Expert review and test of the Dali Zensor 5 AX Loudspeakers by Australian Hi-Fi Magazine. Free pdf download included.
This year has been a very good one for Dali, because this well-known Danish loudspeaker manufacturer has picked up awards not only for the Dali Zensor 5 AX speakers reviewed here (‘Best Wireless Speaker 2016-2017’ bestowed by Sound & Image Magazine) but also for its Spektor 6 Speakers (a ‘Best Value’ award from EISA—the European Imaging & Sound Association) and its Phantom S in-wall speaker series also picked up a ‘Best Product’ EISA award in the category ‘Home Theatre High-End 2017–2018.’
Active wireless loudspeakers—speakers where the amplifier is built into the speaker itself, and where there’s wireless connectivity so you can stream music from your phone or device—are the hottest products in audio right now.
The only problem is that the vast majority of the units sold are no bigger than a can of soft drink and are designed for desk-top use or ‘casual’ music playback at picnics and suchlike. The problem with this being that such units sound acceptable only at low volume levels; their sound is always monophonic and, despite their sound quality often being remarkably good considering their price and size, it’s still a long, long way away from being high-fidelity.
This lack of fidelity has not gone unnoticed by consumers, but they’ve also noticed the convenience of such systems and, not unreasonably, have asked why home hi-fi loudspeakers can’t be active and wireless. It’s a good question. One answer is that the great majority of manufacturers of quality loudspeakers are not skilled at building either amplifiers or wireless interfaces. Another is that those manufacturers that could build such speakers if they wished prefer not to do so because they want to avoid the increased complexity of international distribution caused by having to conform with all the different electrical standards in each country and the increased possibility of litigation if a powered product causes damage to something—or someone. Distributing loudspeakers is easy. Distributing mains-powered speakers is not.
Dali, however, has decided to take the bull by the horns. The Zensor 5 AX is a wireless, active version of Dali’s highly popular Zensor 5 passive loudspeaker. It’s an extremely clever strategy to use an existing product because Dali has not had to develop a completely new product—just add power amplifiers and interconnectivity to an existing one. In fact, the right channel speaker of the Dali Zensor 5 AX pair is just an ordinary Zensor 5 passive loudspeaker—both the left- and right-channel amplifiers and the Bluetooth Apt-X receiver, and the digital-to-analogue converter are built into the left-channel loudspeaker.
This makes Zensor 5 AX a little unusual, because there’s a conventional passive crossover network in each loudspeaker, each driven by a single Class-D amplifier rated by Dali at 50-watts. Most other similar incarnations use one amplifier per driver, with the crossover duties being done electronically. There are arguments for and against each design approach, but Dali’s is certainly the simplest and most elegant.
Looking first at the way Dali has designed the speaker side of the system, it has configured it in a three-driver, two-way format in a bass-reflex enclosure. The two bass/midrange drivers have cones made from what Dali calls ‘wood fibre’, presumably to distinguish them from cones that use artificial materials, such as plastic, Kevlar or suchlike, but in fact almost all loudspeaker cones that are not made of a synthetic material are made from pulped wood. Dali seems to emphasise the ‘wood’ side of things by leaving the cones a real dark ‘wood’ colour rather than bleaching and/or staining them a more neutral colour.
The two drivers are identical. Each one has an overall chassis diameter of 135mm, a moving diameter of 110mm and a Thiele/Small diameter of 105mm, to give an effective cone area (Sd) of 86cm². Because two drivers are used, the total area available to deliver bass frequencies is 172cm². This means that if Dali had used a single bass/midrange driver to move the same amount of air, it would have had to have had an overall chassis diameter of around 178mm.
The bass/midrange drivers cross to a single 25mm soft dome tweeter at 2.4kHz. The dome is recessed within a small horn that increases efficiency, smooths the dispersion pattern and affords some small amount of protection for the dome if you use the speakers without the grilles fitted (about which more later). The surround trim of the tweeter spells out Dali’s name in full: Danish Audiophile Loudspeaker Industries. (An explanation somewhat changed from the original, when Dali was first trying to break into the US loudspeaker market, which is the world’s biggest. Back then it was said to stand for Danish American Loudspeaker Industries.)
To improve the power handling ability of the tweeter and reduce power compression effects caused by overheating, Dali uses ferro-fluid in the voice-coil gap. To extend the frequency response and improve dynamics Dali is using a new fabric for the tweeter’s dome. It says its new dome material is, at only 0.056mg/mm², less than half the weight of the material used in most other dome tweeters. The driving magnet is no slouch either, being rated at 220 Gauss.
As stated previously, the Zensor 5 AX is a bass reflex design, and the single port vents to the front of the speaker. The port is 140mm long and 60mm in diameter (though there’s a bit of a ‘step’ down in diameter where the tube meets the front baffle). The port’s exit is curved (by rounding off the MDF of the front baffle where it meets the port tube). The inside edge of the port is not.
Because the right channel speaker of the Dali Zensor 5 AX pair is just an ordinary Zensor 5 passive loudspeaker it has only the usual single set of multi-way speaker terminals fitted to a small plastic mounting plate. The rear of the left-channel speaker is another story altogether. It certainly has a pair of standard speaker terminals, but in this case they are OUTPUT terminals. You run speaker wires from these terminals to the speaker terminals on the right speaker. Dali supplies a goodly length of standard Figure-8 hook-up cable to enable you to do this ‘out of the box’, but you could consider a cable upgrade, depending on how far away your left speaker is from your right.
Arrayed in a line below the speaker terminals are a mains fuse socket, a mains power switch and a two-pin 240V socket. To the right of the power socket are a 3.5mm stereo phone-jack analogue input, a gold-plated RCA output designed to drive a powered subwoofer, and an optical input (via TOSLINK). We would have preferred if different connectors had been used—a pair of RCA terminals for the analogue inputs and one for coaxial digital, our reasons being first in the case of the analogue input that 3.5mm stereo phone jacks have very small metal-to-metal contact area and second—in the case of the digital input—because it’s difficult to source long optical cables and the cables themselves are fairly fragile. There’s certainly plenty of room on the rear panel for our preferred fittings.
The optical input is capable of reading digital signals of either 16-bit or 24-bit word lengths and at sampling rates up to 176.4kHz. The signal from the analogue input is converted by an ADC to a 24-bit/96kHz PCM digital signal which is then passed on to a digital signal processor that prevents clipping and further converts the PCM signal to 384kHz PWM that is then delivered direct to the two on-board 50-watt Class-D amplifiers. The DSP engine also extracts a parallel signal from the audio stream that is digitally bandpass filtered to deliver only frequencies between 12Hz and 80Hz as analogue audio to the SUB output.
Note that it’s a parallel signal: these frequencies are not stripped from the signal being sent to the Class-D amplifiers. Also note that despite Dali having a DSP engine available to it, it does not use the DSP to do any equalisation on the audio signal to ‘tweak’ the signal prior to it being sent to the left and right loudspeakers.
Above the speaker terminal on the left speaker are three pushbuttons: two for volume control and the other for input source selection. When you switch between the different inputs, a chameleon LED on the front baffle changes colour to confirm which input has been selected: Green for the Auxiliary (Analogue) input, Yellow for the optical (Digital) input and Blue for the wireless (Bluetooth AptX) input. (Plus it glows Red if you switch the speakers off.) If you press both the ‘Up’ and ‘Down’ volume controls together, you will ‘Unpair’ the speakers from whatever Bluetooth device you previously paired them with so you can pair with a different device. (Dali refers to this a ‘Bluetooth Release.) Because of this, you can only pair to one Bluetooth device at a time.
The Dali Zensor 5 AX cabinets are available in three finishes, all of them vinyl—black ash, light walnut and white. We think this is the first time we’ve seen white vinyl, and it looks very good indeed.
However although the cabinets are finished in vinyl, the front baffles have high-gloss painted finishes. This finish looks great… the only pity being you’ll only ever see it if you operate the speakers without their black fabric protective grilles. The speakers measure 825×162×282mm (HWD). The width dimension includes the diameter of the bases, which protrude 25mm each side of the cabinet.
Like all tall, narrow floorstanding speakers, the Zensor 5 AXs can be a little ‘tippy’ if given a hearty sideways push (even more so a push from the rear) so you’ll need to take this into account when positioning them. If it’s a particular issue, stability could be increased by attaching a wider base using the screw threads at the bottom of the speaker bases that would otherwise be used for spikes or rubber feet (sets of both of which are provided with each cabinet). The left speaker is less tippy than the right because of the lower centre-of-gravity caused by the additional mass of the amplifiers and electronics in that channel. Both speakers are quite light in weight—even the left speaker—and very easy to carry around, so if you want to move these speakers from room to room, or place them outdoors for entertaining, it’s a snack to do so. (But don’t leave them outside! Always bring them back indoors after your barbecue or al fresco dinner.)
Obviously it would be rather inconvenient to be running around the rear of the speaker every time you wanted to adjust volume level or switch from one input to another, so Dali has provided* a small remote control that allows you to adjust volume, switch inputs, Unpair, Mute the speakers and turn the speakers from ‘On’ to standby. The remote control is what we’d call a ‘credit-card’ style remote, because it measures 40×85mm and is only 7mm thick, and therefore is likely to be fairly easy to misplace.
*If you’re wondering what that asterisk in the previous paragraph is for, it’s because in some markets, the remote control is an optional extra. Here in Australia, local distributor Dali Distribution (Australia) has generously elected to include a remote control with each pair of speakers.
In Use and Listening Sessions
First off we were pleased to see that Dali has handled the Bluetooth pairing mechanics extremely well. When you first power-up the Zensor 5 AXs they realise they’ve never been paired before and automatically enter pairing mode. It’s then simply a matter of looking for ‘Zensor AX’ on your device’s Bluetooth list to establish the connection. If you go out of range for more than 15 minutes, the speakers will switch themselves off. When you come back into range, just press the ‘Bluetooth’ button on the remote and the Zensor 5 AXs will instantly re-pair with your device.
As an additional aid to useability, the chameleon LED on the front-baffle has three additional modes. If it blinks (blue) quickly it means no device is connected. If it blinks (blue) slowly, it means that that the system is on, and you’ve selected the Bluetooth input, and a paired device is not connected. And if you select ‘Mute’ on the remote control it will blink slowly, with its colour indicating the input that has been muted.
If you want the speakers to continue playing when you move out of wireless range, you’d need to switch to either the AUX or OPT input before doing so, and ensure whatever component was connected to that input was operating. If you do this, and music that’s playing stops for any reason, the Zensor 5 AX will switch itself off after 15 minutes of no-signal detection. Unlike many such circuits, it will not switch itself back on when a signal is detected: you have to do this manually by pressing either the ‘Power’ or ‘Source’ buttons on the remote.
After a little experimentation with room placement, we decided the best sound in our listening room was obtained when the Zensor 5 AXs were positioned around 10cm from a rear wall, with the speakers parallel with that wall, so they fired directly up the room, rather than being toed-in to converge at the listening position. This might not be the ideal configuration for your room, but we’d recommend you use it as a starting point. We found the bass was deeper and more defined with this arrangement, and the treble a bit softer at the listening position (about which more later).
As far as how you get your music into the speakers, we did A–B listening tests prior to starting the main listening sessions to determine which source we’d use for this review. Our results proved that all three input methods—Bluetooth, Analogue and Optical Digital—deliver near-identical—and excellent—sound quality.
We couldn’t really separate the Analogue and Optical inputs into better/best at all, but both did seem to provide sound that was just very slightly superior to what we achieved using the wireless Bluetooth input… though this was audible only when using highly complex, highly dynamic music tracks.
Playing the title track of Cat Canteri’s album ‘Late at Night’ we found the bass response of the Zensor 5 AXs to be tight and clean so Daniel Hobson’s beautifully conceived bass lines came through nice and sharply, with each note right on pitch and the timing spot-on. The level of the deepest bass was slightly back in the overall mix—perhaps the reason Dali has included a subwoofer output on the 5 AXs for those who prefer their deep bass to be at the highest levels possible—but listening to the driving bass and drums on What I Need, (which should really have been titled You Don’t Know What I Need) we can’t imagine too many people will feel the need for any more bass than the Dali Zensor 5 AXs already deliver.
Midrange sound was clear and articulate. Listening to Canteri’s vocals on Dish it Out, you can hear every nuance she adds to her delivery—the tiny inflections, the emphasis on the ‘a’ sound when she sings ‘I’m your family, I’m your friend’ and how she can add just a tinge of roughness to her otherwise pure voice when required. Also on this track just listen to how well the Zensor 5 AXs handle Justin Bernasconi’s screaming guitar leads. You can hear every note, and there’s no hint of overload or distortion. The harmonic accuracy of the overtones is also exceptionally good.
We also loved the lower mid/upper bass sound we heard when playing Leonard Cohen’s ‘Ten New Songs’. Listening to In My Secret Life, with Cohen’s voice all the way forward in its own acoustic, and Sharon Robinson’s voice—sometimes solo, sometimes multi-tracked—omnipresent in the background, and appearing sometimes in the left channel, sometimes in the right, and sometimes centred, was an exercise in sonic intimacy. The stereo imaging of the Zensor 5 AXs is very, very good, as is the channel separation…when a sound is solely in the left channel of the audio stream, there’s absolutely no ‘bleed’ to the right channel speaker (or vice versa).
High-frequency sound was crystal-clear without ever becoming glassy, and nothing we played seemed to be able to interrupt its purity. Listening to the often-confused high-frequency soundscape that is ‘Tame All Those Thoughts’, an album by local band Made in Japan, we could hear all the higher harmonics clearly over the cymbals and despite what we’d be tempted to call an over-produced album, there was still plenty of ‘air’ around the highs, particularly noticeably on the synthesised sounds… of which there are many. If you haven’t yet heard Made in Japan’s take on dream pop, give this one a spin… or even better, the band’s debut album ‘Sights and Sounds’.
Regarding the treble, we did note that it could be a touch bright if we were sitting directly in front of one of the speakers, which was one of the another reasons we suggested that you not toe them in so the tweeter paths converge at the listening position, as noted earlier in this review.
If you’re desirous of a low-cost, easy-to-install, easy-to-carry-round, minimalist hi-fi system to which you can stream music wirelessly from your phone, we think you’ll find it very hard to go past Dali’s Zensor 5 AX system. It has everything you need and it sounds simply fabulous. # greg borrowman
Laboratory Test Results
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 5Ω 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 ‘in-room’ 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