LABORATORY TEST REPORT

Newport Test Labs measured the frequency response of the Dali Zensor 5 AX at 35Hz to 29kHz ±3.5dB, which is an excellent result. The response is shown in Graph 1 and is made up of two different measurements. The trace below 1kHz is the averaged result of nine individual frequency sweeps measured at three metres, with the central grid point on-axis with the tweeter using pink noise test stimulus with capture unsmoothed. The trace above 1kHz was measured directly on-axis with the tweeter at a distance of one metre (this same trace is shown in greater detail in Graph 2). You can see that the trace is very flat across the upper bass and midrange, extending from 150Hz to 3kHz ±1dB. There are slight lifts in the response centred at 100Hz and at 10kHz, plus a small dip at around 3.8kHz. The lifts are 3dB higher than reference axis, and the single dip is at –3dB referred to reference axis. There is no spectral skew, which is to be admired.

Graph 2 shows the high-frequency response of the Zensor 5 AX in greater detail by lifting the low-frequency limit of the graph up to 400Hz, plus it also shows the frequency response with the grille on (black trace) and with it off (red trace). You can see that the grille is mostly acoustically transparent, with the two traces being virtually identical up to 2kHz, then very similar between 4kHz and 21kHz. The grille does appear to induce a sharp, deep dip in the response at 3.8kHz and also a dip at 24kHz. I doubt that either of these dips would be audible when listening to music, even in direct A–B comparison, so I’d recommend leaving the grilles on when you’re listening to these Dalis. If you are interested in whether you can hear a difference, you could put the speakers side by side—one with its grille on, and the other with its grille off—and then, using a mono music signal, use a balance control to listen to one, then the other. (The free Android Poweramp App will allow you to convert to mono and give you a balance control.)

The low-frequency performance of the Zensor 5 AX is shown in Graph 3. You can see that the output of the front-firing bass reflex port peaks at 40Hz and is 6dB down at 28Hz and 72Hz, so there’s quite a contribution at higher frequencies. The bass/ midrange driver’s output rolls off smoothly below 100Hz to a minima at 42Hz.

The impedance of the passive Zensor 5 AX remains mostly above 5 and mostly

less than 10Ω, so the speaker will be easy to drive, though since it’s being driven by an amplifier in the active channel, this is of no real consequence.

There are no wiggles on the trace of the speaker’s impedance that would be suggestive of cabinet resonances, though there is a very small anomaly at 25kHz, which is possibly a minor tweeter resonance. Note that the impedance is 6.5Ω at 20kHz and continues to rise above this frequency, indicating that Dali has made sure the design will work properly with Class-D amplifiers.

Graph 5 shows what is essentially an ‘inroom’ response, graphed using pink noise and you can see that the ‘dip’ visible at around 4kHz in the high-resolution measurements of Graph 1 and Graph 2 has disappeared completely. This graph more accurately represents what you’d hear when listening to the Dali Zensor 5 AXs. You can see that in this graph, the frequency response between 45Hz and 20kHz varies no more than ±2.5dB.

Graph 6 is a composite, where all the responses measured by Newport Test Labs have been put onto the same graph. You can see that there is some unwanted high-frequency leakage through the port between 400Hz and 900Hz, but it’s quite low in level. Newport Test Labs measured the efficiency of the passive Dali Zensor 5 AX at 88.6dBSPL at one metre, using a 2.83Veq input. This is an above-average result and means that Dali has made sure the speakers will be maximising the efficiency of the built-in Class-D 50-watt amplifiers built into the active speaker.

The Dali Zensor 5 AX is a very well-designed loudspeaker, with a very flat and extended frequency response. Stephen Holding