75 Years of the Unidyne Microphone

The 5575LE Unidyne® 75th Anniversary Vocal Microphone is a classic beauty. As such, it’s easy enough to appreciate its iconic design and superior sound quality without any context at all. For the true mic geek, however, the historical details make the obvious beauty shine that much brighter. So, here they are. (Truth: We love to geek out over them too.)

Who invented the original Unidyne Model 55 series?

In 1939, newly out of college, Shure Associate Benjamin Bauer developed the Uniphase Principle, which allowed the achievement of a cardioid polar pattern using only one microphone cartridge. Prior to this, achieving a cardioid polar pattern required electronically combining two separate microphone cartridges: one omnidirectional and one bidirectional.

Problems with the old way of achieving a cardioid polar pattern included inconsistent polar patterns and frequency responses. Plus, these dual-cartridge microphones were often cumbersome and delicate. This breakthrough earned Bauer, an immigrant from Odessa via Havana, his first of over 100 patents for audio technology.

What does “Unidyne” mean?

The name has multiple layers of meaning. The uni part is for three things: unidirectional, the single mic element, and the uniqueness of the product. The dyne part refers to the dynamic mic element as well as to the dyne, which is a unit of force used in acoustical measurement.

Shure 5575LE Unidyne Microphone

The 5575LE

What inspired the design?

The Art Deco-style design is an homage to automobile grilles of the late 1930s, like that of the 1937 Oldsmobile Convertible Coupe.

How did it become such an iconic presence?

The Model 55 was available in three versions:

  • The 55A, a low-impedance version for broadcast applications;
  • The 55B, a medium-impedance version for public address and recording applications; and
  • The 55C, a high-impedance version for two-way radio applications.

Its design caught the eye of iconic performers like Elvis Presley, Frank Sinatra, and Ella Fitzgerald, as well as heads of state. Through that exposure to the public, the microphone gained recognition as both a cultural presence and a sign of quality.

What’s the significance of the Institute of Electrical and Electronics Engineers Milestone Award?

This award was presented to Shure in January 2014 for the Unidyne technology, which puts Shure in the company of the most influential inventors in the realm of electrical, electronic, and computing of the past 200 years, including Guglielmo Marconi, Nikola Tesla, Michael Faraday, and Benjamin Franklin.

Shure Unidyne Microphones, then to now

Shure Unidyne Microphones, then to now

Are any other Unidyne microphones still in production?

Yes! The Super 55, 55SH-Series II, 545SD, 565SD, SM57 and SM58® are all Unidynes, to name a few.

Is the 5575LE an exact replica of the original Unidyne Model 55?

We made painstaking efforts to manufacture the 5575LE in accordance with the Model 55’s original design concept. A lot of advancements in microphone technology have occurred since 1939, though, so we tried to strike a balance between honoring the aesthetic of the original and delivering the best sound quality possible. The microphone element is a Unidyne III, the same one used in the SM58. Additionally, we made some mechanical updates to improve the structural integrity of the product.

A 5575LE Unidyne and an original Model 55 Unidyne side by side

A 5575LE Unidyne and an original Model 55 Unidyne side by side

How can I get one?

For a limited time, the 5575LE will be available from Shure Authorized Dealers.

For tons more information about the history of the Unidyne, download The Unidyne Story, a 48-page brochure carefully compiled by Shure historians.

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Allison Wolcott

Allison Wolcott

Allison Wolcott started singing at Shure and now sings wherever she can. She wishes she were Brandi Carlile, Neko Case, and Johnny Cash all rolled up in a voice box. Her favorite mic is the BETA®87A.

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  • Mike Michelson says:

    I’ve been looking all over for info to compare this to the 55SH and Super 55, specifically frequency charts, but I’m also curious about their cartridges and any interesting electronic differences. So far I’ve only been able to dig up the 55SH chart, and that the 5575LE shares the SM58’s Unidyne III cartridge. Can you shed more light on this?

    • webmaster Allison Wolcott says:

      Hi Mike! I got some help from our product support brain trust on this one. Here’s what they had to say:

      The 55SH Series II uses an SM48 capsule and has a cardioid polar pattern. However, the frequency response is different from the SM48 due to the orientation and architecture of the 55. Here’s a link to the user guide:


      The Super 55 uses the standard Beta capsule that is found in the Beta 56, 57 and 58 and has a super cardioid polar pattern. Much like the 55SH, the frequency response is different from the Beta mics based on orientation and architecture. Here’s a link to the user guide sheet:


      The only other electronic difference is that the 55SH has an on/off switch whereas the Super 55 does not. Beyond that, they’re both magnetic element to transformer to XLR connector.

      Also worth reading is Michael Pettersen’s “The Unidyne Story”:


      • Mike Michelson says:

        Ah, thanks! Yes, naturally there’s far more to the sound than just the capsule. Even the switch would add capacitance and resistance, though I’d imagine negligible.

        As a tangent I’m mildly amused by Shure’s designation of “Beta” as being the next generation–in other industries, “beta” means “not yet ready for public release!”

        • webmaster Allison Wolcott says:

          Haha! The BETA microphone line gets its name from the second letter of the Greek alphabet. Since the SM58 was considered the Alpha mic, and the SM line the Alpha line, we thought it would make sense to call the next step up BETA.

  • Jeff Foland says:

    I was going to enter the 5575 giveaway, but the “access and ability to post” on my social media goes just a bit too far. Sorry, I don’t care to yield that privacy.

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