Fig.10 Revel Ultima Gem, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 45 degrees-5 degrees above HF axis; reference response; differences in response 5 degrees-45 degrees below HF axis.
Fig.11 shows the spatially averaged response (footnote 2) of the Gems and Sub-15 in my listening room, with the rear tweeter on and set to "0" and the front tweeter set as I preferred it, to "-0.5dB." The response trend is very flat, meeting ±1.5dB limits all the way from 160Hz to 10kHz. But you can see a slight excess of in-room energy in the octave above 3kHz, which might well correlate with the slight treble "bite" I occasionally noted in my auditioning. You can see that the Sub-15 does extend the response down to 20Hz, even with the boundary EQ switched into circuit. But note the lack of energy in the 50Hz third-octave band: I could not get a good balance in my room between this band and the ones to either side.
Note also the residual peak at 200Hz. After much experimentation with speaker position, I reduced this but could never entirely eliminate it, the result being a slight warmth to the system's sound. The lower trace in fig.11 is the in-room response of the Gems without the Sub-15, offset for clarity. You can see that the room integration in the upper bass is actually a little better than with the subwoofer, but also that the sub does add a considerable amount of energy in the midbass and below.
Fig.11 Revel Ultima Gem/Sub-15, 1/3-octave, spatially averaged response in JA's room. HF contour set to "-0.5," rear tweeter set to "0." Lower curve is the Gems without the subwoofer, offset by -6dB for clarity.
Footnote 2: For my in-room spectral analyses I average six measurements at each of 10 separate microphone positions for left and right speakers individually, giving a total of 120 original spectra. These are then averaged to give a curve that, in my room, has proved to give a good correlation with a loudspeaker's perceived balance. I use an Audio Control Industrial SA-3050A spectrum analyzer with its own microphone, which acts as a check on the MLSSA measurements made with the B&K mike.—JA
