Bose SoundLink Flex review: Not all that flexible

The Bose SoundLink Flex is part of the American manufacturer’s SoundLink series, which dates back to 2009 and includes various portable speakers.

It’s attractive, waterproof and particularly good at reproducing low frequencies, making it an appealing choice for those who like their music with a generous helping of bass.

However, audio can’t be customised in any meaningful way and the Flex starts to lose its composure when pushed to its limits. So, unless you’re desperately craving simplicity or are particularly attached to the Bose brand, you’ll be better served by one of the many more flexible all-rounders available for similar money.

Bose SoundLink Flex review: What do you get for the money?

The Bose SoundLink Flex is a mono-driver Bluetooth speaker available in four colours (Black, White Smoke, Stone Blue and Carmine Red) for £150. While it has only a single full-range driver, this is supported by a large rectangular passive radiator on the front and a smaller one on the rear.

Bose hasn’t revealed the size of this driver, nor the SoundLink Flex’s total RMS output, but we do know the speaker utilises a Bluetooth 4.2 connection and supports multipoint pairing. There are no physical inputs, however, so this is a speaker designed solely for wireless streaming.

There’s no support for high-resolution Bluetooth codecs such as LDAC or aptX Adaptive either, with the SoundLink Flex limited to SBC and AAC. It does have Bose’s PositionIQ adaptive equalisation on board, though, which seeks to optimise audio based on the speaker’s orientation.

The SoundLink Flex sports a slimline design featuring a steel grille and soft-touch silicone exterior, weighs an eminently portable 0.59kg, and has dimensions of 201 x 91 x 53mm (WDH). Its IP67 rating certifies it fully dust tight and submergible in up to a metre of water for 30 minutes, while Bose says the powder-coated grille stops rust corrosion and UV light damage, too.

You’ll find tactile and responsive control buttons on the body of the speaker that look after power, volume and Bluetooth pairing, as well as a multi-function button for playback control (press once to play/pause or answer a call, twice to skip to the next song and three times to return to the previous track) or activating a voice assistant (by holding it down). There’s also a built-in microphone enabling you to use the SoundLink Flex as a speakerphone if required.

Battery life is stated at a relatively standard 12 hours per charge, with this figure dependent on volume level, while it takes a leisurely four hours to fully charge via the included USB-C cable.

In its price bracket, the Bose SoundLink Flex is competing with numerous highly capable Bluetooth speakers, ranging from the Sonos Roam (£159), which also supports a Wi-Fi connection, to the gorgeous B&O Beosound A1 2nd Gen (£199), so it has its work cut out to stand out from the crowd.

Bose SoundLink Flex review: What do we like about it?

Considering its size, the SoundLink Flex manages to pack a real punch. Bass is the first thing that hits you and helps shape a warm sound signature bolstered by the inclusion of the pair of passive radiators. It’s a tuning I found enjoyable across a range of genres, though naturally tracks backed by bassier rumblings, such as The Haxan Cloak’s droning N/Y, are most satisfying.

The dominance of low frequencies is less noticeable at higher volumes: vocals and upper-register sonics are more prominent and the tuning becomes more v-shaped, which I found preferable when listening to music across various genres. Vocals and lead instruments are crisp and accurately reproduced at volume levels in the region of 60-80%, but any higher than that and some distortion begins to creep in. That’s not unusual for Bluetooth speakers of this size and price, however, and the SoundLink Flex is able to fill small and medium-sized rooms with relative ease.

One advantage the SoundLink Flex has over much of its competition is that it floats. This, coupled with its IP67 rating, means it can accompany you in a hot bath during the winter months or in the pool on your summer holiday. There’s also a built-in strap allowing you to hang the speaker up, while the robust build of the Flex ensures it won’t be damaged if it falls from its perch.

It’s worth reiterating how easy the SoundLink Flex is to transport. Unlike other “portable” speakers such as the Marshall Middleton, the Flex is lightweight and can be carried around with very little effort.

While useful, I found Bose’s voice prompts particularly grating compared to other speakers, so it’s handy you can turn them off in the Bose Connect app. The app itself is fairly bare-bones but does allow you to set an auto-off timer to save on battery, pair the Flex with other SoundLink speakers including the Micro and Revolve, check battery life and switch between the devices you’re connected to.

Bose SoundLink Flex review: What could be improved?

While the SoundLink Flex is a bit of a bass monster, I found it lacked clarity. The lows sounded a little bloated and didn’t have the refinement to match their table-shaking power, while fine details across the rest of the frequency range were lost at lower volumes due to the overwhelming bass response. As previously mentioned, the SoundLink Flex begins to distort when pushed to its limits, meaning the speaker performs best within quite a narrow volume range, which isn’t ideal.

The soundstage isn’t huge, either: you’ll be able to enjoy a broader presentation from the Marshall Emberton II or Sonos Roam, both of which also support in-app equalisation, unlike the SoundLink Flex. There’s no banded equaliser, EQ presets or any other audio adjustment features, so you have to make do with its out-of-the-box sound.

The lack of EQ controls could be better understood if the SoundLink Flex’s automatic PositionIQ equaliser system was more effective. This automatically tweaks audio to optimise it when the speaker is positioned vertically, horizontally or on its back, but I didn’t notice much difference in any of the three orientations. Even if it had more of an impact, PositionIQ isn’t a suitable replacement for those that want to personalise how the speaker sounds. It’s also worth noting that the Flex won’t stand horizontally on its own due to its rounded edges – you’ll need to lean it against something to prevent it toppling over.

There were a few other minor annoyances, too. The speaker’s built-in microphone lets in large amounts of background noise when used outdoors and, while intelligible, was still somewhat crackly in the sonic safety of my bedroom.

And while the fact the SoundLink Flex floats is appreciated, it doesn’t do so evenly. The end with the fabric tag dips beneath the water, muddying the sound, meaning the main benefit of its buoyancy is to prevent it plummeting to the bottom of the ocean rather than enabling it to deliver clear audio when bobbing on the surface.

Bose SoundLink Flex review: Should you buy it?

Fans of bass-heavy music will find a decent amount to like about the SoundLink Flex. It’s lightweight, extremely portable and delivers an impressive low-end punch.

Despite its name, however, the SoundLink Flex isn’t all that flexible. There are no equaliser controls, PositionIQ has no real impact on your listening experience, and audio quality is at its best within a restrictive volume range.

As such, the Flex falls behind a number of similarly priced rivals in the portable speaker pecking order. The JBL Charge 5 delivers a more muscular performance and longer battery life, the JBL Flip 6 offers EQ customisation options, while the Sonos Roam supports Wi-Fi streaming and wireless charging and sounds phenomenal. But if you crave simplicity or already own a compatible SoundLink device and want a second speaker to pair it with, the Bose SoundLink Flex merits consideration.