@Frank Blank - The FRFR is the important bit for colourless, faithful tone reproduction. So in the above - the helix is reproducing the sound of a miced up rig as it would sound if it was recorded in a studio. So when you output sound from the Helix, you want whatever is amplifying the sound to do it without adding it's own character to it... which the majority of bass cabs will not do (most are actually pretty heavily coloured). PA speakers are generally a good option as they are designed for hifi, FRFR reproduction - e.g. what you put in, you get out.