Gayle Martin Sanders co-founded (with Ronald Logan Sutherland) MartinLogan, one of high-end audio’s most iconic companies. Sanders’ greatest contribution was the breakthrough MartinLogan CLS (Curvilinear Line Source), a speaker that exemplified high-end audio’s purist approach. The CLS was a full-range electrostatic panel with no box, no crossover, and a single sheet of Mylar as its transducer. It was speaker technology boiled down to its simplest and most basic (although making a curved electrostatic panel work was anything but). The CLS, and its modern-day descendent, the CLX, set a standard for midrange resolution that has yet to be equaled by any loudspeaker, regardless of price or technology.
Sanders sold MartinLogan in 2005 and headed off into retirement. Or so he thought. With plenty of time on his hands, he couldn’t stop thinking about how advanced new digital-signal-processing technology could be brought to bear on problems in loudspeaker design that he had battled in the analog domain decades earlier. In 2015 he began to conceptualize a new type of loudspeaker, and in late 2019 launched a company, Eikon Audio, to bring to market the realization of his vision, the Image1 reviewed here.
The Image1 is the polar opposite of the CLS. That iconic electrostat was an exercise in minimalism; the new speaker pushes the envelope in complexity. Specifically, the Image1 is a complete integrated audio system featuring four-way active loudspeakers with dynamic drivers, four integral power amplifiers per speaker, digital-domain crossovers, DSP room correction, and remote control via phone or tablet.
Why this radical change in direction? Sanders believes that an integrated system such as the Image1 can address the many technical and commercial challenges that stand in the way of the wider adoption of high-performance music systems. Integrated systems can better fit physically and acoustically in homes; they are easier to use; they are less intimidating to non-audiophiles than component audio systems; they cost less by virtue of integrating many functions; and, perhaps most importantly, they offer the potential of improved performance. This last advantage is partly because all the system parts are engineered to work together and partly because digital signal processing can correct many of the fundamental problems of loudspeakers in rooms. You can read more about Sanders’ thinking on this subject in the accompanying interview.
The Image1 is a self-contained audio system that requires only a source to drive it, such as a computer, music server, or analog component. The Image1 consists of a pair of speakers and the Eikontrol box that contains the digital signal processing and DACs. The entire system costs $25,000, but that includes speakers, DACs, amplification, and cables. The Eikontrol electronics box accepts digital or analog signals from sources, implements a four-way crossover in the digital domain, performs room correction and other DSP, and then converts the four frequency-divided signals to analog with four DACs per channel. The Eikontrol’s output is four analog signals on balanced XLR jacks and unbalanced RCA jacks. These four outputs correspond directly to the four drivers in each speaker. Each output is a band-limited line-level analog signal that, when connected to the speaker via the supplied wiring harness, drives a power amplifier built into the enclosure, which in turn powers one of the speaker’s four drivers. The customer specifies the length of the wiring harness, which carries four XLR-terminated interconnects.
This architecture is different from most integrated systems in that the speaker is entirely analog, with the crossovers and DSP implemented in a separate box. Also unlike many integrated systems, the Image1 doesn’t provide integral support for streaming services. You’ll need a separate streamer or music server to supply a digital signal to the Eikontrol. (I used an Aurender W20’s USB output.)
The speaker itself is a four-way design with a front-firing 8" woofer, a rear-firing 8" woofer, a 5" midrange, and a 1" air-motion transformer (AMT) tweeter. Each of these drivers is powered by its own 100W Class D ICEpower amplifier. The ICEpower modules, chosen after Sanders auditioned a wide range of amplifiers, are modified for the specific drivers they will power. Because of the DSP crossovers earlier in the chain, the amplifiers are directly connected to the drivers, with no crossover components (inductors, capacitors, resistors) in the signal path. The digital crossover features compound slopes; they are relatively shallow near the crossover point so that the drivers’ outputs sum in-phase, but very steep a couple of octaves away.
The 5" midrange driver reproduces the unusually wide frequency range of 125Hz–4kHz. In fact, you can think of the Image1 as a one-way speaker augmented at the top by the AMT tweeter and at the bottom by the two 8" woofers. The idea was to reproduce as much of the spectrum as possible with a single driver, moving the crossover points away from the critical midband. The midrange driver can reportedly extend down to 60Hz (an octave below its operational range in the Image1), and is capable of very high excursion. It is ported out the rear to reduce back-pressure on the cone.
The two high-excursion 8" woofers are loaded in an unusual quasi-transmission-line arrangement. In a full transmission line, the woofer’s rear wave is directed down a labyrinth filled with mineral wool (or other damping material) inside the cabinet. The woofer’s rear wave is dissipated as it travels down the labyrinth, and in theory is completely dissipated at the end of the transmission line (the opening in the speaker enclosure that looks like a port). A transmission line avoids the problem of sealed loading in which the trapped air inside the enclosure acts as a spring against the woofer as the woofer moves in. It also avoids the problem of reflex (ported) loading in which transient behavior is compromised and port artifacts (resonances, the sound of air moving through the port, etc.) can become audible. Although a transmission line has none of these problems, a true transmission line requires an enormous cabinet enclosing a very long labyrinth to fully dissipate the woofer’s rear wave. In a quasi-transmission line such as in the Image1, some woofer energy emerges from the end of the line, but it is greatly attenuated. The Image1’s transmission line gets progressively narrower, forcing the energy into a smaller and smaller area that has progressively greater damping. Sanders says that this unusual approach delivers tighter bass than traditional sealed or reflex loading.
Digital signal processing makes it possible to perform a simple but clever trick that allows the front- and rear-firing woofers to work perfectly together. Specifically, the signal driving the front woofer, the midrange, and tweeter is delayed just long enough for the rear-firing woofer’s wave to bend around the cabinet and reach the front baffle where it combines in-phase with the front woofer’s wave. This technique creates a null at the sides and rear of the cabinet, directing all the bass energy forward into the room rather than omnidirectionally where the bass would more strongly excite room modes. This is a great example of how DSP can solve acoustic problems that are intractable in the analog domain.