Magnetar said:
I don't know how to measure gain. I was hoping Gedlee would address the distinction from a theoretical perspective.
There are papers discussing the JBL "Lens" in the LHF library. It's variously characterized as "refractive" and "diffractive."
What I do know is that the vertical beamwidth narrows severely at VHF. It's not a CD device....
ZilchLab said:
Gain is simple, measure gedlee horn driver at 1.2 K with and without horn and see if there is a gain in amplitude. If there is, and there will be, then it has gain.
The JBL does what it supposed to do- it was not intended to be something it cannot be..........
The gedlee horn IS NOT CONSTANT DIRECTIVITY EITHER, I know of zero true CD Horn or 'waveguide'
Magnetar said:
Well, no, I believe gain, in this sense, goes more to the issue of whether the device loads the driver as opposed to only directing the wave, i.e., controlling its dispersion.
Whether, or how much the SPL is altered due to directivity is not definitive, rather, must be removed from the assessment entirely.
That's what I don't know how to do....
Magnetar said:
On that point, you and Gedlee apparently agree.... 😀
ZilchLab said:
Not sure of the question.
Any device placed on a compression driver loads the same above some LF point. They will all approach the characteristic impedance of air divided by the throat area. So everything "loads" the same. Thats why I ignore "loading" as irrelavent. Loading and cutoff are both concepts that are not relavent factors in a device whose primary intent is to control directivity.
gedlee said:
Hmm... OK. So what does that say about really long horns like the old WE15A or Vitaphone 11' spirals? Both of which I've used and liked.
I was under the (probably mistaken) impression that waveguides were generally shorter than horns, and so loaded the driver less. That's wrong, is it? So why the long horns? Do they do any good at all?
panomaniac said:
The throat is small, the flare is low and long, and the mouth must be big enough. A 'short horn' or summa horn, can be assumed as a bad compromise in the horn world - sooooooooo cal it a waveguide
panomaniac said:
I don't deal in subjective impressions only data.
Length is not a big factor and "no", length and loading have nothing to do with one another. A device can be too short and it won't have enough length to control the waveshaping function, but once its "long enough" the only thing that matters is the mouth size and edge treatment. If the mouth is large enough and the edge treated correctly then the length is completely arbirtary and the driver would have no idea if it was long or short.
gedlee said:
OK, so any device with the same size throat would look the same to the driver? If so, does that translate into measurable electrical impedance? Certainly I see different impedance curves for the same driver on different horns. But maybe that has nothing to do with loading.
Not talking subjective here, just how well the driver and waveguide or horn work together.
panomaniac said:
You are correct, no need to think further. Gedlee himself is a contradiction just like his white papers and speakers (that now I read must be listened to behind a curtain!)
pooge said:
Here here! I am certainly tired of it.
To Magnetar: Why don't you start your own thread entitled "Why Dr. Geddes theories are BS" Then you can join with all the others who are of the same mind. You should enjoy each others company. And then please leave the rest of us alone.
panomaniac said:
There will be effects from mouth termination, as I said before. What you are looking at in the impedance is the LF impedance of the device, which is mostly reactive (mass like), and resonances (which exist in varying degrees). The type of horn has an effect on the reactive load, but the length generally determines the resonances. You are trying to simplify a very complex system. So complex, in fact, that only in the last 10 or 15 years has it really become understood. I can't give you simple answers and then have them be precise in every situation.
gedlee said:
Well theories aren't facts. The thread is titled horns vs. waveguides, your definition (in which you claim to invented 'waveguide') of your own waveguide is it doesn't have gain. It does. Your definition of your waveguide says it doesn't have diffraction - it does - so I am wondering why you even define it that way.
gedlee said:
Of course. Please explain why your definition of waveguide is soooo contradictory to what you have designed and sell .
Jmmlc said:
I think (from experiance with big horns and compression drivers like this) the best way to control the directivity is not to use a big horn in the low midrange but to use cone drivers (maybe arrays of them) on an open baffle.
I say this mainly because the big horn may measure well on axis BUT it will beam way too much in the upper range.
Earl,
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You can put Magnetar on ignore by clicking the "members" button at the top of the page, clicking "Avanced search" and typing in "Magnetar" in the first box, click on the link to "Magnetar", and click on the link to ignore Magnetar at the bottom of the blue table.
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