Back in August, a company best known for its studio vocal and instrument microphones and USB mics for mobile devices announced its first foray into the headphones market with the launch of Mo-Fi. Blue's big and beautiful over-ear headphones promised mobile music lovers a high fidelity listening experience regardless of the source music device. I managed to snag a quick listen at a busy IFA 2014 in Berlin last month and came away wanting more. My ears have now spent more hours than I care to admit surrounded by soft Mo-Fi foam cushions and I find myself reluctant to remove these rather impressive retro beasts.

The first question a digital groover on the move might ask when introduced to Blue's Mo-Fi headphones is, given that music-playing mobile devices already have a built-in amp, why opt for a pair of headphones that pack their own? Well, though the integrated amps of smart devices can happily cope with throwing sounds out to earphones, when faced with large over-ear headphones, they start to struggle and unwelcome distortion or clipping begins to creep into the mix.

A smartphone's amp, for example, might output between 20 and 30 mW, which should be enough to drive earbuds and small on-ear headphones, but those who like to proudly shout "bigger is better" would likely need the services of a pocket-friendly external amp. The Mo-Fi headphones have a built-in 240 mW amplifier, which provides enough headroom for the source device's own amp to output at lower volumes. That's not to say that annoying distortion will never raise its ugly head, but it should make such occasions very rare indeed.

The Mo-Fi headphones also boast 50 mm fiber-reinforced dynamic drivers which have been custom-tuned to match the output of the integrated "audiophile" amplifier. There are two amp modes to choose from, which are selected by using a three position switch at the base of the left earcup. This rotates around the 55 mm long base of the 2.5 mm, 4-conductor TRRS jack of whichever of the two proprietary audio cables you choose to plug into the headphones.

The 2 m (6.6 ft) cable is way to long for mobile use, but should be good for home hi-fi users, DJs or musicians. The shorter cable also sports an inline playback control for iOS devices.

I worried about the switch to be honest. Though I'll not be able to determine long term use problems with the headphones provided for review, the switch didn't quite fit with the robust nature of the rest of the build. It felt a little on the loose side and clicking between modes didn't feel as precise as I would have liked.

It's gonna get loud

The first position is off and has the headphones perform without the assistance of the amp. The passive mode is best suited to listening to CD and vinyl tracks via a home hi-fi system. If your home setup already boasts a decent power amp, then I'd advise against engaging either amp mode on the headphones. Doing so may result in some unwelcome elements gatecrashing to spoil the party.

Turning the switch clockwise by one position powers on the amp. If you already have the Mo-Fi headphones on your head with music playing, then caution is advised as the increase in volume is nothing short of startling.

The user instructions say that "because of the high-performance internal amplifier, Mo-Fi gets loud. Like, really loud. In fact, Mo-Fi delivers more than 6 times the power you'd normally get from your device." And the folks at Blue are not kidding. Lowering your source device volume before you start is not just advised, it's an absolute necessity.

There's an audible click when engaging the amp, which can also be heard if your source device is one of those that turns off its audio circuit between tracks. It's an annoyance, certainly, but one I found myself happy to ignore given the excellent performance of the Mo-Fi headphones.

Though the amp is without doubt the headline act here, the audio delivery experience in passive analog mode is a very pleasing one indeed. The soundstage is spacious and lively, instrument separation is excellent, the frequencies are very well represented and the sound quality is top notch. Perhaps not quite as pleasing to the ears as the similarly-priced Crossfade M-100 headphones from V-Moda, but definitely more comfortable (more on that a little later).

That solid audio performance continues through to the first of the Mo-Fi's powered amp modes (ON), though the signature does lean towards the lower registers here. Having said that, the bass is well defined and doesn't feel overwhelming like with some modern headphones, and leaves more than enough room for lively mid-range texture and crisp (if perhaps a little bright) high end clarity.

Blue has recognized that some like a bit more bottom in their music and has included a second powered on mode (ON+) that engages the amp's analog low frequency enhancement circuit for an immediate warm punch to the bass. Blue says that this adds some thunder to songs that might not have too much of their own already, while leaving bass heavy dance tracks pretty much to their own devices. Other areas of the frequency curve in this mode also seem to have been subjected to some minor massaging too.

A 1,020 mAh battery provides the necessary juice to run the Mo-Fi's circuitry, and is charged via the included 1 m (3.3 ft) USB charging cable. A full charge takes between 3.5 and 4 hours. Yellow/orange LED status lights behind the plastic grilles bearing the company name on both earcups pulse on and off while charging, which is not a hard on/off blink, but a gradual increase and decrease in light intensity. When the battery is full, the lights go out.

The headphones are reported to give at least 12 hours of up time. My real world continuous playback topped out at about 14 hours, while stop/start "normal" use resulted in something approaching 16 hours. When the headphones are removed and placed at rest, the amp is auto powered off to conserve the battery.

If the battery does run out of juice mid-song, fear not. The Mo-Fis will continue to play audio in passive mode, or you can charge while listening (though you'll likely suffer varying degrees of nasty buzz if you do).

Ready to rock

I reckon that I must have clocked up well over 60 hours of listening with the Mo-Fi headphones in the short time I've had them in for review. As such it's a bit difficult to pin down particular songs or genres where these headphones shine. That's partly because of the sheer number of songs involved and partly due to the fact that I can't recall a digital music track that sounded anything but good through these headphones. In most cases, playback sounded great.

Whether plugged into an iPad mini or a Samsung Note 8, or connected to a Nokia Lumia or Huawei smartphone, the internal amp and matched drivers of the Mo-Fis actually seemed to bring compressed audio and (let's be honest) pretty poor audio quality on streamed videos to life. Mobile music creation apps also benefited from the amp modes from Blue's headphones, offering a more dynamic experience than my Sennheisers or Sony MDRs could manage on their own.

It was pretty much the same story for my already impressive Cowon digital music player. Compressed MP3s were given a goodly quality bump, FLAC music simply shone and I can't remember hearing OGG files sound so good. Saying that it was like listening to music for the first time on an iPod is perhaps a bit of a stretch, but the Blue headphones once again proved that there is always room for improvement.

I had kind of settled for the rather poor audio quality being thrown out of the headphone port of my cheap and cheerful portable Bluetooth speakers, but the amp modes of the Mo-Fi headphones most definitely raised the bar. And my laptop's audio port didn't miss its usual play buddy – a smartphone-sized headphone amp - at all.

The Mo-Fi headphones feature a multi-jointed headband that can be adjusted for pressure against the head. Where some headphones can pinch at the earcup tops and barely touch the bottom, the Mo-Fis delivered all-round even pressure for fatigue-free listening. I actually found the noise isolation to be pretty good even at the looser end of the compression span, but felt a little "closed in" at the maximum end. About one turn of the adjustment wheel at the back was my optimum.

The "ear-shaped" cushions really do provide a very good seal for better bass, and improved isolation from the outside world. They're also surprisingly effective at keeping your music from bleeding out to those around you, especially considering how loud it can get inside the Mo-Fi world.

Despite tipping the scales at a not insignificant 16.44 oz (466 g), the Mo-Fis never felt heavy on my head. The combination of those jointed arms and headband and the ear pads makes Blue's amp-packing headphones incredibly comfortable for long haul listening.

On the other hand, there's no way of getting past the fact that these headphones are big. Yes, audiophile headphones tend to be both large and heavy, but they're not aimed at mobile music lovers. I remember asking the Blue Microphones rep at IFA how compact these headphones can get and being told that the photo above is about as portable as they get, though the pivoting arms allow the chunky circumaural earcups to be lowered when resting around the neck between listening sessions.

The bottom line

Let's face it, we've all had to make some serious quality sacrifices in order to enjoy our vast music libraries while we're out and about. With Blue's Mo-Fi headphones, the improvement in quality is evident as soon as the internal amp is powered on. The design might not appeal to everyone, but I'd highly recommend giving them a whirl. Your digital music library will thank you for it.

The Mo-Fi headphones are available now for US$350, which includes two audio cables, a USB charging cable and power adapter, an airplane adapter jack and a 6.4 mm jack adapter ... and a black case with magnetic closures to push everything into when not in use.

Product page: Mo-Fi headphones

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