Off axis Berg 2-15

[Rockbobmel]

I think I understand this some, but what am I supposed to be hearing?
My NV-215 sounds louder when it faces me and I'm out a few feet but I don't really know what to listed (pay attention) to, and how to reference it.
Thanks.

 

[billfitzmaurice]

Your cab will sound loudest when you're in the middle of its cone shaped radiation pattern through the widest part of its bandwidth, far enough away so that the cones are on more or less direct line with your ears, and not so far to either side that you're outside that cone shaped pattern. All drivers have a radiation pattern that narrows as frequency goes higher, and with fifteens that pattern shrinks rapidly above 1kHz.