Okay, I think I now have finally figured out what is going on with the Air Layer tweeters and how to get the best out of them. I'm frankly surprised it took me this long, but, as Robert Greene noted in his review of the passive version of this speaker, the side-firing Air Layer tweeters add another layer of adjustments to the speakers which must be dialed in to get the absolute best performance from them and the speakers as a whole. Another problem is that, for me in my small room listening quite close (55 inches) to the plane of the speakers, the Air Layer tweeters fall into the "gilding the lily" category. While the Air Layer tweeters have been improved since Greene's review, the basic performance of the speakers for an extreme sweet-spot, near-field solo listener like me is so good with the Air Layer tweets turned off that getting the Air Layer tweeters set just right does not usually seem like a high priority. Evaluative listening sessions very frequently turn into let's-just-enjoy-the-music-and-the-great-sound-of-the-music sessions.

A number of other speakers currently or formerly on the market have tried the "auxiliary tweeter" thing. Usually, such tweeters are mounted to fire backwards, however, as opposed to the side-firing arrangement of the Janszen's Air Layer tweeters. Reviews of such speakers often notice trade offs with such auxiliary tweeters; typically, while they may enlarge the presentation in some pleasing ways (e.g., perceived added depth, width, or height), they may also reduce imaging specificity and change the high-frequency balance of the speaker.

When you think about it, the change in frequency balance is almost inevitable if the auxiliary tweeters are played at a level which even remotely matches that of the main, front-firing tweeters. To my knowledge, none of these auxiliary tweeters, when activated, reduce the level of the main front-firing tweeter. Thus, turning on the auxiliaries adds high frequencies to the room sound. If the speaker is already perceived as well-balanced without the auxiliary tweeters, turning on the auxes will create at least the possibility--if not the inevitability--of changing the overall perceived sound balance in favor of more high frequencies.

Now, as Robert Greene's review noted, with speakers like the Janszen which are quite limited in high-frequency dispersion, adding highs to the room sound could be beneficial. Most recordings certainly aren't made to be optimally heard via speakers which put as little high frequency energy into the room sound as the Janszens do. Many recordings will sound a bit dead or muffled through the Janszens when heard from normal listening distances, particularly if you are not in the sweet spot. The imaging and staging will be precise, but the presentation can sound a bit small and airless.

That is, UNLESS you--like me--only listen to the speakers from the sweet spot and that sweet spot is quite close to the speakers. In my set up, the perceived frequency balance from the sweet spot is very fine indeed. And, my measurements showed the spatial presentation should be pretty fine as well; the impulse response shows the driver pulse, then a lot of nothing much for at least the first 11 milliseconds, and very little even later. Early room reflections are minimal indeed, as shown by the fact that clap track tests sound almost as they do via headphones--just the clap, with very little trailing reverb.

For a small speaker whose high-frequency driver is mounted so close to the floor, the Janszens sans Air Layers do an outstanding trick of floating the images and stage to a height just above the top of the speakers, which, from my sweet spot, is basically straight ahead, not down in any way. Still, I could wish for at least a bit more image and stage height in the presentation.

Enter the Air Layer tweeters. It makes sense that since the Air Layer ring radiators are mounted high up on the side of the box, activating them would tend to further elevate the images/stage. And that does in fact happen in a very pleasing manner.

But that is not all that happens when the Air Layer tweeters are turned on. Above a certain level of the Air Layer volume control, the overall response of the speakers gets a bit toppy, as Greene put it. I am particularly sensitive to over-emphasis of high frequencies. The Janszens without the Air Layer tweeters in operation, are balanced just right, I think. But unlike some other speakers with a richer midbass through lower midrange region (my Harbeth M40.1s, for example), there is really no leeway for additional highs in the balance. Any additional high frequency emphasis sticks out, to my ears, in an objectionable way.

In addition, above a certain level of the Air Layer volume control the pleasing expansion of the images and soundfield carries with it a softening and defocusing of images and the stage. This problem never reaches the point of obvious image misplacement or jumpiness, but the aural picture is still impaired just a bit, I think, if the Air Layer level is too high.

My goal was to find a setting of the Air Layer control which added a bit of image/stage height and size enhancement without changing the perceived just-right high frequency balance and without softening/blurring/defocusing the imaging and staging. As it turns out, there IS such a level, at least in my set up.

Finding that just-right setting is another matter. Please refer to the image of the Air Layer volume control at page 18 of this link to the Janszen Valentina Active users manual. My speakers have the outer dial, where the numbers run from minus infinity (off) to zero (fully up). I have previously determined that setting the Air Layer tweeter level control higher than about the minus 3 dB marker defocused the imaging and staging too much for my tastes. I had also found that setting the level control straight up and down (set at the -dB marker on the dial) totally eliminated that problem but still caused a bit of toppiness in the presentation, particularly on recordings with strong upper brass, such as big band jazz.

Sure, I could have diddled endlessly with the volume settings for the Air Layer tweeters listening to music and evaluating these parameters for every small movement of the controls of both speakers. But fortunately a little experimentation with the right type of pink noise as a test signal proved to be a great shortcut.

Many online sources of pink noise are not suitable. For one thing, they really are weighted rather strongly away from the high frequency content, perhaps at least partly to save file size for the typically hours-long tracks one finds. A long online pink noise track is very convenient--much better than the minute-or less-tracks frequently found on test CDs--but it has to have a neutral sonic character to begin with to help evaluate speaker frequency balance.

In addition, many online pink noise tracks are rather decorellated between left and and right channels, tending to produce a rather phasey sound in stereo with a lot of sound as a result appearing to come from positions left and right beyond the physical location of the left and right speakers, as well as up above the speakers. This is not the best type of test signal with which to evaluate image/stage expansion produced by turning on the Air Layer tweeters since the signal is rather "diffuse and directionless" to begin with. I did locate what sounds like wideband correlated pink noise here and indeed there is an article rating this source as the best evaluated online.

Using this two-hour pink noise as a source (streamed via AirPlay from my iPhone to my AirPort Express and thus through the Janszens), the Janszens sounded well balanced from the sweet spot with the Air Layer tweeters turned off. I determined in seconds that, compared with the Air Layer tweeters turned off, turning the Air Layer tweeters all the way up produced an obvious high-frequency hiss "tone" (pink noise, when reproduced by speakers with a flat response, should sound smooth, with no obvious specific tones, kind of like high-pressure air escaping from a valve, or a high-pressure shower running in the next room) placed a bit above the rest of the soundfield and centered between the speakers. I tried adjusting the Air Layer tweeter level controls downward and the hiss "tone" gradually diminished as I did so.

That method would have been enough, but serendipitously I discovered a further shortcut which allowed me to set the correct level in about a minute of listening to each speaker. I noticed that each time as I approached one of the speakers to reset the level control, at certain positions I could hear the sound of the Air Layer tweeter of that speaker "detach" itself from the physical location of the speakers and appear to come from the wall beside the near speaker. There are diffusors mounted in the first-reflection spots of the Air Layer tweeters as viewed from the sweet spot. When I moved to stand inboard of the speaker and faced the diffusor mounted on the wall beside that speaker, the sound of the Air Layer tweeter appeared to be coming from the diffusor, not the speaker.

I thought, what if I try lowering the level of the Air Layer tweeter until that apparent reflection goes away? As it turns out, in my set up, at least, that has proved to be the magic setting and it only took a few seconds to move the level control up and down and zero in on the exact position where the apparent reflection just disappeared and the sound of the Air Layer tweeter was back at the side of the cabinet where the tweeter is mounted. This "magic spot" is at about the minus 9dB position of the level control, about midway between the -10 and -8 markers on the dial.

Subsequent listening from the sweet spot, both to pink noise and especially to music has shown that this position of the Air Layer tweeter level control does in fact produce a pleasing expansion of the perceived vertical height and width of the presentation, while adding no high frequency emphasis and certainly no blurring of images or stage. So there the control will be set until further notice. The lily has been gilded!