RCF HDL 30-A Line Array Salutes Queen 500m Under the Earth Live by Thomas Richard - February 26, 2019 At a concert of the Queen tribute band "MerQury" in Thuringia, Germany, the line array system HDL 30-A from RCF proved it was easy to install and capable of delivering perfect sound even under extreme conditions. Held in Merkers, a former large bunker for potash salt at a depth of 500m