One of the problems with the use of standard public address systems in music theatre is that the front-of-house and monitor speakers may obstruct audience sight lines and interfere with the stage appearance. In some cases, this problem can be solved by hiding large speakers behind set constructions or drapes. In productions with little or no onstage set structures, such as a minimalist modern piece, sound engineers may opt to use higher-cost low-profile speakers, which are slimmer. Alternatively, sound engineers may decide to "fly" the speakers by attaching them securely to the rigging above the stage using steel cables.