Sorry but I have read a number of articles regarding modifications that bring older vintage gear to the level of current production and rarely take them seriously. I could be wrong but having a fairly intimate knowledge of these speakers I am guessing not. If you have a pair why not give it a try!
@jsautter 


On same page as you.  Actually I have my Advent 1's still with me that I bought in 1980..they sound great and would not want to fiddle with them. Perhaps another pair in need of tweeters would be the impetus for that project...

The 1's have never sounded better with a little room treatment and Carver M500t amp and NAD pre with tube pre buffer between the NAD and Carver.

The Advents have wonderful bass and being a Bass player has always been my thing with them.
Even better equipment will make older speakers sound better.  Giant kills probably not but more enjoyable probably YES!


@ishkabibilI understand you liking the Advents, especially the Original (12" frame 10" woofer) I am a drummer and tend to have my bass set at a higher level than others. I had the Original Advents also. They were very well reviewed back then. But a real eye opener was replacing them with Infinity RS5000. Same bass but with  midrange I hadn't heard with the Advents. That was my experience