A que se refieren con "monitores en una posición 2pi"

Alguien escribió:

Figure 1 shows the two-pi frequency versus amplitude and phase response. The amplitude (top trace) holds pretty close to +/- 3 dB, and remains quite consistent whether measured at a distance of 12 inches (upper curve) or 24 inches (lower curve). The phase response (bottom trace) is also consistent with respect to level, but notice that between 500 Hz and 4 kHz, there is an excess delay indicating a lack of coherency. This anomaly could be caused by the NS10's crossover circuit, which centers at 2 kHz.

distante escribió:

Extraído de una duda de https://www.hispasonic.com/foros/tecnicas-raras-estudio/348612

Vi que en las mediciones que hizo Bob Hodas, la primera describe ser : "The test included first measuring the speaker in a two-pi position, "

Y luego muestra esta imagen y su descripción:

Alguien escribió:

Figure 1 shows the two-pi frequency versus amplitude and phase response. The amplitude (top trace) holds pretty close to +/- 3 dB, and remains quite consistent whether measured at a distance of 12 inches (upper curve) or 24 inches (lower curve). The phase response (bottom trace) is also consistent with respect to level, but notice that between 500 Hz and 4 kHz, there is an excess delay indicating a lack of coherency. This anomaly could be caused by the NS10's crossover circuit, which centers at 2 kHz.

Tengo una idea de que quiere decir con "Two-pi" considerando que se refiere a PI matemáticamente, pero puede que este equivocado y prefiero desasnarme con los que saben más

Danke!