speaker placement..

Call Acoustic Sciences Corp (the Tube Trap Company), or, your speaker manufacturer to discuss. Personally, I would try to get the speakers slightly in front of that arch - but you did not say what the overall length of the room was and if that could happen.

The speakers have to be in front of the arch. You will be losing all kinds of signal. As sound waves bounce off of the arch they will come back out of phase to the signal coming from the speakers and cancel what they encounter.

That's too bad because 9' ceilings would be ideal for such a big speaker!

You might want to contact http://www.rivesaudio.com they help in designing and building listening rooms.

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. )