I recently added a pair of these supertweeters on my Nola Viper Reference and the result are fabulous. An article in the magazine Hifi+ has precisely commented the Elac 4PiPlus.2. Here is an excerpt which I found very near from what I feel :
"Transparency and image placement were both improved, while the tonality and harmonics of mid and high-frequencies were both significantly better.
Percussion detail was more natural, the nature of the instrument more apparent. But it was the texture and tonality in the lower-mid and bass that really impressed, with much greater definition and detail readily apparent. Dynamic speed, precision and substance were all improved along with the shape and duration of individual notes, making dynamic contrasts more emphatic and musically effective. This increase in presence extended across the entire range, brass in particular gaining body and a satisfyingly realistic rip to its tone. Overall timing was also improved with musical phrasing making more sense. [...] This Elac super-tweter extends the performance available from existing speaker systems in a significant and musically imporlant way. High-frequency extension is no optional tweak - it's a musical necessity, making your system more natural and more naturally communicative."
"Transparency and image placement were both improved, while the tonality and harmonics of mid and high-frequencies were both significantly better.
Percussion detail was more natural, the nature of the instrument more apparent. But it was the texture and tonality in the lower-mid and bass that really impressed, with much greater definition and detail readily apparent. Dynamic speed, precision and substance were all improved along with the shape and duration of individual notes, making dynamic contrasts more emphatic and musically effective. This increase in presence extended across the entire range, brass in particular gaining body and a satisfyingly realistic rip to its tone. Overall timing was also improved with musical phrasing making more sense. [...] This Elac super-tweter extends the performance available from existing speaker systems in a significant and musically imporlant way. High-frequency extension is no optional tweak - it's a musical necessity, making your system more natural and more naturally communicative."