I have R510
Hi Darius,
When you say "specific macs" are you referring to MAC addresses or Macbook?
If you are referring to device MAC addresses, then yes, you can create a new SSID, enable it only on 2.4 G radio using AP group settings and then create a new L2 ACL, allow specific MAC address in that ACL and only these clients will be allowed to connect to this SSID.
If you want to restrict MacBooks, I think you can use device policy option under Access control.