Dynaudio Evidence Master loudspeaker Measurements

Sidebar 3: Measurements

Although my estimate of the big Dynaudio's sensitivity was fractionally lower than specified, at 90.5dB(B)/2.83V/m, this is still significantly higher than average. In addition, the speaker's impedance (fig.1) drops below 4 ohms only in the upper bass, which, coupled with the generally benign electrical phase angle, will make it relatively easy to drive. However, the combination of 45 degrees capacitive phase and 5 ohms impedance at 70Hz might be problematic with some current-starved tube designs.

Fig.1 Dynaudio Evidence, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)

The saddle in the impedance curve at 28Hz defines the tuning of the large, 4"-diameter ports on the rear of the woofer subenclosures, which in turn implies excellent low-frequency extension. This can be seen in fig.2, which shows the individual outputs of one each of the ports and woofers, and the midrange/tweeter module (footnote 1). The port output is the bandpass centered on 28Hz, the same frequency as the notch in the woofer outputs. (At this frequency, the back pressure from the port resonance effectively holds the woofer cones still and all the acoustic output comes from the port.) There is some hashy-looking output from the port between 200Hz and 700Hz, but this is well down in level and will be further suppressed by the fact that the ports are on the rear of the two woofer enclosures. The four woofers handle the 45-200Hz range, with their output above the crossover frequency free from cone breakup problems.

Fig.2 Dynaudio Evidence, acoustic crossover on tweeter axis at 50", corrected for microphone response, with the nearfield midrange, woofer, and port responses plotted below 600Hz, 900Hz, and 700Hz, respectively.

Fig.3 shows the Evidence's farfield response, averaged across a 30 degree lateral window on an axis centered between the tweeters and spliced to the complex sum (magnitude and phase taken into account) of the nearfield responses of the woofers, ports, and midrange units. This response is astonishingly flat, with just a very slight lack of energy in the mid-treble and a slight shelving down in the port region. The latter is probably the right thing to do, given the usual amount of low-frequency "room gain" in all but the very largest rooms.

Fig.3 Dynaudio Evidence, anechoic response on tweeter axis at 50", averaged across a 30 degrees horizontal window and corrected for microphone response, with the complex sum of the nearfield midrange, woofer, and port responses plotted below 300Hz.

Footnote 1: All acoustic measurements are made with DRA Labs' MLSSA system and a calibrated B&K 4006 omnidirectional microphone.
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