Dynaudio Contour 3.0 loudspeaker Measurements part 2
Fig.4 Dynaudio Contour 3.0, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 15 degrees-5 degrees above HF axis; reference response; differences in response 5 degrees-15 degrees below HF axis.
The Dynaudio's step response (fig.5) is typical of a flat-baffle design in that it is not time-coherent, despite the use of first-order crossovers. And, in fact, closer inspection reveals that while the tweeter and woofer are connected with positive acoustic polarity, the midrange unit inverts polarity. Not too much should be made of this, but it does lead me to suspect that the measured lack of lower-midrange energy is crossover-related, and, in turn, that this lack will be more audible in drier, smaller rooms.
Fig.5 Dynaudio Contour 3.0, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).
The Contour 3.0's cumulative spectral-decay or waterfall plot (fig.6) is fundamentally clean, but a slight ridge of delayed energy can be seen at the cursor position, 1.5kHz. This is probably low enough not to have any subjective consequences other than at very high levels, when it might add a bit of hardness to the sound.
Fig.6 Dynaudio Contour 3.0, cumulative spectral-decay plot at 50" (0.15ms risetime).
Finally, LG commented on the Dynaudio's rocklike construction. I used a simple plastic-tape accelerometer to examine the cabinets' vibrational behavior. Despite its large panels, what resonances there were had been pushed up high in frequency by the rigid internal construction, minimizing their audibility. For example, fig.7 shows a waterfall plot calculated from the accelerometer's output when it was fastened to the sidewall 8" from the top. The only detectable mode is very high in frequency, just under 500Hz, and is low in level. This is excellent cabinet design.—John Atkinson
Fig.7 Dynaudio Contour 3.0, cumulative spectral-decay plot of accelerometer output fastened to cabinet back wall above crossover panel. (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz.)