If you have a look at the linear resistance for 1/0.6mm single core equipment wire Rob, you'll see it's around 0.064 ohms per meter. Thus the loop resistance for a loudspeaker cable based on a similar (the same?) dimension of wire will be double this per meter. For a one meter length about 0.13 ohms - or as I measured the DNM loudspeaker cable about 0.15 ohms.

A three meter length having loop resistance of about 0.45ohms equates to around 1dB level loss into a 4 ohm load. A nominally rated 8 ohm loudspeaker will typically dip to around 4 ohms thru the midbass. So it's not difficult to see how loudspeaker cable having relatively high resistance can cause audible frequency-specific level losses.

Not necessarily a bad thing since it's all subjective, but neither neutral in the sense of the loudspeaker cable having no effect on the frequency response of a hi-fi system.

By keeping the loop resistance of a loudspeaker cable to no more than 5% of the minimum loudspeaker impedance - for any given length of cable - is a good rule of thumb.