(Un)fortunately our hearing acuity in the vertical plane is not so good same as our not so good visual vertical plane. 
Borresen vs. some other tower 3-way speakers - Vertical normalized response
Recently at Erin's Fb group someone asked if speaker's midrange has wrong polarity. There is no step response available but that might be possible, an error in design or manufacturing line. It might be the reason for poor on-axis response and strange vertical polars.
Recently at Erin's Fb group someone asked if speaker's midrange has wrong polarity. There is no step response available but that might be possible, an error in design or manufacturing line. It might be the reason for poor on-axis response and strange vertical polars.
I can tell you the mid impedance blip on the Audax HM170CO is the spider based on my investigations. I use this woofer alot and love the way it sounds. The cone is highly dampened on this driver with minimal issues until getting into the main midrange breakup modes. If you don't believe me, take one of these drivers and sweep it with a sine wave around 800 hz, then place your finger on the middle point of the spider radius and hear the harmonic disappear.
Every published measurement of Borresen X3 shows similar on-axis response, so it is is a systematic bad decision or assembly line error. If it is latter, they are not doing any quality control! I have seen commercial speakers and diy kits with such systematic fault.
Borresen head designer came from Raidho, who use also planar tweeters and show strange (and similar to B) mid-tweeter response... https://www.stereophile.com/content/raidho-td38-loudspeaker-measurements
My Amphion Helium II
Borresen head designer came from Raidho, who use also planar tweeters and show strange (and similar to B) mid-tweeter response... https://www.stereophile.com/content/raidho-td38-loudspeaker-measurements
My Amphion Helium II
YOu should not use that Audax that high i think, it's more a small woofer than a midbass, and should be crossed below 500Hz just for the reason that is found here, that anomalie at 800Hz. Therefor it's not a very usefull driver for me, and there are way better options availeble today.
And about that Borresen X3, it's just a bad design in general. That is clearly shown in all measurements.
And about that Borresen X3, it's just a bad design in general. That is clearly shown in all measurements.