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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, 12:25 AM   #11
gedlee is offline gedlee  United States
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Quote:
Originally Posted by NV&H View Post
From what I've read, one of the major objectives of your work is to eliminate HOMs while controlling dispersion to limit early reflections.

Years ago I worked in a power station. Very, very loud environment. Telephones in the loud environments were all mounted in partially enclosed V-shaped housings lined with perforated metal behind which was sound absorption material. Open ended as they were, it was amazing how quiet it was in those things, in spite of the 130+db environment.

Similarly, waves bouncing around at tall angles inside a horn would get quickly absorbed, while the waves moving along the hard but perforated horn surface would not be so quickly absorbed, it seems to me. You may wind up with fewer dBs at the mouth, but whatever sound that made it that far would be HOM-free. And I don't see why the horn's dispersion angle would be affected either. Finding the optimum size and distribution of the sound absorbing perforations would need to be engineered, of course. I can easily see why the Altecs and JBLs not trying this back in the day, since they were interested primarily in getting maximum sound pressure, with HOM colorations being of little concern.

But since the objective of your work has been to fight inside-the-horn HOMs and early room reflections, I thought perhaps you considered this approach.

Thoughts?
I've dabled with the idea and there is a Japanese patent on this precise concept (its referenced in my patent). It seems workable albeit somewhat difficult to envision how to do it in practice.
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Old 1st January 2010, 12:57 AM   #12
TrueSound is offline TrueSound  United States
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Originally Posted by gedlee View Post
That my speakers sound better than "normal" horns is indisputable (see the reviews), there are a lot of things that I do to improve things. Do we know that5 HOMs are the whole story - no we don't and I have always said that. But HOM are not some "made up" concept they can be shown to exist theoretically and they can be measured on compression drivers, but to your point, no I have not actually taken the time to try and trace down an HOM from any other waveguide aberation. That in no way makes any of your statements correct however because "did not" which is true, is quite different than "could not" which is not true since that implies a trie and failed, which never happened.

So the misinformation here is clear - ignoring the vast amount of data that "something" makes my speakers sound better than everything else, and instead focusing - incorrectly - on a small aspect of their not having been measured directly. Your later point is irrelavent while the first point is the key.

There is, by the way, absolutely no evidence that HOMs do not exist and are not a problem. Makarski did in fact measure them for your information, but he concluded that they were a small effect, and they are, but then so id THD. The size of the effect and its perception are entirely different things.

Get your story straight next time.


Your reviews are not valid. There are no controls what-so-ever where your speakers are compared to any horn loudspeakers what-so-ever. If you have any real evidence to your claim the speakers you sell sound better than "normal horns" then please post the URL. When you can present to the community a valid double blind peer review comparing your loudspeaker to a horn loudspeaker that statistically proves they "sound better" then you have the right to make such claims. For example the Edgar Titan, the CAR T-1, even a Klipshorn. Until then you are just using the reviews as advertising and it proves nothing to your claim.

Please post the URL for the Markasi measurement methodology and test for HOM since you have never measured your invention and never proved the audibility of it. As you know "no claim they do not exist" is a laugh - you cannot prove a negative.
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Old 1st January 2010, 01:02 AM   #13
sdclc126 is offline sdclc126  United States
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Quote:
Originally Posted by gedlee View Post
...There is, by the way, absolutely no evidence that HOMs do not exist and are not a problem...
Proving something deosn't exist is neither possible nor necessary, nor relevant.
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Old 1st January 2010, 02:55 AM   #14
sneakmasterg is offline sneakmasterg  United States
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Quote:
Originally Posted by NV&H View Post
Years ago I worked in a power station. Very, very loud environment. Telephones in the loud environments were all mounted in partially enclosed V-shaped housings lined with perforated metal behind which was sound absorption material. Open ended as they were, it was amazing how quiet it was in those things, in spite of the 130+db environment.
We have some of these at my work. I pulled a patent number off it:

DOORLESS TELEPHONE BOOTH - Google Patent Search
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Old 1st January 2010, 03:12 AM   #15
thoriated is offline thoriated  United States
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'Truesound' is taking a completely objectivist position regarding Dr. Geddes' horn designs. To fully maintain scientific credence, Dr. Geddes ideally should be able to provide objective measurements demonstrating the specific advantages of his horn flare that he claims for it.

I'm more subjectivist than most (but not to the exclusion of objectivity), and I tend to agree (not even having listened to date to his designs) with what Dr. Geddes claims, but providing some real world validation rigor is probably a good idea in validating his claims as witness the global warming alarmist hoax as perpetrated by the UEA CRU, NASA's Dr. Hansen and Penn State's Dr. Mann.

Last edited by thoriated; 1st January 2010 at 03:17 AM.
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Old 1st January 2010, 05:55 AM   #16
gedlee is offline gedlee  United States
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Originally Posted by thoriated View Post
'Truesound' is taking a completely objectivist position regarding Dr. Geddes' horn designs. To fully maintain scientific credence, Dr. Geddes ideally should be able to provide objective measurements demonstrating the specific advantages of his horn flare that he claims for it.

I'm more subjectivist than most (but not to the exclusion of objectivity), and I tend to agree (not even having listened to date to his designs) with what Dr. Geddes claims, but providing some real world validation rigor is probably a good idea in validating his claims as witness the global warming alarmist hoax as perpetrated by the UEA CRU, NASA's Dr. Hansen and Penn State's Dr. Mann.
To Truesound: if you eliminate subjective perceptions as "data" then no other loudspeakers provides any "data". Your position is simply ** and I am not going to respond to it any further.

Thoriated: I concur completely, but there is reality to face. In a world where few loudspeakers are ever shown with sufficient objective data, what I provide is light-years ahead of the norm. That I do not have valid scientific data on HOMs is indeed unfortunate, but at least I provide some data. I would love to have more data, but none exists. To have such data would truely be "a good idea", but to provide nothing, as is the norm in this business, is surely "a bad idea".

Let's put things in perspective here. I provide more valid data than virtually any other loudspeaker designer that I know. That I don't have data to the infititesimal degree that anyone could ask for is certainly not a failing, but more a practical limitation. I am not trying to hide anything. Indeed, that is what the other manufacturers are so good at.
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Old 1st January 2010, 05:57 AM   #17
gedlee is offline gedlee  United States
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Originally Posted by sdclc126 View Post
Proving something deosn't exist is neither possible nor necessary, nor relevant.
True, but not having data to prove that something does exist does not prove that it doesn't either.
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Old 1st January 2010, 09:48 AM   #18
norman bates is offline norman bates  United States
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actually looking at the off axis response of those geddes' horns, the response where you sit, or 10' away from the speaker, you will have less highs...........

What you hear at the listening spot usually closely resembles the off axis response of a loudspeaker.

If I was crossing to a 15", especially near 1khz, I'd want a 1.4" throat compression driver, especially if it is not 24db slope. There are some beyma 1.4" drivers (mylar I think) that are only 4-5db down at 20khz, easy to passively eq the highs back in. Then again, due to the less off axis, I'd assume the geddes OS horn does pinch a bit above 6-8khz, so that would be free boosting there without any components needed.

I'd go for a wider dispersion horn, assuming you can keep it reflection (echo) free.

Here is a winning combination, the mylar beyma 1.4" drivers, the 18sound xt1464 horn, and a 15" or 2. Crossed at 1khz steep, and time aligned.

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Old 1st January 2010, 02:45 PM   #19
soongsc is offline soongsc  Taiwan
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Originally Posted by gedlee View Post
I've dabled with the idea and there is a Japanese patent on this precise concept (its referenced in my patent). It seems workable albeit somewhat difficult to envision how to do it in practice.
wouldn't the holes also generate diffraction waves?
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Old 1st January 2010, 02:49 PM   #20
TrueSound is offline TrueSound  United States
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Sorry - Did not mean to thread jack

Sound Absorption Of Perforated Metal
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