Okay, so I get this phone call from the University of Utah. The accent is a little thick and I'm really tired. He informs me that he has a background in audio, and is curious as to why I don't use air core inductors in my low pass sections. Red flags start going up, because well, I'm the guy that can hear the difference between capacitors but now have to blurt out that I can't hear the difference between coil types (if inductance and DCR are kept the same). He insists there is a difference and that it's quite easy to measure. I'm having some trouble understanding him, but there is an air (ha ha) of competency to his speech. The only thing I can think of that might be applicable is in the area of hysteresis. So, even though I don't think the bigger horn loudspeakers come within a light year of experiencing this problem, I realize I might actually be wrong.
I start thinking that if this guys thinks this way, then others probably think this way too. This brings us to the question of using something you don't think makes a difference, but you do it because someone else might. So, to cover my backside, I decide to ask Mark Cooper of Universal Transformer if he might be interested in winding up a 2.5mH air core for me in 14AWG. It won't win a beauty contest, but these guys don't mess around when it comes to winding stuff. Alright, it's ugly, but it's tight and varnish impregnated/dipped. I specified the peculiar shape -- the conventional method takes up too much geography on the board.
Edited by DeanG, 12 November 2013 - 08:10 PM.