For instance, a speaker with a woofer and a tweeter is 2-way. "A Woofer in Tweeter's Clothing" was released in February 1973. "A Woofer In Tweeter's Clothing" received mixed to positive reviews by the majority of critics. "A Woofer in Tweeter's Clothing" has been re-released numerous times since 1973. A woofer is a driver that reproduces low frequencies. The premium sound system head unit with sub woofer was dropped as an option. In most cases the woofer and its enclosure must be designed to work together. Only at design time do the separate properties of enclosure and woofer matter individually. This handles the upper frequencies that are too high for the woofer. More often they are heavy-duty two-way systems with a woofer and a high-frequency horn. This resonance simultaneously reduces the amount that the woofer has to move. The 375 shared the same basic magnet structure as the D-130 woofer. This cabinet design employed a transmission line labyrinth for the woofer. Those issues were addressed with the invention of the acoustic suspension woofer. However, there is often a problem with integrating such a woofer with the electrostatics.