Thiel Owners

Thosb - Wow, what a ride! The topic of amps driving Thiels is, of course, of great interest and concern to me. Jim did his thing for his reasons, and I disagreed (about impedance mostly), but he was the designer-engineer. The interacting variables are very real. My hope was that by developing our own in-house driver manufacturing we could circumvent some of the hard problems of magnetic gap electrodynamics, etc. that limited the overall system design. Thiel drivers did indeed become quite radical. But to my dismay, the system impedances fell rather than rose, which disappoints me as I re-assess these designs.

I wish that Thiel speakers presented a minimum 4 ohm load! That didn't happen. The nearly magic work-around that a poster mentioned on that thread, is to add a second input for a separate amp for the 3 bass drivers. Most of the problem evaporates, but cost is incurred for 2 more amps.

I find it interesting that in all that discussion and examples, that Benchmark AHB-2 didn't surface. My question about it on this thread also got no response. Is it invisible or somehow inappropriate? Absolute Sound rated it Class A. I find it exceptionally clean, uncolored, versatile and affordable. Am I missing something?

Thosb & Tomthiel,

I've read the "Class D and 2 ohm load" thread, and there's lots of interesting discussion - but quite a bit of rude argument as well. I don't know if I agree with the poster who claims that Class D amps are a bad match for low impedance speakers because they typically don't double the power output at 2 ohms compared to 4 ohms. There appear to be a number of Class D amps that can provide reasonable wattage at under 4 ohms, but I don't have enough personal experience with those amps to know if they really have the low-ohm current to power hard-to-drive speakers like several of the Thiels.

What I do know, however, is that my PS Audio M700 monoblocks do a great job with my Thiel CS 2.2 speakers. I don't know, though, if the M700s would do as well with some of the Thiels that are harder to drive than the 2.2s. The M700s (Class D) took over for an Adcom 555-II (Class AB) I've had for many years, and the new amps really made the 2.2s come alive, improving both bass control and naturalness/openness across the spectrum.

I don't have any experience with the Benchmark AHB-2, but I would assume that it would power the 2.2s well even if it might have more trouble with some of the Thiels that present lower impedance loads to the amp.

Good question tomthiel re the Benchmark, I convinced myself a while ago that if I were to spend my audio $$$$s on a ss amp, it would likely be this one, but thus far I have not tired of tubes.  My guess is very few Thiel owners have tried this amp, but for the life of me I don't know why, as on paper it seems a match made in heaven.  Maybe it's a question of distribution?  Maybe the classics (Bryston, Classe, Pass, Ayre, etc) are the no-risk choice of high current amps?

And once again, reading some of these other threads reminds me of why I so much enjoy coming back to this one - the regular posters have a lot to offer newish users like me, and they are generally very open to others' experiences and philosophies.  Rock on Thiel Users!

If you try the Benchmark, you could consider a pair for either horizontal or vertical biamping.  Just don't bridge them... (see the parallel thread on bridged stereo amps into lower impedances...)

I bought a pair of AHB-2s about a year ago and am thrilled. I specifically want to hear bridged vs stereo and how this amp stacks up against my well-known Classe DR9s (also a pair). They are remarkably similar and grain-free. The Adcom GFA555mkII exhibits the kind of problems that plague Thiel users. The 3 amps provide a good window into what might be going on.

BTW: John Siau (AHB designer) told me the following, based on my speaker schematics and his load analysis:CS7.2 Stereo or mono (bridged)CS5: Stereo onlyCS3.7: Stereo onlyCS3.6: Stereo onlyCS2.4: Stereo onlyCS2.2: Stereo or mono

Believing him, I have nevertheless tried both modes on the 2.2 and 3.6. The 2.2 does fine either way (Its impedance is higher and more benign.) The 3.6 sounds a little sweeter on stereo. When bridged and pushed hard the amp clips with very effective momentary protection. Amidst the thunder the only evidence for me was seeing the red lights flicker. This amp is Class H power feeding a class A output. Very unusual distortion profile. Essentially clean until it's not, which shuts down instantly.

Twoleftears: that single vs dual input scheme is high on my list, but I haven't implemented it yet. I'm wired for vertical bi-wire/bi-amps.