Don’t have the technical know-how of most on this thread but I’ve been using a Slagle/Jackson(EMIA) elmaformer for the last few years. I haven’t shot it out vs other passive designs but it did beat out a Levinson no.28 and a McIntosh c220 in my high efficiency horn system. Beautiful large step attenuated volume knob and a three input switch.
looks-wise it’s my favorite piece of gear in any system I’ve had/seen