Well, all I know is what Tannoy say about there super tweeters and there wideband tweeters, here is a little bit what Tannoy say about there expensive Dimension speakers:
Modern programme material and sources (e.g. SACD / DVDA) have driven the requirement for loudspeakers with extended frequency bandwidth performance. Always at the forefront of audio evolution, Tannoy has been developing just such wide bandwidth loudspeaker technology over many years.
Music contains transient information and rich harmonics beyond the range of human hearing for pure tones. Even bass notes have leading edge transients reaching 30kHz. Operating between the roll-off point of the Dual ConcentricT high frequency unit and 54kHz, the Dimension SuperTweeterT will accurately reproduce the leading edge of individual notes allowing the listener to experience the entire bandwidth information of instruments.
In addition, by extending the frequency response by two octaves corrects time and phase response within the bandwidth of normal human hearing. Taking these acoustical phase anomalies beyond the range of human hearing adds realism to the soundstage by improving imaging and placement of instruments.
Musical instruments have energy up to and beyond 100kHz, but can we perceive it?
Researchers monitoring brainwave activity on subjects exposed to wide bandwidth material to 60kHz have conducted controlled experiments. By careful monitoring and noting subjective scores under blind conditions, it was discovered that the listeners were indeed responding to the ultrasonic components in the music.
Further experiments have deduced that profoundly deaf subjects rely on ultrasonic detection in their discrimination of speech and tones. These tests concluded the mechanism was through bone conduction, probably to a small organ in the inner ear called the saccule, which is effectively wired to the cochlea, the organ responsible for hearing as we know it.
The proof as always is in the listening; whatever the source - whether vinyl, compact disc or the latest SACD / DVDA technology. All of the technical features and attention to detail combine in the Dimension models to provide discerning audiophiles with incredible wide band detail for the ultimate musical experience.
Research continues into the actual mechanism of the perception of sound above 20kHz, but it can be clearly shown that the addition of a SuperTweeterT will better preserve the harmonic relationship between instruments.
To me they do add air, but I still like the old soft dome tweeter.