The Sphere microphone uses a large diaphragm condenser capsule, and is optimized to model large diaphragm mics most accurately. For vintage large diaphragm condenser microphones, in particular, our target is to meet or exceed the accuracy of currently available reissues, clones or other modern versions of the corresponding mic. In most cases we achieve or surpass that standard of accuracy.
For other types of microphones, such as dynamics, ribbons, and small diaphragm condensers, the models are generally accurate when used on-axis. Beyond 45 degrees off-axis the models may deviate substantially, but still maintain the overall polar pattern. Generally this means that close miking will be more accurate than distant miking. Keep in mind, when close miking a guitar amp, for example, the speaker is large compared to the mic, so much of the sound pickup is off-axis.
Handling noise, plosive sensitivity, electrical noise, and headroom are not directly modeled. The plosive sensitivity of the mic is comparable to a typical high quality side-address large diaphragm condenser microphones. At 60mm in diameter the Sphere L22 headbasket is relatively large (the same size as a U47), and all other things being equal will have less plosive sensitivity than a mic with a smaller headbasket. The microphone and modeling algorithms are designed to produce the lowest noise and highest headroom possible, even if the original microphone being modeled is noisier and has less headroom.
The Sphere microphone uses a capsule with very tight tolerances, so that the models will sound consistent no matter what mic hardware is used. Microphones, in general, have more variation from unit to unit than just about any other piece of equipment in the recording signal chain, so when comparing any two mics of the same type there will likely be some difference. Sphere models the specific microphones that we measured, so it will likely not exactly match similar mics in your collection.