![]() While the port extends the Lumina III's output to just below the reflex tuning frequency, the midbass is shelved down a little. There is the usual peak in the upper bass due to the nearfield measurement technique. The black trace below 300Hz in fig.4 is the complex sum of the nearfield midrange, woofer, and port responses, with the latter's acoustic phase compensated for by the fact that the port is on the base. (As the port fires downward at the floor, this behavior is probably irrelevant.) The woofers hand over to the midrange unit (green trace) at the specified 350Hz the crossover appears to use asymmetrical slopes.įig.4 Sonus Faber Lumina III, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with the complex sum of the nearfield midrange, woofer, and port responses plotted below 300Hz. The upper-frequency rolloff is initially clean, though some low-level liveliness can be seen between 300Hz and 700Hz. The port's output (fig.3, blue trace) has one peak between 30Hz and 60Hz and another, smaller peak at 100Hz. The minimum-motion notch in the woofers' summed output (fig.3, red trace both woofers behave identically), which is when the back pressure from the port resonance holds the woofer cone still, lies close to the same frequency. In addition, with tube amplifiers that have high output impedances, the shape of the Sonus Faber's impedance magnitude trace implies that the treble will sound exaggerated.įig.2 Sonus Faber Lumina III, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of side panel level with upper woofer (MLS driving voltage to speaker, 7.55V measurement bandwidth, 2kHz).Ī saddle centered on 47Hz in the impedance-magnitude trace suggests that this is the tuning frequency of the port on the speaker's base. The Lumina III is best used with amplifiers that don't have problems driving 4 ohm loads. The EPDR (footnote 1) is 1.5≡.6 ohms between 96 and 120Hz and 1.6 ohms between 660Hz and 810Hz, with a minimum value of 1.25 ohms at 111Hz. For example, there is a combination of 3.75 ohms and ≤3° at 110Hz. The electrical phase angle (dashed trace) is occasionally high when the magnitude is low. The impedance magnitude (fig.1, solid trace) remains between 4 ohms and 8 ohms in the midrange, with minimum values of 3.3 ohms at 123Hz and 3 ohms between 450Hz and 560Hz. The Lumina III's impedance is specified as 4 ohms. My estimate was even higher, at 91dB(B)/2.83V/m. Sonus Faber specifies the Lumina III's sensitivity as a high 89dB/2.83V/m. I measured the speaker's impedance with MLSSA, checking the results with Dayton Audio's DATS v2 system. ![]() I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Sonus Faber Lumina III's frequency response in the farfield and an Earthworks QTC-40 mike to measure the nearfield and in-room responses.
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