I have done it myself but I think the cable may have a bit too much capacitance. The sound lacks a bit of transparency and the bass is a bit compromised. And those CAT5 cables are not cheap. I think you're better off buying some decent affordable speaker cables such as QED or the likes which have quite better transparency.
What do you think of the DIY Cat 5 speaker cables
The Chris VenHaus DIY cat 5 speaker cables what do you think of them anyone who has tried them? Do you think they sound as good as a mid priced cable you would buy? He said some AMPS may become unstable and need a Zobel network has any one had that problem with them?