what are the thoughts of stand alone super tweeter

One thing to keep in mind with any add-on supertweeter that was not designed as part of a speaker system is that the transition between the main speaker and the super-tweeter is going to be widely variable.

The Townshend, for example, says its range is 20KHz and up with a -3dB point at 12KHz.

The Tannoy (depends on model) has a third order crossover starting at 14KHz. That means it'll be 18 dB down at 7KHz but there is still a lot of energy output below 14KHz as it comes up to crossover frequency.

In both cases, the tweeters have significant output in the range where many main speakers already have significantly flat output by themselves.

If coupled with a speaker with significant high frequency energy, you would have a rising frequency response above 10 or 12KHz. If coupled with a speaker with dropoff in highest octave, you couple have a dip in the high response with the frequency response then rising above the dip.

What is simply a roll of the dice is whether your resulting high frequency response bears any resemblance at all to a uniform, smooth output. Most serious speaker companies put a tremendous amount of effort into getting a seamless transition between drivers. With an add-on tweeter, that simply isn't going to happen unless by sheer accident.

While the idea of extending a speaker's high frequencies is admirable in theory, this seems to be a bit of "throw a spit wad and see if it sticks" approach. I find it interesting that basic preamp tone controls have long since been banished from high end equipment but audiophiles have found all manner of new ways to tinker with tone balance through products such as this and others.

The net result is that you can only try a unit and see if you like it. Just don't get the idea that you are necessarily improving the "accuracy" of your high end response. ;-)

Thg said: "I think that you should have no response below 15K Hz in a supertweeter."

While that is a nice sentiment, it is highly unlikely.

The Murata is rather vague about its crossover mechanism but if its range is given as 15KHz and up, it almost certainly has output below that (just like the other two supertweeters mentioned.) If it is a simple capacitor, the crossover slope would be 6 dB. Mechanical characteristics will likely add to that slope at some lower frequency but we don't know where that is.

If it is a 6 dB slope, that means output could only be down 6 dB at 7500 Hz.

Even if there is some super-high frequency magic taking place, it is pretty easy to see there is also a fair amount of energy being added in frequency bands that are already being serviced by the main speaker.

Back when I worked in a stereo store in the 1970s almost all equipment had tone controls. It was nearly universal for a customer (regardless of system, age, type of music or any other factor) to turn the treble up a notch or two. They just liked the way it affected the sound.

I hardly find it surprising that an add-on tweeter that clearly has output in the 10KHz band (even if the specs indicate it starts higher) is going to be audible.

There is an old saying that when you hear hoofbeats you should usually think of horses before you start looking for zebras. Maybe there is a zebra out there at 40 Khz but I sure see a lot of horses in the clearly audible 10KHz to 15Khz range in all these products.

As noted previously, Murata is rather vague about the internals of their device. If there is no electrical crossover then the cutoff is being handled by the inherent mechanical parameters of the tweeter. There will still almost certainly be output under 15KHz since drivers don't just stop working at a precise frequency. (Ever watch a woofer move with a warped record? With one warp in a record that is about 0.5 Hz but the driver is still trying.)

I've got some fairly sophisticated audio processing software (Adobe Audition) that I used for mixing and editing and it is interesting to play with the several different equalizer options. One can create a nearly infinite number of slopes and crossover points and easily apply them to real music. Frankly, there is precious little to actually "hear" as music when one does steep slopes above 10KHz.

I applied a variety of curves to some material to model possible Murata outputs. I can guarantee you that with a curve set around 10KHz for cutoff there isn't much music to hear. Yet if one applies the inverse curve to the same music, the sparkle and air disappears. And all of that happens with no output above 20KHz since I used CD material.

In short, I was able to duplicate the effect you talk about by limiting the output to above roughly 10KHz but yet without using any super-high frequencies.

I know the super-tweeters have a following. One doesn't have to have uncontested exotic scientific theories at work in order to enjoy the effects of a piece of audio equipment.

As noted before, if the original poster is interested in one of these, he simply needs to try it. If it gives him more listening pleasure then he doesn't need to worry about whether it is ordinary high audio frequencies at work or super high ones.

...without frequencies above 15k Hz.

That is not what I said.

I said without frequencies above 20KHz from a CD (actually 22,050 Hz from the Nyquist theorem but there is only 1/10th an octave difference between 20K & 22K.)

Arbitrarily decreasing a number I used by 5,000 isn't a very on-point response. You in politics? ;-)

However, even with non-CD material, one has to wonder where the super-high frequency info comes from. The majority of microphones used for professional recording don't have response past 20 KHz and many only get to the 15KHz or 17KHz range.

Anyway, having been exposed to these devices over the years I remain a skeptic that any significant portion of the effect these devices have is due to energy above 20KHz.

Obviously, others disagree.

Tgb said: "what you say is true only for those supertweeters that extend down into the music range."

Earlier you've stated that a supertweeter shouldn't have any output below 15 KHz. Let's grant that for a moment just for the sake of argument: it is stipulated that we have a tweeter that cuts off very sharply right at 15 KHz.

If one can step back and think about the implications for a transition from the speaker's tweeter to the supertweeter, what you get is a completely unpredictable response.

Take a speaker with strong response from 15 KHz to 20 or above. Adding a supertweeter in this situation would give you a response that would have a significant peak in this range.

Take a speaker with more limited output in the highs (say a single full range driver design that falls rapidly above 10 KHz) and now you have a major dip in response before the supertweeter kicks in.

High frequency curves vary widely among the thousands of speakers on the market, so the above are hardly the only two examples.

So the argument essentially becomes, no matter what the characteristics of the main speaker, more is always better when it comes to high frequencies.

I find that a suspect proposition. In virtually every other aspect of audio reproduction, effort put into having well-integrated, carefully crafted matches between individual components yields better results than simply throwing a mishmash of parts together, even if each part is excellent in its own fashion.

I guess the red flag just goes up for me anytime I encounter a situation that says one product or solution is always the answer no matter what the circumstances.

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.