Thankfully all this hard work isn't blown when you plug the ACS T15 in. They use just a single driver, have a decent frequency response of 16Hz ~ 20KHz and slightly high impedance of 41.5 Ohms. But while these are mostly familiar figures, as with counting megapixels or megahertz, they far from tell the whole story. Instead it is the sound signature which comes to the fore and here it is truly remarkable what ACS has managed to squeeze out of a single driver.
First and foremost, the expanse of the sound is unlike anything we've ever heard before from a single driver. It really is no exaggeration to say these deliver the sort of performance we would normal expect required at least two drivers per earpiece. Treble doesn't quite extend as far as we might like, but for the price they're astonishing. Bass, meanwhile, is just right. Many single-driver sets either crank up the bass and sound muffled or cut it altogether for the utmost in high-end sparkle. The T15s manage to get a good balance between the two. The soundstage is also surprisingly large, giving a satisfying spacious feel to your music.
All this combines to make the T15 excel with the subtlety of classical and acoustic music, as well as the bombast of hard rock, dance or hip hop. In other words, they're the perfect all-rounders.
Quibbles? Very few. Given the single driver the T15 performs best when you crank up the volume on heavier tracks, and in this regard they do benefit slightly from being amped (as in fairness do all earphones and headphones), but it's by no means a requirement.
Conversely the beauty of the fit and isolation is you don't need to hurt your ears just to distinguish your music from environmental noise. A perfect example is on the London Underground where 50 per cent volume on an iPhone 4S was all that was needed to silence the rumbling of the tracks. In fact on exiting Piccadilly Circus we didn't realise we had walked past a busker until we were half way up an escalator. If anything ACS has done itself out of one lucrative part of its business: custom moulds. Custom moulds for the T15 cost £90, but we suspect that for the vast majority they will be unnecessary. In this age of phones replacing MP3 players it would also be nice to see the T15 made with a mic option to answer and end calls, and stop or start music.
We say 'option' here because we wouldn't expect it at the T15's RRP. £149.99 is a snip for earphones that can match rivals at twice the price. The gauntlet has been thrown down, affordable earphones just leapt to a whole new level.
The ACS T15 trumps vastly more expensive rivals and blows away the competition in its price range. Runners will find the small design and superb silicon tips deliver a fit that doesn't slip, frequent travellers will love the noise isolation that means they don't need to ratchet up the volume to hear their music and the flush finish means some people could even wear them in bed. Build quality is also superb with a Kevlar reinforced cable that keeps cable noise to a minimum and is as durable as anything we have seen. There are a few minor tweaks we'd make but for the price we really can't complain. ACS has done it again. Rivals should be afraid. Very afraid.