The notch tha occurs at all angles is due to interaction between the diaphragm and the throat. This is interesting, and there might be a possibility to optimize that part.
Jean-Michel
Using sound rays in the throat part of a waveguide is grossly over-simplified and I wouldn't accept any conclusions that hence resulted.
I would apologize too because I thought the same thing.
Bentoronto, you actually made conclusions and posted some harsh opinion on the topic with in a short time frame. Honestly, if someone wants to learn they should read or skim 463 pages before they post there is nothing here. If there are specific questions, just ask them as you go.
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Thanks good and true points about linking-in. I hope I never said there is no research or that there is no solid stuff in prior 4500 posts. I do suspect there is a great shortage of behavioral smarts all over hifi-land (and everywhere engineers and engineer-wannbees gather).
I recognize your legitimate point of view. But it is legitimate for a newbie like me to ask to a shortcut or summary.
Pretty upsetting to think any thread gets their bowels in an uproar when asked for evidence and the response of this thread (including "somebody" who wanted me to step outside for a fist-fight) was, I think it is fair to say, along those lines, eh.
If someone asked, "Hey, can you point me to a peer-reviewed-kind-of paper that examines the validity of Thiele's enclosure model?" Or "Is there Doppler distortion?" That would be easy, I suppose. Why not with Geddes' concepts? Waiting.... waiting.....
This important and obviously complex topic deserves a wiki, as some forums provide.
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Hello, i am new on here and new to this.. but very interested in this thread as i am employing a friend of mine to build my cabs for me and have searched everywhere for the math to do it without results.. can anyone help me with this?
It is an os waveguide for a bms compression driver.. if someone can advise me on how to work out the math i would be very grateful.... thankyou in advance,
Jamie.
It is an os waveguide for a bms compression driver.. if someone can advise me on how to work out the math i would be very grateful.... thankyou in advance,
Jamie.
Looking at the CSD before and after extending the baffle, it seems where is something going on below 5KHz. Another hunk of energy seems to come in later, from the impulse which is not shown, it seems to come with a delay that matches the depth of the WG. So I would assume, the lip blend radius will determine the spectral content of this hunk of energy. This means a much bigger wave guide is necessary. But now this also is a very good test article to see what EnABL patterns will do at the edge if we want to keep the small form factor. For the sake of convenience, the exact pattern format will not be followed, but rather just eyeballing a pattern to see what happens.
Attachments
I don't respond well to demands and impolite accusations, so you won't get a response from me. But if you are unable to find any "scientific" literature under my name then you really havn't looked very far.
All my posts have been asking for anybody to help with a summary of the evidence about directional factors and that post certainly did not single you out. Quite the opposite if you read it again.
What did I say that made you think I was looking at you? Tell me and I will apologize.
Can anybody please supply a link to a neutral and respected source that will enlighten me on the directional factors? (Toole's 2008 book will be in my hands next week, I believe. Of course, he is respected although maybe not neutral.)
Hi Jamie,
If you search this thread for the word:
spreadsheet
you should find a ton of info.
The program Hornresponse will calculate it for you
Telstra BigBlog -
Excuse me for wasting bandwidth but a good question. I suppose I am most concerned about authors with close dollar tie-ins. But even so, a Toole or Geddes paper in a peer-reviewed professional journal would be OK. A BBC paper or book from their researchers like the old James Moir book would be good but not something originally issued by HK, for example.
Am I the only person looking for evidence?
Footnote: folks with big one-meter-square dipole ESLs are very interested in this topic for obvious reasons even if we don't have Geddes speakers on our immediate shopping list. Right.
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To most people "nuetral" means that you agree with them.
In this area of discussion there really aren't any nuetral parties. Floyd's not, I'm not, who's going to have studied this and is nuetral?
I do like to point out that my beliefs were established and well documented long before I became "biased". Therefor they were established on nuetral ground, no matter how tainted it is today.
I've read some of your posts, but I really cannot comprehend what you are looking for and what you point is, so I stopped reading them.
So in short, what evidence are you looking for?
I believe that his request is for evidence that a narrow directivity is preferential to a wide one. The whole premis of a waveguide is that this is true. It's a resonable thing to ask, but, as I have already explained, what he wants does not exist. All one can do in this regard is to use what we do know about hearing and small rooms and hypothesize that a narow directivty would work best. He doesn't seem to accept the hypothesis and wants proof. Well there is nothing concrete enough to satisfy him I guess, although Markus posted several studies.
It seems to be hypocritcal to ask for solid scientific work and then to suggest doing some studies at "trade shows". Nothing usefull is going to come out of a trade show IMO.
It seems to be hypocritcal to ask for solid scientific work and then to suggest doing some studies at "trade shows". Nothing usefull is going to come out of a trade show IMO.
In order for a narrow directivity to have any possibility of being preferred, it has to be so narrow that the interaural effect is very low. This might be possible if a device like this has sufficient bandwidth, which I doubt it has.
Audio Spotlight - Add sound and preserve the quiet.
Audio Spotlight - Add sound and preserve the quiet.
A very broad statement that I cannot see any justification for. Can you explain?
Bentoronto,
At first glance it looks like there's a big discrepancy between what Toole advocates and what Earl Geddes is doing. But I don't think that's really the case.
To start off, let us note that the speakers are only part of the Geddes equation; a relatively "live" room, which supports a slow-decaying reverberant field, is another. So while the initial radiation pattern is narrower than what Toole advocates, as we will see the net result (in terms of reflection intensity and duration) is similar IF one follows Earl's recommendations on setup and room acoustics.
My understanding of the methodology typically used in the studies Toole cites about the desirability of reflections is this: The tests are carried out in an anechoic chamber, and the "reflections" are generated by a second loudspeaker. So the reflections that are judged to be desirable are spectrally identical to the first-arrival sound. In order for a loudspeaker to generate in-room reflections that are spectrally nearly identical to the first-arrival sound, it would need to have extremely well-behaved off-axis response. This is one of the areas in which a Geddes-style system excels.
Toole also characterizes reflections coming from the sides as contributing strongly to a sense of "envelopment", while reflections from the front or rear of the room are not particularly beneficial, and in fact he recommends absorbing them. The criss-crossing Geddes configuration puts more energy into lateral reflections than a conventional configuration does; instead, most of the energy of conventional wide-pattern speakers goes into front-to-rear reflections that are of little or no psychoacoustic benefit.
Finally, Toole says that de-correlation of the reflections arriving from the left and right channels is desirable in creating a sense of envelopment. The Geddes 45-degree toe-in results in the first strong sidewall reflection from the left speaker arriving at the right ear, and vice versa.
So what Earl is doing results in a lot of spectrally-correct, laterally-arriving, decorrelated reverberant energy. This is pretty much what Toole calls for.
Now for a few things the Geddes approach does better than a conventional approach:
Something Toole criticizes two-channel sound for is the way the image collapses to the near speaker for off-centerline listeners. This does not happen with a stereo pair of Geddes speakers; you get a center image that holds up quite well across a very wide listening area, and the timbre holds up well also.
Freedom from coloration at high levels is something Toole would surely approve of, and Earl uses prosoiund drivers that remain thermally and mechanically linear at much higher sound pressure levels than home audio drivers at anywhere remotely near the same price range.
This last thing I'm not saying cannot be done by a wide-pattern speaker, but I have yet to hear any speaker disappear as the apparent sound source so completely as does the GedLee Summa. I haven't heard the Abbey, Nathan, or Harper so cannot make any subjective comments on them, but they are clearly cut from the same cloth.
Duke
At first glance it looks like there's a big discrepancy between what Toole advocates and what Earl Geddes is doing. But I don't think that's really the case.
To start off, let us note that the speakers are only part of the Geddes equation; a relatively "live" room, which supports a slow-decaying reverberant field, is another. So while the initial radiation pattern is narrower than what Toole advocates, as we will see the net result (in terms of reflection intensity and duration) is similar IF one follows Earl's recommendations on setup and room acoustics.
My understanding of the methodology typically used in the studies Toole cites about the desirability of reflections is this: The tests are carried out in an anechoic chamber, and the "reflections" are generated by a second loudspeaker. So the reflections that are judged to be desirable are spectrally identical to the first-arrival sound. In order for a loudspeaker to generate in-room reflections that are spectrally nearly identical to the first-arrival sound, it would need to have extremely well-behaved off-axis response. This is one of the areas in which a Geddes-style system excels.
Toole also characterizes reflections coming from the sides as contributing strongly to a sense of "envelopment", while reflections from the front or rear of the room are not particularly beneficial, and in fact he recommends absorbing them. The criss-crossing Geddes configuration puts more energy into lateral reflections than a conventional configuration does; instead, most of the energy of conventional wide-pattern speakers goes into front-to-rear reflections that are of little or no psychoacoustic benefit.
Finally, Toole says that de-correlation of the reflections arriving from the left and right channels is desirable in creating a sense of envelopment. The Geddes 45-degree toe-in results in the first strong sidewall reflection from the left speaker arriving at the right ear, and vice versa.
So what Earl is doing results in a lot of spectrally-correct, laterally-arriving, decorrelated reverberant energy. This is pretty much what Toole calls for.
Now for a few things the Geddes approach does better than a conventional approach:
Something Toole criticizes two-channel sound for is the way the image collapses to the near speaker for off-centerline listeners. This does not happen with a stereo pair of Geddes speakers; you get a center image that holds up quite well across a very wide listening area, and the timbre holds up well also.
Freedom from coloration at high levels is something Toole would surely approve of, and Earl uses prosoiund drivers that remain thermally and mechanically linear at much higher sound pressure levels than home audio drivers at anywhere remotely near the same price range.
This last thing I'm not saying cannot be done by a wide-pattern speaker, but I have yet to hear any speaker disappear as the apparent sound source so completely as does the GedLee Summa. I haven't heard the Abbey, Nathan, or Harper so cannot make any subjective comments on them, but they are clearly cut from the same cloth.
Duke
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