[SoundStage!]Factory Tour
Feature Article
May 2004

Innersound Factory Tour
by Jeff Fritz and Marc Mickelson

Innersound's Roger Sanders and his Eros ESL speaker


Roger Sanders penned The Electrostatic Loudspeaker Design Cookbook (published in 1993 by The Audio Amateur) after years of research, and it is widely read amongst electrostatic-speaker enthusiasts. Many consider Sanders the expert on the genre, even though he’s not related to the other electrostatic-speaker guy with the same last name. It’s therefore not surprising that even though Innersound as a corporate entity has only been producing speakers since 1997, the designs and processes behind the company are all much more mature.

In 2003, Innersound changed hands and relocated from Georgia to Boulder, Colorado. The new owner and CEO, Gary Leeds, was kind enough to let us visit with him and Sanders (who is still the chief engineer and designer) while they were setting up their new facilities. The production facility Innersound will be occupying wasn’t quite finished for our visit, but the company was beginning to produce loudspeakers nonetheless -- we saw a wide array of raw materials and partially constructed cabinets. The listening area and business office -- located some miles away -- was fully functioning on the day of our tour, and it was there that we found out much of what would satisfy our curiosity about Innersound.

A full lineup

Perhaps one of the most surprising facts that we were presented with was regarding Innersound customers and their buying habits: about 50% of them prefer a soups-to-nuts Innersound system (the missing piece of this being a source component, which is coming soon). Although the company is perhaps most well known for electrostatic speakers, Innersound’s electronics have been steadily drawing attention. According to Leeds, there is roughly a 50/50 split between sales of Innersound speakers and electronics -- a balance he likes. And to connect it all, Innersound will launch the iConnect interconnect and iCable ESL loudspeaker cable (prices to be announced).

The current full product lineup consists of two loudspeakers: the brand-spanking-new ESL/transmission-line Kaya Reference ($19,000 per pair) and Kachina ($11,000 per pair). The company still has stock of the older Eros Mark III and the somewhat smaller Isis Mark III. These speakers are being sold at reduced prices in preparation for the new models. Contact Innersound for details and pricing. Also new is the Tehya hybrid center-channel speaker at $5500.

Innersound UltraStat panels...


...and speaker cabinets in need of UltraStats.


Innersound's office area. The listening area is at one end, so it's the duty of those working here to listen to music.


The office system at the time of our visit: Eros Mk III speakers, ESL 800 monoblocks,...


...iTube power amp,...


...and (from top to bottom) Origin Live turntable, Innersound iPhono phono stage, MSB CD player, and the crossover/bass amp for the Eros Mk III speakers.

Sanders gave us the crash course in the electrostatic design his speakers employ, and here’s the condensed version. A very thin Mylar diaphragm is mounted between two "stators." The stators -- "electrically conductive, acoustically transparent grilles" -- are equipped with copper conductors running through them. The amplifier delivers "several thousand" volts to the stators via a step-up transformer. Then according to Sanders, "Like north and south magnetic forces, positive and negative electrostatic forces are attracted to each other, while similar polarities are repelled from each other. Music drives the amplifier to produce a positive voltage on one stator and a negative voltage on the other. These voltages alternate back and forth between positive and negative very rapidly to produce a tone."

Sanders continued: "At a given moment in time, in response to the musical signal, let's say the front stator has a positive voltage. The rear one will be negative. Let's assume that the diaphragm has a negative voltage. Remember that the diaphragm's voltage is static and comes from the little power supply and does not change like the voltages do on the stators.

"The negatively charged diaphragm will be attracted to the positively charged front stator because opposite charges attract. It will be repelled from the negatively charged rear stator because like charges repel. A moment later, the amplifier will reverse the voltage polarity on the stators, so the diaphragm will move the other way. As the diaphragm moves, it produces pressure waves in the air that we hear as music."

Got all that?

Then there are the amps to consider. Whether you want an amp to drive an entire Kaya/Kachina loudspeaker, just the upper electrostatic section, or another loudspeaker altogether, Innersound has you covered. In the new Reference line, there are DPR-500 500Wpc stereo ($12,500) and DPR-1000 1000W mono amps ($25,000 per pair), and the RCPI-1 fully balanced, remote-controlled preamplifier (price to be announced). There are also the new iPower 330 stereo amp that delivers 330Wpc ($5000) and iPower 750 monoblocks that offer 750W each ($10,000 per pair), and the iControl balanced, remote-controlled preamp ($3900). As with previous speaker models, older electronics are still available at reduced prices, and they are being phased out in anticipation of the new products. If vinyl is your thing, there's the iPhono phono stage ($2800). The amplifiers, in particular, are designed specifically to drive electrostatic speakers, due to their ability to handle low-impedance loads and their non-current-limiting design. If you need gobs of power for your ‘stats, or any other speaker for that matter, Innersound makes an amp spec’d for you.

You’d think that Innersound would be through, but you can look for more product debuts from the company in 2004, including a reference multiformat player and DAC, and reference full-range electrostatic speaker.

Hearing is believing

Sitting down in Innersound’s comfortable office-space listening room proved that one company can make an impressive-sounding (nearly) complete system. Gary Leeds led us through a listening session that was quite impressive. The Eros Mark III is a limited-dispersion loudspeaker, which, according to Sanders, minimizes room reflections. This meant that only one of us could occupy the somewhat narrow sweet spot at a time. However, once centered properly, we found the sound of the system transparent and focused -- and flexible. Leeds demonstrated how the adjustable crossover/bass amplifier could tailor the sound; he altered the tonal balance of the system by making the bass a bit more or less prominent. We soon found a setting we both felt served the music and sat back and enjoyed ourselves.

At the end of the day we came away with a feeling that Innersound as a company was going places. We were equally impressed with Sanders’ technical knowledge and Leeds’ business savvy. It takes both to succeed in today’s market, so Innersound is a company to watch.

To find out more about Innersound, visit www.innersound.net.


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