Most savvy consumers recognise that the 'freebie' earphones supplied with music portables belong in the bin.

However, the upgrade options can be bewildering; there's in-ear, on-ear, noise-cancellingÖ plus the awkward paradox that big isn't necessarily better. So what's the best solution and what makes the ultimate earphone for music on-the-go?

Anyone who has used headphones outside can grasp the benefits of the electronic noise-cancelling systems currently on the market and likewise, 'noise-isolating' systems — a more natural approach with earplug-like headphones — offer tangible benefits in blocking out outside noise, leaving just you and the music.

So imagine, then, a custom-fit earplug moulded for your ears, with a high-quality drive unit systems inside. Enter the TS2 'in-ear monitors' from Advanced Hearing Solutions (ACS).

Custom-made

The specialist provides custom-fit in-ear monitors for performing musicians and hearing protection/communication systems for motorsport applications, so they know a bit about earphones.

When you buy a pair of T2s you'll be given a voucher to arrange a quick custom fitting session at an audiologist in your area. In less than 15 minutes, a mould of your ear is taken which is then sent off to ACS to transform into your own, personalised set of in-ear T2 monitors.

The clever design is based around two tiny drivers that ACS claims deliver, ìan incredibly detailed responseî and a frequency range of 20Hz to 16kHz.

The driver unit is moulded within the custom-fit earpiece, which is made from high-grade silicon ­– a substance that lends itself particularly well to the inner ear—quickly reaching body temperature whilst retaining crucial flexibility. Sound travels a mere 10mm from the tiny drive unit to the aperture, down a 1mm diameter 'tube'.

ACS says the T2 blocks out 26dB of background noise and when fitted correctly the blocking effect is incredible, enabling you to see the world but not hear it.

Rather brilliantly, this means you only need around half the volume you would normally require to get the same listening levels, dramatically reducing the risk of long-term hearing loss, something ACS founder Andy Shiach is extremely passionate about.

Sound Quality

The benefits of a custom-fitted earphone are abundantly obvious in use. It allows the earphone's driver to operate in a near-perfect environment, free from intrusive background noise and external influence. This allows for extraordinary levels of detail that few earphones (and few high-end hi-fi systems) can achieve. And to simply use the word 'detail' doesn't do the T2 justice.

What it does offer is unparalleled intelligibility of music, uncompromised neutrality and the kind of 'rediscover your music collection' resolution that traditional hi-fi manufacturers collectively aspire to. There's so much transparency of offer, in fact, that the T2s will effortlessly reveal detail in music that you didn't even know existed!

Compared to a full-size hi-fi headphone such as the excellent £160 Sennheiser HD 595, there's a sense that some 'scale' and dynamics are missing, but the insight the T2s give quickly becomes addictive. But plain sailing it's not.

Many users will find the 'intimacy' of the fit takes some getting used to and the slightly fiddly fitting procedure can seem troublesome at first. This is a product for the dedicated user, however, but persevere and the rewards are there for the taking.

We've yet to find a more accurate earphone and if you can afford £500 in the pursuit of commuting heaven, it really makes a sound investment.