@CumSum I feel like audio could be similar, and Amir has even brought it up before in a few of his reviews, but it always leads me back to the Harman studies, which basically refute the idea(unless I'm misreading).
I don't know the intricate details of the Harman study, but for a quality speaker system with true full range sound, that means bass extension all the way down to 20Hz, then I believe a perceptibly neutral sound, resembling Harman's target curve, is what we all prefer, a bump in bass and roll off to the treble. I DIRAC my speakers systems to a Harman like curve and I have had no complaints from people about the tonality of my systems and I always ask them about it. For my systems I typically bump the bass to about +6db at 20Hz and roll the treble off to -6dB at 20KHz.
That being said, if you did not have a full range speaker, and none really exist (subwoofers and proper subwoofer integration are the only way to actually get it) then a speaker with a bit more emphasized bass will probably sound better given it will add some warmth to the sound and help make up for the deficient bass extension. Conversely, the added bass will dull the treble, so you probably have to jack that up a tad as well to balance out. Now you have a V shaped speaker that may very well sound better than a flat speaker, but again they aren't full range. Also normal people don't bother with proper placement, especially in the vertical plane. So they are probably listening to the speaker off-axis, so a ton of the treble has already been rolled off. The Harman study is I would assume strongly controlled, so all the variables go down the toilet in the real world for people who have no clue. And honestly for most audiophiles as they also have no clue.
@CumSum This is the only part of your post I for sure disagree with. To me it looks like JBL messed up with the 305p somehow. I'm really curious what went wrong in that speakers designs, but it's definitely quite a bit worse than the 308p. Crossover?. Looking at the measurements of both speakers, I honestly doubt they sound that similar at all. I would expect the 305 to sound very bright, and lacking mids, whereas the 308 is almost perfectly neutral. I'm very interested to see the 306p measurements. Will it show the same problems as the 305? or will it be more well behaved, like the 308?
Do you or anyone have the link to the 305P's updated measurements from Amir? The 305P was his first speaker review and I vaguely remember him remeasuring them at some point, though I maybe wrong.
The 306P from other someone else's measurements shows an almost identical frequency response to the 305P. Only difference is a slight dip on the crossover point, so technically the 306P measure worse. But frequency response is only one metric of a speaker's performance which I why I standby by what I said previously. If the 305P and 308P showed different distortion levels, resonance issues, etc., than I may change my view point as those speakers start to be come vastly different in many aspects of objective performance. But if the only difference is FR, and that difference is relatively close, lets say within 3dB, then the sound will be too similar.
Also, I DIRAC all my systems to a similar, if not identical target curve. So frequency response measurements means very little to me as my speakers are EQ'd identically. Of course I won't buy a speaker with a garbage FR, but given I exclusively buy studio monitors, and most measure very well, it isn't an issue for me. I actually don't like the out of the box sound of most speakers. That being said I don't disregard a speaker because I don't like its sound out of the box. What matters to me is how it sounds when DIRAC works its magic on it. That is definitely where the JBL's sound like the JBL's and the Emotiva's sound like Emotiva's. Performance gap gets closer after DIRAC, as tonally the speakers fit my preferred sound signature, but that gap still exists as tonality is not the only performance metric. The 308P's won't bridge that gap.