I don't think this applies here: as far as I understand, the primary issue with HOMs lies in degrading overall sound quality, not imaging. The ITD and ILD issue concerns mostly localization (imaging).
But I could well imagine that HOMs are most damaging precisely when the many delays of the reflected original signal fall within a range close to the "recharge" window (latency) of sensory and neural cells. This would then either smear the sensory input, or worse, impede the cross-correlation and other perceptual tasks that the neural network performs with the sensory inputs.
In the frequency domain HOMs as a multitude of delayed signals all mixed together, I imagine, would have a constructive / destructive interference effect with the original signal, and that would (akin to comb filtering) be capable of producing sharp FR anomalies (possibly not picked up by our FFTs due to sampling constraints, and the FFT windowing, and averaging).
I could also imagine that reflections a la HOM, if well randomized, could have a much more benign effect than a small number of dominant modes in an unlucky time window. Like with jitter, maybe it's the correlation to the data, and a certain time window, that are responsible for the degrading effects.
Could you elaborate on this a bit more? Sure, HOMs will also degrade imaging in the process, due to the mangled phase/delay relationships but I consider imaging more like a yardstick or proxy as to how well the speaker performs. Per se I don't always care for it much, due to the sometimes odd mastering practices. It just annoys me when the recording places sources in illogical locations (absolute stereo separation in 60's recordings with instruments panned exclusively to one side, or the current practice of having the singer consistently slightly off center).
Also, I was under the impression that almost all imaging on typical close miked records is produced by simple (loudness) panning, i.e. ignoring any phase or physical delay, and that the reverb is then blanketed on top of this (studio recordings) or mixed in from ambience microphones (concert halls).
I admit that I find my system's sound most natural when I am walking around the room, randomly off axis. On axis it is more detailed of course and there is all the depth and imaging etc, but it's just not as natural sounding to me. Although I had good results lately emulating your suggested positioning technique (from the Summa white paper), the axis firing at 45 degrees into the opposing side wall.
MBK said:
If there is not a quality image on the original recording then thats the recordings problem not the speakers.
I use "sound quality" to mean any and all aberations within the reproduction chain which subjectively degrade the reproduction from its original intent. We are talking about A REPRODUCTION, so the playback can be good, bad or whatever the original was - its ALL sound quality.
Differentiation like you suggest leads to detailed discussions using terminology that is usually ill-defined and often subjectively based - certainly not mathematically defined - which I loath to discuss. Discussions, from my point of view, are best when they are precise in language and terminology and are correlated to concepts which can be defined in a scientific manner and proven to be valid with good subjective testing. Deviations from this class of discussion lends itself to arguments and hand waving and never seem to me to lead to anywhere useful.
Yes, Imaging is sound quality normally describing localisation issues of a sound stage.
See page 10-12 at:
http://www.prosoundweb.com/recording/books/focal/ch2/ch2_10.shtml
b
I just downloaded Earl's AES preprint and I must say that it is interesting. It is also a confirmation that I am on the right track by using transient-improved crossover topologies despite their othen shallower slopes with increased IMD.
Regarding imaging:
I was attenting an AES meeting recently where John Watkinson was holding an interesting speech. He "complained" about the fact that there is still no widespread measure for "imaging".
It is indeed quite strange that all measurements on speakers are done in mono and after that they are used in stereo systems (or even multichannel).
Regards
Charles
Regarding imaging:
I was attenting an AES meeting recently where John Watkinson was holding an interesting speech. He "complained" about the fact that there is still no widespread measure for "imaging".
It is indeed quite strange that all measurements on speakers are done in mono and after that they are used in stereo systems (or even multichannel).
Regards
Charles
Well, this all pertains to philosophy of science, really. I am a scientist too (not in acoustics though, rather in biology) and I don't quite understand how my remarks could have come across as subjective or ill defined. I actually intended to give the various aspects of "sound quality" precisely a more specific meaning (better defined, less subjective).
I'm all for non-differentiation of a perception that is whole (sound quality) but for all I know, in your research, you also differentiate between different aspects of a phenomenon, like most scientists do. How else would you find out what is important to "sound quality" and what is not? How would you find out where the aberrations in the reproduction are?
When you say
how do you define this quality, "sound quality", non-subjectively and mathematically? Ultimately, we are left with statistics on subjective testing, which is fine but probabilistic. One can always claim (or even predict with near certainty) that some individuals will perceive differently.
Another pathway is to go by known capabilities of our physiology and how it might perceive things. I speculated about what HOMs might actually do to our sensory system. I don't see anything ill defined or subjective here. All science starts with a "why" question and a speculation for an answer.
Scientific Rigor or Methodolgy
Hello out there,
I'm a new one. What made me curious are the claims around HOM by Mr. Geddes. May be I'm not quite on track but could You help me out, please?
HOM denotes special solutions of the wave equation in horns or alike
- I couldn't find some paper on that topic or didn't want to pay for as much as multiple 20$$ without knowing what I get for
HOM is made responsible of being the most may be only reason for really bad sound of horns when played loud
- Again: no paper on that. To derive this assumption from the observation claimed regarding the perception of THD is a very weak concept.
HOM has never been measured directly, has it?
HOM has never been generated artificially to isolate its effect on aural perception, has it?
In spite of the lack of information on my side, HOM may be coped with using foam somewhere in the throat of a horn. Some people claim to have heard tremendous improvements though.
What I miss really bad is the right order of things as I have learned it in school:
- have an idea
- formulate a theory in that You relate Your idea to something already known
- derive at least one method to prove Your theory as faulty (right this way, try to prove it false to conclude its evidence)
- if not faulty derive technical applications
- be happy (become rich)
This is not to flame anybody. But I didn't get anything yet regarding the evidence of HOM but its mathematical possibility and a very weak if not invalid derivation from THD tests!
It would be a real pleasure to have some sturdy information on the topic.
Thanks a lot
Hello out there,
I'm a new one. What made me curious are the claims around HOM by Mr. Geddes. May be I'm not quite on track but could You help me out, please?
HOM denotes special solutions of the wave equation in horns or alike
- I couldn't find some paper on that topic or didn't want to pay for as much as multiple 20$$ without knowing what I get for
HOM is made responsible of being the most may be only reason for really bad sound of horns when played loud
- Again: no paper on that. To derive this assumption from the observation claimed regarding the perception of THD is a very weak concept.
HOM has never been measured directly, has it?
HOM has never been generated artificially to isolate its effect on aural perception, has it?
In spite of the lack of information on my side, HOM may be coped with using foam somewhere in the throat of a horn. Some people claim to have heard tremendous improvements though.
What I miss really bad is the right order of things as I have learned it in school:
- have an idea
- formulate a theory in that You relate Your idea to something already known
- derive at least one method to prove Your theory as faulty (right this way, try to prove it false to conclude its evidence)
- if not faulty derive technical applications
- be happy (become rich)
This is not to flame anybody. But I didn't get anything yet regarding the evidence of HOM but its mathematical possibility and a very weak if not invalid derivation from THD tests!
It would be a real pleasure to have some sturdy information on the topic.
Thanks a lot
MBK said:
Actually I nevr said that your remarks were subjective or ill-defined, only that I saw this discussion going in that direction and I would just as soon avoid that. Sorry if I was out of line.
Well speculation is not something that I am inclined to do. And I think that the word "hypothesis" is more appropriate. If you can phase something as a hypothesis then you have made a good start. Speculation is easy.
Yes your points are well taken. My point is that if we look at reproduction of the original source as the goal and call it all "sound quality" then differentiation of the different aspects becomes less important. But yes, somewhere along this line you have to scale the effects to find out what to work on and what to ignore. I had always thought distortion in a loudspeakers to be a big issue - it was not true to the original - but after scaling the effect I find that it is insignificant. Its still there, it just doesn't matter to our perception.
Keep the discussion along the lines of scientific quantification with a testable hypothesis, not speculation, and we can talk all day long. But I'm not going to comment on speculation or subjective impressions. Its not a meaningful exercise.
In subjective testing one finds that no one is typical but the group behaves very consistently despite this fact. Individuals are neither typical nor very consistent - which makes talking about someones experiences kind of pointless doesn't it.
Re: Scientific Rigor or Methodolgy
Bordering on a negative tone that I normally would not respond to, you are quite incorrect in your assertions as a review of the AES literature will show. Get your facts straight about the research that has been done and we can talk further. Accusations which clearly show that you have NOT done your background search will not be given any merit.
schuschu said:
Bordering on a negative tone that I normally would not respond to, you are quite incorrect in your assertions as a review of the AES literature will show. Get your facts straight about the research that has been done and we can talk further. Accusations which clearly show that you have NOT done your background search will not be given any merit.
Scientific
Dear Mr. Geddes,
Please don't see me as an inflamatory ignorant. I have a degree in physics besides some further academic merits. I'm just interested to get things right. To not bother You I will keep it brief.
Every AES article has to be paid with 20$$ for non members:
https://secure.aes.org/store/cart.cfm?ItemsToAdd=8:13404
So would You please at least give me some advice which article to read on some topics listed hereafter. Such hasn't been done yet, at least not in this discussion. But it would ease the study a lot!
- Higher Order Modes may be derived form the wave eq. with special boundery conditions. What is the calculus? How to quantify then the HOM given contour, obstacles, irregularities and so on? Can it be distinguished from other flaws of wave propagation in a horn, e/g difraction at the mouth?
- If HOM may be quantified by modelling a special device how is it measured and has it been done yet? Do the results fit the theoretical predictions?
- As it comes to perceptibility has it been proven directly and how with which result?
- Has the benefit of Your invention of a phase plug or the yield of foam somewhere within the waveguide been quantified?
My motivation for my query for the right papers regarding the topic of HOM is this thesis
http://134.130.184.8/opus/frontdoor.php?source_opus=8
Within this paper the author gives very strong evidence to the fact that phase and amplitde disturbances at high frequencies are not perceptable up to a very high degree of contamination as to say. Especially with horns. On the other hand a special device my be identified by some peculiar binaural signature. The latter being an effect of ampl./phase distribution over angle. And that has a big deal to do with listening distance. How did You perform Your tests on percepibility of HOM then?
Thanks a lot
gedlee said:
Dear Mr. Geddes,
Please don't see me as an inflamatory ignorant. I have a degree in physics besides some further academic merits. I'm just interested to get things right. To not bother You I will keep it brief.
Every AES article has to be paid with 20$$ for non members:
https://secure.aes.org/store/cart.cfm?ItemsToAdd=8:13404
So would You please at least give me some advice which article to read on some topics listed hereafter. Such hasn't been done yet, at least not in this discussion. But it would ease the study a lot!
- Higher Order Modes may be derived form the wave eq. with special boundery conditions. What is the calculus? How to quantify then the HOM given contour, obstacles, irregularities and so on? Can it be distinguished from other flaws of wave propagation in a horn, e/g difraction at the mouth?
- If HOM may be quantified by modelling a special device how is it measured and has it been done yet? Do the results fit the theoretical predictions?
- As it comes to perceptibility has it been proven directly and how with which result?
- Has the benefit of Your invention of a phase plug or the yield of foam somewhere within the waveguide been quantified?
My motivation for my query for the right papers regarding the topic of HOM is this thesis
http://134.130.184.8/opus/frontdoor.php?source_opus=8
Within this paper the author gives very strong evidence to the fact that phase and amplitde disturbances at high frequencies are not perceptable up to a very high degree of contamination as to say. Especially with horns. On the other hand a special device my be identified by some peculiar binaural signature. The latter being an effect of ampl./phase distribution over angle. And that has a big deal to do with listening distance. How did You perform Your tests on percepibility of HOM then?
Thanks a lot
Re: Scientific
This was shown in a series of AES paper - some three of them - in the early 90's. They are readily available and have to be read to even begin to understand what you are questioning. My book also contains a discussion. Mouth diffraction is virtually indistinguishable from an HOM in the far field since they are both form of diffaction, just originating from a different place.
A guy in Achan Germany, Gottfried Behler I believe, did show that HOM exist and were measurable, although he concluded that because they were small they were not an issue. However, he never did any subjective work to prove that these small effects were not audible. We discussed and disagreed on this point. His work is avaialble from various sources.
It is difficult to impossible to manipulate the HOM directly. However, it has been proven that minimizing them makes the waveguides subjectively better. In a recent study Lidia and I simulated the HOM's in a large subjective test and found that they were quite audible with an audibility that increased with SPL level. So while this may not be "proof" to your satisfaction, it is clear evidence that my hypothesis is correct, and there is no evidence to the contrary.
The answer is yes, the data is not something that I should share as now we are talking about a proprietary product and not theory. The proof will be available to all in a very short time trough our line of loudspeakers. If I am right, this line will sweep through the industry as the sound quality is markedly better than anything else out there. If I am wrong then you can relish in the vast time and money that wqas spent on a failure. Only time will tell on this one.
From what I could tell the paper is not applicable here.
We did several audiblity tests on compression drivers and waveguides. One was on the audibility of distortion in a compression driver which concluded that nonlinear distortion was not audible at any useful level (below the thermal meltdown point). This was co-authored with B&C loudspeakers and was published in JAES last year. Another was on the audiblity of HOM like effects and was presented at AES last year. It is available as a preprint.
Hence, given
1) nonlinear distortion in a compression driver is not audible (proven) and
2) HOM like effects are audible and increase in audibility with SPL level (proven) and
3) lowering the HOM improves the subjective perception of the waveguide especially at higher SPL levels (demonstrated by myself and numerous people at this site)
the available data strongly supports my contention that HOM are what makes horns sound bad.
Do you refer to your Profs as Mr.? I suspect not, especially in Germany!!
This was shown in a series of AES paper - some three of them - in the early 90's. They are readily available and have to be read to even begin to understand what you are questioning. My book also contains a discussion. Mouth diffraction is virtually indistinguishable from an HOM in the far field since they are both form of diffaction, just originating from a different place.
A guy in Achan Germany, Gottfried Behler I believe, did show that HOM exist and were measurable, although he concluded that because they were small they were not an issue. However, he never did any subjective work to prove that these small effects were not audible. We discussed and disagreed on this point. His work is avaialble from various sources.
It is difficult to impossible to manipulate the HOM directly. However, it has been proven that minimizing them makes the waveguides subjectively better. In a recent study Lidia and I simulated the HOM's in a large subjective test and found that they were quite audible with an audibility that increased with SPL level. So while this may not be "proof" to your satisfaction, it is clear evidence that my hypothesis is correct, and there is no evidence to the contrary.
The answer is yes, the data is not something that I should share as now we are talking about a proprietary product and not theory. The proof will be available to all in a very short time trough our line of loudspeakers. If I am right, this line will sweep through the industry as the sound quality is markedly better than anything else out there. If I am wrong then you can relish in the vast time and money that wqas spent on a failure. Only time will tell on this one.
From what I could tell the paper is not applicable here.
We did several audiblity tests on compression drivers and waveguides. One was on the audibility of distortion in a compression driver which concluded that nonlinear distortion was not audible at any useful level (below the thermal meltdown point). This was co-authored with B&C loudspeakers and was published in JAES last year. Another was on the audiblity of HOM like effects and was presented at AES last year. It is available as a preprint.
Hence, given
1) nonlinear distortion in a compression driver is not audible (proven) and
2) HOM like effects are audible and increase in audibility with SPL level (proven) and
3) lowering the HOM improves the subjective perception of the waveguide especially at higher SPL levels (demonstrated by myself and numerous people at this site)
the available data strongly supports my contention that HOM are what makes horns sound bad.
Do you refer to your Profs as Mr.? I suspect not, especially in Germany!!