what are the thoughts of stand alone super tweeter

It might be helpful to look at the paper by Martin Colloms on his web site. He is the author of HIGH PERFORMANCE LOUDSPEAKERS as well as being a speaker designer and audio critic. It is too long to reproduce but in part it states:

2.5 Anecdotal Consumer Press Reporting
I have considered that informal, anecdotal reports from reviewers concerning the advantage of addon
super tweeters to be rather suspect since I feel that generally the basis of their evaluations has
generally been so flawed that the results may be discounted. The difficulties encountered are
manifold and only a few need be considered to confirm my negative view. Firstly the test for
response extension benefit will only be valid if the extended response is achieved without affecting
the performance in the existing ‘audible’ range.
Testing for a subtle effect, which may well be barely audible, is a manifest nonsense if it changes
the uniformity and loudness in the already operative treble range. Yet this is what is happening in
these tests. So far, no commercially available add-on tweeter and matching crossover can avoid
this fundamental error. Note that when such a driver and crossover is patched on to an existing
audio chain, as it often is, it will inevitably change the loading on both the cable and the amplifier,
and thus very likely impart another audible difference.
These ‘super tweeter’s typically operate in parallel with the existing tweeter over about an octave
bandwidth, and may destructively interfere with the primary tweeter output. Thus there is a potential
to impair as well as alter the results. Sadly, some critics are so pleased to have heard a difference
they are tempted simply to judge it as an improvement. Often the crossover is a simple capacitor
feeding a metal dome tweeter, perhaps with a beryllium composite diaphragm. Such a crossover is
something of a disaster since a calculated 20kHz ‘crossover’, comprising a single capacitor for a
nominal 5ohm rated tweeter, provides the response shown in Figure 1. The intrinsic output is
compared with the crossover objective, which is seen to be markedly different from the practical
result generally obtained with such a single element filter. The cause is the complex impedance
presented by the high frequency driver compared with a plain resistor load. Even with more
complex, higher order filters, the practical crossover points for super-tweeters are often placed well
into the audio band. It is not surprising that audio professionals dismiss such published subjective
results, which often seem to be produced in support of media and equipment marketing.

In my last post I failed to give a complete guide to the article. It is Archive A10
DO WE NEED AN ULTRASONIC BANDWIDTH FOR HIGHER FIDELITY SOUND REPRODUCTION?
Martin Colloms, Colloms Electroacoustics London, 2006
It is found on the AUDIO CRITIC magazine section of the web site.

Stanwal, the fallacy of his argument is saying, "These ‘super tweeter’s typically operate in parallel with the existing tweeter over about an octave
bandwidth, and may destructively interfere with the primary tweeter output." This is what you have continually argued also and it is just not true of the Muratas and, I think, the Townshends.

Tbg, we seem to be in a circular argument.

First let's state a hopefully agreed fact: whether the Muratas, Townshends or another supertweeter, their frequency bandwidth starts at some point. For example, you use the figure of 15KHz for the Muratas.

Not every speaker on the market is polite enough to stop at that selected point. Some fall short before. Some run past that frequency. Perhaps a few stop where the supertweeter expects them to.

Your position seems to be: no matter what the main speaker, a supertweeter always makes things better.

Some of us are less credulous of that position. In Martin Colloms case, he is one of the most respected and experienced voices in the world of speaker design and evaluation. I, and many others, give his views great credence. A supertweeter, if used, deserves the same effort toward integration as any other driver. Otherwise the effectiveness of the results will be haphazard.

I guess we just need to agree to disagree on this point.

Mlsstl, my Acapellas extent supposedly to 30K, so there is overlap. But the Muratas play no music. You hear nothing that you would mistake as music on them when played alone. I participated in a demonstration at CES several years ago when I initially heard this. Martin Colloms whom I respect greatly is right in my previous experience with super tweeters. I always preferred the speakers without the super tweeters.

The Muratas worked well with the Lowther drivers in my Beauhorns which were rolling off above 14K Hz. When I got the Acapellas, I thought they would be of no use. Much to my surprise, they added greatly to the soundstage width and realism.

As always, I really don't care what the logic you and Martin state means if I hear otherwise. I know full-well the limits of our understandings.

I don't really disagree with you, I think your explanation fails to account for observations. I know from my science training that an explanation that fails to account for observations is a failed explanation whether or not it is broadly accepted.