This invention relates to apparatus and methods for intermittently bonding a substrate web in fabricating a blank subassembly for an absorbent article. The invention comprises ultrasonic bonding apparatus including an anvil roll, a substrate web thereon, and at least one rotary ultrasonic horn. The substrate web can comprise at least first and second layers of material. The rotary ultrasonic horn, in combination with the anvil roll, ultrasonically bonds intermittent segments of the first and second layers of the substrate web to each other. Such intermittent bonds can comprise end seals for the absorbent articles. The ultrasonic horn and anvil roll are periodically separated from each other to provide the intermittent bonding of the substrate web. An actuator apparatus periodically moves the anvil roll and ultrasonic horn from engaging contact with each other preventing bond formation. The actuator apparatus can include a cam mechanism moving one of the anvil roll and ultrasonic horn from engaging contact with the other during rotation of the rotary ultrasonic horn. The cam mechanism can create a physical gap between the ultrasonic horn and the anvil roll. The cam mechanism moves either the ultrasonic horn and the anvil roll toward the other of the ultrasonic horn and anvil roll at a velocity of no more than about 80 millimeters/second to prevent bounce or impact loading when the horn and anvil roll are in engaging contact. The anvil roll comprises a substrate-receiving surface generally moving the substrate web through the nip at a surface speed of at least 300 meters per minute. The ultrasonic system generally creates bonds between the first and second layers of the substrate web at least about 600 times per minute.