c-j technical questions

Unsound

I own Thiel 3.6's and my MF2500A had no problems driving them and sounded very good. I did upgrade to the premier 350 and obviuosly it does a better job in all aspects. But I would not be concerned about the 2500A driving your Thiels. Thiels are not nesessarily difficult to drive because their impedence curve, at least the 3.6's, is relatively flat. What makes them a challenge to drive and why they need current is because their impedence curve does dip below 2 ohms at least the 3.6's do over certain frequencies. Difficult loads are when impedence curves bounce all over the place creating a constantly changing load to the amplifier.

Having siad all this I would be more intersted in what the impedence curve of the 3.5 looks like as I am assuming it is similar to the 3.6 which may be a poor assumption. If you have not already I would contact Thiel and ask them.

Chuck

Chuck, Thiel rates the 3.5's as having a 4 Ohm nominal, 4 Ohm minimal load. I have seen two independent tests that both show this to be pretty accurate. Both tests show a slight peak at about 33 Hz where the impedance rises to between 8 and 10 Ohms and basicaly flat across 4 Ohms the rest of the way. The testers attributed the peak to the sealed box resonance. I agree with you that Thiel's present a constant steady load with out the peaks and valleys most speakers present. Most amplifiers appreciate this kind (of) load. That the 3.5's don't drop below 4 Ohms is even easier on amps. It's the demands of the equalizer that concerns me. I'm sure you are aware that your 3.6's dip into 2 Ohms will require an amps 8 Ohm rating to double down twice to provide the appropriate power. If I am corect in my assumption(?) the equalizer's 12 db push will require the amp to double out(?) 4 X to provide appropriate power. That might be like a -2 Ohm power requirement (not really, but you get the idea). If my assumptions are correct(?) then perhaps Thiels maximum recommendation, may be their best. I take that to mean 500 watts into 4 Ohms. C-J has quoted different opinons on their 4 Ohm rating to me at different times. Once it was "we don't offer 4 Ohm ratings on our solid state amps". Once it was "close to to doubling down". Once it was "close to 400 watts". Once it was "480 watts". Well what it is it? This inquiring mind would like to know. Mind you I have been using c-j solid state pre and power on Thiels CS 2's for years and have always recieved very good customer service from c-j. I don't have an axe to grind, I'd just like to have needed information to make informed choices.

I had an MF2300A for a while. Only reason I sold it was to go back to tubes.

That amp drove a pair of CS2s with significantly more authority that some other 100W and 150W SS amps I borrowed to try. As mentioned before, it is a warm sounding amp and that was a very good match for those Thiels. I bought it from an other agon member who, if i recall correctly, stated that he blew a circuit breaker without causing the 2300As clip indicator to illuminate. Hyperbole? Possibly, but I never clipped it and I played the Thiels very loud at times. (imagine me cranking ozzy when the neighbors were playing abba on repeat over the deck speakers)

Mcmiller, I also have a pair of CS 2's which I used a c-j MF 80 on. Worked great! Not to beat a dead horse, but, it's the 3.5's equalizer that concerns me. Though the 3.5's are 2 db more sensitive than the 2's, the 2's unequalized impdeance at 5/6 Ohms is pretty easy compared to the 3.5's equalized 4/4 Ohm load. I think the sound starts to get hard when moderately pushed. I think, I just need more power. I was happy with MF 80, so I naturally thought of a bigger c-j for the 3.5's.

Hi Unsound, Stereophile reviewed and tested the mf2500. I'm pretty sure that they test 4 and 2 ohm loads, as well as 8 ohm loads. It's all part of thier normal bench tests that they do on a lot of reviewed equipment. If you go to Stereophile's web site, you should be able to pull up thier review of the mf2500 at no cost. The mf2500 is a very nice and musical amp. Best of luck. Stan