Horn vs. Waveguide

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#741
gedlee said:


Frank

Thanks for taking this on. I refuse to deal with such foolishness.

The 80 dB limit is quite correct, and stated in the paper. above this point requires FDA approval and a whole array of added and expensive requirements. Thus we were limited to testing at what is really a very low level. Since the data ALL showed a significant trend towards higher audibility at higher SPLs, there is no doubt that at some point any level of HOM will be audible.
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How could You as an academic be that insultant?

80dB IS loud as can be seen imediatly from the fact that is not allowed to test human beings at this level. To speculate from findings at that level to higher ones is as non scientific as can be. We know to much of saturation effects, masking etc to dare extarpolations.

HOM as an explanation for the bad in audio remains a speculation that hasn't been proved as being perceptable. At least with recent devices as 18s XT1086 and the like. Not to forget the one that this thread has been started with, JBL el'cheepo:

Geddes:

"..., it is a diffraction horn. It acts just like every other diffraction horn that I have measured ...
From the noise signal I could tell that it was very resonant and the data shows that quite clearly.
... but I'm not about to tell you that it good quality. The results speak for themselves."

A horn with +/- 1dB ripple condemned as sounding resonant, bad, no good quality. From a subjective listening test in the lab with noise unequalized.
 
#744
xpert said:

A horn with +/- 1dB ripple condemned as sounding resonant, bad, no good quality. From a subjective listening test in the lab with noise unequalized.
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There was no listening.

I'm not suggesting that's wrong, just clarifying that it didn't happen.

If there is coloration, however, it's clearly not so massive as implied, given that only two parties who have never heard it assert that it sounds like a horn, whereas the many who HAVE heard it affirm it doesn't.

This is subjective, of course, and by definition, dangerous territory, best avoided. 😉


gedlee said:


And most importantly, uncorrectable.
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But mitigable by a reticulated foam plug.... 🙂
 
#748
xpert said:


How could You as an academic be that insultant?

80dB IS loud as can be seen imediatly from the fact that is not allowed to test human beings at this level. To speculate from findings at that level to higher ones is as non scientific as can be. We know to much of saturation effects, masking etc to dare extarpolations.

HOM as an explanation for the bad in audio remains a speculation that hasn't been proved as being perceptable. At least with recent devices as 18s XT1086 and the like. Not to forget the one that this thread has been started with, JBL el'cheepo:

Geddes:

"..., it is a diffraction horn. It acts just like every other diffraction horn that I have measured ...
From the noise signal I could tell that it was very resonant and the data shows that quite clearly.
... but I'm not about to tell you that it good quality. The results speak for themselves."

A horn with +/- 1dB ripple condemned as sounding resonant, bad, no good quality. From a subjective listening test in the lab with noise unequalized.
Click to expand...
This HOMs and diffraction are all audible effects as well as measurable. This is not to say that everone knows how to interpret the data or can hear the effects. They gould be burried in the room modes, driver decay, and other forms of imperfection of greater significance. It would be much appreciated if you can point us to, or show here some of your own work rather than trying to get people to talk using provoking remarks. It does not show you know more than geddes.
 
#753
Aw, c'mon Zilch. I respect you but all the sly attacks against Earl are getting old. Maybe this is HOMs and maybe it isn't. Paul W measured a DDS waveguide with and without foam, with the mic near the edge of the waveguide. Top trace is the signal and bottom is what the mic picks up.

Without foam:
attachment.php4


With foam:
attachment.php4
 
#754
soongsc said:

A part of it I have already explained in the Geddess thread. Sorry, can't lend you my old ears to let you hear them.😉
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How about providing a link as a courtesy, perhaps?

Given the plethora of profuse HOM generators I have on hand, I should be able to see some.

Otherwise, we are confounded with a conundrum here.... 🙂
 
#755
If you want a simpler view of higher order modes, one place to look is a book on microwave theory, where much of this has been addressed for decades. In essence, they can also be modeled as EM waves bouncing in conductive pipes. Some terminology to watch out for:

In microwave theory, the term waveguide generally refers to a tube which guides EM waves, although optical fibers and even wires carrying DC can be modeled as waveguides (it is an interesting way to prove that a wire can guide power at 0Hz, i.e. DC, BTW).

Audio horns and waveguides would all be considered as different types of horn antennae.

One of the more important effects of HOM in microwave theory is dispersion, i.e. different frequencies have different propagation velocities. A free space analog would be multipath distortion (remember ghosting on analog TVs?)They can be a problem in wide bandwidth systems, and limit the information carrying capacity of a channel.

While I can't comment on the audibility of HOM personally, they are a real and known issues in EM theory, which also deals with wave propagation.

Study up,
John
 
#756
catapult said:
Aw, c'mon Zilch. I respect you but all the sly attacks against Earl are getting old.
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I am not attacking Earl, his products, or his design principles here; what's old is others suggesting that I am. Put me in the "Advocates" column, as I endure plenty of trashing for being one elsewhere. I have paid my dues.


Originally posted by catapult Maybe this is HOMs and maybe it isn't. Paul W measured a DDS waveguide with and without foam, with the mic near the edge of the waveguide.
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Link us to the study, please.

That's the Engebretson? Do we conclude it's not a "Waveguide" from this finding?
 
#758
ZilchLab said:


I am not attacking Earl, his products, or his design principles here; what's old is others suggesting that I am. Put me in the "Advocates" column, as I endure plenty of trashing for being one elsewhere. I have paid my dues.




Link us to the study, please.

That's the Engebretson? Do we conclude it's not a "Waveguide" from this finding?
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http://www.htguide.com/forum/showthread.php4?p=329361

I don't know what an Engebretson is. I think the only thing we can conclude is that foam makes the impulse response look better with the mic in that particular location with that particular horn. It does lend a bit of credence to the notion that reflections inside a horn are a Bad Thing (Martha.) 😉
 
#760
catapult said:
Aw, c'mon Zilch. I respect you but all the sly attacks against Earl are getting old. Maybe this is HOMs and maybe it isn't. Paul W measured a DDS waveguide with and without foam, with the mic near the edge of the waveguide. Top trace is the signal and bottom is what the mic picks up.

Without foam:
attachment.php4


With foam:
attachment.php4
Click to expand...
May I ask what kind of original signal is being used? If it's generated from SoundEasy, it sure looks very different from what I usually see on various systems.
 
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