Thiel Owners

2018 will bring me to 30 straight years with Thiel's too!

not exactly the same thing :-)

Note: The 4th-order crossovers in the JLAs are not compatible with the 1st-order crossovers in Thiel speakers.

Hi Kent,

I have examined the CS2.7 coax that you returned. The failure mode was a buzz generated by the midrange cone. Upon closer inspection I found one of the joints between the diaphragm and the coil former was broken or loose. This will definitely be covered by your warranty, and you can disregard the memo bill sent. Thank you for your business.

Best regards and Happy Listening!

Rob

^please delete the first "not" in the second sentence.

 sorry

Hi David, please accept my apologies if I wasn't clear in my previous post.

As for the Pass Lab users not using Pass Labs X amps instead of Pass Labs XA amps, every Thiel user I know that asked for guidance directly from Pass Labs has reported that Pass Labs has suggested that the X's would better serve Thiel's, with X250 and X350 with their various "." derivations most commonly recommended.

Yes, there are truly pure Class A amps that can double down while maintaining Class A all the while (the early Mark Levinson ML2 w/ 25 Watts output certainly jumps to mind). I was merely trying to make a generalized comment to a larger audience that might mistakenly believe that all amps that tout Class A, don't necessarily do so all the time. If I recall correctly the Aragon mono's dropped all Class A output below 8 Ohms despite being touted as pure Class A. I remember another manufacturer of a very highly regarded amp admitted when pressed that despite claims to the contrary, that his amps weren't really Class A and argued that it made no difference except in the market place perception. The current Pass Labs XA's aren't really pure Class A, as they provide extra Class AB Watts when power demands require it. To their their credit they only advertise the true Class A output, but unfortunately some leave thinking that these (advertised) relatively low output amps prove that extra power isn't necessary and/or that Class A is more powerful than Class AB.

Doubling the minimum recommended power is not my axiom. I've been at this for a few decades and it existed long before I became involved. Which is why I chose to use it previously. It is merely a long used generally accepted starting guide. I do believe that time has been kind to this guide, and though one might find less or more power might be required, and as difficult as it is find any specific guide I've found this one to be especially helpful as a general starting point. Heck, I can remember a time when 200 Watts was a broad brushed minimum recommendation for a serious system. That I think is an over simplification.

 As for an amp being able to handle a 2 Ohm load, keep in mind this is more of a prerequisite with some Thiel's (especially at lower power outputs) if one cares a whit for frequency and amplitude linearity. Despite what might appear to be technically true, the 200 Watts that your Accuphase puts out at 2 Ohms is really not so different than 50 Watts into 8 Ohms. Which really isn't all that much. Now in a smaller rooms playing music without much in the way of dynamic contrast such as much small choral works or chamber music 50 Watts might be more than enough, but for realistic symphonic music in larger rooms it might be lacking. There's a reason Jim Thiel allowed his loudspeakers to handle such big power inputs, Many other speaker manufactures discourage such power, as their speakers can't handle it. Sure one can get sounds out of most any Thiel with even the most low budget low powered amplifiers, but if one wants all that Thiel's are capable of, then more high quality Watts are needed.

The halving of Class A output with impedance drops isn't really all that much of a problem. I just pointed it out because many attribute the sound of some amps due to their Class A output, when if fact it might be due to something else. Most of the time our speakers really don't require that much power. It's really only when things get loud do the speakers drink up copious Watts. But then the demands really ramp up. The thing is that as things get loud our ears aren't as sensitive to all the delicacies', that is until real distortions start to rear their ugliness. Personally I'd rather deal with an adequately powered Class AB amplifiers cross-over distortion than even the impending clipping of an underpowered Class A amp. Especially with solid state amplification. That is not to say I'm suggesting tubes with Thiel's, I don't. Though some do.

I do think we're really much more in agreement than not. I was not specifically trying to tell you what to do, or what to use, but rather to offer a more generalized response to a larger audience for your rather good question. I used to often say that we all hear differently, but I now realize that it's probably more correct to say we all listen differently. I don't like to argue with success; if your happy, enjoy!

David, welcome! In answer to your question as to why more Thiel users don't use pure Class A amplification: cost. And heat.

To my ears, though typically advantageous, Class A is not the only criterion of the many upon which an amplifier's sound is determined. 

 Jim Thiel's power recommendations were based upon standard solid state 8 Ohm ratings (with a level of quality expected), where it could be assumed that the power doubled down as impedance halved, not the impedance load of the specific speaker.

Let's take your 3.7's

https://www.stereophile.com/content/thiel-cs37-loudspeaker-specifications

 for example: with power recommendations given as 100 - 600 Watts per channel. Of course actual power needs will vary with rooms and desired volume levels amongst other things. But, for the sake of this post, let's fall on the old audiophile axiom that one should first consider starting with double the minimum power recommendation, which in the case of the 3.7's would be 200 Watts per channel. 200 Watts per channel of pure Class A amplification comes with some expense.

Many high quality amps runs their bias towards Class A before sliding into Class AB. For example I run my 3.5's with their  recommend power of 50 Watts minimum 250 Watts maximum (with hints of 300 Watts max).  My Threshold amplifier is rated at 250 Watts (8 Ohm) per channel. The first 20% (50 Watts) biased towards Class A, then sliding into Class AB. Now into my 3.5's 4 Ohm minimum impedance; as the impedance is halved, the power doubles to 500 Watts per channel, but the Class A bias output is halved to 25 Watts per channel.

This not only true for some Class AB amps. Some amps that claim pure Class A output really only do so in their standard 8 Ohm rating, but as the impedance halves and the power levels double; their Class A outputs halve as well, with the increased power correspondingly sliding into Class AB.

https://www.stereophile.com/content/threshold-stasis-sa12e-power-amplifier-page-2

Of course some amps that tout pure Class A output, really don't. 

https://www.stereophile.com/content/krell-ksa-250-power-amplifier-when-class-class

We know that power consumption is not linear but rather exponential, and musical content can demand many, many times it's nominal power requirements. I haven't measured the bias output, but I suspect that much of the time my amp is behaving towards Class A bias. But now with the capability to cruise at 500 Watts per channel all day long (with short term headroom doubling that to 1000 Watts per channel).  

Now some might suggest that some of these power recommendations into actual impedances are outrageously high. To those may I remind them that with Thiel's and most typical speakers for that matter, that as impedances drop and power output increases that speaker sensitivity decreases correspondingly. So for general comparisons one might see the wisdom of the standard 8 Ohm ratings. Or not?

Would I prefer more Class A output? Probably, double that would be dandy. All 500 Watts per channel into 4 Ohms Class A? Sure! But, for my money I'd probably move up the line in speakers first, and settle on less Class A output with Thiel CS 5i's.
  

 Thiel's weren't made as cost no object super premium products, though in their time the CS 5's were knocking on the door. Given the cost of pure Class A with enough power to drive most Thiel's, some of which approach 2 Ohms (and some with challenging phase angles), I think many might find the money might be better off spent elsewhere. For example with the 3.7's, and given enough room, I can easily see someone spending the money on Thiel's own subwoofers before committing the funds towards up to 600 Watts of pure Class A amplification (if you could find it). As a general guide (and with adequate funds available), perhaps a reasonable starting point might be amplification meeting the minimum power recommendation with Class A and the maximum into power recommendation sliding into Class AB. If one could afford to provide the maximum power recommendation all in pure Class A output into actual minimum impedance load, perhaps all the better. But be prepared to pay!