30 yr old speakers- time to replace drivers?

If the speakers are all working, with no defects, not sure it's worth touching. 

However, the XO might be in need of an update. yes, caps can last decades, even out of spec can work almost perfectly. Just replaced the caps in my XO's, while my speakers sounded just fine, after swapping out the 10 caps (5x per speaker) WOW, like OMG WOW, sounds like a new set of speakers! Way more bass, way tighter bass, silky midrange, high top end. My tone controls needed to be reset, tweeter went from +3 to 0 bass went from +6 to +3. 

It was the best $50 and 2hrs of work ever spent in my system. 

I don't understand the logic with some on here saying don't put money into 30 year old speakers and don't fix it if isn't broken.  Well, I went exactly against all this advice and put money into an old pair of Infinity Kappa 9's nobody wanted. 

I spent $200 for the speakers in rough shape that were missing 3 out of 4 of the 12" woofers and the polydome mids were trashed.  They were made in 88'-89' so about 35 years old, the crossovers needed attention and that's where the new life came back for them.  Some tweeters were not working as result of the crossovers failing. I fixed everything and replaced every capacitor, about 23 total per speaker.  It was about $700 in capacitors and I have about $1300 into them.  I find they sound phenomenal now, brought the efficiency up fixing the crossovers.  Capacitors definitely go bad, drivers if the surrounds are still good, you're good there. 

Do what you feel is right and your budget can handle.  I know there's always better speakers out there than your NHT or my Kappas, but for me it was the right decision to fix up and not buy newer for much more.  I smile everytime I fire up the Kappa 9's paired the Parasound JC-5 amp, Ayre KX-5 Twenty preamp and my little budget Schitt Bifrost 2/64 DAC.  I'd like to add another JC-5 and some Rythmik subs and maybe get into streaming one day.  But for now what I have will do..  I'm not made of money, going out and seeking new speakers wouldn't have been a good decision, but $10k for the amp and preamp was...and so was fixing the 'old' speakers..

I have a pair of Infinity 7 Kappa’s i bought new in 1992 that I power with a Yamaha M70 amp I purchased new  in 1983 when I was 23 years old. I had the amp recapped for $350.00 by a local shop recently, in Dallas. I had  the subs refoamed a damping upgrade added to the spiders and the polydomes rebuilt by Miller Sound in Pennsylvania(they have the parts to fix the polydomes made) for a total cost of speaker repair $405.00. I swear they sound better than new. The kappas are as beautiful as the day I bought them. This system has a very warm sound and is perfect for my family room. I do have a listening room/Man Cave with Zu Omen def supremes powered by a Pass Labs XA 25 amp that is obviously superior by most any measure, but with DAC and streamer added in is an $18,000.00 investment. While I love the Zu ODS/Pass Labs system if I didn't have a spare 20k including cabling laying around I could live with my old system and be happy. I say if you like the sound of your system tune it up and save some cash.

I wouldn't spend money upgrading the drivers and crossovers unless the speakers have a real special place in your heart.....it's just not cost smart in my opinion.

I did that on my original 1980s Infinity RS Kappa 7s, but I've owned them since new and were my first audiophile speakers.....and are very important to me and my journey; won't ever let them go. Plus they now sound amazing

Short answer:

If they’re being used as surrounds, I’d leave them alone and play them until the woofers fall out.

Long(er) answer:

I’ve been doing speaker mods for decades (including owning a speaker patent).

Here’s some thoughts on the subject of "fixing" old vs new:

It’s very unlikely that a "healthy" woofer will degrade much over time. Rubber surrounds have a long life expectancy. We’re pretty proud of our work, but are still surprised (and often stunned) at how much music can come out of vintage drivers when you get things out of the way that make them sound worse. There’s a difference between "fixing" (repair/replace damaged components) and upgrades (improving the sound quality) of a speaker. "Fixing" old speakers is usually very cost effective and a no-brainer.

The following comments refer to upgrades.

We set a budget before we begin upgrades. This budget is 40% of what it would cost to replace the item with a new(er) version of a similar design. If the hot, new version (same brand, or other brand) is, say, $2,000/pr, then I set a ceiling at $800 for modifications. This number is not arrived at scientifically, but is merely a performance vs cost evaluation based on my experience. It represents a number that is less than half the cost of a new replacement.

While it is possible that the modded version of an older model may not exceed the performance of a new model, it is also VERY likely that a modded model will do SOME things better than the new model. I say this with some level of confidence in that a modded speaker will most certainly have better internal cabling, better components in the critical signal path, improved connection/termination methods, more attention to vibration, etc. than the production version of the new model. WIth the new model, you’ll still be "hearing" components that are cost-driven, performance compromises due to strong considerations about production efficiency, and serviceably in the field (without a soldering gun), and just hitting a target price point.

This methodology has produced predictable, consistent, and reliable results over many decades.