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Sound Potential

PRO AUDIO is about working with sound that's going in or out of a human body. But for Soundwave Research Laboratories, developing the next-generation of ribbon microphones means focusing on more than just mouths and ears.

Amplifying the voice of instructors through the use of soundfield systems has been linked to higher test scores in certain studies. 

Amplifying the voice of instructors through the use of soundfield systems has been linked to higher test scores in certain studies. 

PRO AUDIO is about working with sound that's going in or out of a human body. But for Soundwave Research Laboratories, developing the next-generation of ribbon microphones means focusing on more than just mouths and ears.

In pro AV, the Ashland, MA-based company is best known for its Crowley & Tripp ribbon microphones, named after co-founders Bob Crowley and Hugh Tripp, a former Boston Scientific engineer. But Soundwave Research Labs also is a player in the medical technology industry, where it makes intravascular ultrasound equipment for looking inside blood vessels to ferret out blockages. That sounds like an odd pairing, but it's born partly out of necessity: When it comes to attracting R&D funding, audio in general — and pro audio in particular — is lucky to get the crumbs off of video's table. (For a look at why that's the case, see “The State of AV R&D” in the August 2004 issue of Pro AV.)

By developing audio technologies that can be used in both pro AV and medicine, it's easier for Soundwave to justify the R&D spending. That wouldn't be the case if the mic technology were destined only for the AV market. “The equipment to do the medical transducers is pretty intensive,” Crowley says. “If you did just that alone for microphones, it would be a pretty high hurdle. So we get to share quite a bit of the facility, techniques, and know-how from the medical area and bring that over into the pro audio area — specifically into microphones.”

Rethinking ribbons

Besides its experience in the medical space, Soundwave also is leveraging its founders' experience with composite materials such as zirconate titanate, whose piezoelectric characteristics make it a good fit for transducers. Why composites? They're usually far stronger than other materials, with few trade-offs in terms of electrical conductivity.

Now the company has turned its attention to another composite: carbon nanotubes, which Soundwave's founders already have some experience with. “I was the inventor of the carbon nanotube antenna array system back in the mid-'90s,” Crowley says. “This is somewhat of a continuation of that type of work, where we discovered that we were able to get very high strength, very highly conductive materials that had relatively low mass, which is good for things that move, like the membrane of a microphone.”

Carbon nanotubes are microscopic cylinders roughly 10,000 times thinner than a human hair. Discovered in 1991, they can conduct electricity, making them a viable option for a wide variety of AV products. For example, Eikos, a Franklin, MA-based company, has developed a method for using carbon nanotubes in displays to replace indium, a metal whose price has quintupled over the past few years. (For a look at nanotechnology's impact on AV, see “Think Small” in the December 2004 issue of Pro AV, and “Heavy Metal Alternatives” in the October 2004 issue.)

Soundwave believes that carbon nanotubes also are a good fit for ribbon mics — specifically for replacing the ribbon itself, which is an ultra-thin strip of aluminum foil that's loosely suspended between the poles of a powerful magnet. In terms of performance, the decades-old design is solid because the pickup is linear, with low distortion. The Achilles heel is the ribbon, whose flimsiness makes it difficult to manufacture, which in turn drives up the mic's price.

“The ribbon mic has been relatively unchanged since it was first put together by pioneers like Harry Olson in RCA Labs,” Crowley says. “Historically it's been difficult to make. It's touchy because you're using very thin aluminum foil, almost like gold leaf. The wind could blow it away. What's worse is that the piece-to-piece variability is high because it requires hand assembly.”

By using carbon nanotubes to create a tougher, more consistent ribbon material, Soundwave hopes to streamline the manufacturing process. For example, as a composite material, carbon nanotubes could be created using common manufacturing processes such as thin-film deposition. Although the mics still would require some hand assembly, it could be significantly less than what's required using aluminum foil ribbons. The combination of increased automation and leveraging manufacturing processes from outside AV —including the medical industry — should help reduce the mics' cost, at least in theory.

“It probably will be approximately the same,” Crowley says. “The price for mics is based a lot on the quality of the overall assembly. It may be more economical to manufacture these in the future. We don't know yet.”

Hammering home the benefits

Once the mics are in the field, carbon nanotubes provide a second benefit: toughness. “Ribbon mics have a reputation, and it's good and bad: The good part is that they sound great,” Crowley says. “The bad part is that they're fragile. We're doing everything that we can to completely overcome that. We want to be able to hammer the nail into the board, just like Electro-Voice did back in the 1950s with the 664.”

After toughness, Soundwave hopes that, like its current pro mics, its forthcoming carbon nanotube-based models will be able to capitalize on the perception that the ribbon designs offer smoother sound. “A lot of people are realizing that the harshness that they sometimes get with, say, a large diaphragm condenser on a vocal isn't there with a ribbon microphone,” Crowley says. “So we started to tailor ribbon mics so that they're more suited for vocal applications as our entry product, almost as an experiment to see if they'd be accepted in the marketplace.”

Soundwave sees the initial adopters of carbon nanotube mics being the same as its current pro audio customers: musicians, engineers, and producers looking for benefits such as greater purity, higher output, lower noise, and lower distortion. The catch is that unlike toughness — which is difficult to dispute when a mic still functions after hammering a nail into a board — sound quality is in the ear of the beholder.

“We're going to be conservative as we roll these out because we're not sure how we're going to introduce these technologies to our customers,” Crowley says. “When you introduce a new technology to something as subjective as music, sometimes just the suggestion that it's new can influence how people perceive the sound. So what we'll probably do is in a beta round: have some mics with the tech, and some without, and compare the results.”

Ramping up

Crowley and Tripp founded Soundwave in 2004, yet the company was already manufacturing and selling mics less than 18 months later. However, they're mum about when their first carbon nanotube mics will appear. “We're not saying much about how far along we are in the implementation and development,” Crowley says.

The company's carbon nanotube ribbon microphone technology will make its debut in the form of ultrasound imaging for mapping the inside of blood vessels via intravenous catheters. That application speaks to how sensitive and small these mics must be. But when Soundwave starts offering pro mics based on the technology, size probably won't be much of a market differentiator, except for customers who require a svelte design for field recording, or hidden mics for theatrical sound reinforcement.

Soundwave plans to manufacture the carbon nanotube mics, but it also might allow other vendors to make them. “The conversations have already started about licensing,” Crowley says.

If the carbon nanotube mics build a following in pro audio, it will be yet another example of how the industry increasingly depends on R&D work that benefits more than just AV. “We're musicians and audiophiles, and we love this area, and we realize that there's a need to make sound better,” Crowley says. “But sometimes the cost isn't justified. The R&D dollars wouldn't be available for various reasons. So by sharing that with another area, such as medical imaging, we hope to get some more mileage for a dollar.”

Tim Kridel is a freelance writer and analyst who covers telecom and technology. He's based in Kansas City and can be reached at tkridel@kc.rr.com.

 


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