The invention discloses a system for delivering acoustic energy to a subject in connection with high intensity focused ultrasound (HIFU) systems. In an embodiment, the system comprises an optionally disposable waveguide-attached ablation applicator coupled with an optionally re-usable waveguide, and an optional acoustic power source. The systems may comprise acoustic energy exit port intensity control, waveguide heat-sinking, and transducer operational adjustments that accommodate waveguide effects on the traversing acoustic power.