Horn of Plenty

Horn speakers have been around almost since the invention of electrical-to-mechanical transducer technology, and they still enjoy widespread use today, especially in commercial cinemas. But cinema speakers use horns that limit the vertical dispersion of their sound, whereas circular horns used by a few high-end speaker manufacturers radiate sound in a spherical pattern. Among the proponents of this approach is German maker Acapella, which introduced a new model to its lineup at CES, the High Violoncello II, which, like all Acapella products, is distributed in North America by Aaudio Imports.

The most obvious feature of the 5-foot-tall, 308-pound High Violoncello II is the 19-inch midrange horn that sits atop the main cabinet and can be ordered in any automotive color and finish you wish. Unlike many horn speakers, those from Acapella do not use compression drivers; they use modified conventional drivers—in this case a 2.2-inch silk dome sourced from Dynaudio—while retaining the inherently high efficiency of a horn-loaded design.

Directly below the horn is Acapella's ion tweeter, which, amazingly, uses no diaphragm at all. Instead, the current in a high-voltage electric arc is modulated with the audio signal, which causes nearby air molecules to vibrate in response, sending sound waves into the room. As a result, the tweeter has literally zero mass and can easily reproduce frequencies as high as 100kHz with no resonances, break-up modes, or other bugaboos that can plague conventional tweeters.

The low end is handled by three 11-inch woofers in the speaker's non-ported main cabinet. Two fire forward through grille cloth and one fires downward through a gap between the cabinet and the integrated base.

The resulting frequency response is specified to be flat from 20Hz to 40kHz. (Acapella limits the ion tweeter to 40kHz because that yielded the best results in extensive listening tests.) And with a sensitivity of 93dB/W/m, the High Violoncello II can be driven by low-power tube amps, though the company says it can also handle lots of power if desired.

How much for such performance? $80,500/pair. That's some serious coin, but if Acapella's claims are justified, the High Violoncello II could be well worth it.

Share | |
GT's picture

"the tweeter has literally zero mass" - not literally: air molecules have mass, surely?

Gabriel Iordache's picture

No, the tweeter has no mass. The air is there to propagate the vibration. The tweeter is actually a high voltage arc... think of a silk dome tweeter. Replace the silk dome with the high voltage arc, and you'll see that we are talking electrons (vs. silk molecules), which for all but the most demanding of purposes can be assumed to have no mass.

Scott Wilkinson's picture

Good point, Gabriel. Perhaps I should have said "virtually no mass," since electrons do, in fact, have mass, albeit so small as to not matter in this context.

Enter your Sound & Vision username.
Enter the password that accompanies your username.