Soliloquy 5.3 loudspeaker Measurements

Sidebar 3: Measurements

The Soliloquy 5.3 was fractionally less sensitive than specified, my B-weighted estimate coming out at 88dB/2.83V/m, but the speaker is still a little above average in this respect. It is also relatively easy to drive, its plot of impedance (fig.1) indicating a generally mild electrical phase angle, and a magnitude that remains above 8 ohms for most of the midrange and treble and drops below 6 ohms only in the midbass and lower midrange. Relatively low-powered tube amplifiers should work well with this speaker, though if they have a high output impedance, the large changes in impedance magnitude might result in a too-forward upper-midrange balance.


Fig.1 Soliloquy 5.3, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)

The saddle in the impedance curve at 40Hz indicates the tuning of the port, and implies moderate LF extension. The very slight kink in the curves around 150Hz might be associated with a cabinet resonance, but the Soliloquy's enclosure was actually well braced. The only mode I could find was around 350Hz (fig.2), which is probably too high in frequency to be subjectively irksome.


Fig.2 Soliloquy 5.3, cumulative spectral-decay plot of accelerometer output fastened to front baffle beneath woofers. (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz.)

Fig.3 shows the individual outputs of the drive-units and port. The port's output is the bandpass curve centered on the tuning frequency of 40Hz, and while there is a severe notch between 200Hz and 300Hz, this is inconsequential. The woofers' output peaks a little in the upper bass, but is otherwise flat in the midrange. The crossover to the tweeter features steep rollout slopes and appears to be set a little lower than specified at 1.9kHz. Residual cone-breakup modes in the woofer's output are well suppressed by the crossover, but the tweeter's output appears to be somewhat boosted on-axis.


Fig.3 Soliloquy 5.3, acoustic crossover on tweeter axis at 50", corrected for microphone response, with the nearfield and port woofer responses plotted below 300Hz and 1kHz, respectively.

This can also be seen in the Soliloquy's overall response, averaged across a 30 degrees angle on the tweeter axis (fig.4). In fact, the response has a distinct double hump, the on-axis boost in the top two octaves being balanced by a similar energy excess in the bass. When well handled by the designer, the result can sound musically balanced—witness the classic BBC LS3/5A. When carried to excess, the result is as KR describes on first hearing the Soliloquy 5.3 in his listening room. That the speaker sounded more acceptably neutral after its long break-in means that it must have been even more peaky out of the box. Note that about 3dB of the apparent boost in the bass will be due to the nearfield measurement technique, but that, even taking that into account, the speaker will easily sound boomy if care is not taken with room placement.


Fig.4 Soliloquy 5.3, anechoic response on tweeter axis at 50", averaged across 30 degrees horizontal window and corrected for microphone response, with the complex sum of the nearfield woofer and port responses plotted below 300Hz.

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