These sit in different price classes - ELAC Navis ARF-51 costs roughly 7.6x what Fluance Ai81 does. Expect it to lead on paper; the question is whether the gap is audible enough in your room to be worth it.
| Area | Better | Why |
|---|
| Bass | A | Fluance Ai81 digs deeper - 30Hz against 43Hz. |
| Built-in power | B | ELAC Navis ARF-51 has the bigger amplifier (300W vs 150W RMS). |
| Connections | A | Fluance Ai81 adds digital inputs. |
| Size | depends | Fluance Ai81 is easier to place; ELAC Navis ARF-51 is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | A | Fluance Ai81: a sub output. |
| Price | A | Fluance Ai81 is cheaper - $499 against $3,798, about 87% less; arguably a different class. |
A Fluance Ai81 B ELAC Navis ARF-51
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?
Fluance Ai81 is the easier recommendation: it leads on most of the measured areas and costs less. Take ELAC Navis ARF-51 if its size, looks or fit in your room suit you better. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 43Hz anyway, so judge these on the other rows instead. In a large or open-plan room, ELAC Navis ARF-51 has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, Fluance Ai81 is the easier speaker to get right.
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.