Pros: Sound quality, relatively neutral turning, physical buttons, comfort, replaceable earpads, noise cancelling quality, excellent battery life.
Cons: Not foldable, no LDAC (though not necessary), not as featured as some cheaper, competing models, price.

Late last year I received an unexpected message from DALI, asking if I’d like to try their new headphones. As I was heading to the Tokyo FUJIYAAVIC Headphone festival, I quickly arrived for a pair of IO-6. The other headphones in DALI’s stable are the IO-4, which differ only in that they don’t have noise cancelling.

Arriving just before I had to leave, the unboxing was an interesting experience. Opening up the box, a wordless (presumably for international convenience) guide flap greets you with essential information. Aside from an instruction manual and sticker, everything else is in the case.

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The first surprise was that they don’t fold. While that makes them less fiddly to put away versus something like the FiiO EH3C, it makes them more bulky. That had them taking up a bit too much room in my Tom Bihn Synapse 19, which seems to end up stuffed to its limits on these trips.

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Also surprising is the lack of LDAC support. While ultimately I don’t consider there to be a significant enough benefit for a pair of headphones like these, especially if the intended use is in a noisy environment where the benefits of a supposedly better codec would be extremely questionable, it would have been nice to see.

The IO-6 is reasonably light and comfortable. It doesn’t quite match the absolutely lovely earpads of FiiO’s EH3C (which is in for review) but the basically padded headband and suitably thick (removable and replaceable) earpads were comfortable enough.

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Inside the liner pouch of the case lid are a USB A to C cable, a 3.5mm cable, and an airline adaptor. The latter was most welcome on flights where in-flight entertainment is available, as even a half-decent pair of noise-cancelling headphones beats the heck out of the cheap headsets one is normally provided with.

The IO-6 can be used in 3 ways: Wireless via Bluetooth, wired via the 3.5mm cable to an analog headphone amp, and wired via USB. Of those modes, via the 3.5mm cable can be done with the power off if the battery is low. With or without the power on, an analog source requires a volume control, as it disables the built-in control. Via USB, input up to 24/96 is accepted.

Set-up and control

If you’ve set up Bluetooth headphones before, the story is much the same with with IO-6. Nicely, they have a physical on/off switch, though it is really a soft-power switch disguised as a hard-power one. Really, the headphones always drain at least a very tiny amount of power. In my use of them, I could leave them for weeks without the battery going flat.

Not half way around the right cup from the power switch is a button that cycles through the noise cancelling modes: Off, noise cancelling, and “tranparency” (monitor mode) which passes through background sounds for use in situations where hearing what is going on around you is important. Between those buttons, lights for Bluetooth and power respectively use colours to indicate the status of the headphones.

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On the right cup, the centre silver area is a physical play/pause/answer calls button, and the areas immediately above and below are also physical buttons for volume up and down. That keeps the overall operation simple and is, at least for me, less vague than the swipe gestures some headphones have.

Most uniquely, the driver in the IO-6 uses a DALI-designed paper cone! Along with that was the pleasant surprise that the tuning is rather unlike other well-known brands of noise cancelling headphones. However, the noise cancelling is not as good as can be had from Sony or Bose. Allow me to explain.


With a little variation between wired and wireless modes, as well as with noise cancelling in noisy environments, the IO-6 has a fairly consistent, relatively neutral tuning, without an emphasis anywhere in the frequency range. It managed to deliver the bass rumble on Truth is a Beautiful Thing by London Grammar. Vocals were delivered pleasantly well, as were instruments, neither forward or recessed.

Mirrors, by the SEED Ensemble, a UK jazz outfit, was delivered with a pleasant degree of competence. Drum hits had a reasonable amount of smack, instruments were not overwhelmed by the bass and cymbals were clear enough without being overwhelming.

The treble is the only area where I noticed a significant difference. With the headphones switched on, the treble was spot-on for me, with enough sparkle, but never fatiguing. However, in wired mode with the power off, even with a good headphone amp, the treble is slightly harsh. Likewise in USB wired mode from my computer. In the case of USB, this could simply be the result of electrical noise interfering with the sound.

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However, while the sound balance was spot-on and the delivery pleasantly capable, there was a degree of veil over the music, even in the quiet of my office, the music sounding slightly smothered, regardless of set-up. The IO-6 simply isn’t going to match something like the Drop Sennheiser HD6XX or HiFiMan Sundara, both of which are cheaper (at current retail) than the IO-6. Though both are open-backed headphones only suitable for indoor use in a quiet space.

Of that, the IO-6 has reasonably good passive noise cancellation. Thankfully, switching on noise cancelling doesn’t harm the sound quality. On an airplane, however, it did a great job of knocking out the background rumble of the engines, leaving only some high-pitched hiss, but not enough to make listening to music unpleasant. Most importantly, the noise cancelling didn’t ruin the quality of the treble.

Every time I’ve flown with in-ear monitors, interference from background noise has made the treble unpleasant, and listening for more than about an hour uncomfortable. Noise cancelling headphones solve this, and it was far easier to listen for extended periods with the IO-6. Whether AAC from my iMac or LDAC from one of the various portable players I have here, music was represented pleasantly enough for me to enjoy listening, even to good jazz and classical, where normally I’d want for better sound quality.

Overall, the DALI IO-6 bucks the trend of bass-strong noise-cancelling headphones with a balanced, and somewhat nuanced sound, while still delivering very good, if not excellent noise-cancelling. The retail price is high, and this is definitely a pair to look out for at a discount.

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Pros: Superb quality sound in a wireless headphone that's scalable in analogue mode with well made 3rd party cables, long 30 hour battery life, AptX/ACC support, premium feel, well constructed
Cons: Unreliable power switch in long term use, no multi point Bluetooth support, no LDAC support, packaged cables don't match the premium feel of the headphones, delay in action (FF/RW, etc.) button response

Audiophiles would probably be familiar with the name “Dali” as they have been making speakers for the past 36 years. During that time they offer a range of entry to premium level speakers. However, recently they have taken a stab in making headphones which has resulted in the Dali iO-4 and iO-6, and Dali were courteous enough to offer me a pair of iO-6 for review a few weeks’ back.


Specifications and Design

Whilst both headphones are wireless, the iO-6 offers noise cancellation with a 30-hour battery life, whilst the iO-4 forgoes the noise cancellation but with a 60 hour battery life. Both headphones offer support to Bluetooth 5.0, AptX, AptX HD and AAC protocols, however Sony’s proprietary LDAC is not in the list. Both headphones can also be used wired should the battery resources run depleted. The iO-4 and iO-6 use 50mm paper cone drivers in almost identical enclosure cups aside from the odd noise cancellation button in the iO-6. The rest of the design is identical.

Dali offers each model in 2 colours, Caramel White (which is the one I have for review), or in more stealthy iron black. The materials utilised are primarily polycarbonate and synthetic leather however are incorporated together in such an aesthetically pleasing way that exudes sophistication and finesse. Even the assembly and construction demonstrate precision and class; the buttons are firm and definitive, the ear cups swivels smoothly, the headband adjustment is firm, and even the switching of the ear pads are symmetrical.

Dali has also opted to use the more current USB-C standard for charging which (at least in the iO-6, and presumably with the iO-4), comes with cables inside in a rather trendy looking carry pouch.


Comfort and Ergonomics

Whilst initially the iO-6 clamping felt firm and uncomfortable for extended use, after about 10 hours of break-in, I found I could, and did, wear them for a few hours at a time. They are proper circumaural headphones and my ears sit comfortably in the earpads. Whilst I’ve read other reviewers may have felt the ear pads were shallow for them, this is not the case with me. I don’t feel my ears touching the inner dust mesh.

The memory foam in the synthetic leather earpads do a good job in moulding providing a good seal even without my glasses. The cups swivel sufficiently across both axes to provide the right angles to provide the good seal.

The top of the headband is also padded and rests comfortably on my head. The overall headphone feels light and effortless without feeling flimsy.


Operation and Use

Electronically, I feel Dali has gone with simplicity with their wireless headphones. Whilst both models support the latest AptX, AptX HD, and AAC protocols (aside from LDAC), connectivity-wise Dali has adopted the traditional single point connectivity, and it does this well with Bluetooth 5.0. I live in a double story home and in one occasion I was upstairs in my bedroom when I switched on my iO-6 and it connected to something. Being a typical technologist, I have many Bluetooth devices - may it be my iPhone X, iPad Pro, iBasso DX200, Sony NW-WM1Z, etc. It took a while to realise it managed to pair to my iMac Pro downstairs in the TV room - separated by bricked walls. The connectivity was strong enough that I was streaming music through walls without any dropouts.

However, for those who do wish to pair their Dali headphones with multiple devices, one would need to disconnect from the current paired device before the new device can take over.

Dali has continued with the trend of traditional physical buttons instead of touch controls. Personally, for me, I’m very comfortable with physical buttons as I have had rather unnatural experiences with my former Sony MDR-1000X touch controls. It’s still not second nature to me and I prefer an actual physical click to provide me with assurance that I have performed an action. Dali’s implementation of the physical buttons is what one would and should expect out of a premium-designed product - buttons that don’t wobble, and have firm definitive clicks.


I found that I have experienced some 0.5 sec delays in response to the controls however.

Edit [8th July 2020]: Long term use :-
The power switch seems to have developed an issue where it doesn’t power on. It requires the button to be toggled a few times before it powers on, combined with it being a soft power, one can’t toggle too quickly. This issue isn’t specific to my unit but to other iO-6 owners too.

The battery of the iO-6 lasts for 30 hours, whilst I’ve not timed it but for the times I have drained and charged it, the duration sounds about right. Whenever one switches on the headphone, a report on how much battery life (in percentage) is provided.


The Dali iO-6 headphones come with 2 cables and an adapter. One cable is for analogue use, whilst the other is for USB-C charging. An airplane adapter is also provided. Here, is one area where I feel there’s room for improvement for Dali. The analogue audio cable does not feel as robust as what I am used to seeing in other headphones. I do feel that was provided more as a contingency when the headphones run out of battery and the owner still wants to continue listening to them, rather than for the owner who wants to have a wired experience as the primary form of listening.

The USB-C cable feels a little more robust, however both cables are wrapped in a rubber material that I suspect may melt and stick together in extreme heat, and now that I am in the middle of an Australian summer where we have had a string of 36-40C days, I’d be cautious not to leave the cables by the window sill or my car parked in the open. Mind you this is speculation as it has not happened yet however I have seen other cables with the same material react that way.

Thankfully though there is nothing unique about the analogue and USB-C cable. 3rd party cables work fine with the Dali iO-6. This opportunity opens options to those who like to “fine tune” their Dali headphones with premium cables.


As the iO-6 is more circumaural it isolates decently even without ANC. Comparing to the V-Moda Crossfade series, the iO-6 isolates more passively than the V-Moda’s.


Naturally some ambient sound still leaks in, especially of the lower frequencies, however this is where the ANC comes in. When ANC is enabled, it’s that lower range that the ANC isolates. Some of the higher frequencies still do leak in but to a lower volume and is not cancelled by the ANC. Thereafter any music played through the headphones drowns out any remaining ambient noise. As such I feel the ANC works well enough. Without ANC, the ambient sound in a busy area can still be distracting even with music playing.

There’s also a transparency mode which reamplifies what the external mic pics up to the headphones. This is presumably to be able to listen to external conversations without removing headphones. With iOS devices at least, transparency mode pauses music. Presumably it does the same with Android devices.


In Bluetooth mode, I’ve found the iO-6 is able to drive with sufficient volume for most songs. There are some odd songs where I could do with more volume but for the most part I’m satisfied. In wired mode, naturally it’s up to the external amp and the headphones can go louder if needed.

Bluetooth Use for Conversations

These headphones are designed primarily for audio and whilst it can be used for SIP calls, the microphone does pick up ambient noise in conversations. This is typical of other Bluetooth headphones too.


Bluetooth AAC

Overall, the iO-6 has taken a more evenly balanced frequency response. As a comparison, the V-Moda house sound tends toward a bossier signature. Whilst initially out of the box, I felt the iO-6 had a light bass response, over time I found that it was tight and had a satisfying impact. Dali, having made quality speakers for such over 3 decades, have recreated a sound quality of sophistication and finesse into their headphones. Once the iO-6 drivers are well exercised after couple of hours of use, it settles to a sound reproduction that is exudes refined quality.

Whilst on the topic of frequency response, as mentioned the bass is tight and decently impactful, but it tapers off in the sub-bass region. Texturing is ever so light and this kind of bass characteristic lends well to songs where there is a fast transition from beat to the next.

As for the midrange, the iO-6 is second to none in the current wireless headphone range. Vocals are simply crystal clear and very refined in reproduction. Especially in vocal jazz, the texture reverberation of vocals can be discerned clearly.

Similarly, with the treble region, the iO-6 is precise, airy, and crystal. However, for listeners who are treble sensitive, may find them a little uncomfortable. For my ears though I do like them.

Across the frequency response however, there is no bleed nor smearing as one (bass, midrange, treble) range crosses from one to the other. I feel Dali has taken care to ensure they do their best for each range however, ensuring the different frequency ranges remain coherent.

In terms of soundstage, the iO-6 sets a wide and tall virtual stage space. In fact, when I first unboxed and listened to the iO-6, it reminded me of the HD800 (but naturally not as wide as the HD800). For a pair of closed back headphones, it is impressive. Over time when the mid-bass and midrange presence have blossomed, it fills in the empty virtual space it has created.

Overall, to my opinion and preferences I feel the iO-6 excels well in the genre of Classical, 50/60’s jazz, 70-80’s pop, vocal jazz. However, if it’s more current EDM and R&B, I feel a pair of headphones with more expressive sub-bass to be more suitable.


As touched upon earlier, the ANC works sufficiently well although it may not necessarily cancel out some of the higher frequencies that my leak in. it seems to cancel out as well as majority of the noise cancellations headphones - with the exception being the Sony series which seem to create total isolation (which to me, at the cost of sounding somewhat “digital”).

It has also been commented on the forums, there have been quite a few comments that bass is more impact with ANC on. For as far as I’ve been able to discern, I don’t think this means there’s more bass quantity, however with the ANC on, clarity of the bass is more clearly heard and therefore sounds more impactful.


Rather interestingly there seems to be a slight tonal shift whilst listening wired with the iO-6 on, and off. With it off, the iO-6 the upper mids seem to have a little bit more bloom. This isn’t something I expect as I would have thought all internal DSP would be bypassed.

Having said that, with it wired and volume adjusted accordingly, there is an added smoothness and a tad more “rawness” (less perceived processed?) to the signature, especially when paired with a decent external DAC/amp or DAP. Although I’ve not tried different cables extensively, I did try with an Ortofon 6N POCC cable and one can definitely fine tune the iO-6 signature with a cable of their preference. The iO-6 clearly demonstrates its potential in scalability.



As a first take on headphones by Dali, the iO-6 clearly has made an impact to the wireless headphone market. In wired mode, it’s making its first steps to the audiophile category. It is definitely one of the most finest sounding wireless headphones I have heard. There is room for Dali to improve on a few aspects of the headphones such as supporting multipoint, improve on the delayed response times of the music controls, better quality cables to match the sophisticated design and feel of the headphones itself, and if possible, add LDAC support to the list of protocols. Whilst other users may demand a more aggressive noise cancellation, personally for me this isn’t necessary - especially if there is potential for unexpected side effects such as making the signature sounding overly digital.

The Dali iO-6 demonstrates that one can get refined quality with wireless headphones.


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