There are free SPEAKERS, that sound is very delicate and loud. The sound was very powerful with ROCK MUSIC and BASS sound so that you can enjoy. By the way, the speakers(more than TWO) are owned by the outside music PUB and RESTAURANT and this restaurant is not close until 4 AM!!!!!
If you don't want to sleep, I can strongly suggest this because you can go to the terrace with Elevater and long stairs. But it is NOT PRIVATE so every people in this building would share with view of very very small Agora ofAthens.
Good Luck.