Electro-Voice RE20

By Andrew Thompson

History

An industry standard and a visually distinctive fixture of the broadcast studio, the Electro-Voice RE20 is a large-diaphragm dynamic microphone introduced in 1968. It was the fourth offering from Electro-Voice to feature the company’s “Variable-D” technology and followed the RE15, a small diaphragm dynamic that had gained a healthy following in the broadcast sector. The RE20 was devised by EV and engineer Tom Lininger to deploy Variable-D in a package that would compete with the performance of condenser microphones.

Construction

All pressure gradient microphone designs are subject to some degree of what is called proximity effect – an augmentation of low-frequency sensitivity relative to the rest of the audible spectrum that increases with proximity to the recorded source. Variable-D designs compensate for this by means of a special acoustic labyrinth – a series of ports along the microphone’s barrel that correspond with pickup areas on the capsule assembly that are tuned to respond variously to different frequency bands. The intended effect is that the microphone can be extremely closely addressed without an appreciable increase in bass response.

The RE20 is a top-addressed moving-coil dynamic microphone with a fixed cardioid pattern. The mic is large for a dynamic, the steel chassis measuring 216.7mm by 54.4mm at its widest point, and weighs a healthy 737g. The mic is transformer-balanced, and signal is carried via the standard 3-pin XLR connector with the positive signal on pin 2.

The RE20’s spec sheet claims a frequency response range of 45Hz – 18kHz. Sensitivity is 1.5 mV/Pa or around -56dBV; perhaps slightly above average for the class of microphone.

Since its introduction, the RE20 has been issued in a number of different finishes and variants, such as the PL20, which was functionally identical but marketed at instrumental applications and featured selectable impedance, and the RE27N/D, which included a neodymium-alloy magnet and re-engineered diaphragm resulting in increased sensitivity and extended HF response and sensitivity.

Response

On-axis sensitivity hews closely to zero between 80Hz and 300Hz, becoming slightly negative though flat between 400Hz and 1.5kHz. Bass response drops off below 80Hz, reaching -5dB slightly below 40Hz. Engaging the high-pass filter produces a modest decline in sensitivity below 400Hz, becoming steeper below 150Hz and reaching around -8dB attenuation at 50Hz. The midrange is characterised by two small dips, one reaching around -2dB attenuation centred on 2kHz and the other about -3dB around about 4.4kHz. The 5kHz-6kHz is nominally neutral, and a shallow high-frequency “hump” is evident between 6kHz and 12.5kHz, although reaching no more than +3dB. Response crosses into negative territory at 12.5kHz, reaching -5dB by 20kHz. Engaging the low-pass filter introduces a 4.5dB drop in sensitivity between 400Hz and 100Hz and a further -5dB of attenuation between 100Hz and 50Hz.

Polar response is reported as being, broadly, a classic cardioid pattern below 700Hz, becoming slightly hypercardioid (with null points at 210 and 150 degrees attenuating around -27dB) above 700Hz. Off-axis attenuation is a fairly consistent -5dB at 90 degrees.

Rear rejection is a fairly stable -16 to -18db between about 140Hz and 6kHz. Attenuation becomes relatively moderate between 7kHz and 18kHz; as little as -13.5dB at about 12.5kHz. Attenuation greatly increases below 140Hz, reaching about -23.5dB at 70Hz before moderating somewhat to about -20dB at 50Hz.

Whatever extent to which the RE20 was realistically expected by its designers to compete directly with studio condensers of the day, its on-axis response – close to neutral between 80Hz and 6kHz, with a gentle high-frequency boost in the presence region – makes a plausible case for its ability to at least promise a respectable substitute. One might expect a touch more air above the 10kHz mark in a condenser design, however, along with an audible difference in transient response.

Uses

The core component of the RE20’s enduring popularity is its reputation among vocalists and producers of vocal performance, and it’s likely that the microphone’s claim to eliminate proximity effect is a major reason for this. Performers who prefer to closely address the microphone should be able to do so without needing to apply compensatory equalisation, and the destructive effects of plosive consonant sounds should be ameliorated. In non-acoustically treated environments and other settings such as live performances, radio or podcasting studios where background noise can compete with or impair the quality of recorded material, the ability to closely address the mic and hence maximise the dynamic range of the recorded material can be crucial in obtaining satisfying results, which goes some way to explaining the RE20’s celebrated status in the radio and podcasting sectors. It’s fair to note, however, that performers who are accustomed to using proximity effect creatively to enhance the fullness or intimacy of a vocal performance may not appreciate the loss of that facility in the RE20.

Similarly, the linearity of the RE20’s frequency response will not appeal to those looking for a flattering or hyperreal character from a microphone, though by the same token, the microphone should provide a fair representation of all types of voices.

This sense of transparency is reflected in the consistency of that response between on- and off-axis points of address. Response at 180 degrees features a gentle attenuating slope below 400Hz and centres its relative high frequency “boost” in the 10-15kHz region rather than 6-12.5kHz, but otherwise looks very similar to the on-axis plot. In contrast to many other microphones whose off-axis response is appreciably darker than their on-axis response, the RE20 may sometimes sound slightly brighter off-axis, albeit somewhat quieter. Combined with the fairly moderate level of attenuation, this effect recommends the microphone for ensemble spoken performances, where the off-axis response of the microphone can be used to provide a sense of space without compromising intelligibility.

The RE20’s immunity to proximity effect also recommends it for close-miking instrumental performances of all kinds from the baritone range upward, with the caveat that its modest sensitivity may disadvantage it on very quiet sources. A condenser design, or indeed a microphone with a smaller diaphragm, may of course also be preferred for capturing fast transients.

In complex live performance applications, the RE20’s fairly forgiving polar pattern should be taken into account – a hypercardioid design may sometimes be preferred – although the microphone’s hum-bucking voice coil should help protect its signal path from magnetic interference. Otherwise, its neutral frequency response makes it a tempting option for any information above around 80Hz. The lack of proximity effect means acoustic sources can be addressed as closely as is necessary, while its off-axis response should produce a natural-sounding ensemble sound on sufficiently energetic instrumental sources.

Andrew Thompson

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