• tower: 45 Hz to 20 kHz ±9.4 dB, 300 Hz to 10 kHz ±5.1 dB
• center: 63 Hz to 20 kHz ±6.5 dB, 300 Hz to 10 kHz ±4.6 dB
• surround: 70 to 120 kHz ±11.2 dB, 300 Hz to 10 kHz ±9.4 dB
• subwoofer: 19 to 144 kHz ±3 dB
• tower: 1.3/5 ohms
• center: 3.1/5 ohms
• surround: 2.8/5 ohms
Sensitivity (SPL at 1 meter/1 watt)
• tower: 88.8 dB
• center: 92.6 dB
• surround: 88.7 dB
Bass output, tower speaker (CEA-2010 standard)
• Ultra-low bass (20-31.5 Hz) average: 82.7 dB
20 Hz: NA
25 Hz: 84.4 dB
31.5 Hz: 97.2 dB
• Low bass (40-63 Hz) average: 114.8 dB
40 Hz: 110.0 dB
50 Hz: 114.9 dB
63 Hz: 119.6 dB
Bass output, subwoofer (CEA-2010 standard)
• Ultra-low bass (20-31.5 Hz) average: 104.6 dB
20 Hz: 100.5 dB
25 Hz: 103.8 dB
31.5 Hz: 109.4 dB
• Low bass (40-63 Hz) average: 116.4 dB
40 Hz: 113.3 dB
50 Hz: 116.9 dB
63 Hz: 119.1 dB
I measured the frequency response of the EM-C2 in my usual way, putting them on a 2-meter stand with the measurement microphone at 2 meters, and averaging the 1/12-octave-smoothed results at 0°, 10°, 20° and 30°. Bass response was measured by close-miking the ports and woofers, adding these results and splicing them to the averaged quasi-anechoic response at 300 Hz. My technique for the EM-FX2 was similar, except I measured it mounted to a 2-by-4-foot plywood panel with its edges covered in foam to prevent diffraction; this simulated the acoustic effect of being mounted on a large wall. Also, because the EM-FX2 is intended as a diffuse, wide-dispersion surround speaker, I combined measurements taken at 0°, 15°, 30°, 45°and 60°.
I measured the EM-ESL differently. Because an electrostatic speaker emits sound forward and back, much of its sound is the result of the back wave, which is ignored in quasi-anechoic measurements. So to measure the EM-ESL, I ran six in-room measurements, averaged them, and smoothed them to 1/6 octave to get minimize the effects of minor room reflections. I then spliced this result at 300 Hz to a ground-plane bass measurement taken at 2 meters. I measured the Dynamo 1000 sub using ground plane technique at 2 meters.
Technically, the EM-ESL doesn’t measure very flat because of some treble roll-off and a bass hump centered at 80 Hz. (Scaling the bass response to the mid/treble response in a spliced curve is an imprecise process, but that hump showed up no matter how I measured the EM-ESL or combined its response curves.) But except for a peak of +4.5 dB at 400 Hz and another of +2.9 dB at 1.3 kHz (possibly the cause of the slight upper-midrange emphasis I sometimes heard), the response is extremely smooth.
Same goes for the EM-C2 center speaker, which measures quite flat except for a -8.2 dB dip centered at 2 kHz (although that dip will certainly be audible, and I wonder if created some psychoacoustic effect that caused me to perceive the EM-C2 as lacking body in the voices.)
Even the EM-FX2 measures pretty flat; most dipolar or bipolar on-wall surrounds have a huge treble roll-off above about 5 kHz, but with the EM-FX2, the roll-off doesn’t occur except above 14 kHz, where it will be sonically benign. But like other non-directional surrounds, it shows large peaks and dips due to diffraction and interference between drivers.
These speakers warrant an amp or receiver with enough current to drive moderately low-impedance curves; I’d recommend at least a good midpriced receiver, and adding a separate stereo amp to power the EM-ESLs would be a great idea if you have one available. Minimum impedance for the EM-ESL is a very low 1.3 ohms at 20 kHz, with phase shift of -18°. For the EM-C2, it’s 3.1 ohms at 215 Hz with a phase shift of -13°. For the EM-FX2, it’s 2.8 ohms with phase shift of -6°.
However, the speakers’ high sensitivity will lessen the load on the amp or receiver. I measured the sensitivity of the EM-C2 (the only “normal” speaker in the bunch) by taking a frequency response measurement at 1 meter with a 1-watt (2.83-volt) signal from 300 Hz to 10 kHz, then averaging the result. For the EM-FX2, I took the measurement at a 45° angle. For the EM-ESL, I backed off to 2 meters to get the full output of the tall electrostatic panel, then added +6 dB to the result. My rating on the EM-ESL is at least a few dB lower than you will get in-room because the measurement excludes the back wave, but still, it’s nearly 89 dB. Results were excellent for the EM-C2 at 92.6 dB and good for the EM-FX2 at 88.7 dB.
CEA-2010 output measurements were impressive for the Dynamo 1000 given its size; a lot of similarly small subs can’t deliver measurable output down at 20 Hz. The EM-ESL tower puts out loads of bass in the low-bass (40-63 Hz) octave, but below that it takes a dive (predictable enough given that its published bass response limit is 42 Hz).
I think the EM-ESL is one of the best bargains going in an audiophile music speaker. It gives audiophiles all the things most of us seem to want (huge soundstaging and a dramatic presentation) and all the things we should want but sometimes neglect (like neutral tonal balance and natural sound). If stereo music listening is your priority, I highly recommend these. And you can add the EM-C2, the EM-FX2 and the subwoofer of your choice for those occasional nights when you want to relax with a movie instead of digging deep into your music collection.
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