resonance is the build house, DD is the brand... DD audio.com I don't know if you're familiar with build houses... that's like who puts the subs together... kinda like how nissan sources parts and a factory in oklahoma or whatever puts all the parts together, they're the build house.. I don't understand your question fully perhaps... TCsounds makes eclipse subs, eclipse doesn't make their own subs... kinda like that... elemental designs subs are made by image dynamics... one thing different than car factories there are only about 4 build houses for subwoofers world wide... TC sounds, King audio, Eminence and a couple others who escape me.... I think King is possibly down already, they used to make subs for like Concept back when concept 1st came out with the CSP 18" quadcoil sub... Resonance is NOT RE resonant engineering, they're not affiliated what so ever, sometimes people confuse the two and think they're one or what have you, so I specify they're not together..