Loudspeakers

This is just the second occasion on which we have recorded a genuine 100dB-plus sensitivity from a loudspeaker – and without any recourse to stratagems like low impedance. Just horns, and both from Avantgarde [see HFN Feb 19]! Measured at 2m on the tweeter axis and corrected to 1m, averaged pink noise sensitivity for the two channels was 102.5dB SPL for 2.83V input – not the 107dB (for 1W) claimed by Avantgarde but still an astonishing figure, particularly when the Duo Primo XD's impedance drops to a (high) minimum of 7.5ohm at a high 7.9kHz! Coupled with low impedance phase angles this results in the minimum EPDR being a high 4.9ohm at 3.7kHz (at a very narrow dip), which makes this speaker one of the easiest to drive that we have encountered, as well as the most sensitive.

Its tweeter-axis response flatness isn't quite in the same class, exhibiting the large ripples typical of horn designs even at 2m measuring distance [Graph 1, below]. However, the errors of ±4.8dB and ±5.2dB are acceptable and the pair matching remarkable for such a design at ±0.8dB up to 18kHz, beyond which it rapidly deteriorates to ±1.9dB at 20kHz because of a mild mismatch in the two treble horns' steep roll-off. (Ignore the LF roll-off below 500Hz – an artefact of the short measurement time window resulting from the 2m measurement distance.) Bass performance is astonishing too, the nearfield response (not shown) being essentially flat to below 20Hz. Numerous kinks and ripples in the impedance versus frequency plot and the uneven forward response both attest to the Duo Primo XD having numerous resonances, and yet the cumulative spectral decay waterfall [see Graph 2] is remarkably clean for a horn design. KH