Subwoofer Reviews

Test Bench: Monitor Audio Shadow On-Wall Speakers and RXW12 Subwoofer

Frequency response

• Main 89 Hz to 20 kHz ±7.6 dB
• Center 89 Hz to 20 kHz ±7.2 dB
• Mini 112 Hz to 20 kHz ±6.6 dB
• Subwoofer 37 to 98 Hz ±3 dB

Sensitivity (SPL at 1 meter/1 watt)

• Main 85.6 dB
• Center 85.6 dB
• Mini 80.2 dB

Impedance (minimum/nominal)

• Main 4.0/5 ohms
• Center 4.0/5 ohms
• Mini 4.8/7 ohms

Bass output, subwoofer (CEA-2010A standard)

Ultra-low bass (20-31.5 Hz) average: 99.8 dB

• 20 Hz: 94.9 dB
• 25 Hz: 98.0 dB
• 31.5 Hz: 103.9 dB

Low bass (40-63 Hz) average: 120.5 dB

• 40 Hz: 117.5 dB L
• 50 Hz: 120.9 dB L
• 63 Hz: 122.3 dB L

Bass limits

• Main 93.0 dB at 63 Hz
• Center 93.0 dB at 63 Hz
• Mini 94.0 dB at 63 Hz

Because the Shadow speaker line is designed primarily (or, in the case of the Shadow 60, exclusively) for on-wall applications, that’s the way I measured them: mounted on a 2 x 4 ersatz wall, ringed with foam to eliminate diffraction from the wall edges, and attached to my measurement stand. I later measured the Shadow 25 mounted on its included foot and placed atop my normal measurement stand to see how the freestanding performance compares with the on-wall performance.

For these measurements I used quasi-anechoic technique to remove the effects of reflections from nearby objects. I measured the Shadow 60 and Shadow Centre at 2 meters to incorporate the contributions of the widely spaced drivers and diffraction from the speaker edges, and measured the Shadow 25 at 1 meter because its smaller size allowed me to do so. With the Shadow 25, I adjusted the microphone position for the flattest on-axis response; with the other speakers, I placed the mike on-axis with the tweeter. Woofers and passive radiators were close-miked and, when necessary, summed to get the bass response. I averaged the measurements at 0°, ±10°, ±20°, and ±30°, spliced in the bass response at 180 Hz, then smoothed the result to 1/12th octave. The subwoofer was close-miked. Results are normalized to 0 dB at 1 kHz for the Shadows, and +3 dB for peak response of the subwoofer. Frequency response measurements were made with a Clio FW audio analyzer and then imported into a LinearX LMS analyzer for post-processing.

You can see from the frequency response chart that the speakers’ performance is pretty smooth and flat above 1 kHz, with a few minor response anomalies above that plus a gentle rolloff above 10 kHz. But the on-wall mounting gives rise to a large bass-reinforcement hump in the 150-Hz to 200-Hz vicinity, depending on the speaker. There’s also a mild lack of energy in the region from about 500 Hz to 1 kHz, which probably caused my subjective perception that the lower treble was a little hot.

Off-axis response for the Shadow 60 and Shadow 25 is very good. There’s just a gradual treble rolloff as you move off-axis. At angles of ±30° a dip starts at 2.5 kHz, but it’s mild — only about 9 dB even at ±60°. The Shadow Centre shows the effects of interference between its midwoofers at angles beyond ±20°: dips of 8 to 18 dB between 800 Hz and 2.5 kHz, depending on the angle of the measurement. This is the norm with a 2-way center speaker, though.

In the second graph that accompanies these lab notes, you can see how the Shadow 25’s measurements compare when taken on-wall (purple trace) and freestanding (green trace). As expected, the freestanding response is smoother: ±4.6 dB versus ±6.6 for on-wall. The main difference is that the on-wall mounting reinforces frequencies below 500 Hz by an average of about 4 dB.

The impedance curves (also measured with Clio FW, and shown in the fourth graph) are a little demanding in the case of the Shadow 60 (blue trace) and Shadow Centre (red trace). Both drop to a low of 4.0 ohms and run at about 5 ohms through most of the audio band. In the Shadow 60, the low occurred at 1.6 kHz with a phase angle of +14°; in the Shadow Centre, the low was at 1.5 kHz with a phase angle of +9°. (I expect this difference is due to slight measurement-to-measurement variation, or perhaps slight variation among review samples.) The Shadow 25 (green trace) is more forgiving, with a low of 4.8 ohms at 265 Hz/-1°. Sensitivity (average output on-axis between 300 Hz and 10 kHz with a 2.83-volt signal at 1 meter) runs a tad below average in the Shadow 60 and Shadow Centre at 85.6 dB, and well below average in the Shadow 25 at 80.2 dB. Note that all of these measurements are taken on-wall.

The RXW12’s response is basically a hump centered at 62 Hz, but it rolls off gradually above and below that so its useful response extends across the entire bass range. That’s in EQ1 mode. EQ2 mode (shown in the fourth graph, green trace, with EQ1 shown in red) boosts the low bass only, by a max of 7.2 dB at 20 Hz. Combined low-pass function of the internal crossover (set to 80 Hz), driver, and enclosure is -19 dB.

Although I measured the RXW12 when I reviewed it before, I wasn’t doing CEA-2010 bass output measurements then, so I re-measured it, first using the CEA-2010A procedure with the microphone at 3 meters and then scaling up the result by 9.54 dB so it is equivalent to 1-meter results. Numbers with an L next to them indicated that the sub’s internal limiter determined maximum output. I used EQ1 mode; I tried switching to EQ2 mode, but the measurements were about the same.

CEA-2010A results show that this sub’s output is strongly focused in the upper part of the low bass octave, where it hits an impressive peak of 122.3 dB at 63 Hz. That’s amazing for such a little sub. Average output in the low bass octave (40-63 Hz) is also great at 120.5 dB. Average output in the ultra-low bass octave (20-31.5 Hz) is much lower at 99.8 dB, but still, I’m always impressed when a small sub like this can do a legitimate 20 Hz.