They make a racket, not round/resonant like a tuba or euphonium, and just doesn't "carry" as much.
French bassoons are smaller bore, and more nasal (not louder, but more attention-getting - such as with the more-piercing sound of a smaller-bore trombone).
some cool pics, and several are of French bassoons:
https://kingkristopher.com/tag/french-bassoon/
If you've not played on an ophicleide, pick up a baritone saxophone (saxophone fingerings are the same fingerings as recorder, and the octave key is the same as the hole on the back - though no "half-holing", because the instrument does that automatically), plug a trombone mouthpiece into the neck, and mess with it. That will give you a very good idea of the (I would describe as "hollow") resonance/output potential of an ophicleide.
If this sidebar is supposed to be a debate (??), I need to hand my "side" (??) if it off to someone else, eat dinner, and resume working on @tubaing's Holton's valve section mounting job (which is coming along pretty well).
