Sonus Faber Amati Homage loudspeaker Measurements
Only occasionally do I find a high-sensitivity loudspeaker whose manufacturer's specifications agree with my own measurements. "92dB/W/m," says Sonus Faber of the stunning-looking Amati Homage; my estimated B-weighted sensitivity came in at 92.5dB(B)/2.83V/m. The speaker is a moderately demanding load, however, as can be seen from its plots of impedance magnitude and electrical phase angle against frequency (figs.1 and 2). With a maximum of 7.8 ohms, but a value below 6 ohms in the midrange and below 4 ohms in the bass and high treble, a good 4 ohm-rated amplifier will be called for.
Fig.1 Sonus Faber Amati Homage, electrical impedance (solid) and phase (dashed) with both ports plugged. (2 ohms/vertical div.)
Fig.2 Sonus Faber Amati Homage, electrical impedance (solid) and phase (dashed) with both ports open. (2 ohms/vertical div.)
The woofer ports can be blocked with supplied plugs. Fig.1 shows the impedance, plotted with both ports plugged: the speaker behaves as a sealed box tuned to 37Hz. With both ports open (fig.2), the speaker is now a reflex design broadly tuned to 24Hz. By using one plug, two plugs, or none, the Amati's low-frequency performance can be optimized for the room in which it is used.
The Amati's enclosure is extremely dead to the knuckle-rap test, but I did find a couple of very low-level modes. Fig.3, for example, is a waterfall plot calculated from the output of a plastic-tape accelerometer fastened to the speaker's side 12" from the floor. The main resonance that can be seen is too low in level to have any audible effect.
Fig.3 Sonus Faber Amati Homage, cumulative spectral-decay plot of accelerometer output fastened to side wall 12" from floor. (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz.)