards driver.

Agree with the chaos, disagree with the weird and unusual.

Changing the distance to the wall would seem to me to be essentially the same as swapping between dipole/bipole.

I'm happily proven wrong, have at it.

 

[Cosmik]

How much evolution did we have to undergo to appreciate the kick-drum?

---

The phase of the reflection of any specific frequency relative to the phase of the source is dependent upon the distance (in wavelengths) to the wall.

Dipole or bipole will be measurably different, yes. Move the wall or the source a little, and there will be another set of differences.

I think we are already able to handle it without further evolution.

I think they probably "sound the same".

I'm not equipped to prove it in any way, other than some demonstration like comb filtering at the listening position.

A very steady state, frequency domain view of audio!

 

[oivavoi]

Agree with the chaos, disagree with the weird and unusual.

I think the question is how dipole radiation would compare to whatever one sees as an optimal radiation pattern. Stereo is inherently unnatural, because the phantom images do not excite reflections in the room, as opposed to what real instruments placed at the same location would do. So the question is how one achieves the best approximation of a natural sound field, given these limitations. Subjective hedonic pleasure can be derived from all kinds of sound reproduction, it seems, even in the cases where it's far removed from any semblance to natural sound.

 

[Blumlein 88]

No! Is it an animal..?

Edit: has your computer autocorrected 'Bodhran' to the above word?! If so, I agree you could classify it as dipolar, but aren't we talking about situations in the natural world that human hearing may have evolved to interpret?

Yes bad autocorrect. Bodhran.

 

[fas42]

I think the question is how dipole radiation would compare to whatever one sees as an optimal radiation pattern. Stereo is inherently unnatural, because the phantom images do not excite reflections in the room, as opposed to what real instruments placed at the same location would do. So the question is how one achieves the best approximation of a natural sound field, given these limitations. Subjective hedonic pleasure can be derived from all kinds of sound reproduction, it seems, even in the cases where it's far removed from any semblance to natural sound.

Again, my experience is that the reflections in the room, or absence of them, matter not one whit - given adequate quality of playback. The sound field which is that of the recording itself, whether massive, or extremely intimate dictates, dominates the subjective sense of "what's going on". Which also includes a convincing projection of "natural sound" - even if the production is highly, or totally 'artificial' - a giveaway is that a vocal line amidst all the "weird stuff" sounds completely right; it could easily be mistaken for a real person behind the speakers.

 

[oivavoi]

Again, my experience is that the reflections in the room, or absence of them, matter not one whit - given adequate quality of playback. The sound field which is that of the recording itself, whether massive, or extremely intimate dictates, dominates the subjective sense of "what's going on". Which also includes a convincing projection of "natural sound" - even if the production is highly, or totally 'artificial' - a giveaway is that a vocal line amidst all the "weird stuff" sounds completely right; it could easily be mistaken for real person behind the speakers.

Come on. Does a horn speaker and an omni sound the same to you?

 

[Blumlein 88]

A very steady state, frequency domain view of audio!

Usually that is okay. It isn't uncommon to tout the time domain, and often with it the evolutionary view. Seems to lead to little additional understanding. Plenty points to our hearing not much caring about time domain above 1500 hz.

Dipoles radiate differently. Usually have less bass response, activate room nodes differently due to the cancellation to the sides, and the response of sidewall reflections is very different as well. All of those confound whether the reverse phase of the reflections would be more important than simply the size of the frequency response differences which are not trivial.

 

[fas42]

Come on. Does a horn speaker and an omni sound the same to you?

They should!! If the systems driving them were fully competent, and the speakers themselves were completely sorted - and you put them both behind a curtain, on a stage in front of you - I wouldn't be sure about passing an ABX on a comparison ...

 

[Cosmik]

Usually that is okay. It isn't uncommon to tout the time domain, and often with it the evolutionary view. Seems to lead to little additional understanding. Plenty points to our hearing not much caring about time domain above 1500 hz.

Dipoles radiate differently. Usually have less bass response, activate room nodes differently due to the cancellation to the sides, and the response of sidewall reflections is very different as well. All of those confound whether the reverse phase of the reflections would be more important than simply the size of the frequency response differences which are not trivial.

Quoting John Watkinson with whom I seem to agree on the subject of traditional speaker manufacturers and their aversion to DSP:

One of the ways in which one knows one has become a cynic is when the realisation dawns that someone who claims something is unnecessary or impossible is doing so simply to avoid having to admit that they don’t know how to do it. Since that realisation, I only accept impossibility when the laws of physics need to be violated.

There is thus a marvellous symmetry whereby manufacturers, who hold to be impossible things that physics does permit, sell products to hi-fi enthusiasts, who hold views that physics does not permit.

All of the evidence suggests it is those who hold time accuracy to be important that are correct. A modern understanding of human hearing suggests that it is theoretically important and the dramatic increase in realism that is obvious to any unbiased listener when the original sound waveform accurately traverses the entire reproduction chain confirms that it is practically important.

 

[Fitzcaraldo215]

Quoting John Watkinson with whom I seem to agree on the subject of traditional speaker manufacturers and their aversion to DSP:

Ok, but DSP is not necessarily antithetical to time domain accuracy. It might even be used to improve it. Or, do I have that wrong?

Also, has Watkinson provided any test data validating his belief?

 

[Blumlein 88]

Quoting John Watkinson with whom I seem to agree on the subject of traditional speaker manufacturers and their aversion to DSP:

John Watkinson also says this writing about ESLs:

Both stators need to be perforated to allow the diaphragm to move and as a result all electrostatic loudspeakers are dipoles. The same sound comes out of the back, only inverted. That is one of the great advantages of the electrostatic speaker over the legacy moving coil speaker and one of the reasons why they have their adherents, because the sound from the back is as accurate as the sound from the front and the ear can recognise it as reverberation after it has bounced around the room. Unlike conventional speakers, electrostatics don’t require heavy acoustic treatment, but they can’t be placed flat against a wall.

The Quad ESL63 sections were time delayed to mimic a point source. The ESL63 could reproduce square waves better than most speakers. Yet a phase reversed sound goes out the back.

BTW, I would prefer for the timing to be done right as rain all the way thru. It simply doesn't seem making that a primary design goal is necessary. Nor does making a speaker accurate in frequency response mean it is wrong in the time domain. Quite the reverse.

Some of it probably comes from recordings that keeps it from being as important. You put up a mike. It responds to several instruments playing. Move the mike two inches the phase relationship between the instruments is now all different. Which one is right? There is no answer to that.

 

[Cosmik]

Ok, but DSP is not necessarily antithetical to time domain accuracy. It might even be used to improve it. Or, do I have that wrong?

Also, has Watkinson provided any test data validating his belief?

JW thinks that passive crossovers cannot maintain an accurate waveform in the time domain and that people are making excuses for the status quo rather than embracing methods to improve accuracy.

Re. test data, I rather think it should be the other way round! JW is advocating fidelity to the signal using readily-available methods. Anyone who says that the time domain doesn't matter should be prepared to justify why they are not being faithful to the signal

 

[Cosmik]

John Watkinson also says this writing about ESLs:

Both stators need to be perforated to allow the diaphragm to move and as a result all electrostatic loudspeakers are dipoles. The same sound comes out of the back, only inverted. That is one of the great advantages of the electrostatic speaker over the legacy moving coil speaker and one of the reasons why they have their adherents, because the sound from the back is as accurate as the sound from the front and the ear can recognise it as reverberation after it has bounced around the room. Unlike conventional speakers, electrostatics don’t require heavy acoustic treatment, but they can’t be placed flat against a wall.

The Quad ESL63 sections were time delayed to mimic a point source. The ESL63 could reproduce square waves better than most speakers. Yet a phase reversed sound goes out the back.

Well I disagree with him on that then! It seems to me he is contradicting another article he wrote - I'll try to find it...

Edit: Here he says

One of the few transducers that exhibits a good step response – and consequent realistic reproduction of percussion – is the electrostatic loudspeaker. Unfortunately, for good performance, these must be large and sited well away from walls

so I think he is acknowledging the flaw.

He also talks about ported speakers that emit a delayed, inverted version of the front wave (not much different in principle from an inverted reflection).

...the output is increased and the low frequency response is extended, this is achieved at the expense of wrecking the speaker’s time response...

...It is only in the case of a sine wave that a delay is indistinguishable from an inversion and we know a sine wave carries no information. In the case of a transient, the transmission line speaker destroys the waveform. The baby is thrown out and the bathwater is retained.

The only woofer design that is capable of being made time-accurate is the sealed enclosure.

 

[Blumlein 88]

https://www.thebroadcastbridge.com/...logy-part-2-the-time-domain-and-human-hearing

Above is where he writes about the time domain.

Here is an excellent example of why I dislike invoking too much of the evolutionary explanation of what is important in hearing.

What would be the most important information that a hearing mechanism could tell an early living being? Pretty obviously the location of a source of sound must be at the top of the list, closely followed by the size of the sound source. Is this sound a threat or does it reveal our next meal? In the absence of speech or music, the concept of establishing pitch was of limited importance; indeed the frequency domain was of little importance and means to deal with it evolved later.

Really? I agree direction was a big deal in hearing. But frequency is of no importance? Dealing with it evolved later? Come on. How about for humans big animals are associated with more low frequencies than little animals? Big animals might be of more interest to early human hunters. Everywhere humans went large animals were hunted out of existence first. And despite what his article claims for directional hearing of steady state sounds you do indeed hear a direction very well with below 1500 hz and especially below 800 hz signals even a steady sine wave.

 

[fas42]

Some of it probably comes from recordings that keeps it from being as important. You put up a mike. It responds to several instruments playing. Move the mike two inches the phase relationship between the instruments is now all different. Which one is right? There is no answer to that.

The answer is that the ear/brain knows how to handle this, from a lifetime of "learning" - all the complexities are dealt with completely automatically, unconsciously. Which means one doesn't have to be fussed with getting this right in a system ... assuming competency .

 

[Cosmik]

https://www.thebroadcastbridge.com/...logy-part-2-the-time-domain-and-human-hearing

Above is where he writes about the time domain.

Here is an excellent example of why I dislike invoking too much of the evolutionary explanation of what is important in hearing.

What would be the most important information that a hearing mechanism could tell an early living being? Pretty obviously the location of a source of sound must be at the top of the list, closely followed by the size of the sound source. Is this sound a threat or does it reveal our next meal? In the absence of speech or music, the concept of establishing pitch was of limited importance; indeed the frequency domain was of little importance and means to deal with it evolved later.

Really? I agree direction was a big deal in hearing. But frequency is of no importance? Dealing with it evolved later? Come on. How about for humans big animals are associated with more low frequencies than little animals? Big animals might be of more interest to early human hunters. Everywhere humans went large animals were hunted out of existence first. And despite what his article claims for directional hearing of steady state sounds you do indeed hear a direction very well with below 1500 hz and especially below 800 hz signals even a steady sine wave.

I think he is not so much concerned with 'pitch' as with 'time constant' and amplitude being used to determine the size of the threat.

 

[Fitzcaraldo215]

Whatever. Is there a particular subject this thread was about?