I've tested many Bluetooth speakers, but this 5-star one is a 2025 top pick – and surprisingly priced

We're in the throes of a summer heatwave in the UK, which means I'd opt to work outside – if I wasn't ill with a temperature, hiding indoors behind curtains – with one of the best Bluetooth speakers at my side.

While it's certainly not specifically designed for outdoors use, Harman Kardon's latest, the Onyx Studio 9, is a really stellar portable – that surprised me in the most positive of ways when I reviewed it earlier this year. It's a 5-star product through and through – and with a price that surprises too.

This portable mightn't be the smallest, although that's besides its point, but it's been enough for me to say 'forget Sonos' as I've gleefully used it around the home and (in the past) outdoors too. It's not weather-sealed, mind, so you'll need to swerve rain and any water – but it still sounds great in the garden under some sunshine.

Big sound without a huge price

Some of the best portable Bluetooth speakers can cost a pretty penny. Another favourite of mine, the Bang & Olufsen Beosound A1 Gen 3, is my go-to speaker for travel. It's perfectly designed for that, but actually costs more than the Harman Kardon I'm discussing here.

That's one of the great things about the Onyx 9: for just a couple of hundred you can acquire really big, bold, bassy sound that'll rock whichever room you place it in. Or turn the output down for something more soothing and it'll deliver that as needed too.

As the upgrade to an earlier Onyx 8 model, the 9 has a much larger battery (4722mAh versus 3283mAh), which means it can deliver 8 hours of output away from a plug. I've found that really solid in practice, too, ensuring a full working day needn't be spent wired in.

Note that this is a Bluetooth only speaker, there's no Wi-Fi or any other connectivity (save for Auracast for connecting other speakers). You can wirelessly connect, say, your phone or tablet, and blast the tunes from that source with ease. There's an app to make that easier, or you can use the physical controls atop the product, which are handy.

Any low notes?

From the very moment you switch the Onyx 9 on, the amount of bass this relatively small speaker can emanate is hugely impressive. There's lot of low-end, so it'll cater for your pop, hip-hop and other sub-focused genres really well. Yet thanks to a trio of tweeters, it can separate the higher frequencies nicely, for a full and accomplished range of sound.

While I find the Onyx Studio 9 super-easy to carry around the house from room to room, although the lack of any charging cradle is a bit of a shame. Some older Harman Kardon products had such a design – something ready and waiting plugged into the wall, so you could pop it back on charge rather than having to fiddle about inserting the Fig-8 cable again.

At this price, I never expected the Harman Kardon Onyx Studio 9's quality to be so top notch – but this Bluetooth speaker knows how to deliver sound in Sonos-rivalling ways for even less money. It's a great-looking and great-sounding speaker that I didn't expect to be as accomplished as it is.