This is my latest project...a DIY CAT5 speaker cable.  There are a couple of designs on the www and the one that I have chosen to try is by gomer because it is much easier and quicker to make compared to braided CAT5 designs.  

Even though this design is easier and quicker to construct, it still retains low inductance measurements.  I found a WWW site by a professor called Eric who  tested the cable and recorded the following: 150 pf/ft and 0.3 uh/ft.  Gomer quotes his cable at 260 pf/ft.  Unfortunately, I cannot vouch for these measurements but I tested my cables on my very inaccurate LC meter and got: 260 pf/ft and 0.1 uh/ft.  The same LC meter indicated that my old Van Den Hull MC D 300 S cables were: 11 pf/ft and 0.15 uh/ft.

What I found is that the initial turns rate of 14 turns per foot is good, however the second turns rate of 10 turns per foot is a little high and in hindsight I would recommend 9 turns per foot.  Overall, the finished cable, using Belden 1585A, has a nominal diameter 7.0mm (but has infrequent random peaks at 7.5mm dia).  If you want to 'dress up' the finished cable with a braided sheath, or just want some good spade terminals, then try Take Five Audio.  I used their polyester expandable sleeve (Techflex)1/4" diameter to get a professional looking finish.

The first picture below is a test run I made using 'regular' CAT5 cable while I waited for the Belden 1585A CAT5 cable to arrive from Australia.  The overall diameter of this trial cable is 10mm.  By comparison with regular CAT5 cable, Belden 1585A is a high quality cable that utilises teflon insulation which has a high dielectric constant meaning the capacitance of the finished cable will be lower.  I have only read good reviews about CAT5 based speaker cables and they are a lot cheaper that any commercial product!

How does the cable sound?  I never bought into the idea that cables have a sound however, from a measurement perspective a cable's inductance and/or capitance can form a network with the speaker (particularly an electrostatic speaker like my Quad 63's which are essentially large capacitors) which results in early roll off of the high frequency.  so, in my system, these CAT5 cables seem to extend and give a greater clarity to the high frequency information. 

Trial cable using 'normal' CAT5 cable

Completed Speaker cable - Note once the cable is installed behind the speakers/amp if actually looks 'blacker' than it does in the photo.  It's not until you get right up close (say 1m) do you see the colour of the CAT5 strands.