It’s all in the implementation. The crossover plays a most important role in determining how the tweeter will be utilized in the context of the design (in crossover frequency, rate of roll-off, and shape of slope). The speaker enclosure also plays a role (in diffraction, dispersion, frequency support, and back-wave control). Just when you think you have the sound of different types of tweeters figured out, a design comes along that changes your perception. A safe recommendation would be to judge the high frequency fidelity of speakers you are interested in by how they sound to you rather than based on the type of tweeter being used.
soft dome versus hard dome tweeters
As my internet window shopping continues, I was reading on some speakers that listed for the tweeter textile dome and also silk dome.
So then I used the 'search discussion' function on this site on the subject of soft versus hard dome tweeters and it seemed as if most of the members who offered opinions used that "harsh" and "fatiguing" and "ringing" to describe how they felt about hard dome speakers. In the admittedly short time that I spent reading, I was not picking up a lot of love for hard dome tweeters.
But there are reputable speaker manufacturers that seem to have gone the extra mile to make their hard dome tweeters as hard as possible using, for example, beryllium or artificial(?) diamond dust.
I wouldn't expect a consensus on much of anything audio, but did I just by luck to find responses by mostly people who prefer soft dome tweeters? Because if they really sound that bad (harsh/fatiguing/ringing) in comparison, why would reputable manufacturers choose this route? And I do realize that appreciation of a sonic effect is subjective, so did I just happen on responses by members who had mostly the same subjective perception?
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Excursion is distortion. With that knowledge one wants a rigid driver that oscillates very little. Hence the proliferation of dome midranges, like on TAD and Yamaha speakers. That said they aren't particularly efficient or cheap. Beryllium's difficulties drove Yamaha to develop aramid drivers coated in Monel. There other "exotic" tweeter materials because of the aggravation of beryllium. Many have made peace with it. Study your options. Do not be ashamed of your budget. Price is a criterion of degree of difficulty. If you speak another language look the model up on foreign sites you understand or can translate. Biases are hidden in adjectives. Also think about your listening space for sizing.
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I have berylium tweeters in my Usher Be-718 bookshelf speakers. The folks who’ve said it’s all about the presentation are correct. I have two pairs of large floor standers that are both unique and outstanding speakers for different reasons. My other two pair are Martin Logan, Summit and Ohm Walsh LE-5. My electrostatics are outstanding as far as both higher and mid frequencies are concerned, they sort of excel in that area. Not kidding, or even exaggerating, the Be-718’s actually do violins better than my electrostatics. It has everything in the world to do with how that sexy berylium tweeter is married to the woofer, which is apparently the same model they put in their big daddy floorstander model. And a few other things about the speaker in general, but the point is that an exotic feature like that, of course, isn’t going to really shine if it’s not in the right company, including what’s driving them. Because all the reviews said the BE-718 is an exceptionally good speaker, but when you drive them with the right electronics that that’s when you will go Wow. I definitely concur. They’re able to create such a deep and also solid bass response with some pretty amazing dynamics for such a small speaker, that I've never even bought a sub for them, which is hard to believe but completely true. I never intended to run them full range only without a sub, but apparently they’re that good. The sexy berylium tweete kind of accentuates everything else that’s there, kind of like icing on the cake, imo. This review corroborates: https://www.soundstagenetwork.com/revequip/usheraudio_be718.htm |
I'm all about that midrange too. But a lot of tweeters go a significant way down in to it. And, how that midrange marries to the other frequencies matters. So, what's the best approach to a coherent, uncolored, beautiful midrange? It would make sense to have no crossover in that range. According the chart I'm looking at, that would ideally go from about 250 Hz to 4000 Hz. What kind of a driver could cover that range with a good dispersion pattern? I'm thinking a fairly large horn, maybe 90 degree flare, and a not too big driver. Center to center on the tweeter is going to be a problem, but it might be worth it. I don't know. I'm currently running 600Hz on up on a CD horn and it does some magical things. But I suspect it'd be better if I could get it down to 250 Hz on the same horn. Maybe the multi entry horns are the answer. It just bothers me that they require holes be drilled in a horn flare that is meticulously intended not to create diffraction events inside. I know guys are working hard to optimize those designs because they feel that point source coherency is worth a little trade-off in diffraction events. |
For what it is worth, the KEF Reference series uses aluminium drivers and aluminium coils. According to KEF's white paper, the ideal tweeter dome shape for best dispersion is spherical, but the best shape to resist distortion in pistonic motion is egg-shaped. So their tweeter has both, with the ovoid dome inside the spherical, touching at the top. They join again at the outer wall forming a triangular shape, much stronger than the single sheet normally found. The KEF tweeter is concentrically located in the throat of the midrange which forms part of a waveguide. The base driver(s) use almost flat surfaces, in part to avoid diffracting the tweeter / midrange output. I agree they sound very different from Sonus faber - but I prefer to hear the sound of an orchestra accurately re-created |
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