B&W Nautilus 801 loudspeaker Measurements part 3
Fig.7 B&W Nautilus 801, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 20 degrees-5 degrees above HF axis; reference response; differences in response 5 degrees-10 degrees below HF axis.
The impulse response on the tweeter axis (not shown) is absolutely conventional, while the step response (fig.8) indicates that all three units appear to be connected with the same, positive acoustic polarity. As is usual with a high-order crossover design, however, the Nautilus 801 is not time-coherent, the tweeter's output arriving at the microphone a small fraction of a millisecond before that of the midrange unit, and the woofer's output lazily following that.
Fig.8 B&W Nautilus 801, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).
Fig.9 B&W Nautilus 801, cumulative spectral-decay plot at 50" (0.15ms risetime).
Finally, the cumulative spectral-decay plot on the tweeter axis (fig.9) is astonishingly clean and free from resonant modes. No wonder the B&W sounds so grain-free and easy on the ear.---John Atkinson