Different kinds of product: one is active with its amplifier built in, the other passive and needs one. Judge them on how you want to own the system, not just the specs.
| Area | Better | Why |
|---|
| Bass | A | Fyne Audio F5E digs deeper - 55Hz against 59Hz. A subwoofer would even that out. |
| What you buy | depends | KEF LSX is a complete system - just add a source. Fyne Audio F5E also needs an amplifier: more money and another box, but you choose it. |
| Connections | depends | KEF LSX has Bluetooth, Wi-Fi and streaming built in. With Fyne Audio F5E that all comes from the amplifier you pair it with. |
| Upgrade path | depends | Fyne Audio F5E can be re-amped later and outlive several amplifiers; KEF LSX ages as one unit. |
| Size | depends | KEF LSX is easier to place; Fyne Audio F5E is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | B | KEF LSX: a sub output. |
| Price | A | Fyne Audio F5E is cheaper - $699 against $1,250, about 44% less; arguably a different class. Speakers only - an amplifier narrows that gap. |
A Fyne Audio F5E B KEF LSX
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
KEF LSX suits you if you want one box, ready to play, with nothing else to buy. Fyne Audio F5E suits you if you already have an amplifier, want to choose the electronics, or expect to upgrade in stages. Neither is the better speaker in the abstract. In a large or open-plan room, Fyne Audio F5E has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, KEF LSX is the easier speaker to get right. Think about the whole system, not just the speakers: the roughly $551 saved by taking the cheaper pair would buy a subwoofer or a better amplifier, and either usually does more for the sound than the difference between these two.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.