horn loudspeaker
loudspeaker or loudspeaker element which uses an acoustic horn to increase the overall efficiency, used either for HiFi purposes or for distributing spoken information to larger audiences in public
en-US/ˈhɔɹn ˈlaʊdˌspikɚ/
en-GB/ˈhɔːn laʊdˈspiːkə/