Sony’s MDR-XB40EX in-ear canal-phones are designed for lovers of big bass beats, with great isolation and very low frequency extension. While this makes them well suited to hip hop or drum 'n' bass, they are not as suitable as some other headphones for overall fidelity and sound quality.

Usually canal-phones are miniature and disappear almost entirely into the ear canal when worn — Etymotic Research’s ER6is are a good example — but these in-ear monitors (IEMs) are a similar size to full ear-buds like the Sennheiser MX Series. This means they’re easy to position when wearing, but the downside is that they are quite bulky. This can lead to discomfort when the canal-phones move around.

They look stylish. A brushed metal fascia with the Sony logo is what the outside world will see if they examine your ears. This fascia is around four centimetres long — we think this is too long by at least a centimetre. This is another contributing factor to an overall uncomfortable experience.

The main reason for the excessive bulk of the earphones is the "direct vibe structure" — a long stroke diaphragm which allows for a comparatively large amount of air to be moved — the secret behind the bass notes.

Sony supplies the earphones with three different tip sizes to allow for some adjustment. We found the most appropriate tips to be the standard, medium-sized ones, which offered a good compromise between comfort and noise isolation.

The MDR-XB40EX earphones are rated at 4-24,000Hz. We’re sceptical of such claims — see our review of Sony’s MDR-XB700 for more on this. There’s no question that the MDR-XB40EX earphones are incredibly bass-focused but they are not as dynamic as Sony claims.

Bass extends decently low and has a slow decay, leading to reverberating notes with a very impressive sound. This is best suited to synthetic beats like drum ‘n’ bass music, so you may find complicated music — classical compositions, for example — muddied by excessively persistent bass.

A very rich mid-range gives music a warm timbre with vocals sounding very earthy and husky — think Ella Fitzgerald circa 1945 in a smoky jazz club. Treble is let down by the powerful bass, with higher piano and brass registers lacking clarity and fidelity.

If you want bass and convenience, these headphones are hard to pass up. For a more well-rounded musical experience you may want to consider different canal-phones, though.