Revel Ultima Studio loudspeaker Measurements

Sidebar 3: Measurements

The Studio was 5dB more sensitive than my reference Rogers LS3/5A, giving a B-weighted, quasi-anechoic figure of 87.5dB/2.83V/m, which is a shade above average. Its impedance magnitude and electrical phase angle (fig.1) indicate that it is a moderately demanding load. Though the phase angle is generally low, the magnitude drops to 4 ohms throughout the bass and lower midrange, and in the high treble with the control set to "+1dB" and the rear tweeter on and set to its maximum level (bottom traces). This graph shows the best- and worst-case conditions: the top pair of traces is with the front tweeter set to "-1dB" and the rear tweeter switched off. (Peculiarly, switching the rear tweeter off also raises the impedance in the lower frequencies by about 0.6 ohm.) The big port appears to be tuned to a very low 23Hz.

Fig.1 Revel Ultima Studio, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)

Other than at 30kHz, where a small discontinuity reveals the presence of the tweeter's ultrasonic resonance, the impedance traces were free from the wrinkles that would otherwise indicate the presence of resonant panel or drive-unit modes. That finding was supported by further investigation with a simple plastic-tape accelerometer (basically similar to a piezoelectric guitar pickup): The only mode I could find was on the sloped top of the midrange/tweeter enclosure (fig.2), and even that was at a sufficiently high frequency and low enough level that I can confidently declare that the Studio's cabinet will have no adverse effects on the speaker's perceived sound quality. Impressive.

Fig.2 Revel Ultima Studio, cumulative spectral-decay plot calculated from the output of an accelerometer fastened to the cabinet top panel. (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz.)

Turning to the Revel's acoustic performance, fig.3 shows the individual responses of the port, woofers, and midrange-tweeter module. The port's output covers the octave between 20Hz and 40Hz, while the woofers' minimum-motion frequency of 27Hz is a little higher than the port's maximum output. There is also a peculiar second notch in the woofers' response at 36Hz. The woofers cross over to the midrange unit at around 190Hz, rolling off with a steep 24dB/octave slope, and both these drivers and the port are free from out-of-band spuriae. After rolling in with what appears to be an acoustic 18dB/octave high-pass slope, the midrange unit is astonishingly flat on-axis in its passband. There is a slight notch in the crossover region to the tweeter, and the HF unit rises slightly on-axis between 6 and 12kHz.

Fig.3 Revel Ultima Studio, acoustic crossover on tweeter axis at 50", corrected for microphone response, with the nearfield midrange, woofer, and port responses plotted below 450Hz, 500Hz, and 300Hz, respectively.

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