I wonder if this effect exists in HYBRID receivers such as the Yaesu FTDX-101 and also the K4HD? Incidentally, the tuned speaker is an old concept. There is a guy in TX that has been building them for years with PVC tubing. Only problem is that his resonanted around 750 HZ. Even 600+ sound high when I'm used to around 420 Hz or so. 73 Dennis W0JX .