I bet you can't tell exactly. In fact, I bet you got no clue where it is by just looking at the speaker's phase response. I can't tell shit either. Which is my point. There are other easier ways to determine that which do not involve the step response. Actually on the MR5 I think the tweeter is quite a bit behind, allegedly to align the responses. Really? Well we couldn't tell shit by looking at the phase response. I maybe pressing the matter here, but you sometimes say "I can't tell exactly" and the you say it "will make itself known in the phase response". You can't have both. The phase response is there and I personally can't tell shit. What's you approach to figure this out. What do I look for? It may have to do with a discontinuity in the frequency response. Possible the delay is not over multiple cycles or a full cycle even. I know that because the offset is about 360 degrees. IMO is a measurement artifact. But you can tell shit is not perfect. No way that's minimum phase either. Well that's just a bad example. The reason your phase is all jagged and all over the place is that the frequency response you took was not in anechoic or semi-anechoic conditions. There will be combing all over the place due to room interactions. I can't tell shit from that plot's phase response. In room measurements will behave like that. And the phase on in-room applications will be fucked all over. Because the speaker interacts with the room. Such is life. Your Superlux results are not like the KSC75 or a K812 results, because your Superlux is not a KSC75 or a K812. Almost every measurement I've seen on a KSC75 exhibits a severe null in the same area. It is these nulls that produce not only discontinuities in the magnitude, but the phase as well. Dynamic drivers are not minimum phase. You keep saying that, but those IR definitively exhibit zeros outside the unit circle. I've done this with my HD600. I'm not sure what else to tell you. By definition those headphones are not minimum phase. All drivers are pistonic. Planars and stats move a lot less, that's all. All drivers compress air volume mechanically. The larger the driver, the less it's got go move. Stats have a huge driver, so they almost don't move relative to a dynamic driver. Their theory of operation is also a little different. But you better believe it moves, or no sound will come off of it. The apparent excess phase likely comes from the discontinuity. IMO is a measurement artifact. Still, there is no way I'm calling that minimum phase.