Revel Ultima Gem loudspeaker & Ultima Sub-15 subwoofer Measurements Page 1
Other than impedance, all acoustic measurements were made with the DRA Labs MLSSA system and a calibrated B&K 4006 microphone (footnote 1). The Gem's voltage sensitivity (measured using a noise signal and a B-weighting filter to discount the effects of peaks and dips at the frequency extremes) was around 87.5dB/2.83V/m, which is fractionally if inconsequentially higher than specified.
Figs.1 and 2 show the Gem's impedance with its controls set to give the most demanding amplifier loading (fig.1, front tweeter "+1" and rear tweeter "+4") and its kindest load (fig.2, front tweeter "-2," rear tweeter off). The variation at high frequencies is wide, from 2.5 ohms between 10 and 20kHz in the former case to 11.5 ohms in the latter. Fortunately there is not much energy present in this region, so even with the speaker's controls set to the fig.1 conditions, the partnering amplifier shouldn't be severely taxed. But in any case, I wouldn't expect a speaker in this price class to be partnered with anything but excellent amplification.
Fig.1 Revel Ultima Gem, electrical impedance (solid) and phase (dashed) with HF contour set to "+1" and rear tweeter set to "+4" (2 ohms/vertical div.).
Fig.2 Revel Ultima Gem, electrical impedance (solid) and phase (dashed) with HF contour set to "-2" and rear tweeter off (2 ohms/vertical div.).
Moving down in frequency, the saddle between the twin magnitude peaks in the bass indicates the tuning of the flared port on the rear panel to be 42Hz, the frequency of the lowest string of the 4-string bass. Even without the subwoofer, the Gem offers reasonable extension. Note that the traces in figs.1 and 2 are free from wrinkles and discontinuities, implying an absence from cabinet resonant problems.
Footnote 1: To minimize reflections from the test setup, the measuring microphone is flush-mounted inside the end of a long tube. Reflections of the speaker's sound from the mike stand and its hardware will be sufficiently delayed to not affect the measurement. For full details of how I measure loudspeakers for Stereophile reviews, see "Loudspeakers: What Measurements Can Tell Us—And What They Can't Tell Us!," AES Preprint 4608, presented at the 103rd Audio Engineering Society Convention, New York, September 1997. The preprint is available from the AES, 60 East 42nd Street, Room 2520, New York, NY 10165-0075. The AES internet site, www.aes.org, offers a secure transaction page for credit-card orders.—JA