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What is Dualdyne? Understanding the Shure KSM8

The Shure KSM8 Dualdyne is the world's first dual diaphragm dynamic handheld microphone - a ground-breaking feat of engineering that essentially reverses the flow of a dynamic mic. To explain what makes this so significant, we take a look at the Shure Unidyne.
January, 22 2016 |

The Shure KSM8 Dualdyne is the world's first dual diaphragm dynamic handheld microphone - a ground-breaking feat of engineering that essentially reverses the flow of a dynamic mic. To understand what makes this so significant, we must first understand the Shure Unidyne.

Unidyne to Dualdyne

In 1939, Shure introduced the world's first single-element unidirectional dynamic microphone – the Unidyne 55. Prior to Unidyne, the common way of achieving a directional cardioid polar pattern was to combine an omnidirectional element with a bi-directional (figure eight) element in a single housing. These early designs lacked consistency in performance and were large and bulky by nature. All this changed with the introduction of Unidyne.

From here on, the world of live performance microphones would surge forward as other manufacturers replicated the design. All unidirectional dynamic microphones to this day are still based on those founding principles established by Shure in 1939.

Shure Engineer, Benjamin Bauer was the driving force behind the development of Unidyne. Ben Bauer recognised that the best way to address the difficulties of feedback and inconsistency was to use a single element. He understood that if a single element was exposed to sound only from the front, the result was an omnidirectional response. Additionally, if the element was exposed to sound at the front and back, a bidirectional response could be obtained. By examining these underlying physics, Bauer realised that if he could partially block the back side of a microphone element, he would achieve a response halfway between omnidirectional and bidirectional. His research led to the Uniphase acoustical system.

Bauer's Uniphase system was a carefully calculated network of front and rear opening ports that enabled sound waves to reach both sides of a microphone's diaphragm. The sound waves destined for the rear diaphragm had a longer path to pass through, which acts as a time delay. By purposely allowing sound to enter the rear of the mic, Bauer was able to delay the sound in a way that resulted in sound from 180 degrees off axis striking the front and rear at exactly the same time, which results in a net diaphragm movement of zero. Hazar! The first unidirectional dynamic microphone had become a reality.

Sleek in design, the 55 Unidyne came to symbolise the word 'microphone,' as countless performers and public figures were pictured with the extraordinarily photogenic microphone. Elvis, in particular, became synonymous with the Unidyne –  an image later encapsulated in a first-class stamp issued by the United States postal service. Having celebrated its 75th birthday in 2014, the Unidyne remains as desirable today as ever, with modern iterations continuing the great tradition of turning heads as the "microphone that needs no name." Arguably, the Unidyne is the most recognisable microphone in the world with the most significant stage presence of any microphone made to this day.

Never the type to sit still, Shure engineers continued developing the Unidyne concept – honing its design and perfecting performance.

In 1959, Unidyne III became the first high-quality unidirectional microphone designed for speaking into the end rather than the side of the microphone. It was the predecessor to the SM57 and the foundation of Shure's legendary SM series (In other words, Shure were the first company to start putting ball grilles on microphones).

By 1964 Shure created the pneumatic shock mount – an extremely complex design that's integrated into the cartridge acoustics and can only be found in authentic Shure products. You can read more about what makes the pneumatic shock mount special in our previous post.

In 1966, the SM58 was quickly adopted by the rock-and-roll community for its combination of high-quality sound and durable performance. The SM58 remains the most popular vocal microphone in the world, having undergone several continuous improvements over its 50-year lifespan. While it's important to continue evolving the manufacturing process, the SM58 you hold in your hands today has the Unidyne III at its core. Ultimately, every dynamic microphone on the market today is based on the founding principles laid out in this article.

So what's next? Where do we go from here?

While single-element unidirectional microphones mitigate the problem of feedback and poor intelligibility, there are trade-offs in other areas: namely the proximity effect and off-axis sound colouration.

Enter KSM8 Dualdyne – the world's first dual-diaphragm dynamic handheld microphone, and the most significant advancement in microphone technology since Unidyne in 1939.

At the heart of KSM8 is a new-to-the-world cartridge design with two ultra-thin diaphragms and reverse airflow. The result is a mic with virtually no proximity effect; exceptional off-axis rejection; and unprecedented vocal clarity with minimal need for EQ and processing.

The graphics below illustrate how the KSM8 performs next to standard dynamic handheld microphones:

Proximity Effect

Controlled proximity effect vastly increases the working distance without on-axis coloration, delivering the most accurate frequency response available in a dynamic microphone.


Frequency Response

The red line in the graph below represents the KSM8; note the significantly flatter frequency response – particularly around the presence peak area.


Polar Pattern Consistency

The final graph demonstrates how consistent the KSM8 performs at multiple frequency checkpoints.

Just like Unidyne before it, KSM8 brings a whole new microphone element to the world. The ability to virtually eliminate proximity effect and master off-axis rejection is made possible by reversing the airflow of a dynamic mic and utilising two ultra-thin diaphragms — one active and one passive. The passive diaphragm is part of the cartridge acoustics that provides a previously unattained mastery of proximity effect. The active front diaphragm, coil, and magnet pole assembly produces the most accurate frequency response available in dynamic microphones.

Does this microphone replace other Shure microphones?

No. All microphones serve various applications – no one microphone is the solution to every problem. The Unidyne III cartridge has yet to be bettered as a single diaphragm microphone with a pneumatic shock mount at its respective price point. The Dualdyne is a new category of cartridge that improves many key performance areas – as described in this article – by incorporating key design learnings from Unidyne. In doing so, Dualdyne offers a new generation of performance standard in applications where these improvements matter.

Take Mumford and Sons as an example:

"Marcus really enjoyed the KSM8 on his first gig with it last night at Rock in Roma. As did I. Really clean, flat response, smooth HF and the reduction in spill is quite amazing! He'd like to change the mic out mid-tour, Marcus also commented on how good the mic looked, and wanted to use it immediately...." – Chris Pollard, FOH Mumford & Sons.

In this instance, Marcus benefits from the consistent cardioid polar pattern in receiving a more intelligible monitor mix. Coupled with a preference for flat frequency response and a smooth top-end, the KSM8 is a perfect fit for this application. Should you find yourself in a situation where the performer prefers a sharp presence peek, you may find the SM58 – or even the Beta58 – remains the safer option.

Likewise to Mumford and Sons, Hozier provided similar feedback about the KSM8's consistency:

"Just want to let you know that we used the new mic today and we were all blown away by it and love it. Especially Andy (Hozier).

The gain structure was the same as the beta but it was a lot smoother in the 3-5k range and it has a really nice presence without being overpowering. It placed his vocal really nice in the mix. All in all an absolute winner. It will be used as Andy's main vocal for the foreseeable future."

Hozier's vocal-forward songwriting style benefits from a consistent, flat frequency response that comes from virtually no proximity effect and a flat frequency response. Given a different vocal style and genre of music, other performers might find they actually benefit from proximity effect (thickening out a thin vocal, for example).

The Bottom Line

KSM 8 uses brand new technology to expand the capability of dynamic microphones. No single microphone can truly fit all applications or suit every vocal style. However, the KSM8 does succeed in addressing most of the common challenges faced by engineers when using conventional dynamic microphones. Just as Unidyne addressed the common issue of feedback in 1939, the Dualdyne address common dynamic microphone challenges since 2016. It signifies the next generation in microphone technology and a history of innovation – a tradition we're proud to uphold. Benjamin Bauer, we hope, would be proud.

Marc Henshall
Marc forms part of our Pro Audio team at Shure UK and specialises in Digital Marketing. He also holds a BSc First Class Hons Degree in Music Technology. When not at work he enjoys playing the guitar, producing music, and dabbling in DIY (preferably with a good craft beer or two).

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