Revel Ultima Salon2 loudspeaker Measurements

Sidebar 3: Measurements

My estimate of the Revel Ultima Salon2's voltage sensitivity was 86dB(B)/2.83V/m. This is slightly lower than the specified 86.4dB but within experimental error of that figure. The speaker's impedance (fig.1) drops to between 3 and 5 ohms between 17Hz and 600Hz, but as the electrical phase angle is generally low in this region, the Salon2 should not be hard for the partnering amplifier to drive. However, the shape of the impedance curve suggests that the speaker might sound a little bright with tube amplifiers having a high output impedance.

Fig.1 Revel Ultima Salon2, electrical impedance (solid) and phase (dashed), switches set to Normal. (2 ohms/vertical div.)

The traces in fig.1 are free from the small discontinuities that would imply the existence of cabinet resonances of various kinds. Indeed, investigating the panels' vibrational behavior with a plastic-tape accelerometer uncovered very little untoward going on. The only mode I found (fig.2) was high enough in frequency and low enough in level to have no subjective consequences.

Fig.2 Revel Ultima Salon2, cumulative spectral-decay plot calculated from the output of an accelerometer fastened to the center of the main cabinet's sidewall 8" from the top (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

The saddle centered on 22Hz in the impedance-magnitude trace suggests that this is the tuning frequency of the large downward-facing reflex port. The black trace in fig.3 shows the port's acoustic output measured in the nearfield. It does indeed peak broadly between 16 and 32Hz, which implies excellent low-frequency extension for the Salon2. There is a slight shelf in its upper-frequency output around 100Hz, however. The three woofers measured identically, and the sum of their nearfield outputs is shown as the green trace in fig.3. It shows the usual minimum-motion notch at the port tuning frequency and peaks between 40 and 120Hz, before crossing over to the lower-midrange drive-unit (red trace) at 150Hz. This unit in turn crosses over to the upper-midrange unit at around 500Hz. The crossover filter slopes all appear to be symmetrical fourth-order, 24dB/octave, and all the drivers appear to be well behaved both in and out of their specified passbands.

Fig.3 Revel Ultima Salon2, nearfield responses of port (black), woofers (green), lower-midrange unit (red), and upper midrange unit (blue), all plotted in the ratios of the square roots of their radiating areas.

Fig.4 shows how these individual drive-unit outputs add up on the tweeter axis in the farfield. Looking through this graph's small ups and downs, the Salon2's response is extraordinarily flat, from the upper bass all the way through its 30kHz upper limit. In fact, the tweeter's output starts to rise just below 30kHz, suggesting that the beryllium dome's primary resonance lies above this frequency. (My measurement microphone is calibrated to only 30kHz.) At lower frequencies, the broad rise in output in the upper bass will be mainly due to the nearfield measurement technique. The speaker's low-frequency response extends almost down to 20Hz. This is a true full-range loudspeaker.

Fig.4 Revel Ultima Salon2, anechoic response without grille on listening axis at 50", averaged across 30° horizontal window and corrected for microphone response, with the complex sum of the nearfield responses plotted below 300Hz.

The measurements taken to generate fig.4 were taken with the Salon2's five-position Tweeter Level switch set to its central, "0dB" position. Fig.5 shows the effect on the Revel's tweeter-axis response when this switch is set to its maximum +1dB and –1dB positions. The Salon2's output in the top two audio octaves is hinged up or down by up to 1.6dB.

Fig.5 Revel Ultima Salon2, effect of HF control set to ±1dB on tweeter-axis response.

The flat quasi-anechoic response on axis will not necessarily correlate with a flat perceived balance in-room because the latter also depends on the loudspeaker's dispersion; ie, on how that response changes to the sides and above and below that axis. The Salon2's horizontal dispersion is shown in fig.6. The loudspeaker's behavior is almost textbook perfect, with smooth, even off-axis behavior up to 8.5kHz or so, the frequency where the tweeter's waveguide begins to restrict its off-axis output. Due to this increasing directivity in the top audio octave, the Salon2 might sound a bit airless in large or overdamped rooms; the Tweeter Level control, set to one of its two boost positions, will help compensate for this. In the vertical plane (fig.7), the Revel's flat response is maintained over a wide (±10°) window centered on the tweeter axis, which is a good thing—the tweeter is a very high 49" above the floor.

Fig.6 Revel Ultima Salon2, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90–5° off axis, reference response, differences in response 5–90° off axis.

Fig.7 Revel Ultima Salon2, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 10–5° above axis, reference response, differences in response 5–15° below axis.

Fig.8 shows how all this added up in LG's listening room. To generate this graph, I took ten 1/6-octave–smoothed spectra for each speaker individually in a rectangular grid 40" wide by 18" high and centered on the position of Larry's ears in his listening chair. (I used an Earthworks omni microphone and a Metric Halo ULN-2 FireWire audio interface, in conjunction with SMUGSoftware's Fuzzmeasure 2.0 running on my Apple laptop.) My goodness! Even though there is some lumpiness at the low end of the graph, due to room modes that have not been eliminated by the spatial averaging, this is, to again use the phrase, an extraordinarily smooth, flat response, especially when you consider that it was taken in an actual room rather than an anechoic chamber. As LG noted, the speaker offers full output down to below 20Hz. At the other end of the spectrum, the gentle rolloff in the top two octaves is due to the increased absorption of the room's furnishings in this range.

Fig.8 Revel Ultima Salon2, spatially averaged, 1/6-octave response in LG's listening room.

Turning to the time domain, the Salon2's step response on the tweeter axis (fig.9) indicates that all five drive-units are connected with the same positive acoustic polarity, and that each one's step smoothly hands over to that of the next lower in frequency, this correlating with the excellent frequency-domain integration of their outputs. The Revel's cumulative spectral-decay plot on the tweeter axis (fig.10) is superbly clean in the region covered by the tweeter, but some low-level delayed energy can be seen in the low treble.

Fig.9 Revel Ultima Salon2, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Fig.10 Revel Ultima Salon2, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

Even so, the Revel Ultima Salon2 offers superb measured performance. It is a pleasure to be able to measure such a well-engineered loudspeaker. It is fair to say that not only do my measurements validate the speaker's engineering, but that the converse is also true: the speaker's measured behavior validates my test procedures! I have asked Revel to send me a pair of Salon2s for a "Follow-Up" review to appear later in the year.—John Atkinson

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