Evaluation system: A very modest system Magnepan 1.6 Lexicon NT power amp (it's a rebadged Bryston 4bST) HK 650 receiver as pre-amp - stereo mode analog input Sony CD/DVD player AR interconnect. Wires and construction: Version 1 - Cat 5e riser type source Home Depot manufacturer likely Carol (PVC insulation and PVC jacket) - 4 lengths twisted together and taped over with black tape to maintain tight twist. Length approx 7 feet for each channel Version 2 - Cat 5e plenum type source mail order manufacturer unkown (Teflon insulation PVC outer jacket) - 4 lengths twisted together without the outer PVC jacket. Twisted wire taped over with Teflon plumber's tape to maintain tight twist. Length approx 7 feet each channel 12 gauge speaker wire Belden as is. Length approx 25 feet each channel coiled up. All wires terminated to banana plugs from Monoprice. Observation: My reference is the 12 gauge speaker wire I have been using since mid 1980s. It has been in the current system for last 3 years. Why 25 feet each channel? My old set up in my previous house the speakers were that far away from the old receiver. I am loathe to cut them short. Replacing the 12 gauge with the either Cat5e wire resulted in a highly significant significant improvement in clarity - suddenly voices were clearer and finer details obvious. Virtually no smear. The short comings of the 12 guage could be partly due to the length and that it was coiled up and sat under jumble of power cords, interconnects etc. Bieng untwisted it would have poor RF rejection. Difference between the two Cat5e - Version 1 - Well balanced freqency response across my audible range with a very slightly more presence on both male and female voices. I kind of like the slight presence. Solid localization of instruments on the stage both side to side and front to back - so much so that I could discern if the trumpter swayed side to side on some recordings. Very good clarity and attack e.g. triangles and cymbals sharp and clear, strike of the drum stick on the drum skin clear with no fuzziness. Magnepans are well known for their attack response and clarity. Version 2 - The frequency response biased to the highs with a sucked in mid-range. Made the Magenpans sound almost like horns or honky. Not sure how to describe it - heard a lot of resonance of the high frequencies much like ringing - unpleasant to my ears. Cannot say if it is an artifact of the wire or the wire is bringing out what was recorded. Disappointment overall. Using either Cat5e for extended periods did not change its sonic characteristics, i.e. no observable burn-in effect. However, there was a discernable sonic change within a few minutes of playing this happened everytime I switched the wires. Version 1 started sounding lightly thin then achieved its own sonic characteristics. Version 2 started a little fuller then achieved its own sonic characteristics. Perhaps it is due my hearing. But I have a conjecture, perhaps the change is due to re-equilibration of the amplifier, wire, speaker circuit. Next attempt Version 1 with the PVC jacket removed. I will add to this post when I am done.