InnerSound’s Isis Loudspeaker
|InnerSound’s Isis Loudspeaker
|5 October 1999
Speaker dimensions: 11.5″W × 14″D × 62″H
Speaker net weight: 54 pounds
Speaker shipping weight: 65 pounds
ESL size: 10″ × 39″
Power handling: 250 watts
Impedance: 4 ohms nominal,
2 ohms minimum @ 20 kHz
Bass driver: 8″/transmission-line design
Woofer impedance: 4 ohms
Sensitivity: 90 dB/2.83 volts, @ 1 meter
Frequency response: 34 Hz to 27 kHz, +/-2 dB
“I’d like to congratulate InnerSound for its Isis speaker–for creating a product whose tonal balance, imaging, and air belies its $2500 price-tag. I consider it a bargain in the high-end audio world.”
Many speaker manufacturers want to lay claim to the greatest speaker ever designed and that their speaker does it all. Try as they might, each design exhibits its own signature, its own feel, and we react positively or negatively to that signature.
The goal of many speaker designers is to design a speaker to reproduce the recorded musical event as accurately as possible, without adding coloration or distortion. After all, this is the Holy Grail of speaker design.
We also know that there are some designers that purposely design with a particular sound in mind. Some add upper midrange emphasis for increased palpability, or pad the lower midrange/upper bass for chestiness and warmth on vocals and added richness on strings, just to name a couple.
These are all approaches that many listeners find acceptable and enjoyable and there have been many successful designs that have won critical acceptance by both reviewers and the buying public. Personal preference, after all, is the final arbiter in the market place.
As a reviewer, I’m not constrained by market place pressures and each product I review is given a full and honest appraisal. My own prejudices and preferences enter the picture as well, but I will report to you what my ears hear as accurately as possible. Since we all hear differently, let any review be used as a beginning in your own listening and evaluation quest.
InnerSound has produced its second product in an electrostatic/dynamic hybrid design called “Isis”, a bi-wireable design. For this review, I used a single run of speaker cable with the provided jumpers in place. Roger Sanders, the company’s guru and one of the industry’s acknowledged experts in electrostatic speaker design, has taken a very interesting approach. By eschewing a wide dispersion design and producing a very directional speaker he has successfully minimized room interaction which can often result in smearing of transients, loss of imaging and muddying of the sound. In other words, he wants you to listen to his speaker, not the room. Incidentally, you can take the money you were going to spend on all those exciting room treatments and find some other uses for it.
“…dipoles do not radiate to the sides, minimizing initial side wall reflections. The end result of all this is that the listener hears the arrival of the direct sound achieving wonderful clarity and holographic imaging.”
It has often been the goal of many designers to marry the clarity and transparency of electrostatic panels with the bass output of dynamic woofers to achieve full-range response. More often than not, these hybrid designs have problems in achieving a coherent sound, with the dynamic cone bass driver lagging behind the speed of the electrostatic panel, as well as controlling wave front interactions created by the different sound sources.
How does this speaker approach this hybrid goal? By using an eight-inch transmission-line woofer in a non-resonant enclosure, producing a quick, clean bass response with minimal overhang. Also, by choosing a crossover point that minimizes driver interaction, Sanders seems to have allowed the best qualities of each to manifest themselves and produce coherent sound.
The electrostatic panel in the Isis is approximately 40 inches high and is very directional and beamy in the vertical plane, which minimizes floor and ceiling reflections of the midrange and higher frequencies. Additionally, dipoles do not radiate to the sides, minimizing initial side wall reflections. The end result of all this is that the listener hears the arrival of the direct sound achieving wonderful clarity and holographic imaging.
Before we get any further, we must talk about the setting up of the speaker system – which is very, very critical. These speakers, according to Sanders and the instruction manual, must be precisely and symmetrically spaced, as well as toed-in directly at the listening position. We are talking within a quarter of an inch here. Get the point! Also, do not place any sound absorbent materials behind these speakers or on the side walls. They require a hard surface behind them to sound their best, just the opposite of most panel-type speakers. Additionally, place them near the side walls, not out into the room as you would more traditional speakers. In my set-up, they’re only 12 inches from the side walls and two feet from the rear walls. Another way of checking your position is to see your reflection on each speaker’s screen equally by either wearing a white shirt or using a flashlight. This sounds a bit obsessive but the payoff is worth it.
Getting the bass to midrange relationship correct, is another key to getting the best performance from these speakers. A bass level control is provided on the rear of the speaker allowing adjustment of the bass output up or down. In reality, it acts as a midrange control. “How?” you say. When the midrange clarity and tonality sound just right, you’ll know you’ve achieved the optimum bass setting. As with other speakers, corner placement has its effect on bass attenuation. You’ll need to experiment with that as well.
Now, after all that positioning and adjusting, the reader is breathlessly wondering…How does it sound? Was it all worth it? In a word…”yes”.
The Sirens Beckon…
“These speakers throw a wide and deep soundstage that was seductive without feeling artificial. If the CD had it, these speakers would make it happen.”
Settling back in my listening seat, precisely measured of course, I found myself enjoying CD after CD. The music came through with such clarity, air and spaciousness that I couldn’t stop smiling. Instruments were three-dimensional with immediacy and air but without that in-your-face quality that some people equate with hi-fi. The overall presentation was relaxed and non-fatiguing, as opposed to being up-front, in the first row. It had all the detail and clarity without that hard electronic edge that some other highly detailed designs can produce. Did I say, “soundstage”? These speakers throw a wide and deep soundstage that was seductive without feeling artificial. If the CD had it, these speakers would make it happen.
When listening to speakers, we’re obviously listening to the last line in the audio chain. My reference digital playback includes the Camelot Uther 3.0 DAC, the Sony DVPS 7000 as transport, playing directly through the Berning ZH 270 OTL power amplifier. My analogue playback system, while not state-of-the-art, is a good one that has served me well and is comprised of my trusty Thorens TD 115 Mark II with a Shure V15 Type V with MR tip, playing through an Audible Illusions Modulus 3 preamplifier. All cabling and power cords are by Harmonic Technology (interconnects are Truth-Link; speaker cable is Pro-11 Plus; power cords, Pro-AC11).
Playing the Oscar Peterson Trio + One, Clark Terry (Mercury Stereo SR 60975) record was a revelation. Clark Terry’s trumpet was full, live, and lush with the trio’s back-up coming in loud and clear. Even though I’ve already characterized these speakers as relaxed, it doesn’t mean they don’t swing nor have any punch. Just listen to Terry’s trumpet on cut 3, “Roundalay,” with Ed Thigpen’s drumming and cymbal work driving the group, as evidence that these speakers can drive you where you want to go.
Voices are focused and full, possibly with the slightest leaning toward the warmer side of neutral—a tough call. Diana Krall’s CD, All for You (Impulse IMPD-182), is so present and intimate on cut 5, “Boulevard of Broken Dreams,” that you walk the boulevard with her. Listen to the piano on this cut—it’s alive. The palpability and clarity these speakers send forth is illuminating.
Orchestral works were handled with equal aplomb. RCA’s Living Stereo CD Rhapsodies(D-183974), with Stokowski conducting Richard Wagner’s Tannhauser Overture is a perfect example of how these speakers handle space and depth with instrumental definition. The castanets and triangle came through clearly, without losing their location back in the soundstage. The strings were rendered with a natural warmth and separation.
At the listed specification of 34 Hz, -2 dB, bass freaks would probably want to look into using a subwoofer. Without one on hand, I couldn’t tell you of any interaction/balance problems that may or may not result. I’ll leave that to you to explore.
One other observation to report: after about two months of auditioning and playing many, many CDs and records, an occasional CD’s treble would be rendered a little hard or strident—probably more related to the particular CD itself.
“In order to hear all the benefits of these speakers you must be at the perfect sweet spot for listening. It is a very small sweet spot, and as soon as you move off that spot, the high frequencies seem to disappear and the holographic imaging flattens out.”
Another factor to consider is amplifier matching. My Berning only puts out 70 watts per channel into 8 ohms, and large orchestral crescendos left my amplifier wanting with these speakers. I would like to have had a more powerful amplifier on hand for this review. Possibly, what I perceived as lacking in bass impact would be ameliorated with a more powerful amplifier. Additionally, the 2 ohm impedance of the electrostatic panel at high frequencies caused some problems with the Berning amplifier, resulting in that occasional treble response problem previously noted.
Roger Sanders informed me that he has a new solid-state power amplifier in production (400 watts per channel into 8 ohms), and I’m looking forward to its arrival on my doorstep. Stay tuned.
Comment: The Double-Edged Sword
One drawback to this speaker system is also what makes it so successful: directionality. In order to hear all the benefits of these speakers you must be at the perfect sweet spot for listening. It is a very small sweet spot, and as soon as you move off that spot, the high frequencies seem to disappear and the holographic imaging flattens out. All speakers share these characteristics to some extent, but it is very pronounced with the Isis. For serious listeners it shouldn’t be a problem.
Summing up, I’d like to congratulate InnerSound for its Isis speaker–for creating a product whose tonal balance, imaging, and air belies its $2500 price-tag. I consider it a bargain in the high-end audio world.
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