Thiel Owners

thoft - among your short list, the Dunlavy is phase/time coherent like Vandersteens and Thiels. The others are not.

brett - I don't know how many of 'us' have ventured into DSP / active, etc.

"That bass affect" is present in all reflex bass alignments. The 3.6 passive is in proper polarity, pumping out when the woofer pumps out, but it is a whole cycle out of phase - 360° phase shift, just like other reflex systems. That same 360° phase shift is present in most "modern" crossovers which use 4th order filters on all drivers. The ear-brain compensates or learns the phase lag. But Thiel fans tend to appreciate the lack of that phase shift and resulting naturalness of zero phase shift through the crossovers.

Among Thiel speakers, those with sealed bass (like your Kappa 8s) include the model 01, 03, 03a, CS3, CS3.5, and CS5 plus the PowerPoint / PowerPlane with the 6.5" PowerDriver. The others have either ports or passive radiators.

@tomthiel, re: your earlier post re: bi- or tri- amping the CS 5's;  this would require modifications, 2 to 3 more outlets, 2 to 3  more shelves, 2 to 3 more power cords, 2 to 3 more pairs of interconnects, 2 to 3 more pairs of speaker cables. The extra  Benchmark's would still be limited to the Thiel minimum recommended 100 Watts per section. 
 With all due respect, I really don't put much stock on what a manufacturer claims off the record; let them put the specs in writing or provide third party measurements (interesting that Stereophile excused the Benchmark from full 2 Ohm testing, either in stereo  mode single channel, simultaneous dual channel stereo mode, or mono configuration measurements). While I do respect the Benchmark's low distortion specs, and especially the adjustable gain options, their amps don't read as suitable candidates for sub 3 Ohm loads, and are not exactly power houses above 3 Ohms. In that the Thiel's shallow 1st order cross-overs have so much more overlap than other networks, using identical amps for multi-amp use is of even greater importance. 
One used Krell FPB 600 costs about the same  (actually a bit less) as two used Benchmarks and can provide substantially more power to each and  every driver, without compromising frequency linearity into a speaker thirsting for power, and do so maintaining Class A operation the whole while.  One Krell seems like a much better match for the CS 5's.
 While with appropriate amplification ( the Krell KMA 400's are the best I've heard them with) I think the CS 5i's are on absolute terms the best sounding Thiel's ever made, and amongst the best speakers I've ever heard, including much more expensive alternatives. Without appropriate amplification they can be disappointing.  
I found your earlier posts suggesting reshaping the CS 5's baffles in order to simplify the cross-over as a more interesting/promising proposal.

P.S. I started this post some time ago. I've been a bit busy, but I hope to respond to your other inquires in the near future.
 

I agree with unsound. The large Krells drive the CS5i as well as the CS 7.2 with ease. Ive owned FPB 750cmx and they didn't sweat one bit driving them. 
I have Pass X600.5 and they deliver as well. 

Hi Y’all!

so finally got to give my C6’s a good listen with the Ampzilla 2000 mono blocks. Spatially it’s very layered and textured. But I’d say overall the sound is now ‘wooly’ and a bit hollow sounding in the 1kHz-6khz range. There’s definitely too much upper bass. Vocals feel recessed. 
I have been using as my amps of choice two mono blocked Yamaha p2250s. Yes I know I’m crazy but they are great! These are very clean amps—no junk—but not as luscious, textured or spatial. With these I still have a bit too much bass but frequency wise they are near perfect. 

Any thoughts? The speakers are on a carpet that’s on a plywood floor which is on a concrete slab—no spikes or decoupling of any kind. Should I give that a shot?  Right now I am using two infinity Kappa 7s as ‘bass absorbers’ and it’s working pretty well. 
Lemmeknow!

Thanks.

Hello brettmcee,  I will chime in.  I have had my CS6 speakers for 16 years now.  I know them pretty well.  As far as amplification they need lots of current.  The impedance drops to 1 ohm at some frequencies.  As a rule if your amp can double wattage from 8 to 4 and then from 4 to 2 ohms then it should handle the Thiels.  But another important consideration is a dedicated power line to your amp.  That also helps the sound quite a bit.  Next, placement:  I find the Thiels sound best when at least 8 ft apart on centers to get a good large sound stage.  I also find that the bass sounds best when the center of the tweeters are 4.5 to 5 feet from the side walls and 5 feet from the back walls.  Yes, they take a large room, in my experience to sound their best.  At those dimensions, I toe the speakers in just a bit, like 1/4 to 1/2" front to back to bring the imaging into sharp focus.  Too much toe in and the imaging gets too much in your face and the large holographic sound stage starts to collapse.  I also find tilting the speakers back slightly affects the sound.  Try tilting the speakers back such that a level on top of the speaker front to back is off by 1/3 bubble.  That should help with the hollow sound.
Now, about the floor.  The CS6 speakers will interact with the floor even when using spikes.  Without spikes you do not stand a chance.  The speakers must be decoupled from the floor to clean up the bass.  Carpeting seems to suck the life out of the music.  I have my CS6 speakers in a carpeted room too (but I am getting hardwood installed any day now) so I have the speakers sitting on stone tiles.  I tried wood boards and stone.  I preferred their sound standing on their spikes on stone tiles on the carpeted floor.  In my last house, I had the Thiels on carpet and then changed the flooring to hardwood.  It made a big improvement in sound.  Decoupling the speakers from the floor is crucial.  
I added subwoofers to get that last 1/2 octave.  I feel I have successfully integrated the subs with my Thiels by having them roll off at 34 Hz and I phased them based on their relative position to the Thiel's woofers.
I have auditioned the Wilson Alexia 2's a couple of times now.  The Wilsons have incredible bass.  They are a little faster than the Thiels and the bass is a bit cleaner.   The problem is that it is not a hands down massive difference.  The Thiels do some things better actually.  So I'm struggling with the idea of changing speakers because I'm asking myself if I will really move up or am I just looking to change for the sake of change.  
The Thiels can be very rewarding.  Even after 16 years they still give me goosebumps and can move me to tears.  These things are very nearly timeless.