EQ, Filters, Switches
As much as designers strive to create a certain frequency response curve with their mics, sound engineers sometimes need to modify that response for particular applications. Some manufacturers offer internal circuitry for that purpose.
One of AKG’s latest achievements is Versatile Response analog filter circuitry. It can be found in the D12 VR large-diaphragm dynamic cardioid mic for vocal, bass drum, and bass amp applications.
The newly designed capsule has an extremely thin diaphragm that is especially sensitive to lower frequencies, mated with the VR circuitry and the original transformer used with the classic 1970s-era C414 studio mics. When the mic is phantom powered, one of three switchable active filter preset can be selected to customize the frequency response; these settings are for open and closed kick drum, and “vintage sound.” The mic can also be used without phantom power and delivers the unfiltered response of the capsule.
The new Telefunken Elektroakustik M82 large-diaphragm microphone also incorporates analog filter circuitry, with two switches that act independently to yield four frequency-response settings. These passive circuits are “Kick EQ” and “High Boost,” with the former reducing midrange frequencies centered around 350 Hz and the latter tilting up the mid and high frequencies with a knee at about 2 kHz. With both filters off, the mic can be applied to vocals, guitar amps, and brass instruments.
AKG D12 VR with Versatile Response analog filter circuitry.
The Avlex Superlux PRO-38MKII condenser vocal mic has an internal 12 dB/octave high-pass filter centered at 100 Hz to minimize pickup of stage noise. Its 1-inch gold-plated thin-film diaphragm is very responsive, as well as fostering a well-behaved cardioid polar pattern and a flat, uncolored frequency response.
Mic diaphragms vary in size, thickness, tension, and material – each of which affects the sensitivity, frequency response, and a variety of other characteristics. Audix uses proprietary VLM (Very Low Mass) technology within its OM Series handhelds, based on “a very lightweight diaphragm that allows for extremely fast, accurate processing of incoming signals” that yields extended frequency response with high SPL handling.
The AKG D7 vocal mic employs a specially developed Laminate Varimotion diaphragm – which varies in thickness from center to edge – allowing response tuning within the mic assembly without the use of acoustic resonators. This technology is also used in the D5 vocal and D40 instrument mics.
Audio-Technica AT4081 ribbon with higher output from a neodymium magnet motor.
Traditionally, ribbon technology has been more delicate, and it’s use in live sound was pioneered by beyerdynamic. The company’s recently introduced TG V90r handheld vocal mic uses an ultra-light and thin aluminum ribbon for excellent responsiveness to transients, housed in a well shock-mounted body. The frequency response covers the vocal range, with specifications of 50 Hz to 14 kHz, with high SPL handling and an output sensitivity of -61 dBV.
Audio-Technica holds several patents in this technology, including the Microlinear ribbon imprint that protects dual ribbons from lateral flexing and distortion. The AT4081 provides a higher output level with the use of a neodymium magnet motor structure, and it has the audio quality to be used for recording and the durability for live use.
Ribbon technology is also used in the Royer R-122 Live and Cascade Fat Head II for guitar cabinet miking and similar applications, while the AEA N-22 can be used for applications ranging from vocals to acoustic instruments to cabinets.
Shure KSM313/NE and KSM353 ribbon mics include proprietary Roswellite “molecularly-bonded film” ribbon material, which provides the tensile strength and durability to withstand high SPL applications. These mics are precisely manufactured, with each ribbon frame being optically measured and its ribbon then custom-cut with a laser to fit it exactly – to a tolerance of .001 of an inch.
These manufacturing processes are normal for Shure, notes John Born, product manager for wired microphones. An emphasis on documentation and process control in engineering and manufacturing, consistency, and optimization is central to a philosophy that states “performance shall not change” over the years and manufacturing runs for a particular microphone model – even as internal changes might be made to improve consistency or find substitutes for obsolete components.
With the introduction of the Digital 9000 wireless system, Sennheiser also made changes to its mic capsule suspension. According to the company’s Brian Walker, the new suspension system “greatly reduces mic handling noise while maintaining excellent audio quality.”
Sennheiser’s new mic capsule suspension.
The bands hold the capsule from six posts, offering significant mechanical isolation from the rest of the mic assembly. Sennheiser has also standardized all of its wireless mic capsules to be used interchangeably across the evolution, 2000, and 9000 Series systems, so that an investment in a particular capsule may be separate from the wireless delivery method.
Across a variety of handheld mic brands and models, interchangeable mics heads thread onto the wireless using a 3-conductor, concentric-ring connector that mate with spring-loaded pins within the transmitter body. This innovation allows a preferred mic head to move across a variety of transmitters, rather than the former method of hard-wiring the head into the transmitter.
These are just some of the examples of the ongoing innovations in mic technology. What’s currently available provides many excellent choices, yet I strongly suspect the search for ever more transparent, unobtrusive, durable, and overall great-sounding microphones will continue.
Gary Parks is a pro audio writer who has worked in the industry for more than 25 years, including serving as marketing manager and wireless product manager for Clear-Com, handling RF planning software sales with EDX Wireless, and managing loudspeaker and wireless product management at Electro-Voice.