Is high frequency extension important to openness

I have noticed that speakers with exceptional tweeters to an excellent job of separating both the sections and individual instruments in an orchestra.
For example: the Mirage 490s, a $600.00 speaker, are terrific at delineating individual instruments on CD, even with as modest a system as an Arcam Alpha 7, Transparent Music Wave cabling, MIT CVT Termintor interconnects, and a JVC XL Z-1050TN CD player. In fact, the level of openness in the high frequencies give the impression of being on a catwalk peering down into the orchestra and being able to hear individual instruments "sitting" near each other.
In contrast, a considerably more high end system, say, a Marsh A400s, with Alon speakers and speaker cabling, Philips/Arcam CD player and Nordost interconnects don't show the "individuality" as well. And the room is quite well treated, thanks (for those suggesting it's room acoustics) and speaker placement is good.
Why is this so? The Mirage tweeter is an older design, but HP once averred the Mirage tweeter (a bigger model,but same line) was superb. Shouldn't a $3-5,000 speaker have better separation than a 12-year old $600.00 speaker?! And of course, I realize that technology is no guarantee of progress, but intellectually I'm curious as to what others think.
What thoughts do you have that would explain this? What speaker below $5,000 are adept at this separation? And is it simply the tweeter or is it the entire design of the speaker?
You would think a $3-5,000 speaker should do this well.But that isn't always the case. I think the crossover is one of the most important factors in designing speakers. There's no doubt the quality of the transducer has it merits as well.I am no a speaker designer by any means but I have experienced the difference in crossover components.There's more of a difference switching components in a crossover than buying overpriced cables IME.There's certainly an art to speaker design and many factors involved in reaching a specific sound.
IMHO, I believe that the better a tweeter is,(assuming all other speaker parameters are correct) the more open and airy the soundstage will be.
"speakers with exceptional tweeters to an excellent job of separating both the sections and individual instruments in an orchestra"
I would call this higher resolution not "openess". High frequency extension can give more detail. Metal dome tweeters like B&W will typically be more detailed than a soft dome (as compared in my room with various speakers like Ellis 1801 and Ascend Acoustics CBM-170). Presentation will be more "airy". Cymbals will shimmer more for example.

To gain what I quoted you as saying above I think these are important:
1) Reduce cabinet vibrations as much as possible. A smaller cabinet will "talk" less. Also a more narrow front baffle will reduce reflections which muck up the sound.
2) Use a light weight driver material. Electrostatics, kevlar cones, and paper like A-P Virgo II's can react quicker to an input signal. Polypropylene eats detail due to heavy weight, and undamped ringing resonances in the driver itself.
3) Consistent off-axis dispersion. Stereophile measures off axis frequency response and lines which are fairly parallel to each other but decreasing in amplitute represent stable off axis response. This is vital to get stable, pinpoint imaging.
I agree with Gmood as far as the crossover goes. There are, certainly, many factors involved in speaker design, but the core is the crossover. The more speakers the more problematic. peace, warren
Yes it is -- but then again, bass notes also help sculpt the "space" (in combination with the upper register). This of course applies in the ideal world where phase is not a problem at all, cabinets do not contribute their own sound, and drivers have very strong magnets & strong cones and minimal moving mass; the drivers are matched with excellent, lossless crossovers that are not affected by coil temperature /impedance changes.
In the real world, it takes more than a 120kHz tweet to reproduce a flawless sense of space :(
Ultimately, if you stumble upon a speaker you really like, you're lucky!
I cannot explain the separation thing, but I can say, that my Harmonic Precision Caravelles, are the most phase coherent, airy, beautifully extended (highs and lows), bass to die for(in a 7" woofer), in a monitor, with an amazing patent pending crossover, that I've ever heard. Whew! You can read my review in the archives about these babies. Really, quite phenominal for the size and price. peace, warren
IMHO, ultra high frequency extension, in itself, is important only to dogs! Its about clarity of tone (call it resolution if you like) and this depends on the quality of the cross over, the driver, the enclosure and the synergy between them. Except for real bass I think you will find that several manufacturers have done a pretty good job of putting this together, GMA comes instantly to mind. In the $3 to 5000 market there are many that do the job very well, including bass. I think you need to get out a bit and actually listen to whats available, your examples suggest that you've been reading too much. :-)
It may be argued that wide dispersion at high frequencies is just as important as extension, if the goal is openness and airiness. Reverberant energy contributes to the sense of ambience and acoustic space, and a wide-pattern tweeter will give you more reveberant energy in the upper treble region. Unfortunately there's a possible tradeoff involved: all else being equal, the imaging may not be as precise because a wide-pattern tweeter will put more energy into the early reflections.