If you don't have a SOUNDBOKS, you can either buy it directly from SOUNDBOKS or from HiFi-Klubben in one of their +90 physical stores.

You can also rent a SOUNDBOKS
You can instead rent a SOUNDBOX at Lejsoundboks.dk . It's smart for festivals where you can split the cost with your friends.
That way you can quickly and cheaply achieve concert level right down to the festival camp. See more at: Lej1soundboks.dk