Article Index
Martin Logan Ethos
Sound quality
Measured performance
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Our frequency analysis shows the Ethos possesses an unusually flat frequency response, here with bass level set ‘flat’ to 0. However, electrostatic dipoles are complex beasts and one measurement says little. We took many forward response measurements, at different mic heights and forward angles to look at dispersion, consistency, phase cancellation effects, bass integration and bass power. The sine burst response shown is representative, but low frequency windowing pulls bass level down a bit. A third-octave pink noise steady state measurement suggests the Ethos will sound a little bass heavy at 0 and flat at -4. Users will find their preference lies somewhere between, according to room gain and tastes. Our pink noise response at -4 was almost perfectly flat from 20Hz to 20kHz and looked astonishing. However, running flat down to 20Hz suggests large bass unit driver excursions and ‘slow’ bass quality.

What our many measurements showed was that the Ethos is smoother and more consistent on and off axis than the Purity and Source. There was some lift below 800Hz down to 400Hz, below which the electrostatic panel rolls down to the box bass unit. The crossover is not perfect and wherever the microphone was placed the dip at 200Hz seen in our analysis existed. This suggests less than perfect integration between box and panel. The bass bin goes very low though, flat down to 30Hz our analysis here shows, helped by the passive ABR tuned to 33Hz our red trace shows.

Another interesting feature of the XStat electrostatic panel was that it measured flat at any distance, including many metres away, and across a wide forward angle. Sound into the room will be very consistent, unlike lower cost models, where sound balance changed considerably with listening position.
Electrostatics are known for low colouration and the decay spectrum over 200mS showed the Ethos is very impressive in this respect. Only below 150Hz does the bass bin get ‘hot’, hotter than most box speakers because it is so small, a lot of internal energy coming out through the cones.

Sensitivity was very high at 91dB Sound Pressure Level for 2.8V (one nominal Watt) of input. Much of this is due to the powered subwoofer and its strong deep bass output. However, the panel is quite sensitive too, it seems. Measured overall impedance was low at 4 Ohms, in fact surprisingly low considering the bass unit is powered. This is due to the electrostatic panel that comes in hard at 400Hz our impedance analysis shows, careering down to 1 Ohm at 20kHz – ouch! A valve amp will shrug this off; solid-state amps need Zobel networks to cope. Most have them.

Electrostatics produce little distortion and the Ethos panel was no exception, around 0.2% up to 800Hz and down to a minuscule 0.05% or so above this frequency, our analysis below shows, much lower than cone drive units. The bass bin worked well down to 60Hz but below this distortion rises quickly (see below), measuring 9% from the forward driver at 40Hz and 2% from the passive radiator. Rock can have massive levels at 30Hz and here distortion was above 20% (94dB SPL at the cone), mostly bass doubling. This is a poor result.

The Martin Logan XStat electrostatic panel measured very well and is quite exceptional in many areas. The bass unit manages quite well but has problems, running lower than is sensible.

FREQUENCY RESPONSE (what it means)


Green - drive unit; Red - port

IMPEDANCE (what it means)


DECAY SPECTRUM 200mS (what it means)

DECAY MAP 200mS (what it means)


DISTORTION (what it means)


BASS DISTORTION (what it means)




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