Technology Showcase: The Heads-Up on Head-Worn Mics
Mar 1, 2005 12:00 PM, By Bennett Liles
A new level of acoustical freedom.
Only a few years ago, friends and associates of country music singer Garth Brooks were kidding him about looking like some kind of cowboy air traffic controller, with the head-worn mic he used in live performances and music videos. Times have changed. Now, if any of them are still laughing, they are doing so through their own headset mics.
As audiences have demanded more spectacular visual effects, musical performers have responded by increasing stage action and mobility. Theatrical companies have also expanded their use of head-worn mics, and it seems that aerobics instructors are now born with them surgically implanted on their heads. The marriage of new miniature mic technology, wireless body-pack transmitters, and modern headset materials has catapulted stage vocalists into a new era of freedom, sound quality, and equipment reliability.
Those working on the mixer end of things have also welcomed the advantages that modern head-worn mics have provided. Wireless lapel mics freed the hands of performers, but they also moved the mics down to the chest area, increasing the vital mic-to-mouth distance and reducing gain-before-feedback. When performers turned their heads to sing or talk in another direction, their voices often faded away momentarily. To most live sound operators, the vocalists' hands-free performance wasn't worth the cost in clear voice pickup. Head-worn or headset wireless mics offer the best of both worlds in hands-free performance and gain-before-feedback, with the added characteristic of staying exactly the same distance from the singer's mouth no matter which way the head is turned or how mobile and active the performers are onstage.
Head-worn mics have become much more than just a tool for stage vocalists and aerobics instructors. Now, it's not unusual to see them used by hosts and guests on interview sets and talk shows. ESPN commentators have found that in situations where they and their guests are in front of live studio or field audiences, the very high gain-before-feedback that these mics offer makes the PA mix easier to maintain. The broadcast mix also sounds much less reverberant than when live sound reinforcement is used with lapel mics. Even lighting directors have been freed from the old curse of mic boom shadows. It seems that with head-worn mics, everyone on the production team gains something.
Head-worn mics offer greatly enhanced mobility when they are used with the same body-pack wireless mic transmitters that have been used with miniaturized lapel mics. Of course, the miniaturization has necessarily included the mic cable connectors that attach to the body-pack transmitter, and in these connections there is a far wider range of connector types and styles than just the ubiquitous XLRs. To add to the confusion, many of the same connectors are made by various manufacturers and have several different names. The most widely encountered connector for small, head-worn mics is the mini-XLR, sometimes known as the Tini-QG or TA4F. The “4” in this designation denotes the number of pins, similar to the way the A3M and A3F indicate the three pins in a standard XLR mic cable connector. The wiring pin assignments for mics made by Shure are representative of the way most (but not all) of the head-worn mics are wired. These have pin 1 shield, pin 2 bias voltage, and pin 3 audio. Pin 4 has a 20kΩ resistor to ground, which is jumpered to pin 3 when used with condenser mics. With the right light angle, careful examination of the face of the connector will reveal these numbers next to their respective pins.
The four-pin HRS connector, manufactured by Hirose, is considered to be one of the more durable types, favored by performers whose stage activity tends to send improperly secured body-pack transmitters flying. Chances are that with the HRS, the mic transmitter will be destroyed before the connector shorts out or breaks circuit. The pins are designated in the typical way; for example, the HRS4F is a four-pin female. The HRS features brass strain relief and a quick-release, pullback locking ring. Popular among dynamic head-worn mics is the B-lock mini connector, which allows a 1/8in. mini audio connector to be secured with a screw-lock. Lemo connectors can also be found on many models, particularly the S-series Lemos with hermaphroditic keying. Each connector is half male and half female so that they can be blind-mated or connected without the need for visual alignment.
Among the latest advances in head-worn mics are interchangeable mic capsules with selectable pickup patterns. Among these, the unidirectional and omnidirectional capsules each have their own advantages and disadvantages, depending on the specific application.
The unidirectional capsules take the gain-before-feedback spec to the limit, which is desirable in high-background noise environments or on stages where the sound level in floor monitor speakers is very high. In fact, many performers using high monitor levels have switched to using ear monitors instead of floor monitors onstage. This solution takes the monitor sound directly to the performer while allowing the voice signal to be picked up within an inch of the performer's mouth. This is the ultimate in avoiding acoustic feedback. But the ear monitors also allow performers to have the choice of using an omnidirectional mic when it suits their purposes.
So, with gain-before-feedback as a priority, why would anyone want to use an omnidirectional head-worn mic at all? Even among head-worn mics, omni's have their advantages. One of these is derived from the fact that head-worn mics are so close to the vocalist's mouth that breath popping can be a problem. Sound experts have long known that omnidirectional mics are less sensitive to breath pops from the “B,” “P,” and “T” sounds. This is why beat reporters have used ElectroVoice RE55s and EV635s for years, even when they are standing beside noisy highways in live shots. Omnidirectional mics also display less of a proximity effect than directional types. This is the bass boost that unidirectional mics tend to exhibit when they are used close to the mouth. Of course, wind comes not only from the performers' mouths, but also from the ambient air, and the same breath-popping rejection advantage that omnis show also reduces ambient wind noise. Head-worn mics are in constant motion, and the omni capsules have proven their worth in generally picking up less cable movement and bumping noise when used this way. Many of the booms used with head-worn mics are extendable and can be slightly shortened if breath popping becomes a significant problem.
The choice between condenser and dynamic models can also be mission-critical. Among the condenser models of head-worn mics there is a wide variety of pickup patterns and frequency response specs. For the ultimate in frequency response, the condenser models can't be beat, but their requirement for phantom power in a small, mobile body-pack transmitter can complicate things slightly and reduce battery life. The condenser types also don't tend to handle breath-popping problems as well as the dynamic capsules. Dynamic mics traditionally have been known for their ruggedness, and the head-worn dynamics are no exception.
DON'T SWEAT IT
Headset mics have introduced a new problem, but the solutions to it have been inventive. A high-energy performer under hot lights is going to sweat, and this perspiration runs off the side of the face, down the mic boom or stem, and into the mic capsule. This flood of saltwater into the mic element can be fatal to the mic's function. Many of the boom designs have included a “drip loop,” a concept borrowed from plumbers and cable TV installers, to divert perspiration away from the mic's pickup capsule. The sweat runs down the loop and, since it will not climb the other side of the loop, it harmlessly drips off prior to reaching the mic element. As an added safeguard, some designs include a small sweat bead similar to a plumber's grommet that fits around the stem just ahead of the mic element. Some models, such as the Sennheiser MKE2 Gold with its Umbrella Diaphragm, are advertised with anti-sweat features.
Mics are usually anchored with ear loops and worn like a pair of glasses. For more active performers, there are rigid bands that encircle the back of the head and use elastic bands to go around the ears. Theatrical uses have required some custom headset creations using floral wire. These may be used with hats, headdresses, bald-caps, and even through hair. With these arrangements, the mic cable is run along with the floral wire and fastened firmly to it with heatshrink or rubber tubing. If heatshrink is used, mild heating will form a tight fit around the floral wire and mic cable. A small bit of slack in the mic cable can be made as a drip loop. Be warned, however, that a performer who wears a hat with a headset mic may sound substantially different with the hat on from how he does with the hat removed. Experiment with this ahead of time.
CURRENT MARKET SAMPLES
Head-worn mics have been around long enough and have become popular to the degree that there is now a wide variety of respectable products in this market. Based on the aforementioned considerations, the perfect match of mic to mission can be made.
AKG offers the C 477 WR featherweight as the head-worn version of its CK 77 WR, which the company claims is water- and perspiration-proof. This model uses a dual-diaphragm design in which the output is summed in such a way that mechanical noise from rubbing on clothing and such is minimized. The boom features a thin foil drip loop, and the capsule is hermetically sealed to prevent any water or perspiration from entering the housing.
The C 477 WR uses a thin steel band to span the back of the performer's neck. This band can be bent to conform to the shape of the head and neck, thereby making a custom fit to anchor the mic in place. The mic is available in left- or right-side versions for the mic; it comes with either stripped and tinned leads or a Switchcraft connector; and it can be bought in either black, white, or beige flesh-tone colors with matching foam or wire mesh windscreens. An earlier version had a small hole in the capsule to equalize ambient pressure, but in the WR model, AKG has applied a sealed cavity that can internally expand or contract with pressure changes and keep the capsule sealed against moisture. The company has applied for a patent on this design. Currently, this model can be found for around $400.
On the lower end of the price range in professional head-worn mics is the Audio-Technica ATM73a. This mic features a cardioid pickup pattern in a condenser-style diaphragm, requiring phantom power from 9V to 52V at 9mA supplied by a AA battery. The frequency response is specified at 60Hz to 15kHz with a representative sensitivity of -56dB. The mic weighs in at about 1oz. The connector is an XLRM type with the inline AT-8530 power module (which contains the AA battery) on a 3ft. cord. The maximum input sound level is rated at 135dB SPL. The product is also available with a four-pin HRS connector and in an unterminated configuration. It currently sells for slightly more than $150.
Available early 2005 is the Audio-Technica AT892 MicroSet omnidirectional condenser head-worn mic. The MicroSet utilizes a .09in. diameter condenser capsule for applications requiring minimum visibility. Intended for church/house of worship, lecture, broadcast, or theater applications, the mic is available in either a non-reflective black or theater-beige finish. Various terminations are available to work with Audio-Technica as well as other manufacturers' wireless systems. Accessories include two windscreens, two element covers, a cable clip, and a protective carrying case.
Countryman Associates bills its condenser, phantom-powered E6 as the smallest, lightest, and least visible head-worn mic presently available. The E6 is indeed tiny, only slightly larger than the nearly invisible mic boom that clips around the performer's ear. With 50Hz to 20kHz frequency response, it provides truly high-fidelity vocal sound. The product is available in omni, cardioid, and hypercardioid models, which can be bought in hard-wired or wireless versions. The E6 can also handle high sound pressure levels with an SPL spec of up to 145dB in the high sound level model. The mic and boom are available in black, light skin color, and cocoa colors. The hard-wired model can be purchased with a standard XLR connector containing a preamp, and the wireless version is available with either pigtails for customer modification or any number of specialized connectors to suit many present wireless body-pack transmitters. The E6 weighs only .07oz. The product is available for less than $400 and includes a carrying pouch, belt clip, set of three protective caps, and a windscreen.
Clockaudio's CMH2000 lightweight head-worn mic offers a flexible boom arm and perspiration drip barrier. This model features an omnidirectional capsule with a frequency response of 30Hz to 18kHz and a maximum SPL specification of 115dB. The condenser capsule is powered by 1.5V to 9V DC, and the units are available in either black or beige. Each weighs approximately .9oz. The hard-wired mics come with 55in. of mic cable with an open end for attachment of any type of sound connector.
Crown Audio now offers the CM-311A and CM-311AE mics for stage performers who need high ambient noise rejection. The condenser mic has a cardioid pattern and high SPL rating (more than 140dB) and includes a pop filter for distortion-free, high-level singing. The design relies primarily on a pair of heavy-duty ear loops to hold the mic in place. The CM-311A is a hard-wired version and includes an XLR connector extending from a battery belt-pack that includes an on-off switch and a “mic on” LED. The CM-311AE is available with pigtail cable for attaching the appropriate connector for a wide range of wireless mic body-pack transmitters. The manufacturer notes that XLR connectors may not be used on the CM-311AE. The mic housing is high-impact plastic, and the headband is a thin steel wire that may be bent to best fit the performer's head. The frequency response is rated at 50Hz to 17kHz, and the purchase price is around $200.
DPA Microphones markets the DPA 4066 and DPA 4088 head-worn mics, differentiated primarily by their polar pattern characteristics. For all of the considerations previously discussed, the choice of the 4066 or 4088 will be made to suit the expected performance conditions and the preference of the performer and crew. Both of these products feature a metallic band that wraps around the back of the performer's head and twin ear loops for additional stability. Maximum sound pressure level is above 140dB on these condenser mics, and they can be powered by common 48V phantom. The cable, connector, and mic weigh about .5oz. The 4067 is a low-sensitivity version of the 4066, allowing use with a 3V power supply.
Lectrosonics offers the HM162 headset mic featuring an over-the-ear and around-the-head band with a flexible mic boom. The unit contains a bidirectional, dual-element capsule with an adjustable elastic neck band. Available with locking micro and five-pin connectors, the HM162 will work with a variety of Lectrosonics body-pack transmitters. The actual bias voltage range is 1.3V to 20V DC. The maximum sound pressure level is 120dB, and the frequency response is 200Hz to 6kHz. The HM162 is available for about $175.
Mipro has introduced the MU-55HN and MU-53HN head-worn mics available with mini-phone plug, mini-XLR, or Switchcraft TA4F connectors. The models are differentiated by their pickup patterns. The MU-55HN has the omnidirectional capsule, and the MU-53HN has the unidirectional pattern. The cable clamps to the headband so that when the capsules are changed, the cable can be unclipped and replaced. Capsule shaft is fully rotatable and may be adjusted for different lengths. Both units are available in black and beige and respond from 40Hz to 20kHz ±3dB. Maximum SPL is listed at 145dB. Cable length is 55in., and each model weighs .8oz.
As a part of its Airline series of wireless mics, Samson offers the AH-1/QV vocal headset transmitter with a unique design feature that actually incorporates the transmitter into the headband itself rather than having it be worn on the belt. This eliminates any problems with compatible connectors between the mic and transmitter because both are part of the same physical unit and are positioned a mere inch or two apart. The system operates in the 800Mhz range and runs on a single AAA battery for up to 14 hours.
Sennheiser's entry into the head-worn mic market includes the HSP2 and HSP4 mics. The HSP2 is the omnidirectional model, and the HSP4 has the cardioid capsule. Each has an integrated, detachable windscreen and a .03in. diameter fully adjustable mic boom. Each model is available in six variants of connector and color. The mic boom can be attached to either side of the headset. The frequency response is 40Hz to 20kHz, maximum sound pressure level 150dB, and the operating voltage range for these condenser capsules 4.5V to 15V. The weight of these units, without the cable, is .3oz.
Shure brings to the market its WH30 electret condenser mic. The capsule is unidirectional for maximum feedback rejection and has a frequency response of 40Hz to 20kHz. The mic is mounted on a flexible gooseneck, and the wire frame adjusts to any size. The integrated elastic headband secures the headset for high-action performers. The unit also features a shock mount for noise insulation and a snap-on windscreen. Two versions are available — the WH30TQG with four-pin mini connector for $170 or the WH30XLR hard-wired, standard connector version with 10ft. cable and inline preamp for $278.
Special Projects bills its SP-H2O heavy-duty head-worn mic as a waterproof design. The mic has a rubber-coated steel headband and detachable cable. The polar pattern on this electret condenser mic is bidirectional, the frequency response is 100Hz to 15kHz, and the maximum rated SPL is 120dB. The thick ear loops and elastic rubber headband offer a solidly anchored headset for very active performers. There is also an inline battery module available as an optional extra. The mic lists for about $200.
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Bennett Liles is a freelance television production engineer and audiovisual technician in the Atlanta area. He specializes in government video production, distance learning, and videoconferencing.
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