February 11, 2013, by Gary Parks
When a company has a great vocal microphone, the first question is “where’s the wireless version?” After Earthworks released the SR40V hypercardioid vocal microphone a year or so ago, that very question soon arose – both from users and wireless manufacturers.
The result is the WL40V vocal head for handheld wireless transmitters. Integral to completing the project was a significant technological challenge: how to retain the microphone’s frequency range, transient response, and other audio characteristics when a wireless link is substituted for copper between the transducer and mixer preamp.
A wireless transmission begins with the audio signal from the transducer, processes it with either analog or digital technology, modulates it onto an RF carrier wave, which is then demodulated and converted back to analog audio (or sometimes remains in the digital domain) before the signal exits the receiver bound for the next audio device.
To optimize the WL40V head’s response through a wireless channel, Earthworks concentrated on presenting the transmitter circuitry with a well-controlled, very flat audio signal across the full audible spectrum, and properly matching the amplitude of the microphone output to the input parameters of the transmitter. The consistency of the frequency response throughout the mic’s polar pattern was also a critical element.
By presenting the best possible signal to the wireless link, the only coloration introduced is a result of any audio anomalies within the wireless itself. And when coupled with the highest quality, most uncolored wireless systems, the signal that reaches the mixer retains the transparent sonic character of the wired version – as borne out by listening tests.
Founded in the late 1980s by David Blackmer (also the founder of dbx), Earthworks was first know known for its measurement microphones, used for testing the response of audio systems and in live settings for tuning concert arrays.
The WL40V head works with a variety wireless transmitters using 1.25”/28-thread-pitch mating. (click to enlarge)
The company, now under the direction of David’s son Daniel, began developing performance mics over the past decade, with the SR40V being the first vocal microphone, released in later 2011 after several years in the development and field-testing phase. The wireless version started development soon after, and was released this past fall.
Because the wireless head is basically the same microphone transducer and electronics, describing the characteristics of the wired version is a good starting place. The SRV40V uses a relatively small (9.7 mm) diaphragm, because of its desirable response characteristics which include higher dynamic range, wider frequency response (especially in the high frequencies), and high SPL handling.
To achieve a highly accurate impulse response with a minimum of ringing and resonances, Earthwork engineers optimized the tension on the diaphragm, achieving a noise floor of 22 dB A-weighted while producing an impulse that goes from zero to full signal and back to resting state in a bit over 100 microseconds – and with most of that action happening virtually instantaneously. What that translates to is an accurate reproduction of the finest details of the source audio.
The polar pattern is hypercardioid, with a very uniform frequency response throughout the coverage pattern; for example, the frequency response from the side at a 45-degree angle is almost identical to the on-axis response.
The SR40V has deep attenuation at the rear of the polar pattern for excellent gain before feedback, and a smooth and well-controlled back lobe.
The proximity effect is smooth and not overly bassy, even when used close up. At a distance of several inches, the audio response is still natural and not “thin” and lacking low frequencies as I’ve found with other vocal microphones.
As recommended by Earthworks and confirmed by my experience, using the SR40V flat with minimal to no EQ adjustment provides exceptional results.
The construction is definitely roadworthy, with the capsule being physically isolated and shock-proof, and the electronics all hardwired and securely held for long-term durability. A series of mesh-screened tuned ports are located just below the windscreen to further control any capsule resonances. The windscreen is rugged and also as acoustically open as possible, and can be removed for cleaning as desired.
The time domain of the audio signal is a very important part of the microphone’s conceptual design, because the ear is highly sensitive to phase and time differences to localize a sound source and to have it perceived as “live.” This is the main reason that the frequency response is extended flat out to 40 kHz, because those frequencies above the normally accepted limits of hearing as far as pitch is concerned still have a perceptual effect.
Polar (above) and impulse response of the SR40V. (click to enlarge)
For the same purpose, no capacitors are used in the electronics to interfere with the phase relationship. Each mic is hand-tuned and its electronics handwired, with multiple response measurements taken during this process.
The wireless version maintains the hypercardioid polar pattern and frequency response of 30 Hz to 40 kHz, +/-2 dB at a distance of 1 foot. Maximum acoustic input is 135 dB SPL.
To minimize the possibility of overloading a transmitter’s circuitry, the output of this version is attenuated approximately 10 dB within its internal electronics, compared with the wired version.
As a condenser mic, it requires The screened tuning ports circling the bottom of the windscreen are retained. The entire head assembly weighs a little over 3 ounces.
The Real Deal
In performance, the wired and wireless versions of the Earthworks SR40V are virtually identical to the ear. Using a Shure ULX-D digital wireless system as the base, and setting the levels equal, both spoken word and sung vocals retained the same audio quality and transparency when switching between them. No change was noted in the off-axis response or gain before feedback.
With an analog Shure UHR system, there was a slight anomaly centered around 250 Hz in the wireless version, which a wide-Q, -3 dB equalization corrected. This effect may have been introduced during the wireless modulation or demodulation. No EQ adjustments at any other frequencies were necessary to match the responses.
I also supplied the SR40V and WL40V for evaluation by Kevin Windrem of Sweet Spot Sound (Grass Valley, CA ), and he summarized his observations for me. Kevin had not yet tried the Earthworks microphone, and his favorite vocal microphone is the Neumann KMS 105, and he notes that unlike most vocal mics, it has no presence peak.
“Most vocal mics with a ‘mechanical’ presence peak are so ragged that they can’t be removed with EQ and the ‘gnarliness’ remains,” Kevin notes. “Not so with the SR40V. It’s presence peak is smooth and well controlled, so removing it with EQ is simple. I can make the Earthworks sound substantially the same as the KMS 105 with modest EQ – or visa-versa. Both the wired and wireless versions have a very consistent on-axis versus off-access response.”
Both versions were also used at the main arena stage for the 2012 Monterey Jazz Festival. Nick Malgieri of McCune Audio was the house engineer for the three-day outdoor event. The wired version was used for lead vocals during Eddie Palmieri’s show on the first evening, with the vocals clear and present throughout the show. Nick applied no EQ on the mic other than a high-pass filter at approximately 150 Hz to control stage bleed.
The SR40V was also used as the talk mic for Gordon Goodwin”s Big Phat Band, and during the Monterey Jazz Festival On Tour set. The wireless version was the announce mic for all the shows.
After the shows were over, he shared his impressions: “I feel comfortable saying that the Earthworks mic is easily in the same league with my other favorite vocal mics (Neumann KMS 104, Audio-Technica AT 4055, Shure KSM9). I found it to be transparent and airy, without any of the treble coloration often associated with other mics of the genre.”
The SR40V and WL40V both provide studio-quality, detailed vocal reproduction in a live setting. The attention to design and manufacturing details makes this a superior microphone, and in the tests it lived up to its ambitious specifications. And both carry a 15-year limited warranty.
This quality does come at a price – the SR40V wired vocal mic lists at $1,499, while the WL40V wireless version is $1,399. But if you’re serious about achieving the best live audio reproduction, with an extremely well-behaved and transparent microphone, it is worth the investment.
Note: To check out comments from the community as well as to ask questions about the SR40V and WL40V, go to the Road Test Forum here on PSW.
Gary Parks has served as marketing manager and wireless product manager for Clear-Com Intercom Systems, and also handled RF planning software sales with EDX Wireless in addition to doing loudspeaker and wireless product management at Electro-Voice.