soft dome versus hard dome tweeters

@erik_squires 

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

@asctim There is a design called "woofer-assisted wide-band" or WAWB for short.  It's exactly what you describe.  A wide band, such as a 4" driver that has credible output in the top octave along with a woofer that crosses in well below 500 Hz. Check out DIYaudio for more information. 

There is a design called "woofer-assisted wide-band" or WAWB for short.  It's exactly what you describe.  A wide band, such as a 4" driver that has credible output in the top octave along with a woofer that crosses in well below 500 Hz. Check out DIYaudio for more information. 

@erik_squires (or anyone).  How do they keep those full range drivers from beaming above 3000 hz or so?    I love the concept of no to minimal crossovers, but, don't they tend have pretty narrow off-axis response?

@asctim 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.

That’s it right there in a nutshell! Well said.

@tunefuldude You should add a virtual system to your profile. I’d love to know what you’re feeding those Ushers.