Monitor Audio R952MD loudspeaker Measurements
The frequency response of the speakers was measured in the room—spatially averaged across the listening window in order to minimize the effects of low-frequency standing waves—using 1/3-octave pink noise; this also gives an idea of a speaker's dispersion characteristic in the upper midrange and treble. In addition, the nearfield low-frequency response was measured with a sinewave sweep to get an idea of the true bass extension relative to the level at 100Hz.
With the speakers positioned well away from room boundaries, the in-room response gently rolled off below 80Hz (fig.1), while nearfield, the extension was not that wonderful at –6dB, 45Hz. The tuning seemed well-damped, however, and placement near the rear wall will usefully bring up the bass response, though the resultant balance could never be termed "rich.". The response was pretty flat from the upper bass through the entire midrange, ±1dB limits covering the spatially averaged in-room response from 80Hz to 3.15kHz. Those limits, however, conceal a slight lumpiness between 600Hz and 900Hz, and a very slight lack of energy between 2kHz and 4kHz. Above that frequency, there was a 2–4dB plateau in the 4–6kHz region, followed by a well-controlled roll-off in the top octave. Firing the speakers straight ahead lowered the height of the presence-band plateau at the expense of some upper-midrange smoothness and ultimate HF extension.
Fig.1 Monitor Audio R952MD, 1/3-octave, spatially averaged response in JA's original Santa Fe listening room.
The change of impedance with frequency and voltage sensitivity (using 1/3-octave pink noise centered on 1kHz and referenced to the sensitivity of Celestion's SL600) were also assessed. The impedance didn't drop below 7 ohms across the whole audio band and averaged 10 ohms. Coupled with the highish 89dB/W/m sensitivity measured at 1kHz, this means that the R952MD should produce high listening levels even with relatively low-power tube designs.—John Atkinson