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In the Forum: Horn-Loaded Speakers
In the Thread: New superlative horn build - ESD acoustic
Post Subject: GeometryPosted by jackydai on: 4/1/2019
I’m glad you talk about geometry, but to respond to this I have to refer to other brands. I will only talk about facts and hope it’s not offending anybody.
My basic point is: the flare rate has to be coherent right from the entrance of phase plugs. In this sense, not even Bruce and Sam did it right, I’m afraid to say. In many cases the driver and the horn are designed by different teams and the flare rate within the phase plug, the flare rate from the exit of phase plug to the exit of the driver(the throat), and the flare rate of the horn are all not the same. In another word, most of the horn units you have listened to are not following their own flare rate FROM THE START.
TAD 4001&4003 are back firing drivers, where the throat pass through the center pole, and they narrow the throat flare rate for better magnetic transmission(seems like their engineers don’t agree with you on the importance of magnetic density). That’s one thing. Second is the exit of phase plug has a sharp shift of angle entering the throat area, not a smooth connection. Third is they use rectangular horns.
Cessaro uses TAD units and changes to round horn, but 1.the problem within the driver is still 2. The entrance of Cessaro horn is bigger than the exit of TAD driver -I’m not sure how come they did not think about it.
ALE use front firing drivers, where they use bullet phase plugs. They have very high compression ratio and the sound only pass through dots at the outer ring of diaphragms, which is frequency selective at the first place. The flare rate is changing vastly at different stages too. To compensate for small throat exit they also increase the flare rate of the horn greatly for the first few inches.
Avant-garde does not use compression drivers and uses ABS plastic horns. If you doubt the importance of material please put your hands on an Avant-garde horn when it’s playing and feel the resonance.
These should cover most of the problems current horn units are encountering. We did some of the same things too, but after I become more familiar with Bruce’s and Sam’s knowledges I started to combine the design of horn and driver together. Our geometry as of today features:
1. Round horns only;2. The flare rates in the phase plug slits, throat and horn are coherent;3. The exit of phase plug connect smoothly to the throat;4. The exiting wave front of phase plug is not planar wave front but a slightly curved one which match the supposed waved front of the horn.
As for the flare rate itself, our sub-bass-horn is hyperbolic, bass-horn is exponential, mid-range is tractrix, tweeter is tractrix, and super tweeter is a new kind. Those have been set by Bruce Edgar from the beginning and has remained unchanged, so I’m not sure what are the 10 things you think Bruce wouldn’t do. Perhaps you can list them here and i’ll talk with Bruce on them. Thanks.
I know Romy has some different opinions on the flare rate Bruce has set. I’d be neutral on that, but I can only say this: at least they are true tractrix/exponential/hyperbolic all the way through. Many other impressions on different kinds of horns, I’m sorry to say, are highly influenced by the altered flare rate from the start and thus should not be qualified reference.Rerurn to Romy the Cat's Site