So I did end up restoring these fully. I went a light as possible on all adhesives on the tweeter, as little as I could possibly get away with. So little its almost completly visually transparent. This resulted in higher rolloff at about 19k. Barely noticable at this point. Not extended, but very "balanced" all around. You can't go wrong with any Magnepan.
I own and have owned many amazing speakers, Infinity RSII, ESS AMTs, OHM Walsh CLS driver, but these MG1s deffinitly hold their own, and I love the sound.
I have also owned Dq-10s, I sold last year. Not a speaker ide compare too Magnepan even if from the same era. if anything ide compare Ohm Walsh, which delivers a coherent sound with incredible imaging and swing dynamics. Top to Buttom, with the benefits of far heavier Dynamics, and better highs.
The Magepans with linesource Ribbons assist with the highs immensely, but the diffrence in uppermids, midrange, and bass in minimal at best, even to the newer models. Deffinitly bugs they worked out, but Magnepans all sound like Magepans.
Very thin foils are now used as is minimizes, and increases surface area. That increases efficiency. I have been expermenting and have been building my own Ribbons, and Panels. Fullrange, and mid/tweets.
But to get the best sound from older Maggie's, you can replace all the Brown Meloxone which acts as damping. The mids can sound a bit "dry" if your panels adhesives are super dried out. Not a huge diffrence, but noticeable on my panels. Tightened up midrange detail.
I have seen panels that are preserved, I have several pairs, 1 of which, the meloxone was perfectly fine, and rubbery, but didn't break down into green goop. I live in a lucky location I guess for magnepan preserving in normal/low humidity.
When you tap on the mylar with your finger, it sounds more damped, and less hollow sounding aswell. Less "ringing" so to speak.
They are great speakers, all Maggie's are really. But don't expect any Magnepan to "Rock the House" because their not going to do that. Its inherent to their technology. Everything is a compromise. You can work around inherent limitations, but you're never going to completley solve them.