But he didn't say that to you, did he?
This what he wrote to you, quoting your assertion:
Just because you want somebody to have said something does not mean they said it.
Hello,
Exclusive or not does not matter. Lets say in a given horn there is a given higher order mode propagating. After it exits from the mouth and reaches the ear it's contribution to the sound should sound the same regardless how is that mode generated in the first place because that given mode has it's specific characteristics it is obeying. If the characteristics of the mode should change due to the generation mechanism, then it would not be the same mode.
- Elias
Exclusive or not does not matter. Lets say in a given horn there is a given higher order mode propagating. After it exits from the mouth and reaches the ear it's contribution to the sound should sound the same regardless how is that mode generated in the first place because that given mode has it's specific characteristics it is obeying. If the characteristics of the mode should change due to the generation mechanism, then it would not be the same mode.
- Elias
Sheldon said:
ZilchLab said:
If I define HOM objectively everyone says - "well sure, but what do they sound like? Can you actually hear them?". Then when I describe the subjective results, I get "an inordinate reliance upon subjective opinion " and "subjective results don;t mean anything to me". This is obviuosly not an argument that is being viewed objectively and so there isn't much point in having it any longer.
ZilchLab said:
Yes, well, trampling about in this room is a whole herd of elephants each one belonging to a different person.
FrankWW said:
C'mon why all the playing around with subjective semantics just to defend Geddes?? he does not need defending.
Geddes posted "there is a whole list of people who have reported their impressions of low HOM speakers on my web site."
Have you read the reviews?....please post where they describe the HOMs.
It all summarized up into "Geddes speakers sound great".....It does not concluding anything about HOMs.
Besides does it really matter what I conclude the subjective reviews mean.
If it makes you feel better, Then sure.... you are right and Im wrong. I hope you feel better now 😉
gedlee said:
Thats fair, Im just trying to get down to figuring out what sound HOM produces and not if speakers without HOMs sound great since that is a given with all reviews of your speakers.
This is less about your speakers and more about other DIY options actually so when Im testing other options I want to know if HOM problems are audible.
doug20 said:
If it's just a matter of making good sounding speakers with horns or waveguides, then why not just follow Dr. Geddes prescriptions? He has spent a lifetime studying the problem of making good sounding waveguides, both from a theoretical and practical standpoint. If he hasn't found a good way yet to display HOM, then are you going to wait for that before you start building? Make an OS profile or something with a smooth gradual throat transition, a rounded mouth, and rounded cabinet edges. Try some of the foam in the guide. And listen to music.
I'm really amazed that so many are so eager to challenge work of this depth, with no real evidence to back up contra assertions.
Sheldon
Sheldon said:
Because it is inordinately, perhaps unduly, expensive, and has its own set of issues.
Further, based upon presently available evidence, the "all or nothing" posture of its prime proponent is unwarranted.
His principal teachings have been investigated and incorporated by others to varying degrees, such that he himself now acknowledges performance excellence as a continuum....
ZilchLab said:
HOM is well defined(!) since decades. Websters assumption in what fashion a wave would travel through a waveguide was that it remains a plane wave. Exponential horns were derived from that as being optimum. Every deviation from a plain wave was Higher Order Mode by definition! And as that it was considered as being out of scope of a basic theory of that times. Then tractrix came up. The same with that. Basic mode is a spherical wave. Any deviation is by definition Higher Order Mode and out of scope.
The oblate spheroid waveguide is an exact solution of the problem of wave propagation in a horn. The waves shape is perfectly controlled HOM-less until it leaves the horn, as long as the initial wave is really(!) plane. When the wave leaves the horn the waves shape is arbitrary. The termination of the horn is not foreseen in theory! The horn has to be infinite or the horn will generate HOM.
The OS waveguide will generate HOM. From what else should a wave confined within a horn propagate as such out of the horn in the same way?! Interferences with short time reflections at discontinuities constitute the directivity. The OS is not special in that regard.
Standard diffraction slot waveguides with CD characteristics try to equalize the inner diffractions at the slot with outer diffractions at the rim. HOMs are eaten by HOMs as to say. The result is a reasonably flat frequency response with only a low phase gardient along different directions. Most recent designs (1990) try to lower the harmonic distortion by reducing wave steepening and to smooth out the impulse resonse even further. Ripples in frequncy response lower than +/-1dB are common with top notch vendors as JBL. That is comparable to the most sophisticated dome tweeter designs in consumer home applications.
HOM is well known and well understood. It is any deviation from what has been defined(!) as being the basic wave propagation mode within a waveguide. Any practical horn will have it's arbritary termination, as it can't be of infinite length. So even with OS waveguides a lot has to be left to experimental trial and error methodology. The question for HOM is insubstantial in that. As HOM exists by pure definition within (!!) the horn. What counts is what comes out to the ears outside (!!) the horn. That is measurable by amplitude over frequency and angle, and phase. That is what the ear can hear, nothing else.
regards
wxa666 said:
In which light, would it be reasonable to suggest that such a refined diffraction waveguide with ripples in its frequency response reduced to +/- 1 dB or lower, and thus comparable to said most sophisticated dome tweeter designs in consumer home applications, would be equivalently "HOM-free," as well, in terms of its perceived sonic quality, i.e., clearly head and shoulders better than most diffraction horns?
ZilchLab said:
o/k
ZilchLab said:
Why do You come back to that? To be "HOM-free" is nothing that qualifies the perceived sound with binaural hearing. HOM is a technical term to integrate all what can not be considered by theory in the first step. More than that it is a mathematical term.
Again, HOM is generated by every horn, OS included. At least because even an OS has to be terminated somewhere. It has to have a mouth that inevitely will lead to interferences of the axial part of the wave with reflections from the discontinuity. By what magic should a wave constrained to a 90° solid angle within a horn propagate in the same fashion outside of it? The original proponent of OS waveguides E. Geddes published a second paper on the topic of finite horns, as far as I remember. The first was on the OS contour itself. Alas, the second hasn't gained to much public attention*.
Horn design is about multiple interferences, that at best could be well balanced, even with OS. A bit like the multiple subwoofer idea: If You can't avoid an issue (diffraction aka HOM, room interaction) try to scatter it down below the level of perceptibility. From that perspective nowadays many horns/waveguides are available for litte cost and effort that should meet Your requirements. It's Your choice, and don't forget about the driver and it's phase plug ...
buy
* E R Geddes, "Acoustic Waveguide Theory Revisited," AES Journal, Vol.41, No.6, (1993 June)
Sheldon said:
First, no one is challenging his work (Theories, principles), I have not read one posts that disagrees with his work. Actually we are all here at this point BECAUSE of his work. We are allowed to ask questions are we not? Even dumb ones can be asked? I will asked the dumbest questions just because that is the way ALL information is put out there for others to learn from. Its the only way that ALL levels of skill can understand the complete concept. I will challenge any subjective listening opinion because we all know the numerous variables involved with listening that will cause extreme bias if the listening test is not controlled properly (Atleast I hope we all know).
Secondly, I thought this was a DIY forum meaning we should be discussing cheap alternatives....we build speakers for a fraction of the comercial costs. This is not Geddes forum where at the end of the day its about his speakers. We should keep the two separate, his theories and experience is what this should be all about and this should have nothing to do with his actually speakers.
Thirdly, I believe we can do it cheaper and I hope companies will findout a way to do it cheaper.....Geddes knows the foam is the key (hence the patent) so he has no reason to worry about anything.
Fourth, have you seen the waveguides built by Geddes? Im sorry but for that much money they should be professionally done. the molding, the cuts and routing on the baffle isn't professional at all. Sure its all about sound to Geddes but some of us desire good looks too. I do not want to pay that much for something that looks like it was made for the first time in someone's garage no matter if its the best sound in the world. Im sorry but that is just me.
Its funny how people protect him but allow him to consistently talk down, partonize and post extremely condescending remarks at others who do not exactly agree with him, I guess he gets a free pass because he is after all Dr. Geddes (Sigh 🙁 ). Anywhere he posts and someone has a different opinion even a subjective one, he is quick to post something rude and he talks down to everyone.
Now can we get back to just talking about HOMs and less back and forth "Geddes is......" stuff?
Sorry but that is false....post HOM over on any forum and ask how many know about it or understand it. I doubt most can even post want HOM means.
You may understand it and it may have been defined for a long time but its UNKNOWN in the overall world of audio. Call up a JBL engineer, how about a QSC engineer (I know one)?
doug20 said:
Hi,
Sorry but that is false... . 😉 The term HOM propagates itself due to the flap people get in when uppermost superiority in sound quality is promised. But the basic concept is as old as our western culture. If one can not solve a problem as a whole try to analyse it. Solve the main part and leave the rest to those that buy Your patents.
With horn theory You find Websters plain wave in expohorns or the sphere that constitutes the tractrix contour. Both are meant as approximations. The part that doesn't behave like plain or spharical is - by definition - "HOM". Of course the inventors of plain or spharical wave solutions were aware of the limitations of their concepts. They simply didn't talk that much about it. It was to obvious that "higher order modes" for instance alterate the directivity pattern compared to the - basic - theoretical predictions.
I would answer the question that is the topic of this thread evasively. HOM can not be measured because HOM is by the most of it a matter of arbitrary definitions. What is considered as the basic mode and what is following to that the "higher order"? The best approximation to measuring HOM is to scan the sound pressure distribution, phase included on (a) a plain or (b) a sphere area in some distance to the horns mouth. Or, if You've funny bones You measure on a surface that is an analogon to Ms. Spears trizeps. Nevertheless when finished You may define Your basic mode and all the rest will be HOM in the same moment.
regards
wxa666 said:
I think we are discussing to different things, Im stating that HOM is not well know out there in the general audio community.
HOM may have been around but only in Geddes circle since and from all the discussion across all DIY forums its aparent that there is not a common understanding of it.
You can not say "HOM is well known and well understood" and have been reading all the forums lately......
Well known by who, understood by who??
Few skilled DIYers I know knew about it at all....let along speaker builders. Maybe it isnt that imporant to them though.
Doug20,
No one has ever said thatf questions can not be asked. It is the way in which most are asking the questions that are making me shake my head. The listing of all these threads directs questions almost soley at Dr. Geddes. This in of itself is asking for intellectual property. Some people then get perturbed when Geddes mentions his own goods which are the best solution known to him for the problems at hand. The nay sayers all want to shove off the best product and use others just because they are a fraction of the price. This is backed up by you and others saying that it's a DIY forum?! Then start making your horns and WG's because a cheaper alternative is not DIY either.
Mathematically, the OS WG solves the horn equation. Any other derivative to me is incorrect. If there is one thing in this world that is pure and true it's math. Like was said earlier, the HOM's will still exist at some point because of terminations. This is where the foam comes into play. The path differences between the direct sound and HOM make the foam a brilliant, simple idea. The audibility of this effect makes complete sense because of Geddes work on distortion audibility.
The waveguide that you refer to has to be one of the earlier models which were noted as parts of AI baffles. The current crop are and have been a completely different animal from the get go. 1" thick throughout with excellent properties and finish.
No one has ever said thatf questions can not be asked. It is the way in which most are asking the questions that are making me shake my head. The listing of all these threads directs questions almost soley at Dr. Geddes. This in of itself is asking for intellectual property. Some people then get perturbed when Geddes mentions his own goods which are the best solution known to him for the problems at hand. The nay sayers all want to shove off the best product and use others just because they are a fraction of the price. This is backed up by you and others saying that it's a DIY forum?! Then start making your horns and WG's because a cheaper alternative is not DIY either.
Mathematically, the OS WG solves the horn equation. Any other derivative to me is incorrect. If there is one thing in this world that is pure and true it's math. Like was said earlier, the HOM's will still exist at some point because of terminations. This is where the foam comes into play. The path differences between the direct sound and HOM make the foam a brilliant, simple idea. The audibility of this effect makes complete sense because of Geddes work on distortion audibility.
The waveguide that you refer to has to be one of the earlier models which were noted as parts of AI baffles. The current crop are and have been a completely different animal from the get go. 1" thick throughout with excellent properties and finish.
doug20 said:
Ehm, 2 make it brief. The wording "HOM" was upraised by Geddes on the occasion of the inventing of the OS waveguide. Second to that "HOM" was declared as an explanation for the ancient "problem" of so called horn sound. The OS should address that, was said. As I showed above the OS has to have "HOM" due to its finite length. You can read about it even in some of Geddes' early papers (mentioned above).
The point here is, "HOM" - higher order mode opposed to a basic mode - is just an other word for "Analyse The Problem". I'm quite convinced that You know and are able to exhibit the technique of seperating a huge complicated problem to clearly laid out smaller parts.
goskers said:
Hi,
The foam can be questioned too. But first of all it should be cleared how is HOM measured? Then the cure that the foam is said to do can be retraced.
Regards
Patrick Bateman said:
Patrick Bateman said:
Please provide the link or post them here?
I am very interested to view the objective results.
Fwiw, you don't appear to have your email link turned on, or I'd have asked privately first...
_-_-bear
- Status
- Not open for further replies.