Horn vs. Waveguide

[markus76]

Yeah, I know.. "I should get out more". 😉

No, you should conduct a double blind test. Everything else sucks 🙂

Best, Markus

 

[ScottG]

I was being polite. Too much fatuous nonsense:



Doesn't sound as if you know what you're talking about. Market research is very expensive. It's often (nearly always) less expensive for a small operator to put product out in some reasonable venues and see what happens. There's even a chance he might recoup costs or even make money.



You don't know that. You're just making stuff up. The effect could just as easily be in the other direction.



Like I said, you guys should get out a bit more. Raise your horizons, and stop encouraging people to chase after slightly higher than lowest common denominator.

Fatuous nonsense hmm? 😀 I thought you were being trite, not polite. 😉

As for the rest:

1. Marketing research doesn't have to be expensive.
2. Determining your market doesn't have be expensive or time consuming.
3. Most of what you have specifically objected to was presented as something that *could* or *might* be. So yes, I don't "know" that, but then I never claimed that. This doesn't mean that it couldn't or hasn't happend.

It may be "less expensive for a small operator to put product out in some reasonable venues and see what happens", but just "winging it" probably isn't the most effective way.

(In deference to Earl I'll not post direct quotes and links.)

But I will suggest that you consider looking through the "Nathan" thread on the HTGuide forum (DIY "Mission Possible" section). It highlights that sometimes things can go "awry" when you forgo good planning and execution (of that planning). That thread alone could still be hurting his commercial success, significantly. Of course I don't *know* that, but I don't think it's an unreasonable surmise either.

But back to my life.. 🙂

 

[ScottG]

No, you should conduct a double blind test. Everything else sucks 🙂

Best, Markus

..and yet, the paper has nothing to do with double blind tests.

*IF* everything else sucks, then what am I to conclude about the paper? 😀


..but please, continue "helping" Earl. 😉

 

[ZilchLab]

Zilch,

as far as I can see you're the only one that repeatedly stated that the EconoThingy sucks. Earl's last statement was rather positive: http://www.diyaudio.com/forums/showthread.php?postid=1861126#post1861126

After nearly a year of dormancy, apparently giving Earl's "Paper" an objective reading, Noah reopened this discussion with this question @ Post #580:

Was reading about the Econowave and this thread was linked .

Question for Dr. Geddes,

" Horns simply tend to sound harsh. This is exactly what I was trying to solve when I developed the waveguide theory. I have solved this problem and it makes a huge difference. I have been trying to point out in the data how this can be seen, but clearly people can only see what they are looking for."

I'm having trouble reconciling this and some of your other comments with your measurements of the JBL Econowave horn.

The polars look very good to me; why do you say they are not CD?

You've said that about horns using diffraction slots, but these don't have any that I can see.

What about your measurements brings you to conclude that they must sound harsh?

And here was Earl's response @ #597:

Harshness has no concrete deffinition, but here is what I sense when I listen to an older diffraction device. The HFs are colored and don't sound right, although the sound is very dynamic with low compression. Further, as the device plays more loudly the "harshness" gets greater.

I spent a lot of time with different horn designs etc. and there is one thing that comes through very clearly. A regular string of resonances in the pass band and the impedance curve indicates a strong internal reflection which can be from the mouth or a diffraction slit, either way it is a problem and elliminating it goes a long ways towards improved sound quality. The JBL horn had such a periodic progression of resonances and as such it woul fail even my first test of sound quality.

But further to that I have studied the effect of alternate path waves in waveguides and even without reflections from discontinuities these waves will exist. It can be shown (I have done the psychoacoustic studies on this) that delayed resonaces, such as would occur with HOM (alternate path waves) are audible AND that they become more audible with SPL level.

Since nothing was done in the JBL device to improve these HOM I would content that they would be an audible problem.

Yes, the polars were OK, they always are for diffraction devices, thats not their problem. The problem is the diffraction that is used to get these polars creates more problems than it solves.

This was a brief 2 min. discussion of what has taken me 20 years to learn myself, so its going to be lacking in many respects. SOme things that I note in measurements are not so easy to define, but herin lies the basics.

The polars were OK? Well scratch all that stuff about "Not CD," then, the only issue is the +/- 1 dB ripple in the response. After a couple of more gratuitous dumps in the intervening 125 posts, we get back to this issue, and he concedes the ripple could be successfully mitigated with EQ, but even then, the elusive HOMs would remain:

This is true, and I do believe that a great many of the peaks and dips could be controlled with EQ. But thats not the whole story. When there are many peaks and dips then there have to be significant internal reflections. Whenever there are internal reflections there also has to be HOMs created as a result. The HOM cannot be EQ'd because they are both non-minimum phase and non-lumped parameter (or one-paramter if you like). The HOM wave effects are different across the wavefront or put another way the effects will be different in different directions. Hence HOM cannot be correct with any EQ. This IS the crux of the problem. ONLY the acoustical design can minimize the HOM.

So while the actual "peaks and dips" may not look bad to you, their existance is strong evidence of the existance of HOM which will always have a negative effect on the sound and cannot be corrected.

If I were still doing research I would certainly look to ways to better evaluate HOM and diffraction effects (they are basically the same thing) as the techniques for defining them is seriuosly lacking. But I haven't had a chance to do any research in a long time. One often meets a crossroads where you have to decide to be the geologist who finds the gold, or be the miner who digs it out. Here I think that I have done both - but I put on my miners cap daily.

I think that John's point here is well taken. I can present all the theory in the world about the sound quality of horns and waveguides, but in the end they need to be heard to really confirm the theory. All I can say is that no one who has heard my waveguides has ever claimed to have heard better.

The JBL device is a real bargin, of that I have no doubt, but I would bet my reputation on the fact that no one would find its sound quality to be better than a well done waveguide with foam. But then the later isn't $10. Thats the tradeoff and the cost of being state-of-the-art.

Thus, Earl concedes the entirety of his critique, and all that remains is his speculation that it "might" sound harsh, since he didn't bother to listen it, and that his offerings would certainly sound better.

I never suggested EconoWave would sound better, merely that any objective evaluation of Earl's data reveals that it MEASURES better in certain respects, and this thread is about Earl's analysis of THAT data, after all.

Looking at subjective data, all EconoWave owners like their speakers and all Summa owners love theirs. The only person that has heard both stated that the Summa sounds better. So what would be wrong with a colloquial "all other speaker suck" with regards to content?

Newman said more @ #715, now, didn't he? There was also a "However:"

I have also heard the Summas, a pair of massive unity based speakers made by Nick (with the later changes to the throat to improve the FR anomalies) and have heard at least 8 different iterations of the PT Waveguides. The Summas are excellent and clearly better to my ears than the PTs. However, I don't necessarily think that clear difference couldn't be accounted for with crossover work. All of the versions I have heard showed some of the promise that CD offers but all outside of one used a generic low pass. I suspect that with some work, and a proper subwoofer implementation, the clear differnce could quickly turn into a miniscule difference.

This whole thing sort of reminds me of the CD vs Vinyl debate, where in the end, the mastering is what will have the biggest impact. Similarly, the speaker as a whole will have more impact than the form of "waveguide" used. The key should be teaching people about the merits of Constant Directivity moreso than the profile used to acheive it. An entry level modern CD horn still sounds superior to a high end vintage horn to my ears.

What about a double blind test or do you want to keep the discussion on flame war level?

I'm not seeing any flames, actually, but if you want to put a $208 "EconoThingy" up against $6000 Summas, have at it; you may be surprised at the outcome....

 

[FrankWW]

Like I said, you are promoting slightly higher than lowest common denominator.

You got Geddes to measure the thingy, and he did, and he wasn't impressed.

You selectively quoted Geddes's paragraph leaving out the most salient first sentence. This is what you quoted*:

Earl Geddes

It is not a CD device as it only holds CD (reasonably well) in the horizontal plane. In all other planes it appears to be highly directional. Since it is not CD only one plane can be EQ’d and the others just have to follow. This results in a far less than desirable vertical response for example.

Here is the preceding sentence you did not quote:

The JBL horn has a substantial amount of internal reflection and diffraction as is evident throughout its frequency response curves

He's saying it's not going to sound great - maybe even bad - no matter what. This isn't surprising and I can't understand why you should expect anything else from him because he has spent thousands of hours of intellectual and physical labour creating a waveguide which does not have a "substantial amount of internal reflection and diffraction."

This is not true and genuinely derisible:

EconoWave is an entry-level platform for exploring the principles Earl teaches, and we make no apologies for it.

Rubbish. He says waveguides should be without diffraction and reflection products and they should be CD so power response may be uniformly EQ'd. As he says in the report you quoted above, "It is not a CD device as it only holds CD (reasonably well) in the horizontal plane. In all other planes it appears to be highly directional." Thus the power response can not be uniformly EQ'd.

Whatever else the EconoWave horn thingy might be, it is not a platform, "entry-level," or otherwise, "for exploring the principles Earl teaches." If anything, it is an example of things he teaches against.

It appears what you have been attempting to do is co-opt Geddes's work for the promotion of mediocrity. It is peculiarly odd you find it a problem that he won't cooperate in this project.

It's truly absurd you should think Geddes would ever endorse this device, or even give the slightest impression he might approve of it, as it was JBL diffraction horns that set him off on his investigation of bad horn sound.

* http://140.174.80.168/downloads/Horn VS waveguide.pdf

 

[ZilchLab]

Like I said, you are promoting slightly higher than lowest common denominator.

I am promoting nothing, rather, merely attempting to get an objective reading of the data Earl presented for consideration in this thread. Your "slightly higher" contention doesn't hold up under Earl's evaluation of another JBL PT waveguide @ #257:

Actually it is not clear from the photo that it does have diffraction. But I would say from the unEQ'd plot that it does. It is clearly head and shoulders better than most diffraction horns.

Whatever else the EconoWave horn thingy might be, it is not a platform, "entry-level," or otherwise, "for exploring the principles Earl teaches." If anything, it is an example of things he teaches against.

That's a mighty narrow view of what Geddes teaches, and if it's that "Geddes OS waveguides are best and all else is crap," we're having some difficulty with that contention here, apparently.

It appears what you have been attempting to do is co-opt Geddes's work for the promotion of mediocrity. It is peculiarly odd you find it a problem that he won't cooperate in this project.

It's truly absurd you should think Geddes would ever endorse this device, or even give the slightest impression he might approve of it, as it was JBL diffraction horns that set him off on his investigation of bad horn sound.

Not hardly. Let's not pretend that JBL has been asleep at the wheel. Read the PT Waveguide white paper:

http://www.jblpro.com/catalog/support/getfile.aspx?docid=277&doctype=3

They've been making OS far longer than Earl, and are well aware of its advantages and limitations....

 

[markus76]

Geddes OS waveguides are best and all else is crap

What if that turns out to be true?

 

[ZilchLab]

What if that turns out to be true?

There ARE issues.

[I'm only trying to help with that.... 😉 ]

 

[catapult]

I am promoting nothing

Aw c'mon Zilch. It's kinda like when someone tells a woman her kid is ugly -- she gets ticked. Earl told you your kid is ugly. He might not be right but you got offended and told him his kid is ugly too. 😉

 

[ZilchLab]

Aw c'mon Zilch. It's kinda like when someone tells a woman her kid is ugly -- she gets ticked. Earl told you your kid is ugly. He might not be right but you got offended and told him his kid is ugly too. 😉

MY kid doesn't have to be hidden behind acoustically transparent drapes, and ladies ARE allowed in the listening room.... 😀

 

[markus76]

There ARE issues.

Yes I know, my stands are too low. Bose sucks 🙂.

 

[ScottG]

Aw c'mon Zilch. It's kinda like when someone tells a woman her kid is ugly -- she gets ticked. Earl told you your kid is ugly. He might not be right but you got offended and told him his kid is ugly too. 😉

I like the analogy. 😀

But I think it's more like saying your kid is ugly because of they way you've dressed him/her and then pointing out as many fashion foibles in support of that as you can think of, not because the kid is actually ugly.

I have a strong feeling that a good steep filter with a mid-bass driver that has the correct kind of response on and off-axis near the crossover, could easily lead to something far more "fashionable".

I also have problems with the "waffling" in regard to the off-axis response.

 

[pooge]

Ahh..., the benefits of the Ignore List. It's like closing a window to noisey traffic. Don't miss it at all.

 

[ZilchLab]

Rubbish. He says waveguides should be without diffraction and reflection products and they should be CD so power response may be uniformly EQ'd. As he says in the report you quoted above, "It is not a CD device as it only holds CD (reasonably well) in the horizontal plane. In all other planes it appears to be highly directional." Thus the power response can not be uniformly EQ'd.

Yes, we know he said that, and we also know that those statements regarding it not being a CD device, highly directional in non-horizontal planes, and the power response not being able to be uniformly EQ'd are patently false. Econowave met Earl's acceptance criteria in this respect, whereas his own ESP12 did not.

Here are the EconoWave curves, which I have posted earlier in this thread:

Vertical: http://www.diyaudio.com/forums/attachment.php?s=&postid=1838011&stamp=1243376765

Oblique: http://www.diyaudio.com/forums/attachment.php?s=&postid=1847007&stamp=1244230518

Horizontal: http://www.diyaudio.com/forums/attachment.php?s=&postid=1839220&stamp=1243468708

Earl's ESP12 is here:

 

[ZilchLab]

It's truly absurd you should think Geddes would ever endorse this device, or even give the slightest impression he might approve of it, as it was JBL diffraction horns that set him off on his investigation of bad horn sound.

Absurd?

From this thread:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=122717

5/14/2008:

Thats a 50 dB spread on the plot. That makes the axial response about typical for an EQ'd unit say +- 2 dB.

But what about off-axis? Its easy to EQ a poor waveguide on axis, but that will usually screw up the off-axis response. A good waveguide has to have off axis control so that it can be EQ'd without serious off axis problems. Axial response curves are just not very useful in determining a speakers performance.

Only if they also hold that out to 30°!! Thats the hard part, not on axis, thats easy.

I have measured lots of horns like this I know exactly how it will work. I didn't ask about the off axis response because I didn't know. It will fail to hold control off-axis, I guarantee it. Why should I measure yet another diffraction horn? If they worked, I'd use them. They don't work, so I moved on. So has JBL by the way! And that is why they are so cheap!

These JBL devices are a remarkable bargain, I don't question that, but they are not going to sound as good as a truely refined waveguide. For the money, they appear unbeatable and any driver should work fine.

I am not particularly interested in moving backwards in my designs no matter how cheap they may be. I simply have no interest in the horn itself, I was just shocked that JBL - the brand and usually price leader - would be selling anything so cheap. This is a significant departure from the past.

My relutance to "try one" has to do with time - I don't have as much as I need. I can't just try out everything. I would be willing to test this device on the drivers that I have (DE250 or DE25 or DE500) if someone could get one of the horns to me in a few days. I'd pay for it thats not a problem, but time is. I would think that it would be worth the ten bucks to you to see the data that you asked me for!!

Seems like maybe Earl learned something about "diffraction horns" from measuring the EconoWaveguide:

Yes, the polars were OK, they always are for diffraction devices, thats not their problem. The problem is the diffraction that is used to get these polars creates more problems than it solves.

30° is the light blue curve in the above posted plots, and the bold brown horizontals delineate +/- 2 dB....

 

[ZilchLab]

Criteria:

The range of CD is correct as Jean-Michel says, but another way to look at it is that the frequency responses at off-axis positions have to be parallel. There is no problem if the levels fall slightly, in fact this is desirable from my perspective, but they must be parallel. Once the level is down by 6 to 10 dB then there is no longer any significant coverage and I would consider that point to define the Coverage Angle, 45 degrees as pointed out. The low frequency point on the graph is determined by the size of the waveguide and will move lower for a larger device. The angular dependence is a function of the waveguide wall angles and can be set at will. Theoretically there is no HF limitation for the waveguide, but the driver always imposes one.

The lines can cross if they are close to the axis where the responses are quite close, but they should not cross at wider angles where the differences are larger. You are correct, there is no "standardized by the NBS" definition of CD, but that is beside the point. It’s easy to identify and define as has been done here. I use the definition, a little different than Jean-Michel's above that the response needs to be +-2 dB within the window near the listening axis and that the coverage angle and frequency bandwidth is at the -6 dB points. Using the peak values in the "passband" is not as effective I don't think.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=103872&perpage=25&pagenumber=104

I'm not sure that I understand - if the "polar plots to be the same for a wide range of frequencies" is true, then don't the polars have to "be constant amplitude at different angles" if the axial response has constant amplitude? Are you saying that the amplitude should be flat at all axis angles, but not at the same amplitude as the axial response? This later IS the definition of Constant Directivity with a given narrow directivity, i.e. exactly what I design my waveguides to do.

Everyone from Floyd Toole, Sigfried Linkwitz, Sean Olive to myself agree that Constant Directivity is the goal. What we don't all agree on is what that directivity should be. Floyd says "wide", Sigfried says Bipolar (cosine), and I say narrow (less than cosine). It all comes down to what you believe the influence of the very early (first) reflections is. We all differ in this regard.

http://www.diyaudio.com/forums/showthread.php?s=&postid=1720800&highlight=#post1720800

I think that its important to understand that Constant Directivity does not mean that the sound stays at the same level as one moves off axis - and then somehow falls to zero at the coverage angle. Waveguides have a continuous drop in level - independent of frequency however - as one moves off axis up until the coverage angle, and then the drop is steeper.

This slow drop with angle is exactly what one needs off axis in the toe-in configuration.

The wider the angle of the device (as above) the faster the initial falloff with angle and the slower beyond the coverage angle and this tends to not be frequency independent - in other words the wider the coverage angle the more the polar response looks like a piston - not surprising.

At about 90 degree coverage (45 degree wall angle) one gets just about the ideal angular falloff. Narrower than this and within the coverage its not falling fast enough, but then it drops like a stone. Wider than this and the falloff with angle is too great.

http://www.diyaudio.com/forums/showthread.php?s=&postid=1629277&highlight=#post1629277

Is EconoWave CD according to Earl's criteria?

Is ESP12?

 

[TrueSound]

Re: Criteria:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=103872&perpage=25&pagenumber=104



http://www.diyaudio.com/forums/showthread.php?s=&postid=1720800&highlight=#post1720800



http://www.diyaudio.com/forums/showthread.php?s=&postid=1629277&highlight=#post1629277

Is EconoWave CD according to Earl's criteria?

Is ESP12?

It is true the JBL is the better constant directivity device based on the response plots.

The question is - Why do you care if "Gedlee" endorses it?

Why would a manufacture endorse something that is a fraction of the cost of what they sell?

I think you've clearly made your point, and so has Gedlee.

I'm still wondering how the manufacture measures HOM. I don't think that will be done by them for the same reasons.

 

[Robh3606]

"Econowave met Earl's acceptance criteria in this respect, whereas his own ESP12 did not."

Hello Zilch

Econowave will never meet Earls design requirements because it doesn't use an OS Waveguide. That is what his designs are all based upon. That is the basic requirement.

If you want to argue about the merits of the Econowave Horn vs his waveguide have at it but you can't say his designs don't meet his design criteria.


Rob🙂

 

[markus76]

Earl must be sitting at home laughing his head off. This whole quote war just helps spreading the word (btw: good marketing). The real question is what helps building a better speaker: waveguide (plus patent pending cleaning sponge insert) or horn? Without proper listening tests we will probably never know.

Best, Markus

 

[bear]

Gentlemen,

I think that there is a disconnect here...

So a few comments.

I am not a "supporter" of Dr. Geddes, nor his product(s).
However, it is clear that he has done some things of significant merit.

Nothing you hear out of a speaker is independent of everything that is connected to it, nor everything that comes after it (the room, you, etc...). What you or I believe or think or percieve we are hearing is in large measure dependent upon the objective quality (whatever that means) of the equipment AND the subjective "ears" (the experience and perceptive capabilities) of the person doing the listening.

It is quite possible to have a great speaker sound like utter doggie poopie because of what is connected to it. Been there, heard that. Many times. The converse is harder to do.

Another aspect, what is "better" for you depends in large measure upon where your point-of-reference lies before you listen. Apparently, for a majority of participants here on this forum, that point-of-reference is at a comparatively modest level.

It is critical to understand that I am not saying anything bad, but rather that achieving higher and higher levels of performance from stereo systems is more and more difficult past a certain modest threshold. It is the "race car effect". (does this need to be explained?)

(what do you have, an 200kmi econobox, Lexus, or IROC racer?)

So, given that we can not compare sound via this written medium all of the comments about what sounds "good" need to be tempered substantially, and discounted very very heavily, imho.

I have no way to know how the Summa's sound, nor how Zilch's cheapo mod will sound. Quite frankly I have reservations about both, but for different reasons. The flip side of this is that the discussion for the last two pages does not seem to have much merit, nor useful content. Nothing that gives me anything interesting or new to learn or incorporate. Just my 2 cents.

As an aside, I'd welcome a chance to listen to the OS waveguide - anyone between Boston and NYC if they want to can contact me via email...

_-_-bear