What McIntosh Amp With Thiel 3.6 Speakers?

We are Mac dealers - so let me prefix this resopnse with that statement.

Definitely do not drive the Thiel's with anything less than a MC-352. For two reasons - one power rating, and two autoformers. The MC-352 is the smallest amp Mac makes with autoformers, and they really help on speakers with erratic impedance such as the Thiel's. The autoformers effectively add impedance to the circuit which makes the speakers easier to drive and less onerous on the amplifier in terms of current demands, even when the speaker's impedance dips. Also you need raw horsepower to drive those speakers, particularly current. The higher up you go on the chain of Mac amps, the better off you will be sonically. The MC-352 is a great sounding amp and a very capable one at that. But frankly with your Thiel's you could enjoy better sound by moving up to the 652. You don't _need_ to, but it would be worth auditioning. I think you would find the improvement over the 352 significant.

Zaikesman...

Erratic was a poor word choice - thank you for correcting me. I tend to use that word to describe impedance curves that are difficult to drive because more often than not the _are_ erratic in that they fluctuate like a roller coaster, but in the case of the Thiel's the problem is not with the variation.

The Thiel's impedance is consistently low, and relatively flat. It has a reasonably benign phase angle although once you get down to the range where the Thiel's impedance lies for the vast majority of the frequency range, even a slightly capacitant phase angle is going to complicate matters somewhat.

The point that I was trying to make was two fold: one the nominal impedance rating on the Thiel is virtually meaningless and certainly misleading. Second, because the impedance dips down so low, you really need a lot of current, and hence the bigger the amp the better. Err on the side of too much power.

I'm not trying to beat up on Thiel - in fact you are quite right that they are very good about providing information on the minimum impedance of their speakers, etc. I wish more speaker manufacturers would provide this kind of information and would be as upfront about the requirements of the amplifier driving them.

My point was not really Thiel specific - but that in _general_ when you look at the nominal impedance it doesn't tell you anything, and many people will use that figure as a criteria in choosing an amplifier. You really can't do that... you need more information.

A couple of notes...

With respect to my post earlier - I stand corrected. Serves me right for posting a response at 2 AM! MC652 was a typo. It's obviously MC602. And yes the MC202 does have autoformers although it is the only stereo amp from Mac that doesn't have the autoformers physically exposed (though the presence of multiple outputs taps is an indication that it is autoformer coupled)

And the MC6500 integrated does not have autoformers - the 6900 does (though they are not exposed, as with the 202) That is the main difference between the two although there are some other subtle differences. The Shahinians are tricky to drive but nowhere near as difficult or demanding as the Thiel's. The Dynaudio's are definitely tougher than the Shahinian's but the Thiel's still draw more current across the bandwidth.
Nevertheless - I still recommend an MC352. I just think you would be underdriving the Thiel's with anything less powerful in terms of current. Yes the 202 may have autoformers but it doesn't have the "oomph" of the 352. You can tell easily just by lifting up the 202 and the the 352. Then ask yourself which one stores more charge and delivers more current!