I've been running the Dali Helicon 400 v1's for 7-8 years now, very happy with them, but haven't yet heard the Thiels.
The Helicons still did well in a 12x15' bedroom (with queen bed, computer desk, etc), but in this room the placement of the speakers with consideration of the surrounding area/furniture and selecting the right accommodating electronics were key in getting it to sound good.
Now in a 16x21 living room which allows 3' of space behind the speakers and psatisfactory breathing room. Naturally, they sound much more open and free to let the music flow. the ribbon tweeters will be silky unless using bright SS electronics. Lastly, for a taut bass sound, recommend brands known for clean and taught electronics - Sim, Naim, Pass Labs have all sounded great for me.
The Helicons still did well in a 12x15' bedroom (with queen bed, computer desk, etc), but in this room the placement of the speakers with consideration of the surrounding area/furniture and selecting the right accommodating electronics were key in getting it to sound good.
Now in a 16x21 living room which allows 3' of space behind the speakers and psatisfactory breathing room. Naturally, they sound much more open and free to let the music flow. the ribbon tweeters will be silky unless using bright SS electronics. Lastly, for a taut bass sound, recommend brands known for clean and taught electronics - Sim, Naim, Pass Labs have all sounded great for me.