There were several different models, I think that the T-9 was part of the MET 7 system and the T-1 was the original model. In my muddled mind there was a T-3 as well. The T-1s are a nice adjunct to the Quad 57s. Levinson used to sell the HQD system with Hartley 24" woofers, the Quad 57s, and the precursor to the T-1, the Decca ribbons.