“I need to buy or make some extension cables for headphones in my studio. Someone told me I need to buy special cable for this. Is that true?”
Any high quality mic cable should work fine, unless the distance involved is extreme (hundreds of feet) or you intend to drive many sets of phones off of the one cable. Most headphones are wired using cable that has two conductors and a shield, just like standard mic cable. Each conductor carries one channel of audio, while the shield acts as a common ground for the two.
There are some headphones that actually use four conductors with a separate shield (or no shield), where each pair of conductors is for one channel of audio. So the left channel has a positive (+) and negative (-) wire, and the right channel has the same. The shield (if there is one) is connected to ground at the source (the plug). Many of these designs still terminate to a standard TRS connector so at that point the negative wires of the two channels still get summed together with the shield. Until you get well up into the “audiophile” community you will find very few people who will argue that the separate wire method makes any significant difference. Further, if the phones terminate to a standard plug it’s even harder to make this argument.
With that slight caveat we say go ahead and use “standard” cable for your headphone extensions. Most professional headphone distribution systems use standard mic cable as well. You can make the extensions yourself out of high quality mic cable (it really is best not to use the cheap stuff for this), or we sell them already made.