Is the 2.5 way speaker the ideal home speaker?

1. Isn’t crossing at 2kHz or lower in the range of female voice, that has fundamentals between 350Hz and 3kHz?

I refer you to wikipedia on this:

https://en.wikipedia.org/wiki/Voice_frequency

2. Isn’t crossing below 2kHz to close to resonance of most tweeters? I’ve read recommendation to keep crossover frequency at least 1-2 octaves above tweeter’s resonance.

It's at the bottom end of most tweeters, yes. Usually the rule of thumb is to be 2-3x the resonance. What really matters though is not the resonance but distortion and excursion. That is, overwhelming the tweeter. So your choice in tweeter, as well as the slope and knee point matter.  The ring-radiator I use in my desktop speakers is the "deep chamber" version with significantly lower usable crossover point than the normal variety.  The Mundorf AMT I use in my living room has awesome power handling, distortion and a relatively low resonance point.

The crossover also matters. A tweeter may be able to safely be crossed at 2kHz using a fourth order (24 dB/octave) filter, but 5 kHz using a first order filter (6 dB/octave). You see this with the Joseph Audio speakers discussed in other threads. With a fast drop off they push the tweeter lower than average. 

3. Break-up modes for typical woofer might be around 5kHz. Isn’t cutting at 2kHz too close - especially for 6dB/octave? In comparison my 3-way speakers cut at 230Hz and 3kHz - outside of "sensitive" zone.

This really depends on the driver and crossover, and what exactly you mean by a "woofer" or "mid-woofer." The combination of slope, and filters used in the woofer may help push the usable range up. 

Also, I agree with you that small sweet spot, caused by beaming, might be advantage in acoustically bad rooms, but that’s only if you listen alone. For me wide sweet spot is very important. If I’m not mistaken beaming for 6.5" drivers starts around 1.5kHz.

Even if a 6.5" starts beaming, it is not like a LASER. It doesn't switch from omni-directional to flash light at 1.5 kHz. It just gets narrower as it goes up. If your tweeter's dispersion matches you will still have very nice sound off axis, as the entire speaker will seem to diminish, and not just one particular range.  I do not think that a 6" mid-woofer in a 2 or 2.5 way is a terrible idea at all, or that you will have a pin-point sweet spot, but it can give you added clarity when you are constrained in where you put them.

There are many designers who push the idea that crossovers are bad. Either you want no crossover, or 1st order, or you want the crossover completely out of the vocal range, etc. I'm not really with them. Personally ( and I do not insist that you agree with me ) I have not heard a problem with a well implemented crossover in the 1-3kHz range.  I have also not fallen in love with Thiel or Vandersteen or any other perfect time aligned speaker. 

I'm happy to have learned that at least on this subject, Joseph Audio agrees with me, and none of their fans mention any sort of discontinuity in the vocal ranges. 

Best,

E

@kijanki - This is probably not for you, but here is a very different type of speaker that has a lot of fans. The Seas A26. 2-way with a 10" mid-woofer and single capacitor crossover (6db/Octave):

https://www.madisoundspeakerstore.com/2-way-speaker-kits/seas-a26-10-2-way-kit-pair-based-on-the-cla...

You might investigate it and see why people like it so much. :) 

There is no low-pass because the woofer is so very well behaved. 

Best,

E

Thank you Erik.   Link you provided states that range of fundamental for woman voice is 165-225Hz  while I found this:
http://www.seaindia.in/blog/human-voice-frequency-range/

that states: 350Hz - 3kHz for fundamental frequency - about 15 times higher.  I don't doubt Wikipedia and just wonder.  Could this be that "typical" voice is in narrower range while soprano can get 15x (almost 3 octave) higher?   Perhaps it is "talking" (Wikipedia stated "speech") vs. "singing". 

I appreciate your comment about "not laser like" start of beaming phenomena - my tweeters might already provide wider dispersion where large midrange speaker starts to beam.

Be careful reading that. There is a significant difference between the fundamental and the range. The fundamentals are the bottom, pure note. But the range is far higher.

Erik,  Paradigm Studio 60 v2, I had before, was sold at about $1k.  It usually means that manufacturer sell them for $500.  In my company cost of materials is about 30% of the cost of the product.  That would imply $170-200  for three speakers, box, xover etc.  I did not like sound of the metal dome tweeter and found it to be one of the cheapest Vifa tweeters available.  It is very tempting to build speaker using the best drivers available, including underhung motors etc.  Unfortunately I already attempted to replace this Vifa tweeter and to redesign xover with high quality components.  The purchase of Hyperion speakers was direct result of this attempt.  Perhaps I'll learn more and try again one day.