Yes, thanks microstrip … your explanation is same as I received from Roger and only thing I can add (If i didn’t mention before) is that actually the SL speakers will not saturate with the metal core if used within their power rating and if are not over-driven. Amplifiers generally have a lot more power than they did 20, 30 40 years ago and it is now pretty easy to happen to have an amp that is overkill for SL and therefore to over drive and cause saturation of the mids…I personally think Roger became a little tired of having the occasional complaint that the mids did not perform well at high levels and while he can (and did) say that the speakers were being over-driven, it is somewhat easier to not have any complaints and use of the air coil offers that …although the speakers would still be over-driven and damage may eventually occur just the same with or without any saturation … hope it makes sense. Chris