FYI: For our speakers models that use only one tweeter, the vertical design or measurement axis is the strip of cabinet between the tweeter faceplate and the woofer or mid basket. In the dual-tweeter models it's the point between the two tweeters. As your listening position ear level moves up or down from that point you will begin to experience a crossover suck-out due to lobing. Typically it's more pronounced if you are significantly above the design axis, rather than below.