I generally share the reservations expressed by Benedictloafer and I agree with his exceptions to the rule. Nevertheless, I do believe that there are three classes of speakers that can be virtually non-pareil even today.

Within speakers that must avail themselves of the Theil-Small parameters the limitations he cites are spot on. Once one gets to infinite baffle, Karlson and horn speakers things change, sometimes a great deal. The vintage speakers he cites as exceptions are right in the middle of this bubble of excellence. Altec, JBL, E-V, Hartley, Goodmans, University, Tannoy and some others not commonly seen are names to look for. But they must be restored and/or rebuilt virtually all the time. A perfect 50 year old speaker is a rare beast indeed, especially if it has the highly desirable paper cones and alnico magnets. You may count on that repair doubling or tripling your initial cost if the speaker can even be repaired (some cones are no longer made). If you are buying a vintage enclosure as well count on heavy shipping costs (these types of speakers are quite large and the cabinets are usually constructed of good wood and are quite heavy).

If these things are done and your room is reasonably sized you will have a speaker with an incredible sense of ease and if the enclosure is a horn or Karlson cabinet with Altecs, University or E-V speakers, it will have superb dynamic range and do voices in a way that is still difficult to obtain . . . and often for less than $1,000 total if you shop carefully. Not that these speakers cannot be bettered today but it will take a lot more money to do so. Usually an order of magnitude more money.

When moving up to the legendary behemoths care must be exercised. Over time, the E-V Patrician and Georgian; the JBL Paragon and Metragon and others have become extremely expensive when sold as complete units. A careful examination of today's speakers and their cost may cause you to change your mind unless you are a collector.

One last note. These speakers are large and WAF (Wife Acceptance Factor) becomes a real issue. There is an Old Stan Freeburg line that goes, "Your whole house becomes a speaker! You move into your garage!" It isn't that far from the truth. Though the Karlson is (only?) waist high, some of the others are head high and more than 3 feet wide. The JBL Paragon spreads laterally (almost 7 feet) and is waist high besides.

If you can spare the space, there are some incredible values out there in the middle range. If you have to get small enough that Theil-Small parameters become a real issue, take Benedictloafer's advice very seriously indeed.

In any case, always communicate via eBay and pay through Paypal. Whether by ignorance or criminality there is a decent amount of misrepresented and shoddy merchandise sold in this catagory.

Happy shopping!