LABORATORY TEST REPORT

Readers interested in a full technical appraisal of the performance of the DALI Oberon 9 Loudspeakers should continue on and read the LABORATORY TEST REPORT published on the following pages. Readers should note that the results mentioned in the report, tabulated in performance charts and/or displayed using graphsand/orphotographsshouldbeconstrued as applying only to the specific sample tested.

Newport Test Labs measured the in-room audio-band response of the DALI Oberon 9 as being 35Hz to 24kHz ±3dB which is an excellent result, and is very close to DALI’s specification of 35Hz to 26kHz ±3dB.

Graph 1 shows the section of the response below 20kHz measured using pink noise and you can see that the Oberon 9’s frequency response is particularly smooth across the midrange and high frequencies, and not spectrally skewed in any way, so the balance of low to mid to high frequencies is ideal. Although there are some peaks and troughs above 3kHz, all are constrained to within ±2dB.

The high-frequency response rolls off very gently and very smoothly above 10kHz, which is a desirable trait and indicates that the tweeter’s dome has none of the ultrasonic resonances that are typically found in tweeters using domes made of hard materials.

Graph 2 shows the Oberon 9’s anechoic high-frequency response, using magnified scaling and measured without the grille (black trace) and with the grille fitted (red trace). The higher resolution enabled by the use of a sine signal rather than pink noise reveals more peaks and dips in the on-axis response above 3kHz, but the variations are so small (less than ±2dB) that they would not be audible, and the overall response is still within ±3dB out to 24kHz where you can see the tweeter rolls off quite steeply.

The same was not the case for the response measured by Newport Test Labs when the grille was fitted. As you can see, this time there are significant peaks and dips in the response, such that over the region between 1kHz and 26kHz, the response graphed is ±12dB. A very minor re-design of the grille might be worthwhile, perhaps by removing a small circular section of the grille directly in front of the tweeter, but in fact the main variations are so high in frequency and affect such a narrow bandwidth that I doubt they would be audible.

The anechoic low-frequency response of the Oberon 9 is shown in Graph 3, isolating the contributions to the sound from both bass drivers (the two green traces) and both bass reflex ports (the red and orange traces). As you can see, the low frequency response of the bass drivers holds up very well right down to 60Hz, after which there’s the expected roll-off, with the minimum output at about very low 31Hz (the very slightly difference for each driver suggesting that their rear enclosure volumes are not identical).

Both bass reflex ports appear to have been tuned identically, and specifically to deliver output over a much wider range than usual, with the ports delivering significant sustained output from below 20Hz right up to 70Hz. You can see that the shapes of the enclosures behind each of the drivers is slightly different by the differences in the traces above 150Hz.

The impedance and phase angle of the DALI Oberon 9 are shown in Graph 4, as the red and blue traces respectively, with the black trace under being that of a precision calibration resistor. You can see that the impedance of the Oberon 9 dips below 4 at 84Hz and drops down as low as 3.4 between about 100Hz and 150Hz before rising above 4 again at about 225Hz.

Despite this dip below 4 , the Oberon

9 is still nominally a 4 design under the rule applied by the European loudspeaker standard IEC 60268-5 which specifies that the minimum impedance should not drop below 80% of the nominal value. And despite the low impedance in a fairly busy section of the music spectrum, the speaker will be quite easy to drive, due to the benign phase angle over this frequency range.

The saddle between the two low-frequency resonant peaks is at 31Hz, which is the cabinet tuning and means that acoustic output below this frequency will roll off considerably. The rising impedance above 14kHz makes this a very amplifier-friendly design, and one that is particularly well-suited for Class-D amplifiers, old or new.

Graph 5 is a composite response, which grabs the traces from the previous frequen

cy responses and plots them on the same graph, plus Newport Test Labs has added in the anechoic response of the midrange driver (pink trace), which wasn’t shown on the other graphs. You can see the midrange driver operates from around 900Hz out to 2kHz and has a very smooth response. However, you can see that it also has a resonance in its output 3.6kHz, which is what causes the ‘bump’ in the anechoic high-frequency response (dark blue trace). However, this bump would not be audible when listening to music, as shown by the pink noise response (black trace) which approximates what the human ear would hear.

Graph 6 is another composite, this time a single trace where the data below 1kHz was derived from the pink noise room response and the data above this frequency was derived from the on-axis anechoic response when no grille was fitted. This essentially shows the overall frequency response of the

DALI Oberon 9 was measured by Newport Test Labs as 35Hz to 24kHz ±3dB.

Newport Test Labs also measured the Oberon 9’s sensitivity, reporting it as being 90.6dBSPL at a distance of one metre, for a 2.83Veq input. This is notable both for being higher than DALI’s own specification of 90.5dBSPL and also for being more than 3dB higher than the average for floor-standing designs. Indeed it’s one of the highest Newport Test Labs has ever measured, which means the Oberon 9 will make maximum use of amplifier power.

Overall, the DALI Oberon 9s delivered excellent measured performance across all the acoustic tests performed on them by Newport Test Labs. Steve Holding

The DALI Oberon 9s delivered excellent measured performance across all the acoustic tests performed