EROS LOUDSPEAKERS Mike Currie reviewer

Audio Asylum, April 01, 2002, Mike Currie reviewer
The Innersound Eros is a hybrid speaker system, featuring a 10" woofer loaded into an 8 foot transmission line, a solid state bass amplifier/active crossover module, and a planar electrostatic panel operating from 450 Hz and up. The panels are driven by the customer's amps of choice. They present an unusual load to the amps, with impedance starting at 113 ohms at the crossover point, dropping to 2 ohms at 20 kHz. Efficiency is rated at 96 dB/2.83 volts/meter. Level matching is accomplished via a pot on the amp/crossover module.  
I am using Atma-Sphere M-60 OTL monoblocks to drive the electrostatic panels. Conventional wisdom (and Ralph Karsten of Atma-Sphere) will tell you that OTLs do not do well with low impedance loads. Solution: Paul Speltz's Zero autoformers, which effectively increase the impedance seen by the amps by various multiples (starting at 2X), depending on how they are connected. I am presently using the 2.7X taps. These seem to provide the best timbral balance and completely eliminate the slight harshness heard with the 2X taps.

Set Up

These speakers have a comparatively narrow sweet spot. It is essential that they be set up so that the electrostatic panels are facing directly at the listener. Highs drop off fairly rapidly more than a few degrees off axis. For some listeners, this characteristic will be a major limitation.Personally, I am not bothered in the least, and I am quite sure that it contributes heavily to the truly outstanding soundstaging. However, if you wish to wander about your listening room and expect to maintain any semblance of image and/or extended highs, please look elsewhere. This is not what the Eros is about. 

Room dimensions: 14' X 16' X 10', with a vaulted ceiling reaching 12'at the peak. After much experimentation, I have settled on placing the speakers 43" from the rear wall, measured to the front corners nearest the listener. If they are placed further back, I found that soundstage depth decreases somewhat, although not to a drastic extent. Distance to the side walls (as measured from those same front corners) is 28". The Eros seems to be very tolerant of this dimension, presumably because there is little side energy generated. The speakers are spaced 8'apart on center. Finally, distance to the seating position is 8.5'. 

I have always found that a properly designed and executed transmission line produces superb bass. I formerly owned a pair of Meadowlark Hot Rod Shearwaters, which load a 7" ScanSpeak driver into a transmission line. 

One of the best attributes of that fine speaker was the quality of the bass. The Eros does it even better  tight in the best sense of the word, without artificial control. In other words, the music blooms when it should and doesn't when it shouldn't. 

Using the Stereophile test CD and several "woofer killers", I estimate that the system is flat down to about 35 Hz in my room, with usable response into the high 20s. That same tight, tuneful quality of bass is maintained down to the cutoff. 

OK, we all know that speakers that attempt to marry two such dissimilar drivers as cone woofers and electrostatics are doomed to failure, right? Not here, I am very, very happy to say. To put it very plainly, I cannot hear the transition between these drivers, period. 

I am sure that this will offend you Martin-Logan lovers out there, but the Eros do it soooooo much better. This is coming from a former Aerius owner. 

I have also heard the Requests at some length. Bela Fleck's "Uncommon Ritual" provides an interesting exercise for testing the characteristics of the system across the crossover point. 

On several cuts, Edger Meyer runs his double bass up and down the entire range of the instrument, reaching violin territory on the high side. The "breathing", resonant quality is maintained at all times. Large scale orchestral works (try "Pictures at an Exhibition" on Chesky vinyl or any one of several cuts from "Mephisto" on Reference Recordings CD) display the same sort of seamless textures. 

Conclusion: the issue of driver type, as executed in the Eros, is a non-issue. At the same time, the system concept provides major benefits (see "Dynamics" below). 

Midrange quickness, clarity, and accuracy are expected in an electrostatic speaker, and the Eros gives it to you in spades. Massed strings heard on excellent recordings sound truly extraordinary (e.g. Bruckner Symphony No. 9, Reference Recordings). Harry James' trumpet (Sheffield Labs LP) is as close to "in the room" as you are likely to get from a sound reproduction system. And synthesized music ("Don't You Want Me", Human League, 45 rpm single) is immediate and full of life and energy. Yes, this is one of my Guilty Pleasures, but what the hell, it makes me smile and it is extremely well recorded. 

Human voice? What can I say? The Eros does really, really nice things for both sexes. Keep in mind that the crossover occurs at 450 Hz, where it could really do some harm if either the crossover itself or the driver integration were not executed properly. 

The high end provides the biggest surprise for me. The Eros does as well at extending the highs in a coherent and realistic manner as anything I have ever heard, bar none. Cymbals have a very complex harmonic content with quite a bit of very high frequency energy. The effect of hearing them properly reproduced is really quite striking. My son is a drummer, so I get the pleasure of hearing the live thing just about every day.


The Eros produces a superb illusion of a 3D soundstage. In particular, they strike a great balance of great depth without sounding recessed.All too many speakers either project forward in a very unrealistic manner, or, conversely, drop the mids down a notch to achieve greater "depth." The latter, of course, is at the expense of timbre. Width of the image extends somewhat beyond the outer edges of the speakers if the material allows it  simple as that. 

Music recorded in a reverberant, fairly small space (e.g. Beethoven piano sonatas, Stereophile or Desmar's Harpsichord Concertos) is very interesting. The back wall of the recording venue is heard very, very clearly. You can nearly measure the distance to the foot from the instrument(s) to that wall. Individual images of performers and small groups are served extremely well. There is no question that Bela Fleck and his double bass have a very definite height, width, and yes, depth, and that those proportions are realistic. In Jazz at the Pawnshop (Proprius LP), the performers occupy their own correct spaces and their individual instruments are the proper sizes. There's a definite downside here. Multi-miking is mercilessly exposed. Classic Records has produced a version of Led Zeppelin IV that is certainly vastly superior to Atlantic's efforts, but no performers would ever be placed like they appear to be on "Stairway to Heaven."  

Simon and Garfunkel's engineers are guilty as charged as well. Art Garfunkel clearly wanders from the center to a point about one foot left at the start of the third verse of "Bridge Over Troubled Water" (Classic Records). 

I guess this sounds like nit picking. It's not it’s just a commentary on some fairly dramatic effects.  Nor am I complaining. I will happily live with these minor annoyances to gain the benefits detailed above.


Right, this is the area in which I have been most pleased with the Eros, but I will tell you right now that it's at least partially because I am coming from a love/mild annoyance relationship with Quad ESL-63s. 

Quads do not do dynamics, at least not the macro kind, so the comparison is particularly striking. I have played the Eros at very, very high levels with no sense of strain (quite a tribute to the 60 wpc M-60s as well, I think). 

What I was really unprepared for was the sheer speed of change in level of which the speaker is capable. Real music, particularly symphonic pieces, frequently goes from ff to pp in a split second. The Eros captures it. It's an essential part of the experience, and I will not willingly do without it again. The Eros does not do prolonged very soft passages as well as the Quads, but then again, nothing does.


It's worthwhile noting my standards of comparison (apart from live music, of course). I have either owned or listened to the following long enough to form a solid opinion: Quad ESL-63, Meadowlark Shearwater, M-L Aerius, M-L Request, Sound Lab A-1, Quad 989, Meadowlark Heron, Avantgarde Uno, Merlin VSM, Coincident Super Eclipse, Apogee. 

Two things should be obvious to the most casual observer: these are heavily weighted towards planars, and there are no Maggies in the list. Actually, I owned a pair of MG-1s for nearly 10 years, but they are not representative of the current state of the art. I cannot, therefore, compare them to those near and dear to many of you. 

The sharp-eyed will see the Sound Labs in the list. These are great speakers. I honestly do not know which I would prefer. In the end, the greater cost and amplifications needs of the Sound Labs weighs against them. 

Potential downsides for any buyer are obvious the narrow sweet spot and the nasty impedance load. Deal with those, and what's left? For myself personally and it IS very personal, the Eros is the near perfect speaker system. It is very uncolored, it is very dynamic, and it throws a fantastic soundstage. This is what I want out of a speaker, and now I've got it.

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