Hi Duane, The IC-756 series will accept 4 to 16 ohm speakers. The SP-20 is 8 ohms nominal. I have been using an SP-20 with a large variety of Icom HF transceivers since 1989; it worked fine with all my radios, and is now connected to my 756Pro2. Cheers for now, 73, Adam VA7OJ/AB4OJ Scanned by WinProxy http://www.Ositis.com/