Well I had put an EDIT at the end of my post saying "EDIT: to check you mixes on lesser ranged equipment you could just add various Low & High Passes to your flat anechoic speaker to emulate smaller sized speakers that don't have the low end or the high end."I totally understand your point. It is pure logic: you want flat converters, a neutral room, but f****d up speakers? It sounds preposterous but I'm of the current understanding that it's merely counter-intuitive. It's impossible not to bring up the subjective claims that, "Flat responses are too gentle, I need X speaker because it helps me mix," which you can read a-plenty around the net - specifically in the gearspace thread that I posted assuming it hasn't been totally sanitized of even those statements in addition to mine.
Like you, I use subjective terms like 'good' and 'bad' and, in this case, 'rubbish' but I want to expand to the other hemisphere of my brain and include metrical descriptions like 'series of three comb filtering-like, hi-Q 10dB peak-to-peak deviations from 3-6kHz'. I can't argue against 'rubbish' other than to say your rubbish might be a mixer's best friend. Believe me, I'm as opinionated as you and often want to say highly offensive things and just stick to my guns but that's not why I'm here. I'm here because I want to upgrade from HS50 to something that helps me make tracks which exude the utmost in sonic ecstasy and currently believe that opinions alone are not the best guide.
Similar to the far-field graphs Amir puts up, this speaker is not listened to in a vacuum or purely anechoic space. Its raw Klippel-magic'ed response is not what you get even 1m away. This is just to say that its response in room is not as wild as it looks and I posted my measurement in support of this claim. Again, we have certain suspicions but no actual peer-reviewed theory as to why mixers prefer Objectively 'Flawed' Speaker A vs Objectively 'Better' Speaker B. I think it would be a tremendous boon to the pro audio community to know this information.
So if I had the audacity to suggest to a music creator what equipment they make their music on then I'd say full range flat anechoic speakers, and then if you want to check the mix's compatiblity on lesser ranged gear then you can just whack in a few different High & Low Passes onto your speaker to take away the bass and the high end. So I don't think there's any necessity to use randomly rubbish speakers with random horrendous frequency response deviations.