New Old Thiel CS6 Speakers--Too Harsh

Not sure about the Kappa's and how they sound but I can tell you having owned Thiels for 20 years they are great speakers.  I am using CS6 in my system and also own a pair of 3.6's.  You have some great speakers and to get the most out of them, like any great component, you have to build a synergistic system including cables, around them.

I think your source could be an issue, not sure because I don't listen to streaming or rarely digital.  Your Thiels will let you know right away if the tone leads towards brightness which can be a symptom of digital or even some vinyl.

I am familiar with your amp.  I love CJ and considered this amp for my system.  Around this time CJ began using Teflon caps.  The teflon caps are definitely more revealing especially on the top end.  I have a CJ ET5 which also uses teflon caps and is a departure from the warm romantic golden glow of CJ past.  This also takes careful system matching.

What cables are you using?  

Finally, good advice with your room above.  It is on the small side for the 6's but can still work with some placement experimentation and first reflection absorption or diffusion .  Thiels do not like walls, front or sidewalls.

You bought great speakers but they are definitely not plug and play.  They are speakers you build around not finish off.  Good luck and have fun with it!

Your source is causing the sharpness period.  I just went though this with an owner of the 2.4s and the newer versions of the larger speakers. He was amazed when we swapped out the source with a better one.

Happy Listening.

bigkidz,

I can't make sense of your claim.

What could the Oppo 105d possibly be doing to the signal, either playing media or streaming, that could cause "sharpening" of the sound?

I had a similar experience after purchasing a pair of Thiel CS 3.6's.  I thought they'd be a good match for my CJ MF2300A.. Turns out the CJ wasn't capable in this matchup.  Replaced the CO with a Sunfire 300 and was instantly in business.
You'll find plenty posts on Thiels and amp capabilities.  Once you get it right you'll be smiling.  
Enjoy.

To test the room-acoustics hypothesis, you could hang quilts or blankets on the walls temporarily to see if tizziness is reduced. I would put them on the sidewalls 1/2 way between speakers and listener.

To test the "source is the problem" hypothesis, you could borrow a good CD player from a friend and see if that improves things.

Likewise with the "amp is the problem" hypothesis, though I doubt that a CJ Premier amp will be causing tizziness. The CJ stuff tends towards the mellow side, in my experience. And your SF Line 2 got a review from Tom Norton saying it doesn’t emphasize or hype things, which to me means it’s not likely the culprit, either.

To test the cables hypothesis, you could buy some returnable cables by mail order. (That would be my last thing to try, but it’s your choice.)