You're definitely right that I asserted that with too much confidence that the speakers are meant to listen to off-axis, so I apologize about that. DefTech isn't explicit about it, it's just how I interpreted the text and illustration of the manual. To me "toe the speakers slightly" means "you don't need to toe them in all the way." Otherwise they could just say aim to aim them at the listening position as others do, but
@ROOSKIE is right that we sholdn't look at manuals too closely for advice unless they are explicit about intentions (such as Neumann, which tells you very specifically where the reference axis is, down to the millimeter). I can see why you might've interpreted that differently.
However, please keep in mind my off-axis comment was a minor point in my original post. It was primarily meant to suggest the on-axis hot treble of the D9 (which is not present in Amir's measurements of the D11 anyway) probably isn't a huge issue in practice. The bit about listening off-axis had little to do with my main point about why the measurements of the D11 are better than they appear at first glance, and the measurements I posted are all referenced to the on-axis anyway. So my larger point about the use of offset tweeters and how the close-wall reflections are perceptually dominant remain.
But as we're on the topic... I do think it's totally normal for speakers to be designed with listening off-axis in mind. So I shouldn't have said "specifically designed to be listened off-axis ," but I think my later assertment that it "appears to be designed for use with minimal toe-in" was not unreasonable.
Dennis Murphy has mentioned doing so for the BMRs, Buchardt explicitly mentions the S400 and A500 are designed to listened with no toe-in (with the default tuning for the latter), Andrew Jones does it, Dali does it, and different folks at KEF have told me three times that it designs speakers to be listened to off-axis as well (but you have the choice).
It is also worth noting that in the only study that I know that analyzes the typical positioning of speakers in home listening environments(devantier, 2002), the majority of listeners had their speakers set up for off-axis listening:
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So I don't think the idea that engineers making HiFi speakers are designing them to be listened to off-axis is unreasonable.