I dunno. It certainly is more musically satisfying than the other 3 REL's I've owned. It's far better than the R-205 and I've stated a number of times that I should have given the T-1 more time before throwing in the towel. I think it may have been better than I gave it credit for at the time. I'm very pleased with the T5. I think that every REL sub I've used has been a quality sub.