Large Advent Fried Egg Tweeters

Being a poor student and tinkerer, I tend to deal in vintage audio for my hifi and recently picked up a pair of Large Advents. I refoamed the woofers and resealed the boxes and am now listening to then to decide if they stand to replace my EPI 200s. At first I wasnt impressed with their sound in my livingroom but when I moved them up to my bedroom and sat much closer, they sound completely different. The clarity is quite nice in this smaller environment, especially the bass being much tighter than my 200s (passive radiator). However, it seems that I am missing the high end of cymbals and sibilants dont have the same presence as I am used to. Do the fried egg tweeters age and lose their upper frequencies or is this how the speaker was designed? Another possibility is that I am just used to the EPI inverted dome tweeters that push extreme upper frequencies so well. Has anybody else come across dull sounding Advents and found a cure?