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Gedlee, wouldn't perforated horns eliminate HOMs?
Gedlee, wouldn't perforated horns eliminate HOMs?
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Old 1st January 2010, 04:38 PM   #21
sdclc126 is offline sdclc126  United States
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Quote:
Originally Posted by gedlee View Post
True, but not having data to prove that something does exist does not prove that it doesn't either.
While that is also true, it remains scientifically moot - the "burden of proof," as it were, remains with those who theorize that something is actually there.

In any event, perhaps to date HOMs could be described as an audio "dark matter" - there seems to be something making some sort of anomaly, but the cause itself is only known by its effects and is not directly detectable - yet.

Or something like that.
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Old 1st January 2010, 05:48 PM   #22
gedlee is offline gedlee  United States
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Originally Posted by soongsc View Post
wouldn't the holes also generate diffraction waves?
Yes, but if a foam, with a random structure were used, then the diffraction would be incoherent and might not be a problem. Again, its not something that I have tried nor see much value in.
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Old 1st January 2010, 06:11 PM   #23
gedlee is offline gedlee  United States
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Originally Posted by sdclc126 View Post
Perhaps to date HOMs could be described as an audio "dark matter" - there seems to be something making some sort of anomaly, but the cause itself is only known by its effects and is not directly detectable - yet.
I wouldn't agree with that.

HOM have been shown to be permissible wave solutions within a horn - fact. HOM have been measured by Dr. Makarski from Achen and his results were shown at the AES convention in SF several years back. (I am sure that anyone who really cared could easily find this references at Audio Engineering Society (AES)) So that they can and do exist is an established fact.

I have shown how an HOM-like signal modification can be highly audible in certain situations, which also cooborates Brian Moore's, and others. These results too are readily available if one simply looks.

So that HOMs exist in horns and waveguides IS established fact. That under the right conditions they can be audible has also been established. That the "reason" my waveguides sound so good is a direct result of the reduction of HOM is, at the momemnt, a hypothesis that is not yet proven. And quite honestly probably won't be by me. Maybe my speakers sound so good because of some other black magic that I do - whatever. Even if I knew the answer, there is NOT much incentive for me to disclose it. Quite the contrary in fact.

I have no doubt that HOM reduction is a part of the answer just as I am quite certain that other things that I do also contribute. What remains then is not a question of if the effect exists - they do and that is irrefutable -, but subjectively, what is the "degree" of the effect - objectively the effect has been proven. Could its subjective effect be zero? - well yes it could, but all the available evidence suggests otherwise. People certainly have to actually look at the evidence and comprehend it and its clear that the people who are complaining have not.
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Last edited by gedlee; 1st January 2010 at 06:17 PM.
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Old 1st January 2010, 09:28 PM   #24
ZilchLab is offline ZilchLab  United States
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A link to the Makarski paper is posted in this forum.

"Search" might actually find it....
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Old 2nd January 2010, 01:26 AM   #25
soongsc is offline soongsc  Taiwan
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Here is one reference.
Geddes on Waveguides
According to this, HOM excitation seems driver dependent?
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Old 2nd January 2010, 02:21 AM   #26
norman bates is offline norman bates  United States
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all of those compression drivers are in breakup mode for the last 2 octaves.
They do what they can to spread those resonances out so as to make a smooth response, they also can play with the phase plug to flatten out the response (i.e. squash a peak or fill in a null).

I believe mylar is the best diaphram material, as titanium and aluminum tend to have stronger resonances.

I'd drop this whole HOM wording. Reflections or echos in a horn. If it sounds like glare, then it has too much 1-5khz compared to the top 2 octaves.

horn echos will show up on a waterfall plot.
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Old 2nd January 2010, 03:23 AM   #27
gedlee is offline gedlee  United States
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Originally Posted by soongsc View Post
According to this, HOM excitation seems driver dependent?
Of course it is. I've always said that - this fact is discussed in my papers and my book. But the link that you reference is incorrect. The driver establishes the HOM that exist at the start of the waveguide, but the waveguide/horn can alter these as well as create new ones, but both devices most definately contribute. There is a pretty significant discussion of this in one of my patents. Makarski was most interested in the driver aspect and directivity control - he did not consider audibility. Some of the paper was not quite correct which was why it was never printed in the AES Journal and only appears as a preprint (not reviewed). That's why I don't like to quote it. But it did show the existance of HOM beyond any doubt, so its useful in that discussion.

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Originally Posted by norman bates View Post
I'd drop this whole HOM wording.
Since they are Higher Order Modes (HOM) - and that's precisely what they are called in any physics text - I think that the term is quite appropriate.
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Last edited by gedlee; 2nd January 2010 at 03:32 AM.
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