Aircoach €20 return from Dublin, O'Connell Street.
http://www.aircoach.ie/
I'd recommend these coaches over Bus Éireann.
Can anybody from Belfast confirm that the Aircoach destination (Glengall Street) is actually this close to the venue? Seems too good to be true.
https://www.google.ie/maps/dir/Glengall+St,+Belfast+BT12+5AB,+UK/Ulster+Hall,+34+Bedford+Street,+Belfast,+County+Antrim+BT2+7FF,+United+Kingdom/@54.5952905,-5.9361814,17z/data=!3m1!4b1!4m14!4m13!1m5!1m1!1s0x486108f7dcad2133:0x2de413cafd3e90ca!2m2!1d-5.9366433!2d54.5952402!1m5!1m1!1s0x486108f842f3b99b:0x5c77cff6815af1c9!2m2!1d-5.931106!2d54.594642!3e2