It's the size of a sawn-off drink can, it weighs 260g and it's been given the catchy name of SRSXB10. And at $79 it's one of the best bargains in audio right now. It's Sony's smallest Bluetooth speaker, nine centimetres tall and 7.5cm in diameter, and you'll have trouble believing how good it is.

I certainly did.I unpacked it, sighed (another bloody Bluetooth speaker), charged the battery, fired it up and suddenly realised I was hearing way better musical reproduction than anyone could expect from something of this size and price. So I took it downstairs and played it for my considerably better half. She looked at it in disbelief. "That's absolutely amazing," she said, and when she asked the price said "No-o-o… has to be a mistake."

The next day my friend Bob, who runs a radio station, was around for lunch and I put it in front of him. He used the word "incredible" three times. He had the idea of sitting it on the coffee table so that it used the entire surface as a sounding board, increasing the bass – which is already pretty damn impressive.

I wish Sony had invented this 20 years ago when I was in a job that took me away from home a lot, often for three or four days at a stretch. Back then I tried to take a small, active speaker along to plug into my computer so I could fill lonely hotel rooms with something at least approaching a semblance of music, but there was nothing this small, this light, this good at reproducing sounds. I frequently had to make the choice of taking my speaker and checking a bag, or leaving the speaker at home and getting by with carry-on. The speaker always lost.

With this I would have had great music in a tiny package of just a quarter-kilogram. And while then it would have needed to be hard wired to a computer, this runs off anything with Bluetooth. The Bluetooth connection is only standard SBC but in something this size it doesn't matter much – if you're into detailed listening you won't buy one, but if you want something to fill the space while you're attending to other matters at your desk it's just the thing, and two can be set up as a stereo pair. It's available in five colours, the battery is good for up to 16 hours and it has a lanyard that doubles as a horizontal stand. It's even water resistant.

But do bear in mind it's for personal listening only, it doesn't go loud enough for anything else. It has a 46mm full-range driver firing straight up through a grille that's colour-matched to the body, and it's the only driver in the unit, so why are there four vents at the bottom? That's for the passive radiator firing downwards.

What's a passive radiator? Were you to take this apart you'd probably think it was another driver, but in fact it's just a cone that is driven by changes of air pressure inside the unit as the real driver pumps in and out. A passive radiator set up carefully can enhance bass markedly, and it sure does in this, giving the music surprising body and depth without affecting its excellent high range ability.

I listened to this solidly for a couple of days and the only thing that threw it off balance was the high range in Time to Wander by Gypsy and the Cat. Otherwise it was, simply, brilliant.