Naim NBL loudspeaker Measurements part 2

Fig.4 shows the NBL's response on the tweeter axis, averaged across a 30 degree horizontal window to minimize the effect of position-dependent, and hence irrelevant, interference effects. Though it is very even, the entire treble is shelved-up compared with the lower midrange and bass, which is why PM commented on the speaker's bright, forward balance. As I've said, the NBL's low bass will be boosted by the Allison Effect, but this will leave the region between 300Hz and 600Hz depressed in comparison with the regions above and below. In addition, as PM found in his in-room measurements, the upper midrange is somewhat exaggerated, which will make the speaker sound very detailed but also very critical of matching electronics.

Fig.4 Naim NBL, anechoic response on tweeter axis at 50", averaged across 30 degrees horizontal window and corrected for microphone response, with the complex sum of the nearfield woofer and midrange responses plotted below 300Hz.

Figs.5 and 6 show the NBL's lateral dispersion, without (fig.5) and with (fig.6) the tweeter-axis response subtracted. While the upper-midrange energy peak persists off-axis, which will exaggerate its audibility, the speaker's dispersion is relatively well-controlled. What appear to be off-axis ridges in fig.6 are primarily due to on-axis suckouts filling-in to the speaker's sides.

Fig.5 Naim NBL, lateral response family at 50", from back to front: responses 90 degrees-5 degrees off-axis, reference response on tweeter axis, responses 5 degrees-90 degrees off-axis.

Fig.6 Naim NBL, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90 degrees-5 degrees off-axis, reference response, differences in response 5 degrees-90 degrees off-axis.

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