Which B&K ST-140?

Unsound, revealing my ignorance, what is a low impedence speaker generally? I think most are 8 ohms, a few 4 I have heard of. Do you mean 4 ohm speakers? Why is the B&K not good for 4 ohm-ers?

Thanks....

River251, Speakers have minimal impedance and nominal impedance. One should know not only the impedance swing of a speaker, but also the phase angle before choosing amplification for a given speaker.
What is a low impedance? What is a high impedance? Well, I think that might be very subjective, and many here on Audiogon might have very differing opinions on both. IMHO, in the big picture 6-8 ohms is the middle ground, anything below 4 Ohms is low, and anything over 8 Ohms is high, but there are other important considerations, and speakers ultimately decide.

Thanks Unsound. Phase angle? The sales guy never said anything about that.

How do you calculate it?

Hi River251,
Phase angles are imperative to tube amplification, but don't effect ss amps so much, Phase angles tell us how far a apeaker dips or rises between resistive and capacitive loads, you can normally see it in an impedance chart, but some ss amps do not have enough ooomph in the power supply to properly handle a 4 ohm load.
I have an B&K EX 4420 in very good shape that I could sell cheap, it would do a good job on most any load. If interested, let me know and I can list it here on Agon, but there are several nice inexpensive amps that would do a good job for you.

How can one distinguish the year of the ST-140's? There is the brown/champagne colored one, the striped one and ?.

The Stereophile article doesn't really tip you off as to which is which.

And regarding durability, which one is the more sound choice? (no pun intended)