Ohm's acoustic law and stuff

[merlin]

Taken to the exteme, does this mean you can place a subwoofer anywhere you want and not adjust the time delay?

I must admit to hearing definate changes when time aligning subs in the past. So I am at a loss to explain why this should be the case.

 

[michaelab]

oedipus - are you saying that this Ohm's (acoustic) law totally encapsulates everthing about the way we hear in one simple statement? Or is he just covering one aspect of the way the human ear works? I was under the impression that the human ear and the way we perceive sound is an extraordinarly complex and non-linear process which even now we're only just starting to understand.

In any case, it can't be a "law" unless it has a proof which it presumably doesn't so it must be, at best, a "hypothesis".

Michael.

 

[MarkS]

Let me quote what I wrote a few pages back: "there's Ohm's (acoustic) law, which which states only the power spectrum and not the relative phases of the components determines a sounds perceived character."

I'm a little puzzled here...which Ohm are we talking about?

Can you please shed some light on this...

Many thanks.

Mark

 

[oedipus]

Taken to the exteme, does this mean you can place a subwoofer anywhere you want and not adjust the time delay?

I must admit to hearing definate changes when time aligning subs in the past. So I am at a loss to explain why this should be the case.

I think you can answer this question by yourself - with a little help So, from what you've told us so far about your experiment I know the frequency response and output of the main and subwoofer overlapped.

 

[oedipus]

oedipus - are you saying that this Ohm's (acoustic) law totally encapsulates everthing about the way we hear in one simple statement?

No, it says nothing about how we do spatial localaization (the discussion MartinC and I wandered off into).

What it does encapsulate in "one simple statement" is that our ear does not process relative phases of multiple frequencies.

I was under the impression that the human ear and the way we perceive sound is an extraordinarly complex and non-linear process which even now we're only just starting to understand.

A substantial amount of psycho-acoustics has been know for well over a hundred years. There was considerable experimentation in the 1930's too. Which work are you refering to?

In any case, it can't be a "law" unless it has a proof which it presumably doesn't so it must be, at best, a "hypothesis".

The fact is commonly known as "Ohm's acoustic law" and after 160 years of research to prove it wrong, there is a preponderance of evidence for it.

I hope this isn't the usual gambit of "the science is incomplete therefore I must be able to hear spurs/nordost/mana etc they just haven't discovered how yet"

 

[wadia-miester]

Same old Andy we know and love

 

[michaelab]

A substantial amount of psycho-acoustics has been know for well over a hundred years. There was considerable experimentation in the 1930's too. Which work are you refering to?

I'm not referring to any work, it was just my understanding that a great deal of psycho-acoustics was still relatively uncharted waters. I may have been mistaken.

I hope this isn't the usual gambit of "the science is incomplete therefore I must be able to hear spurs/nordost/mana etc they just haven't discovered how yet"

Come on oedipus, you know I'm on your side on this one . I was being pedantic, I thought that for something to be a "law" it had to have a proof. Otherwise it was a theorem or hypothesis. Take Fermat's last theorem for example, which remained unproven for over 350 years. No one had ever found a value for n which broke the theorem and so it was highly likely that it was true but the final proof was only worked out in the mid 90s.

Michael.

 

[merlin]

I think you can answer this question by yourself - with a little help So, from what you've told us so far about your experiment I know the frequency response and output of the main and subwoofer overlapped.

Any two drive units will overlap surely given traditional crossover design?

 

[oedipus]

I'm not referring to any work, it was just my understanding that a great deal of psycho-acoustics was still relatively uncharted waters. I may have been mistaken.


Come on oedipus, you know I'm on your side on this one . I was being pedantic, I thought that for something to be a "law" it had to have a proof.

Well, then, let me put it this way, psycho-acoustics is sufficiently well developed that there has been no audiophile "experience" that has resulted in the conclusion that those rules/laws/theorems are wrong or need to be finessed.

Similarly, it has not been necessary to update the "rules" of physics/electrical engineering to design "audiophile grade" electronics..

You know audiophile's have a habit of demanding proof about what they can't hear, while simultaneously failing to provide proof of what they can (or at least claim to) hear. I was hoping you'd know better than to use the word proof and potentially open the evidence vs. proof debate

 

[PeteH]

Any two drive units will overlap surely given traditional crossover design?

So if I understand this right, all you have to worry about is getting the overall amplitude correct, regardless of any phase changes which may be occurring - for example, where the drive units overlap it wouldn't matter whether you achieve a given amplitude through constructive or destructive interference.

 

[oedipus]

So if I understand this right, all you have to worry about is getting the overall amplitude correct, regardless of any phase changes which may be occurring - for example, where the drive units overlap it wouldn't matter whether you achieve a given amplitude through constructive or destructive interference.

A gold star for you Pete.

Now, let's think about what Pete's said. Imagine yourself at the listening position while a helper is moving the sub around: What changes are you hearing when the sub moves? Why? [Make this problem easier by assuming you're in a very large anechoic chamber.]

Bonus Question: In a real room, does the subwoofers perceived amplitude response change as it is moved?

 

[MarkS]

There are two issues when it comes to phase:

firstly, eletronic components are minimum phase devices which means that the frequency response tells all. [The phase response can be calculated from the frequency response using the hilbert transform..]

Secondly, there's Ohm's law, not V=IR, the other one, which which states only the power spectrum and not the relative phases of the components determines a sounds perceived character. After 160 years of reasearch, there are only a handful of test signals (not real music) which when heard in an anechoic chamber (not a real room), where is it possible to hear phase.

If it wasn't for this second law, a large number of loudspeakers simply would not exist, because they would not work, as only the first order Butterworth crossover filter is minimum phase...

Various electronic components have varying effects on phase shifts on ac signals passing through them. Resistors 0deg, capacitors & inductors +/- 90deg etc etc...

Ordinarily a function is specified entirely in the time domain or entirely in the frequency domain. The Fourier transform then specifies the function in the other domain. The Hilbert transform arises when half the information is in the time domain and the other half is in the frequency domain...

Ohm's Law, the relationship between current, voltage, and resistance, published in his 1827 paper, The Galvanic Circuit Investigated Mathematically, merely shows that the amount of electric current through a metal conductor in a circuit is directly proportional to the voltage across it, for any given temperature - commonly expressed as V=IR.

James Joule first discovered the mathematical relationship between power dissipation and current through a resistance. This discovery, published in 1841, commonly expressed as P = I^2R, is properly known as Joule's Law.

Ernst Siemens was the first to describe the dynamic or moving-coil transducer, with a circular coil of wire in a magnetic field and supported so that it could move axially(filed in a patent application in 1874).

Nowhere do Ohm, Joule or Siemens talk about "power spectrums", "relative phases" or "sounds perceived character".

There is no such thing as Ohms Accoustic Law. This is complete nonsense.

You have taken snippets of information, gleaned from various text books, mixed in some late 20th century buzz words, to form "authoratitive" statements without really knowing what you are talking about. This fits the 3B's law - Bullshit Baffles the Brain.

Mark

 

[stickman]

:duck:

 

[wolfgang]

There is no such thing as Ohms Accoustic Law. This is complete nonsense.

These are taken from this link
http://www.unc.edu/~rowlett/units/index.html
Look under A and then O for the 2 difference of the 2 terms.

acoustic ohm
any one of several units measuring sound resistance. These units got their name by analogy with electric resistance, which is measured in ohms. The sound resistance across a surface in a given medium is defined to be the pressure of the sound wave at the surface divided by the particle velocity, that is, the velocity at which the medium is pushed perpendicular to the surface. Unfortunately, the result is often stated in "acoustic ohms" no matter what units are used to measure pressure and time. In the CGS system, the acoustic ohm equals 1 microbar second per centimeter (µbar·s/cm), which is the same as 1 dyn·s/cm3. In the MKS system, the acoustic ohm is equal to the SI unit, 1 newton second per cubic meter (N·s/m3) or 1 pascal second per meter (Pa·s/m). The CGS acoustic ohm equals 105 MKS acoustic ohms. See also rayl.

ohm [1]
the SI unit of electric resistance. If a conductor connects two locations having different electric potentials, then a current flows through the conductor. The amount of the current depends on the potential difference and also on the extent to which the conductor resists the flow of current. This property of a circuit, the electric resistance, is measured in ohms. One ohm is the resistance that requires a potential difference of one volt per ampere of current. This is a small resistance; in practical circuits resistance is often measured in megohms, millions of ohms. The unit honors the German physicist Georg Simon Ohm (1787-1854). The capital Greek letter omega is used as the symbol for the ohm, since "O" would be easily misinterpreted as a zero.

 

[merlin]

These are taken from this link
acoustic ohm
any one of several units measuring sound resistance. These units got their name by analogy with electric resistance, which is measured in ohms. The sound resistance across a surface in a given medium is defined to be the pressure of the sound wave at the surface divided by the particle velocity, that is, the velocity at which the medium is pushed perpendicular to the surface.

Wolfy, being of somewat limited scientific prowess( ), doesn't that description seem to refer to frequency and amplitude only. Where is the mention of phase?

So if I understand this right, all you have to worry about is getting the overall amplitude correct, regardless of any phase changes which may be occurring - for example, where the drive units overlap it wouldn't matter whether you achieve a given amplitude through constructive or destructive interference.

Pete, not my subjective experience. Using Tact and employing 10th order crossovers, the effect of altering the time delay to the satellites in relation to the sub was quite noticable as I mentioned before in this forum. Now it seems I need an explanation (and it's in your head won't cut it!)[/QUOTE]

 

[wadia-miester]

Datty,
Now you still aint answered my question Andy, instead of quoting the usual read the reference material text book reply, I was hoping you could give a ZG version of the seperate phase charactoristics of linear and minimum, when appiled to this particular application, the theroy used to calculate said/any phase variants present in relation to the drivers arrays/Possible x/over realtionships/dispersal patterns of drivers.
Go on indulge us

 

[wolfgang]

I must admit I have to look up what is this law that Oedipus is talking about. Thinking back my old days in school acoustics are not really well covered in physics and mechanical maths. I was hoping the link at least could move the discussion forward that this is not a complete nonsense and hoping these discussion could carry on and I might just learn a bit more then the usual 'Mana is best' type discussion.

 

[wadia-miester]

Wolfy, being of somewat limited scientific prowess( ), doesn't that description seem to refer to frequency and amplitude only. Where is the mention of phase?

Mike,

I do believe Datty has stated that we cannot detect phase shifts we the ease that we can determine amplitude changes.
"If it wasn't for this second law, a large number of loudspeakers simply would not exist, because they would not work, as only the first order Butterworth crossover filter is minimum phase..."
"In a minimum phase system, if you have a flat frequency reponse, there won't be any time anomalies..."
So it seems that phase may not be an issue here
Though, if one were more convential possibly

"On the other hand, if I were dealing with a non-minimum phase system (and loudspeakers with multiple drivers fall into this category), I would aim for a flatter frequency response at the expense of the group delay rather than vice versa. This is because the ear is sensitive to ampitude response, but not phase relationships, so it makes sense to optimize for frequency response."
I do believe we had this very conversation with Markus and Thorsen a few weeks back?
Phasing

 

[michaelab]

There is no such thing as Ohms Accoustic Law. This is complete nonsense.

Err...no it's not. Take a look at this article. Seems to be relevant to this discussion and the guy also mentions Ohm's acoustic law and in fact has data to confirm its validity.

If you Google for "Ohm's Acoustic Law" you'll find many references to it.

Next time Mark I suggest that you read up a little on both the subject matter and the posts of the relevant forum member before launching a rather silly attack which is just going to end up making you look like a fool.

Michael.

 

[michaelab]

In addition you might like to read AES Preprint No. 3184 from the September 1991 AES convention which has a paper by Michael A. Gerzon the title of which is "The Use of Ohm's Acoustical Law in the Design of Nonlinear Audio Signal Processors and Analyzers" and the abstract of which reads:

Ohm's acoustical law that the ears are insensitive to phase is used to formulate the concept of an Ohm-covariant processor, i.e. one in which audibly indistinguishable inputs yield audibly indistinguishable outputs. A theory of harmonic and subharmonic Ohm-Covariant nonlinear systems is given based on covariance under the action of the phase-shift and time-translation group. A number of theorems about such systems, both nonhysteretic and hysteretic, are obtained which lead to practical design procedures for audio signal processors and analysers. The use of these results is illustrated by examples including speech clippers, pitch multiplieers, spectral analysers, bandwidth compression systems and frequency shifters.

Michael.