Joseph Audio RM7si loudspeaker Signature Measurements part 2
Fig.5 Joseph RM7si Signature, 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 Joseph RM7si Signature, 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.
Fig.7 Joseph RM7si Signature, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 45 degrees-5 degrees above axis, reference response, differences in response 5 degrees-45 degrees below axis.
Apparent in all of these dispersion graphs is the tweeter's limited off-axis output above 10kHz. In well-furnished or relatively large rooms, the RM7si's top octave will sound reticent, as indeed I found in my own auditioning. Fig.8 shows the Joseph's spatially averaged response in my Santa Fe listening room. Note that the output through the mid-treble is superbly flat (as was the regular '7si), revealing that the on- and off-axis behavior does compensate in the manner I suggested. But note also that the in-room output drops off quite rapidly above 10kHz.
Fig.8 Joseph RM7si Signature, spatially averaged, 1/3-octave, free-field response in JA's listening room.
Though both drive-units appear to be connected with positive acoustic polarity, the Joseph's step response (fig.9) is clearly not time-coherent, a side-effect of the crossover topology. The waterfall plot on the tweeter axis at 50" (fig.10) is very clean throughout the tweeter's passband, but there is a distinct "knee" in the graph at the top of the woofer's passband. This might contribute to the narrow-band brightness I occasionally noted in my auditioning.—John Atkinson
Fig.9 Joseph RM7si Signature, on-axis step response at 50" (5ms time window, 30kHz bandwidth).
Fig.10 Joseph RM7si Signature, cumulative spectral-decay plot at 50" (0.15ms risetime).