Silverline Audio Minuet loudspeaker Measurements

Sidebar 3: Measurements

As is to be expected from its small size, the Silverline Minuet offered lower-than-average voltage sensitivity, at an estimated 85dB(B)/2.83V/m. This is significantly lower than the specified 88dB. However, its impedance magnitude (fig.1) remained above 6 ohms over the entire audioband, dropping only briefly below 5 ohms in the mid-treble. The electrical phase angle is overall a bit higher than normal, but given the fairly high magnitude, the speaker will be fairly easy for the partnering amplifier to drive.

The traces in fig.1 are free from the small wrinkles and discontinuities that would imply the existence of cabinet resonances of various kinds. Investigating the enclosure panels' vibrational behavior with a plastic-tape accelerometer, I found little to note. Yes, there was a high-level mode at 879Hz on the side panels (fig.2), but this is sufficiently high in frequency to have minimal subjective consequences. A second mode can be seen at 400Hz; this was present on all surfaces, but is low enough in level to be innocuous. At low frequencies, however, the cabinet sidewalls do appear to "pump" a little at the frequency of the lower impedance peak.

Fig.1 Silverline Minuet, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)

Fig.2 Silverline Minuet, cumulative spectral-decay plot calculated from the output of an accelerometer fastened to the center of the sidewall (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

The saddle between the twin impedance peaks in the bass lies between 60 and 70Hz, implying that this is the tuning frequency of the rear-facing reflex port. The port's output, measured in the nearfield (fig.3, blue trace), does peak in this region, with the woofer's minimum-motion notch (fig.3, black) lying at 68Hz. The port's output is commendably free from any resonances above its nominal passband. The woofer has a slight peak in its response, visible at the top of the midrange, before it begins its second-order rollout. Though a couple of small peaks can be seen an octave or so above the crossover point, these are well suppressed by the low-pass filter. The crossover to the tweeter (fig.3, red) lies at 2.3kHz, rather lower than the specified 3.5kHz. The tweeter rolls off below the crossover frequency with a fourth-order, 24dB/octave acoustic slope.

Fig.3 Silverline Minuet, acoustic crossover on tweeter axis, corrected for microphone response, with farfield responses of tweeter (red) and woofer (black), with the nearfield response of port (blue) and woofer (black) plotted in the ratio of their radiating diameters.

Fig.4 shows how these individual outputs sum on the tweeter axis in the farfield. The Minuet's low-frequency extension is modest, as is to be expected from the fairly high port-tuning frequency, and the usual nearfield bump in the upper bass is missing, implying a rather overdamped alignment. I am somewhat at a loss, therefore, to understand why the speaker's performance in the mid-bass upward was so favored in the auditioning. The speaker is pretty flat in the midrange, but there is then a broad, 3dB-high peak in the mid-treble, due to the tweeter's being a little more sensitive than is necessary. I do wonder if this boost contributed to Bob Reina finding the Minuet to offer superior resolution of "midrange detail." (Although of a higher frequency than the midrange, this boost will act a little like Photoshop's "Sharpen" tool.) The top-octave response is slightly shelved down, but the tweeter is still operating at the 30kHz upper limit of this graph.

Fig.4 Silverline Minuet, anechoic response on tweeter 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 Minuet's lateral radiation pattern is shown in fig.5. The contour lines are evenly placed in the upper midrange, but while the usual off-axis flare can be seen at the bottom of the tweeter's passband, the speaker gets quite a bit more directional in the region between 4 and 7kHz, roughly where the on-axis output features that 3dB peak. It is difficult to predict whether this off-axis behavior will work against or reinforce the audibility of the on-axis peak in the mid-treble. I suspect that the speaker's balance in a typical room will be a little bright, due to the room's reverberant field being boosted a bit between 3 and 4kHz, which is probably why BJR preferred to audition the speakers with their grilles in place. The tweeter becomes very directional above 11kHz, which, in conjunction with the on-axis response in the same region, will make the Minuet sound a little lacking in top-octave air, except in rooms with lively acoustics.

Fig.5 Silverline Minuet, 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.

In the vertical plane (fig.6), the Minuet maintains its balance over quite a wide (±10°) window centered on the tweeter axis, meaning that the speaker will be tolerant of stand height. Large suckouts develop in the crossover region at more extreme angles; as always, don't listen to this speaker when standing up.

Fig.6 Silverline Minuet, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 45–5° above axis, reference response, differences in response 5–45° below axis.

In the time domain, the Minuet's step response (fig.7) indicates that both drive-units are connected with the same positive acoustic polarity, with the tweeter's output smoothly handing over to the woofer's. The cumulative spectral-decay plot (fig.8) is extremely clean.

Fig.7 Silverline Minuet, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Fig.8 Silverline Minuet, cumulative spectral-decay plot at 50" (0.15ms risetime).

Overall, the Silverline Audio Minuet measures well for a relatively affordable design.—John Atkinson

COMPANY INFO
Silverline Audio
936 Detroit Avenue, Unit C
Concord, CA 94518
(925) 825-3682
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