I didn't say anything about not trying reversing the tweeter polarity, did I?
What I did say is that I don't believe this particular dip is associated with a possible wiring issue.....because it's not at the crossover frequency. The info I found on this speaker indicates a xover frequency of 4khz. (Which could be wrong I suppose.)
Dave.
The OP had indicated that the dip was in the vicinity of the crossover frequency. This may have led to confusion, but whether it did or didn't, the most likely explanation for the dip at about 1.8 kHz (judging from the Soundstage plot) remains phase mismatch between the two drivers at this frequency. At the vertical polar angle where the measurement is taken, it is most likely true that the two drivers are nearly 180 degrees out of phase at this frequency. This is unusual, but not impossible, and there is nothing else that comes to mind that could as easily explain the severe notch that is seen very clearly in the Soundstage plot and that is characteristic of phase cancellation between the two drivers. For this to occur, the phase difference between the two drivers would obviously have to be different for 1.8 kHz vs. 4 kHz. This could be simply a result of using different slopes for the two drivers, since the rate of phase change relative to frequency would then be different for the two drivers. Additional phase shift associated with the natural rolloff of the drivers could also be a strong contributing factor.
I don't understand why you would think it meaningful to point out that you hadn't said anything about not trying to reverse the tweeter polarity. We have a disconnect there, but what you did actually say in a previous reply, to popper, is this:
I understand EQ wouldn't be 'your' first move, but that's not what the OP asked about.
You seem to be having a discussion with yourself on how this particular speaker (B&W 603) could be 'fixed'. (Assuming it needs fixing.)
Or that maybe it emerged from the factory defective in some way and it needs to be troubleshot. You might be right in either or both cases.
But regardless, the OP's question was not primarily about this speaker, but rather a more general question. But since he hasn't returned to elaborate, the simplest answer to his question is Yes.
Dave.
I don't know why he would have been having a discussion with himself, especially since you had engaged with him all along. More to the point, while it is true as you point out that the OP had asked the question in a general way, the particular question he asked in a general way was this:
The amplitude-frequency response curves ... may have a dip around the crossover frequency.
Is it correct to eliminate the dip by EQing?
Given that the question he asked in a general way is concerned with dips found "around the crossover frequency", it was well within reason for popper to have responded with an assumption that the sort of dip to which the question pertains is a dip associated with the crossover, even if it isn't at the crossover frequency. You say that you didn't say anything about not trying reversing the tweeter polarity, but your criticism of his posts was undeniably based on his focus on the crossover and the suggestion that before applying EQ, it would be prudent to experiment with the tweeter polarity.