These two measurements showing the exact same slopes are case closed for me.
You are closing too early. Anti-Covid measures?
- From anechoic measurements in post #1 (thanks, Amir!): maximum difference between 650 Hz dip and 2-8 kHz tweeter plateau is exactly
15 dB. The "650 Hz" dip is very wide - between 300 Hz and 900 Hz.
- From in-room measurement in post #61 (thanks, Worth Davis!): maximum difference between 650 Hz dip and 2-5 kHz tweeter plateau is exactly (and only!)
8 dB, including the peak at 4 kHz. Much better! Because of the dip between 6 and 8 kHz (due to two-tweeter interference) I suspect this imeasuring is done with microphone in only one position (i.e. not moving-microphone technique). Also, peak at 5 kHz may be from the same two-tweeter interference and maybe is not "real", so maximum difference is
7 dB. Taking the "0 dB" line as reference, the "650 Hz" dip is between 500 Hz and 900 Hz - big improvement over anechoic 300 Hz and 900 Hz.
- From in-room measurement in post #65 (thanks, spacevector!) maximum difference between 650 Hz dip and tweeter peak is exactly
11 dB, (left surround) and
9 dB (right surround). We can say it is
10 dB average - again, better than anechoic. Also, the "650 Hz" dip is between 550 Hz and 900 Hz - big improvement over anechoic!
- From in-room measurement with moving-microphone technique in post #117 (thanks, Chromatischism!) maximum difference between 650 Hz dip and tweeter peak is exactly
7 dB - again, much better than anechoic. Also, the "650 Hz" dip is between 400 Hz and 900 Hz - improvement over anechoic!
So, we can conclude this:
1. Tweeters between 2 kHz and 8 kHz are too "hot" - both in anechoic and in-room measurements. Why are loudspeaker manufacturers so obsessed with overly loud tweeters?
2. Dip at about 1.5 kHz is real. It can be made much smaller with some sort of phase-plug in front of the woofer cone, as a part of the mounting back plate. Plastic is cheap.
3. The "650 Hz dip" is (kinda) real, but not so severe as in anechoic measurements. In room (and on-wall) it is not so deep and wide. Also, if the high-pass filter of tweeter was done right, the "650 Hz dip" largely disappears.
There is a clear dip here, yes the room modes(and comb filtering, which is this speaker's fault) are hiding how bad it is, but they are not hiding its presence. This sort of extremely broad dip simply does not happen due to room modes alone.
Not sure why you think it isn't there. It 100% is.
View attachment 124691
Oh, cmo'n! You intentionally rejected much of the frequency response. Overall trend is very clear from the complete in-room frequency response:
View attachment 124686
As we can see, below 300 Hz are peaks and dips from room modes, and our reference horizontal line can be anywhere between 72 dB and 76 dB. If we choose the 72 dB line, than
there is no "650 Hz dip", but there is excessive tweeter output (which we know is true). If we choose the 76 dB line, than the tweeter output is neutral (which we know is
not true!) and there is a wide "650 Hz dip" depression between 400 Hz and 900 Hz, but only 4-6 dB deep. For me, the only real problem is too hot tweeter.