Paradigm Reference Active/20 loudspeaker Measurements part 2
Fig.7 Paradigm Active/20, 1/3-octave, spatially averaged response in JA's listening room.
In the time domain, the step response on the tweeter axis (fig.8) reveals that the speaker is not time-coherent, as expected from the flat baffle, but with units connected in the same positive acoustic polarity. Other than some ridges of ultrasonic resonant energy from the tweeter, the associated cumulative spectral-decay plot (fig.9) is superbly clean. The slight treble graininess I noted in my auditioning must originate somewhere else, perhaps in the amplifier.
Fig.8 Paradigm Active/20, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).
Fig.9 Paradigm Active/20, cumulative spectral-decay plot at 50" (0.15ms risetime).
Finally, attaching a simple plastic-tape accelerometer to the cabinet sidewall and calculating a waterfall plot from its output (fig.10) revealed a small amount of panel resonant behavior, with one mode present just above 200Hz and another at 400Hz. The levels are low, however, and I noticed no congestion in this region.
Fig.10 Paradigm Active/20, cumulative spectral-decay plot of accelerometer output fastened to cabinet sidewall (line-level MLS driving voltage to speaker 410mV, speaker level control set to "0").
Summing up, this is superb measured performance for an affordable speaker. There is obviously some superb speaker-engineering talent in residence at Paradigm.—John Atkinson