Hugo Gimenez

I think it depends of the format you´re playing, if you have a 5.1 material, the sub is needed, or you´re lost the LFE channel info. If you have a stereo L/R sistem with a speaker pair with enought low frec. response, teorically, you don´t need a Sub. The DSP of mostly Receivers, change or upgrade formats from 2.0 to 2.1 or 5.1 or more, in this case again, need a Sub.

The HK have two speakers systems outputs, A and B, the minimun impedance spec for each system is 8 ohms, if you charge the two systems with 8 ohms, the output amp `see` a 4 ohms equivalent impedance, if you conect only one system in 4 ohms, you´re right on the amp specification limit.