Jim: I've never heard the Lamda Pro (though I would like to) My "STAX" experience was mostly with mid 80's SR series and some of the newer Classic series (which sound quite nice, although they just can't get the bass quite right -- may be, just may be, Martin Logan should do a headphone, as those folks have finally figured out the ESL/bass equation.)
Speaking of bass, I have found a way to augment my Grados and get response flat to 16Hz, but my shoulders get sore after 5 minutes of carring around the Velodyne 18" and I keep getting the King Cobra PC caught in my hair -- I think I'll move to a pair of 10" subs, as I can carry one one each shoulder for proper stereo imaging :)
On a serious note and to answer your question, Stax has an excellent web site that details the rich chronology of the brand. Your question will probably be answered there; if not, seek out those ear-retentive gurus of headwise.com
I am almost too embarrased to tell you what I've done with my old Stax. I was about to throw them to the newbies on eBay and be happy with my $100. But when I got the Grados, the posts I read about comfort problems turned out to be true -- the damm earpads itched -- it was not so much the shape but rather the material itself. Well, the leather earpads from my retired Stax fit perfectly over the outside of the RS-1 and make the headphones very, very comfortable -- the true test being that I sometimes forget they are on my head! Best tweak I done yet. --Lorne
