Floor Loudspeaker Reviews

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Vimberg Mino's frequency response in the farfield, and an Earthworks QTC-40 mike for the nearfield and in-room responses. The 159lb loudspeaker was too bulky for me to move it outside for the testing. I therefore had to do the quasi-anechoic measurements in my listening room, where the proximity of room boundaries necessarily led to aggressive windowing of the time-domain data, which reduced the graphs' resolution in the midrange.

Vimberg specifies the Mino's sensitivity as 89dB/W/m; my estimate was within experimental error, at 88.6dB(B)/2.83V/m. The Mino's impedance is specified as 4 ohms, with a minimum value of 3.8 ohms at 100Hz. The solid trace in fig.1 shows the impedance magnitude with the upper port blocked, which is how I performed most of my auditioning. Other than for two regions in the upper bass and lower treble, the impedance remained above 4 ohms for most of the audioband. The minimum magnitude was 3.13 ohms between 94Hz and 100Hz, and as there is a combination of 5.4 ohms and an electrical phase angle of –51.5° (dashed trace) at 62.5Hz, the Mino should be used with amplifiers that are comfortable driving 4 ohm loads. Unblocking the upper port gave the impedance magnitude and phase-angle traces shown in fig.2. Above 100Hz, the traces are identical to those in fig.1. In the bass, however, the higher-frequency magnitude peak has been reduced in level, the lower-frequency peak increased, and the central point of the saddle in the trace has risen in frequency from 24Hz to 34Hz.

The traces in figs.1 and 2 are free from the small discontinuities that would imply that there are resonances of some kind present. When I investigated the enclosure's vibrational behavior with a plastic-tape accelerometer, I did find resonant modes at 371Hz and 594Hz on the sidewalls (fig.3). These modes were very low in level, however, and with their relatively high Q (Quality Factor), it is unlikely that these modes will have any audible consequences.

The top woofer appears to extend a little higher in frequency than the middle and bottom drivers. The blue trace in fig.4 shows the woofers' summed nearfield response, taken with the top port open. There is very little sign of the usual peak in the upper bass, which is due to the nearfield measurement technique. The summed output of the ports is shown as the red trace in the graph. It peaks between 30Hz and 70Hz and the upper-frequency rolloff is clean, without being disturbed by any resonances. However, the minimum-motion notch in the woofers' output is barely visible, which suggests that even with both ports open, the reflex woofer alignment is overdamped, tuned for clarity and control rather than maximum low-frequency output. This is even more apparent with the top port closed (not shown). The complex sum of the outputs of the midrange unit, woofers, and ports (with both of these open) is shown as the black trace in fig.4. It features the usual nearfield bump in the midbass with the –6dB point lying at the tuning frequency of the ports.

The woofers cross over to the midrange unit (fig.4, green trace) just below 200Hz, with a fast rolloff that isn't disturbed by any peaks. The Vimberg's farfield response, averaged across a 30° horizontal window centered on the tweeter axis, is shown as the black trace above 300Hz in fig.4. The balance is superbly flat and even up to 10kHz, above which there is a slight rolloff before the output rises to a small peak close to 30kHz. In part, the lack of top-octave energy in this graph will be due to the increasing directivity of the larger-than-usual tweeter diaphragm in this region. There is also the fact that with a tweeter using a pistonic hard dome with a high-Q, high-amplitude, ultrasonic resonance, there will be a lack of energy in the region below that resonance.

Fig.5 shows the Vimberg's horizontal dispersion, normalized to the response on the tweeter axis, which thus appears as a straight line. (The spatial limitations of my listening room meant that I could only measure off-axis behavior to 45° to the speaker's sides rather than my usual 90°.) The contour lines in this graph are impressively evenly spaced throughout the midrange and treble, this correlating with the stable stereo imaging I noted in my auditioning. The reduced off-axis output of the tweeter's output can be seen in this graph. In the vertical plane (fig.6), with again the off-axis response normalized to the tweeter-axis response, the usual suckout in the crossover region between the midrange unit and the tweeter doesn't start to develop until 15° above the tweeter axis. This represents the balance heard by a standing listener. The Mino otherwise maintains its tweeter-axis balance below 10kHz over a ±10° vertical window.

The red trace in fig.7 shows the Minos' spatially averaged response in my room. The Minos had their upper ports blocked and this trace is generated by averaging 20 1/6-octave–smoothed spectra, taken for the left and right speakers individually using a 96kHz sample rate, in a vertical rectangular grid 36" wide × 18" high and centered on the positions of my ears. This tends to average out the peaks and dips below 400Hz that are due to the room's resonant modes and to the interactions between the direct sound from the loudspeakers and the reflections of that sound from the room's boundaries (footnote 1). For reference, the blue trace shows the spatially averaged response of the Tidal Akira that I reviewed in November 2018. The green trace is the spatially averaged response of the Magico M2 that I reviewed in the February 2020 issue. (The Lamm monoblocks were used for these in-room measurements.) While performing these measurements, I noticed that the responses at the listening position of the two Minos were closely matched in the treble.

As you would expect, given that the Vimberg and Tidal loudspeakers were both designed by Jörn Janczak, the in-room responses of the Akira and Mino are broadly similar in the midrange and treble, though the Tidal has a little more energy between 1kHz and 2kHz and the Mino has slightly more output in the mid-treble. The in-room response of all three loudspeakers slopes down slightly above 6kHz, which will be due both to the increased absorptivity of the room's furnishings as the frequency rises and the reducing dispersion of their tweeters in this region. The Magicos' output drops down a little faster than those of the other two loudspeakers, which I heard as a slightly sweeter top-octave balance compared with the Minos.

Turning to the time domain, the Mino's step response on the tweeter axis (fig.8) indicates that the tweeter and woofers are connected in positive acoustic polarity, the midrange unit in inverted polarity. However, the decay of the tweeter's step smoothly blends with the negative-going start of the midrange unit's step, the decay of which blends smoothly with the positive-going start of the woofers' step. This suggests optimal crossover implementation. The Vimberg Mino's cumulative spectral-decay plot (fig.9) is superbly clean overall.

As I anticipated from its pedigree, Vimberg's Mino offers excellent measured performance.—John Atkinson