DALI Ikon 6 loudspeaker Measurements
My estimate of the DALI Ikon 6's sensitivity was close to the specified figure, at 90.5dB(B)/2.83V/m, this a useful 3.5dB higher than average. The speaker's impedance (fig.1) remained within 4.5 and 7 ohms over almost the entire audioband, with a minimum value of 4.25 ohms at 3.5kHz. The electrical phase angle also remained low for most of the band, though there is a combination of 6 ohms and –36° just below 100Hz. The speaker should not be that hard to drive, which, in combination with its highish sensitivity, will make it a good match for relatively low-powered amplifiers and receivers.
Fig.1 DALI Ikon 6, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)
The impedance traces are broken by some minor discontinuities in the midrange that might indicate the presence of cabinet resonances of various kinds. Using a plastic-tape accelerometer, I did find a very strong resonant mode on the sidewalls at 410Hz (fig.2). This mode could also be detected, though at lower levels, on the rear and top panels. It's possible that this mode is sufficiently high in frequency to "fall between the gaps" in Western music, but I do wonder if it contributed to Bob Reina's finding the speaker to sound "a touch compressed, coagulated, and cacophonous" when reproducing orchestral recordings at high levels.
Fig.2 DALI Ikon 6, cumulative spectral-decay plot calculated from the output of an accelerometer fastened to the cabinet's side panel level with the port (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).
The saddle centered on 37Hz in the impedance-magnitude trace suggests that this is the tuning frequency of the 3"-diameter port on the front baffle. However, examining the nearfield responses of the two woofers revealed that these behave slightly differently: the minimum-motion notch of the upper woofer lay at 35Hz, that of the lower woofer at 29.3Hz. The lower woofer's midrange also rolls off earlier in frequency than the upper one's, which extends upward to cross over to the tweeters. The sum of the two woofer outputs is shown to the left of fig.3, taken in the nearfield below 300Hz, in the farfield above that frequency. There is a suspicious-looking peak in the upper midrange before the crossover to the tweeter module between 2 and 3kHz, above which the woofers roll off quickly. The port output's broader-than-usual bandpass covers the two octaves from 20Hz to 80Hz, though it is down a little in absolute terms. Though some midrange peaks can be seen in its output, these are well down in level.
Fig.3 indicates that the dome and ribbon tweeters are balanced a couple of dB too hot. This can also be seen in fig.4, which shows the Ikon 6's farfield response averaged across a 30° horizontal window centered on the ribbon-tweeter axis. A small upper-midrange peak can also be seen, though overall, the DALI's balance is fairly smooth. To the left of fig.4 is shown the sum of the woofer and port nearfield outputs, weighted in the ratio of the root of the radiating areas and taking into account acoustic phase and distance from a nominal farfield microphone position. The upper bass appears boosted a little compared with the lower midrange, but most of this is an artifact of the nearfield measurement technique. The Ikon 6 is actually pretty flat down to 60Hz or so, though the port doesn't fully extend the low frequencies to its tuning frequency. I am a little puzzled, therefore, why BJR found the speaker's midbass to sound a little warm. Perhaps he was responding more to the lively cabinet than to the actual woofer tuning.
Fig.3 DALI Ikon 6, acoustic crossover on tweeter axis at 50", corrected for microphone response, with the nearfield responses of the woofers and port plotted below 300Hz and 1kHz, respectively.
Fig.4 DALI Ikon 6, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with the complex sum of the nearfield woofer and port responses plotted below 300Hz.
The DALI's lateral dispersion (fig.5) is well controlled, with hardly any of the usual flare at the base of the tweeter passband. This correlates with BJR's positive comments about the Ikon 6s' stereo imaging. The ribbon tweeter also maintains the Ikon 6's response off-axis in the top audio octave. In the vertical plane (fig.6), a sharp suckout at 3.37kHz develops above the ribbon-tweeter axis. However, the speaker's balance doesn't change too much between that axis and the top of the upper woofer.
Fig.5 DALI Ikon 6, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90–5° off axis, reference response, differences in response 5–90° off axis.
Fig.6 DALI Ikon 6, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 15–5° above axis, reference response, differences in response 5–15° below axis.
In the time domain, all the drive-units appear to be connected in the same, positive acoustic polarity, each unit's step response smoothly handing over to the next lower in frequency (fig.7). The farfield cumulative spectral-decay plot (fig.8) indicates some low-level hash at the base of the tweeter's passband, as well as some delayed energy associated with the upper-midrange peak.
Fig.7 DALI Ikon 6, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).
Fig.8 DALI Ikon 6, cumulative spectral-decay plot at 50" (0.15ms risetime).
A generally good set of measurements, though I would have expected the Ikon 6's treble to sound a little more forward than BJR found, especially considering its wider-than-usual top-octave dispersion.—John Atkinson