soft dome versus hard dome tweeters

It’s difficult to be accurate with general statements about any tweeter type, but keeping a potentially long post short, there’s never a free lunch, and every option has pros and cons. Choosing becomes an exercise in identifying your objectives, and managing the potential outcomes....."pick your poison"!

Soft domes tend to be easier to work with, are more forgiving of smaller implementation issues, lesser quality parts, and are generally easier to get pleasant results from, but don’t offer the last word in resolution that metal domes can. I’ve had lots of good results from Audax, Vifa, Morel, Seas, and Dynaudio soft domes.

I’ve never worked with Beryllium (Be) domes, but have lots of experience with Aluminum/Mg domes from Seas and some from Vifa. Metal domes tend to be more revealing on everything in the signal path, from the quality of the caps, resistors, inductors, wire, crossover frequency, crossover slope, phase shift, the source, cables, amplification....just about any contributor you can think of that’s in the path can rear it’s ugly head and come through. But....if you can clean up the entire signal path and get it right, some metal domes can be absolutely extraordinary, and result in next level performance.

Ditto the comments about the Magico Be tweeters. Granted they were hooked up to Convergent amp and preamp, with some superb play back gear, but they sound really good even at fairly high levels.

...Soft domes tend to be easier to work with, are more forgiving of "smaller implementation issues,"

@immatthewj when you guys refer to "smaller implementation" are you referring to the size of the speaker or the size of the room the speaker is to be played in or the size of something else?

No, I was referring to some of the smaller issues of a given implementation of using a given soft dome tweeter...for example: less than ideal crossover points and slopes, cheap inductive resistors with steel leads vs non-inductive wire wound types with copper leads , iron core vs air core/heptalitz/or foil chokes, cheap polyester or electrolytic caps vs really nice metalize polypropylene caps, too much treble output, etc. Nothing is perfect, plus what we think sounds wonderful is subjective, but these are all what I consider fairly common examples of "small implementation issues" of speaker design in general. My meaning is that soft domes just tend to be little bit less critical and more forgiving of many smaller contributors in the sound chain in my experience. That same level of cheaper parts and/or minor design flaws on a metal dome are more likely to sound horrible, while they might sound acceptable with the right soft dome.

Audio terminology for describing the sound of things is always difficult. I’d be more inclined to call soft domes in general as a bit "less revealing", more than "warm sounding", but agree that they’re also less likely to saw your ears off if the design is less than ideal.

I realize that’s there’s plenty of controversy over whether many of those parts differences matter at all, but IME they do, and they’re more likely to show up in a well executed design with any tweeter, but perhaps more so with something like an AL/Mg dome matched to a highly resolving system.

Some may even disagree, but that’s been my experience.

As for the ringing, it's hard to say.  Different materials have different break characteristics, and if a poorly implemented metal tweeter were crossed over too low, driven too hard, or underdamped near the resonant frequency, I suppose it's possible.  

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.