Audio Artistry Beethoven loudspeaker system Measurements
The Beethoven is quite sensitive, 2.83V of B-weighted noise generating an spl of 88.5dB at 1m on the tweeter axis. The impedance of the panel, however, (fig.1) drops significantly below 4 ohms between 45Hz and 210Hz, and to 4 ohms in the mid-treble. A good solid-state power amplifier would best drive this speaker, as suggested by Audio Artistry themselves. The impedance peak at 22Hz I assume is due to the free-air resonance of the twin woofers.
Fig.1 Audio Artistry Beethoven panel, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).
The impedance plot of the subwoofer module (fig.2, plotted with a 50 ohm vertical scale) reveals the unit to be very easy to drive, the minimum value being a benign 11.8 ohms at 57Hz. The wrinkles in the trace between 100Hz and 400Hz, however, indicate the presence of some cabinet resonances. Whether or not these will have any audible consequences will depend on the rolloff supplied by the active crossover. The low-pass feed to the subwoofer with the control set to its "Normal" and "Video" positions is shown to the left of fig.3: in the first position, a boost of 14dB at 10Hz is applied to compensate for the dipole rolloff; set to "Video," the boost is curtailed to 2.6dB at 19Hz.
Fig.2 Audio Artistry Beethoven subwoofer, electrical impedance (solid) and phase (dashed) (5 ohms/vertical div.).
Fig.3 Audio Artistry Beethoven, electronic crossover, high- and low-pass responses with subwoofers switched on and off (right-hand traces, bottom and top, respectively) and with subwoofer switched to "Normal" and "Video" (left-hand traces, top and bottom, respectively).
Fig.4 shows the subwoofer's intrinsic response, measured in the nearfield without the crossover (bottom trace below 40Hz, top trace above 70Hz). Flat through the bass, it rises in the lower midrange due to the resonant behavior noted in the impedance plot. However, as shown by the equalized responses (bottom two traces above 40Hz), these peaks are well suppressed by the crossover, allowing the subwoofer effectively to cover just the mid- and low-bass regions.
Fig.4 Audio Artistry Beethoven subwoofer, nearfield response without crossover (bottom trace below 40Hz, top trace above 70Hz) and with electronic crossover switched to "Normal" (bottom trace above 40Hz) and "Video" (top trace below 70Hz)