Short answer: both are discontinued, so this only matters if you are buying used. Used, the Bowers & Wilkins Formation Flex is the better pick: it ranks #18 of 48 powered bookshelf speakers by sound quality (rated 3.5/5), against #23 (rated 3.3/5) for the Kanto YU4. If you want one new, the Audio Smile Little British Monitor ranks #1. The Kanto YU4 has been replaced by the Kanto YU4 G2.
The Bowers & Wilkins Formation Flex is the more accurate choice. A compact wireless streaming speaker with AirPlay 2, Spotify Connect and Roon, which can pair as a cable-free stereo set. Its measured preference score, a predictor of how neutral it sounds, is 3.69 against 2.89 for the Kanto YU4. The catch: Standalone preference is only 3.69.
Why pick the Kanto YU4: A compact powered pair with phono, optical and Bluetooth inputs, a remote and a subwoofer output. It keeps a wired aux input, which the Bowers & Wilkins Formation Flex lacks. Watch for: Standalone preference is only 2.89, with a -3dB point around 86Hz and a 4.2dB midrange response span.
Buy the Bowers & Wilkins Formation Flex only if you find one used in good condition; both are discontinued, and it is the better rated of the two. For a new speaker, start with the Audio Smile Little British Monitor instead.
Want more options? Browse the full Powered Home rankings.
Prices on this page were last checked November 7, 2026 at 7:34 PM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
As an eBay Partner, we may be compensated if you make a purchase.
Specifications Side By Side
| Bowers & Wilkins Formation Flex | Kanto YU4 | |
|---|---|---|
| Price | £898 per pair Discontinued | $479.99 per pair Discontinued |
| Ranked | #18 of 48 in Small Size Powered Bookshelf Speakers | #23 of 48 in Small Size Powered Bookshelf Speakers |
| Enclosure | 2-way active wireless | Powered 2-way, rear-ported |
| Drivers | 1” decoupled double-dome tweeter, 4” woven-glass woofer | 1” silk-dome tweeter, 4” Kevlar woofer |
| Dimensions | 8.5H x 5.1W x 5.1D in | 8.7H x 5.5W x 7.5D in |
| Weight | 5.1 lbs (2.3 kg) each | 6.8 lbs (3.1 kg) powered / 5.5 lbs (2.5 kg) passive |
| Amplifier Power | 100W each (2 x 50W) | 70W RMS / 140W peak per pair |
| Wireless | AirPlay 2, Spotify Connect, Bluetooth, Formation mesh | - |
| Country | United Kingdom (design) | - |
| Spinorama Preference Score | 3.69 | 2.89 |
| Spinorama Preference Score with Perfect Sub | 6.43 | 5.83 |
| Inputs | AirPlay 2, Spotify Connect, Roon Ready, Bluetooth, Wi-Fi | Bluetooth, optical, RCA/phono, 3.5mm |
| XLR Input | No | No |
| RCA Input | No | Yes |
| TRS Input | No | No |
| Optical Input | No | Yes |
| Coaxial Input | No | No |
| USB Input | No | No |
| HDMI Input | No | No |
| AES Input | No | No |
| Aux Input | No | Yes |
| Bluetooth | Yes | Yes |
| Bluetooth Version | 4.1 | 4.0 |
| Frequency Response | 50Hz - 28kHz (Manufacturer specified) | 60Hz-20kHz |
| Bluetooth Codecs | - | SBC, aptX |
| Outputs | - | Subwoofer |
| Subwoofer Output | - | Yes |
Related Speaker Comparisons
More worthwhile head-to-heads for Bowers & Wilkins Formation Flex: