Microphone transducer technology hasn’t changed radically since the development of the “big three”—condenser, moving coil, and ribbon. While there have been incredible refinements, applications of new materials, lighter membranes, stronger magnets, resilient ribbons that resist tearing or stretching, and improved manufacturing techniques that ensure consistency, the basic operating principles for each type of transducer are mostly the same today as when they were first developed.
Shure recently introduced the KSM8 Dualdyne microphone, touted as the first handheld vocal microphone to employ two diaphragms in the same capsule. Nit-pickers may note that AKG produced several “two way” mics in the late 1960s and early 1970s but those operated much like a two-way speaker, with one capsule handling the high frequencies and the other handling the low frequencies. And of course many multipattern condenser mics employ two diaphragms on a common back plate to achieve pattern switching. These were not Shure’s motivations for developing the Dualdyne capsule.
Shure’s goals for the Dualdyne were to provide the sound quality normally associated with a condenser capsule while maintaining the rugged nature of a moving-coil transducer; controlling proximity effect while providing a very wide sweet spot; obtaining a smooth, wide frequency response and an accurate cardioid polar-pattern.
The patented design of the Dualdyne capsule employs two membranes. The front “active” diaphragm is a moving-coil element. The rear diaphragm is passive—sort of like a passive radiator in a loudspeaker—and this diaphragm contributes to the capsule’s inverted airflow system. Energy from the passive diaphragm is re-directed and phase-manipulated to achieve the desired frequency response, directionality, and control over proximity effect.
Most directional movingcoil microphones have three personalities: Move the mic close to the singer and proximity effect becomes an issue; place the mic at a distance from the singer that is “just right” and the mic sounds balanced; move the mic too far away and the voice becomes thin. Omnidirectional mics, on the other hand, do not exhibit proximity effect. The Dualdyne’s second diaphragm, along with the reverse airflow principle, allows the KSM8 to behave somewhat omnidirectionally at low frequencies; omni enough to control the proximity effect, but directional enough to control bleed from nearby instruments.
Not content to stop at the capsule, Shure revisited other features of the KSM8. The pneumatic shock mount was designed to reduce handling noise, and the hardened carbon-steel grille protects the capsule from damage. The grille is lined with woven, water-repellent fabric for protection against wind, plosives, and moisture. Shure’s Diaphragm Stabilization System stabilizes the active diaphragm when it is struck with plosive sounds while reducing handling noise.
Fig. 1. A view of the well-designed KSM8 Dualdyne cartridge. Physically, the KSM8 is nicely designed. Its profile is similar to that of the KSM9, with a slender handle and a sort of squared-off head. Removing the grille reveals the Dualdyne cartridge, which resembles nothing I’ve ever seen and is proudly adorned with the Shure logo at the top (see Figure 1). It’s almost too beautiful to hide.
A peek inside the grille shows a foam pop filter at the top and the water-repellent material lining the sides. Unlike many of the interior “shock mounts” I’ve seen, the KSM8’s shock mount actually appears (and proved to be) resilient enough to do something about mechanically transmitted noise. The KSM8 is available in the wired version, which I tested, as well as versions that are compatible with Shure’s wireless systems.
I used the KSM8 in two very distinct contexts—in a loud rock band for either of two singers, and then on a solo performer with an acoustic guitar. Results in the rock band were very different depending upon who was singing. Singer One tends to sing off-mic and has less-than-stellar mic technique (e.g., he varies his distance quite a bit over the course of the night). His voice sounded great on the KSM8—smooth, present but not peaky and, dare I say, “tube-like” and balanced. His voice sat on top of the mix without ever becoming overbearing. Using other vocal mics with Singer One, I sometimes need an EQ cut of 4 to 5 dB in the vicinity of 3 to 4 kHz to prevent shrillness. Not so with the KSM8. And at no point did I notice any proximity effect. The KSM8 was fantastic on his voice.
Singer Two has a very different technique and a very different vocal quality: I would describe his voice as “smoky.” He tends to consistently work right on top of his mic and he commented how he felt that he could stay close to the KSM8 thanks to its flat grille (as opposed to a round grille). However with his mouth on the grille, the KSM8 did produce some proximity effect, emphasizing the lowmids and reducing presence in the mix. Used with either singer, the KSM8’s noise rejection from the stage was excellent, and bleed was minimal.
In the context of the solo performer, the KSM8 performed like a champ while revealing some interesting characteristics. Leakage from the acoustic guitar into the KSM8 was barely audible, which is not usually the case when miking a singer/acoustic guitar player. And what little guitar did make its way into the KSM8 did not have the weird, phase-y sound that instrument leakage often produces. In fact it sounded like I was using the KSM8 on the guitar, except that the guitar level was a lot lower than that of the voice. More importantly, I didn’t have to lock the singer into a head vise in order for his voice to sound consistent. The timbre of his voice barely changed when he moved, and proximity effect was not an issue for him because he never got on top of the mic.
The KSM8 reduces, but does not eliminate, popping from plosives. Although initial A/B’ing against another mic might make you think that it pops more, when you listen carefully you’ll find that popping on the KSM8 is less severe than on other mics. In addition, the KSM8 is more extended in the low frequencies, so voices simply sound more full in the low end.
A few times I used the KSM8 outdoors and it captured a fair amount of wind noise. But it’s tough to qualify how much wind the KSM8 captures vs. a garden-variety handheld mic because the KSM8 produces higher fidelity than most vocal mics. It’s impossible to know how much wind noise would be present if the rear diaphragm of the KSM8 was turned off, because it can’t be. It’s kind of like that first time you put up a good condenser mic in the studio and hear the air conditioning rumble: The mic reveals the noise because it has the capability to do so. In any case, use of a gentle highpass filter at around 90 to 100 Hz cured the wind issue as well as the occasional sound of foot tapping transmitted through the mic stand.
In regards to distance and position, the KSM8 maintained sonic integrity across a range of about ±50 to 60 degrees—far outside the norm for a typical vocal microphone. The sweet spot is fairly deep, from about 1.5 inches to around a foot away from the grille. There is a subtle loss of presence as the KSM8 is moved away from the singer’s mouth but nothing like what you get with a traditional vocal microphone. In fact you’d be hard pressed to hear a difference in sound as a singer moves closer to and farther from the KSM8, and you certainly don’t feel like anything is being lost. Keep in mind that if the singer does put his or her mouth on the grille, the KSM8 will provide some “warm and fuzzies” from proximity effect.
The KSM8 solves what I feel is one of the main problems exhibited by using condenser mics in a live context: They deliver fidelity and sensitivity at the expense of increased bleed from the stage, while generally providing a narrow sweet spot. The KSM8 provides the fidelity, permits a wide range of movement without changing its sound, yet still manages to control leakage from nearby instruments as well as proximity effect. And it greatly reduces handling noise without loss of low-frequency response. Quite an accomplishment!
Very smooth response. Wide sweet-spot. Leakage is well-controlled. Beautifully constructed.
Extended LF response can result in sensitivity to wind noise or popping.
Steve La Cerra is an independent audio engineer based in New York. In addition to being an Electronic Musician contributor, he mixes front-of-house for Blue Öyster Cult and teaches audio at Mercy College, Dobbs Ferry campus.