Harbeth Hl5 plus and room size?

By themselves, I would say they might struggle in such a big room. But if you're willing to add a sub or two, they might work. How high is the ceiling?

If you can afford it, I think M40.x will be a better fit for your room. But SHL5+ should work with a couple of subs.

P.S. I have owned SHL5+ for a few years now. They used to be in my main system (room: 20x15; 12 ft ceilings) and now in a much smaller home office (12x13 but 20 foot ceilings). They excelled in both rooms. Easily amongst the top 5 speakers I've owned thus far. Many speakers have come and gone but I could never bring myself to part with the SHL5+.

Mine are in a 24x20 room 4 feet out from the wall. I sit 10-12 feet away.  No issues. Plenty of bass for my liking. 

I have 8 ft ceilings and the room is dedicated to my audio. I was concerned about the bass. There not very big speakers but when I heard them in Texas they sounded so full and just right. 

With 8 ft ceilings I think they will work just fine. When I had them in my media room (20x15) they sounded really good. Adding two subs (REL S/510) took their performance to the next level. If you end up buying them, I highly encourage you to add at least one sub, if not two, at some point. They will easily sound twice as big. Good luck!

I’m not a big fan of subs, but I will keep it in mind, thanks

What are you driving them with?

Another factor is where you are sitting in relationship to the speakers. If you aren't the length of the room and are reasonably close to the speakers you will be OK.

Like all things depends on volume and type of music .... With lower ceiling height I think will be fine up to 80db for extended listening .... I had the 30.1 in my listening lounge 7mx5.5m X 3.6m high but didn't quite work so bought big tannoy Arden's which fill the room and even work better at lower volume. My new thesis is bigger is better always if you can ......

I’m digging Altec Santiago and if later I chose Harbeth it will have to be the 40 series

thanks for all the info