For me, there are so many numbers involved in the explanation that it tends to complicate the basic understanding of this microphone system. These two pieces make up the basic mic. Assembled, it is about seven inches long with a diameter of about three-fourths of an inch. Omnidirectional isn't a completely honest description of this mic. It clearly does have 'on axis' advantages.
High frequencies are indeed directional.
Somewhere in the mid-range on down the mic becomes more omnidirectional and, as a result, the mic behaves more like a cardioid mic, but without a proximity effect. In Use My first attempt at using the 3541 was on a session I was doing with the country group Alabama, which featured Christopher Cross as a guest vocalist. I started by recording Chris' vocal with a Neumann U47. His voice is quite clear and open and the Neumann was perfectly suited to him. Teddy Gentry was the featured voice of the group.