Revel Performa M20 loudspeaker Measurements part 2

Figs.5 and 6 show the Performa M20's horizontal dispersion, as actual responses (fig.5) or normalized to the tweeter-axis response (fig.6). A slight flare at the bottom of the tweeter's passband can be seen in the latter graph, but the evenness of the radiation pattern's contour lines is commendable, and gives the lie to the doubts I expressed in this review's introduction. It is also something that correlates with the stable, well-defined stereo imaging I heard. The tweeter gets very directional above 16kHz, but this is a) not important subjectively, and b) an unusually high frequency for a 1" tweeter to maintain its wide dispersion, particularly given the quite wide baffle. This behavior can also be seen in the plot of the Revel's vertical dispersion (fig.7), but of more importance in this graph is the large suckout that appears in the crossover region once the listener gets above the top of the enclosure. It also appears more than 25 degrees below the tweeter axis...but the M20 should always be auditioned on or below its tweeter, which is presumably why Revel's matching stands are high.

Fig.5 Revel Performa M20, horizontal 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 Revel Performa M20, horizontal 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 Revel Performa M20, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 45 degrees-5 degrees above reference axis; reference response; differences in response 5 degrees-45 degrees below reference axis.

How these radiation patterns behaved in my listening room is shown in fig.8, the 1/3-octave response taken with an AudioControl SA3050A spectrum analyzer and averaged across a window centered on the listening position. As might be expected from the anechoic measurements, this is astonishingly flat from the upper bass through the high treble! The relative lack of energy in the 50Hz and 63Hz bands is due to the room (this is something I am starting to despair of fixing), but the room also usefully boosts the low bass: note the flat response down to the 25Hz band, which is why organ and orchestral recordings came over so well. There is the slightest hint of extra energy apparent in this graph, which is why I ended up shelving the tweeter region down by 0.5dB.

Fig.8 Revel Performa M20, spatially averaged, 1/3-octave response in JA's room.

In the time domain, the M20's step response (fig.9) confirms that both drive-units are connected with the same, positive acoustic polarity. Note how the return to the timeline of the tweeter's output hands over to the positive-going rise of the woofer's step, implying good driver integration in the crossover region. The Revel's cumulative spectral-decay plot on the tweeter axis (fig.10) is superbly clean overall, though some low-level spuriae can be seen in the upper midrange. (Ignore the black ridge just below 16kHz; this is due to electrical interference from the TV I use to monitor my remote speaker-measuring system. The speaker, microphone, remote-controlled speaker turntable, and 2.4GHz wireless video camera are outside, in my backyard; I sit indoors, surrounded by the usual creature comforts.)

Fig.9 Revel Performa M20, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Fig.10 Revel Performa M20, cumulative spectral-decay plot at 50" (0.15ms risetime).

Other than the slightly low voltage sensitivity, this is superb measured performance from a speaker at any price, let alone one costing just $2000/pair.—John Atkinson

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