Buying used: how old is too old?

Capacitors are the biggest thing when a speaker is over 10 years old the capacitors  dry out and you can replace with far superior xover parts I have been doing for 20 years now .even $$ speakers skimp unless spending big bucks , even then I had the latest ML 
ststs and Xover parts average at best even in the $80k flagship
using cheaper white Mundorf capacitors fo4 $80k they should have at least Mundorfs best supreme gold silver .
not my cup of tea but VH audio Odam caps are top shelf, 
Duelund great but Waay over priced , jupiter, Millflex very good 
best resistor sonicly is Path audio from Poland. If buying used 
for sure strongly consider upgrading your Xover parts it’s the 🧠 
or ❤️ of your speaker 🔈 everything goes through it .keep all original values just  much better quality ,inductors maybe depending on quality.

hey @jnovak - I had a pair of Polk's back in the 80s - I think is was floor standing 12B's. I liked the open tweeter on top and I was happy like you for a good while, until I heard speakers with bass.

If you have the $$ get something else, you'll be happy you did. There's a ton of options out there. You don't have to spend a lot of $$ either. I would go the dealer way, and they have closeouts when they change their lines or even drop a color. Then you can expect 40-50% discount. Or they may have a used pair from their clientele with upgraditis that they've stolen them from and are willing to give you some of that benefit.

There is a reason why vintage JBL, Altec, Klipsch, AR, QUAD, ls3/5a and other speakers still enjoy robust demand (and prices !) today:  They sound GREAT and in some ways are better than what is available today.   The above mentioned brands enjoy excellent aftermarket support.

5yr old speakers are essentially new designs.

10-15yr old speakers are previous generation designs, in most cases.

With speaker 10yr+ old, I would look for surround deterioration, and eventual breakdown of crossover capacitors.  Both are easy to fix.

One issue to consider, is many speakers of the past 30-50yrs used dome tweeters.  The adhesives and suspensions in these tweeters seem to wear more quickly than other drivers.  Treble performance will slowly deteriorate as the driver ages.   

I’ve actually heard the MOABs in a home situation and they are not junk. They are big. It’s like having two NBA centers standing in your room (ok I exaggerate maybe NBA power forwards).
What I don’t understand is how come music produced over 50 years ago on equipment that was probably made 60 to 70 years ago is far superior to music produced today but today’s equipment is so far superior to the equipment used back then?

Remember danager the Sinatra-Basie you heard that was so amazing was no ordinary LP, it was a Super Hot Stamper. So that was a big part of it. Still, you are right, a lot of those recordings from back then have absolutely marvelous sound. It is hard to understand how they were able to achieve such outstanding results. Especially since you are right, there is no way they had anything back then to play it back on to know. Not like we have today. Certainly not like what you heard at my place.

There are two main reasons I can think of to explain this. The first is that everyone back then was focused on excellence. All the vocal talent, Sinatra, Torme, all of em, they started off with massive talent and then worked their butts off perfecting it. The result is what you heard, the talent is coming at you like from a firehose. It is stunning, scintillating, the feeling you get hearing Sinatra sing like that. How a human being can be in so complete command of so many different things all at once that they are able to have it come flowing out so seemingly natural? It is just spooky. We have nothing like it today. You know what I’m talking about because you heard it.

This same striving for excellence carries on across the board. Every musician in Basie’s group, every recordist, every mastering engineer, right on down to the guys at the pressing plant. People back then were craftsmen and proud of their work. There are still a few like this today but it is the exception not the rule.

The other main reason is a lot of what we are told is better really is not better. All those incredible sounding records were recorded with tubes. All tubes. No solid state. This all by itself pretty much proves tubes are better, no contest, as otherwise all the best recordings would be today with all solid state. Instead of the opposite, where the very best are still done with tubes. Janice Ian Breaking Silence the liner notes even talk about the special tube mic Janice uses.

There’s a third factor harder to pin down. Did you notice the lyrics? Even the lyrics are at a higher level. No contest. That album, you should come hear the whole thing, it is an absolute gem of a record. Leave you in awe. Even more so than it already did! So even the songwriters were striving for excellence.

Today they are striving for the Benjamin’s. There it is in a nutshell.