Avantgarde Acoustic Uno Series Two loudspeaker Measurements part 3

In the time domain, the Uno's step response (fig.7) appears to indicate that the tweeter is connected in inverted electrical polarity, the midrange and woofer in positive polarity. And not surprisingly, given the physical displacement of the drive-units, the speaker is not time-coherent. The cumulative spectral-decay plot (fig.8) is quite hashy, but this is not, I suspect, due to resonances but to the presence of early reflections. The lip of the midrange horn, for example, is clearly in the tweeter's acoustic environment (footnote 1).

Fig.7 Avantgarde Uno, design-axis step response at 50" (5ms time window, 30kHz bandwidth).

Fig.8 Avantgarde Uno, cumulative spectral-decay plot at 50" (0.15ms risetime).

All things considered, there is nothing to be ashamed of in this set of measurements. Although he used horns, the Avantgarde Uno's designer has clearly overcome many of the traditional problems of horn speakers.—John Atkinson

Footnote 1: I have come to believe that the most important thing in designing a horn speaker is to make sure that each horn-loaded unit is not asked to operate over a wide frequency range, thus allowing the traditional problems to fall outside its passband. In addition, the predictable nature of the horn environment would seem a natural for DSP correction.—JA