The t3 I believe had a special compound to treat the woofers, I think they called it Aquaplas? It was supposed to have been researched at Nasa, but, then, who knows what are its properties and real effects in sound. The drivers must be different. I have the small L-20t3, which do not have the larger, "aquaplas" treated woofers. Good rock speakers. Nice tight bass on the 100t3 pairs.