Post by Boomzilla on Aug 26, 2022 9:43:13 GMT -5
Low impedance. Some of the big Thiels fall to just under 2 ohms, if I remember right, over a usable portion of their bass frequency range. That frequency range is where a lot of bass fundamentals lie, and current is required for such a low impedance. Many (most?) amps aren't happy with such low impedances. Mr. KeithL is correct when he says that amps like to see loads that are not too much below their minimum impedance ratings.
I said the Crown PSA-2 amplifier was an excellent choice for the big Thiels. Why? The amp is rated for 2 ohm loads. This alone is far lower than most amplifiers (especially the BasX A-1 amps, that are rated for 4 ohm minimums). This isn't to say that the PSA-2 is a better amp than the BasX A1, only that the PSA-2 is a better amp for big Thiels. The PSA-2 also has a significant amount of self analyzing circuitry included in its design. If the input and output differ, the amp can tell if it is clipping and will adjust to protect the speakers. The amp monitors its own power rails and if it sees sag, compensates by slightly reducing gain. Should the amp encounter a short on the outputs, it disconnects to protect itself.
Such protection features are more common on "pro" amplifiers than on consumer products. Not only are those protection features expensive to design and manufacture, but at the end of the bathtub curve of reliability, the additional circuitry can become problematic. Nevertheless, a powerful, self-analyzing, 2-ohm rated amplifier like the Crown PSA-2 can be an ideal candidate for low-impedance consumer speakers. Mr. DYohn recommends QSC "pro" amplifiers for those who don't wish to peruse the used markets, and the more powerful QSC models are also rated for 2 ohms and have significant self-analyzing capabilities. Now VERY few consumers actually NEED such amplifiers, because virtually no speaker manufacturer produces consumer speakers that have such low impedances any more. So for 99.9% of the speakers on the market, the BasX amplifiers are ideal. But if you want one of the very few speakers that have exceptionally low impedance (such as the big Thiels), then you may want to consider more robust amplification.
Boomzilla
Postscriptum - The specific low-impedance Thiel speakers I have in mind are the CS-5i models owned by my audio amigo (who also owns the Crown PSA-2 to drive them). Not all Thiels drop to such low impedance.
