Performance

The Deva can be used as both a conventional headphone with the supplied cable or a Bluetooth headphone with the Bluemini module. While Bluetooth audio has seen some major advances over the years, both in terms of hardware and codecs, it still is not able to fully compete with good desktop or portable but cabled DAC/amps. In that sense, there is the tradeoff of sound quality vs. portability and ease of use.

HiFiMAN tries to cover all bases with the Deva and Bluemini. For stationary use you have the cable which allows you to use your favorite headphone amplifier and sources at home, and for on-the-go use, simply plug in the Bluemini before heading out. The Bluemini does take up some space and makes the headset look noticeably lopsided. One thing you will miss while using the headphones outside is some noise attenuation, be it passive or active. The Deva is an open-back headphone in its truest form, so there is absolutely no noise attenuation whatsoever. For wireless use around your house, it is of course fine, but for a commute, I would still prefer something that keeps outside noise out and prevents others from listening in.

The Deva is one of the most comfortable wireless headphones I have come across. There are no obvious pressure points, and they weigh very little for their size. They are very generously padded, and the ear pads ventilate really well. Usually, HiFiMAN headphones are in the better end of the field when it comes to preventing your ears from heating up, and in that regard, the Deva is the best one yet from HiFiMAN.

Wired

On first listen, this is clearly a classic HiFiMAN planar magnetic. It sounds close to what you got with the older generation of HiFiMAN planar magnetics, which is a good thing. The bass is tight and has great extension and a small bump which emphasizes the low-end presence. It is a bit mid-centric compared to the Sundara, and although not as dominant as on the Sundara, there are still some treble peaks. Out of the box, the tuning is definitely one that will entice a broader audience. The sub bass is less pronounced than on the Sundara, with the roll off beginning a little earlier, but sub-bass extension is still superior to many headphones that cost much more.

The midrange is great. It is in line with what we have come to expect from HiFiMAN headphones. It is very detailed and without major oddities. Like some of the older HiFiMAN designs, you get a little bit of warmth from a slight boost to the lower midrange. It is nothing huge, but definitely noticeable when coming from headphones that are very close to flat throughout the spectrum. The upper midrange is a little shaky, which does not subtract noticeably from the experience as the oddities are in a very narrow band.

The treble is not quite as detailed as on the Sundara, but seems very close. However, the tuning of the high end is much better on the Deva. The Sundara has piercing highs, and while the Deva is not dull, it is definitely not as pronounced. Especially the dialed down 6 kHz bump makes it much less fatiguing to listen to. There is still something strange in the treble as the 10 kHz seems a little excessive on some tracks, which is perhaps because it is slightly less controlled and rings for a little too long.

In terms of soundstage, the Deva rivals the Sundara and is only bettered by the much more expensive HiFiMAN Ananda. The soundstage is not that different from similar looking HiFiMAN designs. It is on par with Sennheiser HD6xx-series headphones, while getting soundly beaten by their HD8xx-series. These are of course also higher-priced headphones with fewer features.

Wireless with Bluemini

Connecting the Bluemini to the Deva is just as easy as inserting the cable. A small notch on the bottom of the headphones secures the Bluemini to the ear cup. The Bluemini has a small spring-loaded clip that easily goes into the mating geometry on the headphones, which makes it easy to see and feel if you have it mounted correctly. Since the Bluemini mates well with the bottom of the ear cup, it feels quite durable. Given the interface design, it would clearly take quite the effort to break it.

Getting the Bluemini up and running is quick with the OnePlus 7T Pro we used for testing. The connection was solid both inside and outside, and there were no issues when changing the codec and having the device resume connection. The Bluemini has a play-pause button and another that sets it up for pairing. One function that is often overlook is the Bluemini's ability to functions as a USB DAC/amp, so if your device is without a mini-jack, you can actually play over USB.

When coming directly from the O2+SDAC to the Bluemini there are of course small changes to the sound quality. Like with most portable high efficiency gear, the noise floor is higher, which is mostly noticeable when you are not playing anything or there is a really quiet passage in the track. The Deva does reasonably well here. Its noise floor is a little higher than on the Ananda-BT, but not by much, which makes it a non-issue under normal circumstances. The dynamics are a little compromised on the Bluemini, but unless you are in a totally quite place, I doubt you will ever notice it.

Overall, you loose very little sound quality by going from wired to wireless, which is pretty amazing. What makes it even more impressive is that the Deva is well worth the $299 asking price on its own. The fact that the Bluemini is included is a big cherry on top.

Compared to the Sony WH-1000XM2, the sound quality is much better on the Deva. There is a huge difference in the amount of detail throughout, and the frequency response is also much flatter on the Deva. The comparison is of course a little unfair as the XM2 is a closed back with ANC in the loop, which does make it substantially harder to get good sound quality. For on-the-go use, the brilliant ANC performance of the XM2 makes it a better partner for a long commute.

Battery life is stated at 7–10 hours officially, which is probably correct for normal use, in-doors and at normal volume levels. We got a decent spread within this range with different types of music and listening patterns.