In fairness to Sigur Rós, they have self-awareness on their side. In some ways, the BBC's use of 'Hoppípolla' on their Planet Earth series gifted them a double-edged sword, for while it brought the band's work to the attention of a far wider audience than an Icelandic post-rock group may have previously hoped, it also forged an almost unbreakable linkage between their expansive compositions and biome-conquering footage of freshly fallen drifts crowning Alpine crests or shoals of rainbowfish frolicking amongst irritatingly beautiful Pacific islets.

And the band have now rightfully taken hold of this perception and turned it to their advantage . Writing about their set at this week's Boiler Room in Berlin (where they took to the decks as "Sigur Rós & Friends 'Triple Nipple'"), they issued a warning that it wouldn't include their usual, vaulting fare: "this is not going to be wall-to-wall, hair-tossing post-rock. there will be no glacial soundscapes of awesome dimensions. neither warm bubble baths of yoga wind-down muzak. (or any of the other enduring cliches about Sigur Ros)", concluding "if you are expecting a mystique enhancing exercise of deep solipsism, look away now." While they're laughing about it, there's also the hint of something more serious lingering beneath. Their last album, 2012's Valtari, was the end result of fraught recording sessions, a cumbersome partial re-iteration of their older material, only flecked with their triumphant moments that recur throughout previous albums Ágætis byrjun and Takk.... Earlier this year, founder member Kjartan Sveinsson departed, while the band noted the next album would mark a sea change shift to something more "aggressive" sounding.

Kveikur, then does feel like the product of self-reflection. From the faintly sinister masked face surrounded by darkness on the cover to the crunching, bleak drum stabs that laced the trailers leading up to the album's release, the band have made a concerted effort to produce something that doesn't recourse to the sepia-tinged emotive euphoria of old. And, in part, it works.

Opener 'Brennisteinn' arrives in the attenuated, distant hail of the sounds of warfare, slashed across by huge drum strokes and seeping digital noise, quickly shifting into rhythmic metallic clanging. Jón "Jónsi" Þór Birgisson's vocal initially assumes its soothing, familiar tone, but repositioned in this new militant setting forms a kind of magnificent counterpoint. By its close, a panning, spacious coda with Hans Zimmer-esque volleys of brass, it feels like, if not singing off the same hymn sheet as These New Puritans, Sigur Rós are at least standing in the same pew.

Elsewhere, the title track takes up the 'dark' mantle, built out of a matrix of guttural, saturated guitar clanks, Jónsi's voice here fighting to be heard within waves of agitated sonic tumult. It doesn't come together quite as well as 'Brennisteinn', and you find yourself willing the closing clashes of feedback to be amped up just that bit more, but it breaks new, harder ground for the band.

The more well-trodden sonic pathways, meanwhile, are equally strong: 'Ísjaki' is shot through with the fraught urgency that Sigur Rós do so well, propelled by thunderous drums and a keening guitar/string motif that sounds instantly festival-ready. 'Rafstraumur' meanwhile bears traces of their 2007 single 'Hljómalind', reducing some of the sonic atmospherics in favour of fewer instruments and a direct, piledriving hook; the foregrounded bass and snappy snares lend the track an almost post-punk framework, giving Jónsi's voice and guitar a more emotive focus.

The downside of the album, though, is that the other five tracks are too ponderous to be memorable. It's a familiar struggle for the band, where their albums' weaker moments occasionally lapse into feeling like extended intros or outros to the standout cuts. 'Hrafntinna' and 'Bláþráður' are cut from the same cloth as 'Brennisteinn' and 'Ísjaki' respectively, but pass by almost unnoticed, while 'Yfirborð' attempts to map a house beat onto a typical Sigur Rós soundscape, though one so disconnected it ends up sounding like a bad remix.

This all leaves Kveikur reaching a kind of sonic middle ground. The comparative brevity of the album - its nine tracks clock in just over 45 minutes - and the darker hue of some of its material suggest a healthy bit of self-reflection for a band almost 20 years old, though it feels more like a quarter-turn than a reinvention of the wheel. That's not to say to that all previous Sigur Rós albums have been entirely bereft of heavier stuff or that they should do away with their defining characteristics, their "glacial soundscapes of awesome dimensions"; it's more that Kveikur feels more like an unfinished trip (through said glaciers, perhaps), where the destination is in sight, but seen only from the halfway point.