I too did not like the stiffness of the HE-500 cable and the harsh microphonics drove me crazy. Every time I moved my head with the music I heard the cable hitting something and the noise was very noticeable. I also wasn't exactly pleased with the sound signature even after burning them in for three weeks so I went searching for alternatives that would be very flexible, non-microphonic, and sound better than the silver coated stiff copper wire that came with my HE-500's.
I discovered that Moon Audio carried everything I would need to make my own cables in their DIY section including extra HiFiMan connectors in case I screwed mine up.
First pick a cable; I chose their Silver Dragon V2 Bulk Headphone Cable @ $18.00/ft. which uses 4 x 99.998% Ultra Pure Silver 24AWG Teflon insulated stranded conductors. The cable is red in color and I think it looks great against the black HE-500's. They include Black Techflex with the cable which makes it look burgundy but it added microphonic noise which is what I was trying to avoid in the first place, so I removed it. I only needed 5 feet, so it was less than $100. BTW, I tried the Cardas 4X4 cable @$20/ft and was disappointed, the Silver Dragon V2 blew it away . If you really want to save some money and use copper instead of pure silver try Mogami W3106 or Mogami W2534 Neglex Quad Mic Cable from a variety of sources online for less than $2.00/ft. It doesn't sound like the Silver Dragon but is pretty close and far better than the OEM cable. I added another set of HiFiMan connectors and then searched for a suitable plug.
If you want to stick with a 1/4" plug and go whole hog, the Furutech FP704 (G) ($18.75) is the Cadillac but is large and quite heavy though it looks great and is incredibly well made and very easy to work with. You could also use the recording industry standard, the Neutrik 1/4" Stereo Plug for just $5.00, also very well made, easy to solder to but lighter in weight and smaller in size.
If you primarily use an amp or DAP with a 3.5mm headphone jack you might want to consider terminating your cable with a 3.5mm plug. The Switchcraft 3.5mm Stereo Plug ($8.00) will accommodate the thicker cable size, is well made and easy to solder to. In case you are wondering, the Neutrik 3.5mm Right Angled Stereo Plug is too small without modification to use with this cable. I then finished my cable by using some heat shrink tubing which I bought elsewhere for like $0.60 a foot in different sizes and now I have great sounding, highly flexible, good looking, sturdy cables for my HE-500. BTW, I used a small piece of red heat shrink tubing over the base of the right headphone connector to distinguish it from the left one.
Hope this post is helpful.
Here is a picture of the Silver Dragon V2 Headphone cable with a modified Neutrik 3.5mm Right Angle Stereo Plug (5' long)
Here is a picture of the Mogami W2534 Neglex Quad cable with Furutech FP704 1/4" Stereo phono plug (4' long)
Edited by Art inTampa - 11/14/13 at 7:33pm