I'd found directions online, but for some reason can't find them right now. It's just as well as the directions were a little faulty. However you can look up their addresses and map out your route should you ever decide to visit. I do remember that SM was a short subway ride away from JYP, which is literally about a small block away from Cube (like a 1-2 minute walk), and then YG is totally out of the way (in Mapo while the rest are in Gangnam), about another 30-40 minute ride on the subway.
SM Entertainment
서울시 강남구 압구정2동 521521 Apgujung 2-dong Gangnam-gu, Seoul