Maybe they are using a panel exciter of some type. They work quite well for voices. They are not known for great bass and fall off normally at 10-12k.
I've tinkered with panels and exciters, they are a lot of fun actually and a good alternative for odd shapes that need to produce sound.
I've tinkered with panels and exciters, they are a lot of fun actually and a good alternative for odd shapes that need to produce sound.