Wilson Audio Specialties MAXX loudspeaker Measurements part 2
Fig.5 Wilson MAXX, individual nearfield responses of (from left to right): port and woofers. The respective levels are plotted in the ratio of the square roots of the radiating areas.
With respect to the way in which the speaker's response changes with listening height, the midband region changes quickly off-axis, due to the significant vertical separation between the pair of midrange drivers. Even so, any change was minimal over a ±7.5 degrees window, the worst-case difference being 6dB from 700Hz to 2kHz. The wisdom of the slight mid lift seen on-axis is apparent. For the speaker to "sound" correct, the forward "energy" must be in balance. Over a 30 degrees vertical window, the MAXX's midrange output averages to flat uniformity.
In the horizontal plane (fig.6), the MAXX was very well behaved up to 10kHz, with no unwanted peaks developing, and, if anything, a still smoother balance at moderate off-axis angles. Even at 30 degrees off-axis, the response held within 3dB of the reference up to 12kHz—a fine result. While the speaker's analytical ability clearly directs the listener to a "sweet spot," in practice this wasn't all that critical, and very good results were also obtained over a wider spread. In large rooms, several persons could share a good measure of the performance.
Fig.6 Wilson MAXX, lateral response family, normalized to response on tweeter axis, from back to front: differences in response 60 degrees-15 degrees off-axis; reference response; differences in response 15 degrees-60 degrees off-axis..
The room-averaged response (fig.7) is a summary of two speaker positions, eight microphone positions, and a total of 64 readings. While the upper range will naturally roll off in a measurement like this, as the room's increased HF absorptivity, acting in concert with the natural directivity of the tweeter, dulls the high treble, the resultant graph should reveal the speaker's full bass extension plus a good idea of its uniformity of output up to 7kHz or so. The MAXX's in-room response was impressively smooth from 100Hz to 6kHz, meeting ±2dB limits. The result was normal beyond 6kHz, if with some clear evidence of the high peak lingering on at a subdued level.
Fig.7 Wilson MAXX, 1/3-octave, spatially averaged response in MC's listening room
What is undeniably clear in fig.7 is the MAXX's bass lift. Yes, the speaker does extend down to a very impressive (in my room) 24Hz and is still effective at 20Hz, but the midbass is boosted by an average of 4dB—a bit much for average sized, closed-plan rooms of solid construction. Experimenting with a push-fit, soft-foam liner ½" thick and 5" deep placed in the port tube helped moderate the bass. In larger rooms than mine (ie, more than 4235 cubic feet), experience suggests that the MAXX's bass-power level will be fine.
The X-1/Grand SLAMM excels at low distortion, and the MAXX comes a close second to that twice-as-expensive speaker system. At average listening levels (around 86dB spl), the distortion was typically -60dB, or 0.1% from 200Hz up. Impressive. At 300Hz I recorded -70dB of second harmonic and -75dB of third (Table 1). At 90dB spl, at just under an 8 ohm/watt of input (or 2 "real" watts), the MAXX measured around 0.3% below 150Hz, and at higher frequencies averaged -57dB of second harmonic and -65dB of the more potentially damaging third—again, excellent results. The good control of third harmonic at 2kHz was significant, and a tough point for this tweeter. It passed the test. Amazingly, even at 20Hz the distortion was held to 1%, -40dB, predominantly second harmonic. At 40Hz it was better than 0.3%.
Table 1 Wilson MAXX, Harmonic Distortion vs SPL
|Distortion (dB)||Distortion (dB)||Distortion (dB)||Distortion (dB)|