The RDP-X80iP is Sony's answer to the once ubiquitous Bose Sound Dock, but it cleverly takes things further by adding a built-in battery.

Portable and powerful, this sleek black speaker lies across a 20W digital amplifier, and on its own can be used as a permanent speaker for almost any audio source imaginable thanks to its mini-jack audio input on the rear.

Working with any iPhone (including the iPhone 4) and shipping with Apple's dock adaptors 12 and 15, for the original iPhone and for the first 3G model respectively (much like Sony's recent RDH-SK8iP), the RDP-X80iP charges Apple gadgets if the unit is plugged into the mains.

Stylistically this 1.9kg unit doesn't break any new ground, with a gloss black (and fingerprint-hungry) plastic casing that leans back slightly, thanks to it carrying its weight at the base. Whether you'd use this 356 x 119 x 163mm unit as a permanent speaker is doubtful, so its pop-out iPod/iPhone dock does seem an unnecessary, though subtle, design flourish.

Although it is fitted with an OLED screen in its top-left corner, it's a tiny display; the only purpose it serves is to flash-up an icon of a charging battery (when the unit is attached to the mains), let you know which mode it's in (external source or iPod), and display which sound mode you're currently using (along with a representation of the graphic equalisation).

And those five sound modes - rock, pop, jazz, vocal and flat - are key to the RDP-X80iP's excellent sound quality. Considering its compact nature, it pushes out surprisingly convincing low frequency effects alongside some clear mid-range sounds. A run-through of The Killer's challenging Indie Rock 'n' Roll sees vocals and background instruments well separated, with the signature bass line having plenty of impact. Engaging the pop mode puts vocals at the forefront and treble details given a push, though the other modes proved rather lacklustre.

High volumes are possible without any distortion and you'll have no problem using the RDP-X80iP in a large-ish room or garden, though sound is muffled if you move to the extremes of the soundstage. And sheer power, extra bass and a more nuanced sound can be found elsewhere; for example on a dedicated hi-fi system, or even a high-end iPod dock such as the Vita Audio R2i, which served as a control during our test. Neither of those options can be used away from a power supply though, something the RDP-X80iP manages for 7 hours.

Despite some of the advertising stating that this unit has a FM tuner onboard, we're sad to report that it does not. If that could be a deal-breaker for some, our final criticism shouldn't be; its tiny remote isn't quite as simple, or as responsive, as we'd hoped, and lacks a mute button. It's also worth noting that although it just about masters iTunes ("menu" and "enter" buttons are used where up/down/left/right controls as used on Apple's clickwheel would be more logical), the remote doesn't control the iPhone's Spotify service.