speaker placement..

If the arch is 5 feet from the front wall and 3-4 feet from the front of your speakers, it sounds like you have the speakers right up against the wall now (the SC-IV's are 18 inches deep). This usually results in exagerated bass (and these speakers already have a lot) and a reduction of imaging and the soundstage, especially if you have something like a tv or bookcase between the speakers.

You would likely get very good results moving the speakers out into the room -- regardless of the arch. By moving them another 3.5 feet into the room, the front of the speaker would be flush with the arch, which would further enhance the sound. My experience with first order cross-over speakers (Thiels) is that they like to "breathe" and have some air around them, especially front to back.

If I misread your post, then nevermind. But in any case, it never hurts to experiment and move the speakers around, listen to the differences and then decide. Good luck.

Nothing that a sawzall, demolition bar, sledgehammer and shopvac can't cure! Unless it's a structural arch....then try plan B.

Alternatively my guess is that you should be able to wrap the collum in either an acoustical absorption or difusion material to address the problem. I'd definitely consult the experts though, and I would not be one of them.

Marco

Ttrhp & Ozfly, I was glad to read this since I have first-order XOs and a similar room feature, though not so big. BTW Ozfly, what Thiels are first-order ? ( Just curious. )

Even if the arch is structural it can be replaced with a laminated beam or steel beam that will take up less room. I have had to do this at work to remove a column that was not strategically located.

It cost about $1000, which is a lot less than good speakers.

Hi Tobias. I owned both the CS2.3's and the CS6's -- they each had a first order cross-over (i.e., a 6 dB per ocatve slope). My understanding is that all Thiel designs utilize this cross-over (combined with wide bandwidth drivers) to avoid phase shift issues associated with other, steeper-sloped crossover systems. BTW, there have been lots of interesting discussions about that here on the Gon with an overall conclusion that no single factor, such as phase shift, determines the overall sonic calibre of a speaker -- everything is a matter of what trade-offs are to your liking. Happy listening!