Recording - February 2018 - 56

LEWITT

LCT 540 SUBZERO

How can a microphone be quieter than silent?
REVIEW BY PAUL VNUK JR.

ustrian mic maker LEWITT has been very busy in the
past few years, growing its ever-expanding LCT line
of recording microphones to include eleven models at
varying sizes, features, and price points. One of LEWITT's other
obsessions is building quiet mics. I mean, really quiet...
Introduced at last fall's AES Convention was the new LCT 540
SUBZERO. If that model number seems familiar, that's because
one of the company's earliest models was the original LCT 540,
essentially a cardioid-only version of the multipattern LCT 640
reviewed in February 2012. Then came the LCT 550, reviewed in
February of 2016: an update of the 540 redesigned to offer an
electronic self-noise of 0 dBA.
And now again in February 2018 (ah, vocal month!) we return
to the 540 moniker as the LCT 540 SUBZERO replaces the LCT
550. The name comes from the mic's claim to offer-wait for
it!-a noise floor below the threshold of human hearing.

That's cold

The LCT 540 SUBZERO is part of the company's studio
line. All LEWITT products are of Austrian design and overseas manufacture; their look, specifications, and build are exclusive to LEWITT. At 6.22" x 2.04" x 1.42" the LCT 540
SUBZERO is housed in the same rectangular zinc alloy
body, finished in both gloss and matte black, as its previous incarnations. Besides looking good and being a LEWITT
tradition, the rectangular shape helps reduce resonances.
The LCT 540 SUBZERO is a transformerless design with all
modern PCB-based electronics. Its capsule is a center-terminated
K67 style with a 1" externally biased dual diaphragm.
As with most of the up-line LCT models, the LCT 540 SUBZERO
offers a trio of silent 3-button controls on its front side, along with
a lighted company logo and function indicators. The left button
switches between highpass filter settings of Linear (off), 80 Hz, and
160 Hz. The right button engages a 3-position output pad with
settings of Off, -6 dB, and -12 dB. The center button functions as
a key lock to prevent accidental changes while handling the mic.
The package of the LCT 540 SUBZERO has been upgraded to the
same one that ships with the LCT 640 TS reviewed in January 2017.
It includes a square plastic composite-fiber Pelican-style briefcase with
56

RECORDING February 2018

one of the company's custom
LCT 40 SHx shock mounts, a
magnetic clip-on pop filter, a
foam windscreen, and a vinyl
pouch.

Let's get lit

The backlit LEWITT logo is
also not just for show. It changes color and status depending
on what function is selected.
White indicates normal operation;
flashing red warns that the mic input
is clipping. If you missed it and clipping has occurred in the recent past,
the logo flashes white and red as soon
as you enter the Clipping History. To avoid clipping, the mic can
be placed into auto-attenuation mode, upon which the logo will light
solid red. Lastly, if the logo is off, it indicates that the abovementioned
key lock has been activated.

Tonight's forecast: subzero

The LCT 540 SUBZERO has a frequency range of 20 Hz-20
kHz, sensitivity of 41 mV/Pa (-28 dBV/Pa), dynamic range of 132
dBA, and maximum SPL of 136 dB without preattenuation. The LCT
540 S is flat and even across the mids; despite its name and lineage, it's voiced differently from the past 550 and 540 models. It
offers a gently de-emphasized low end dropping 2 dB from 150 Hz
down. It has a small 2 kHz bump, followed by a treble boost that
LEWITT says is 5.4 dB centered on 12.8 kHz.
How is the subzero self-noise spec calculated? The mic has
a 90 dBA signal-to-noise ratio and a 4 dBA equivalent noise
level that, like the LCT 550's, is due to Brownian motion: the
random bouncing of air molecules. LEWITT reports: "That 4
dBA is a cumulative value and not detailed enough. That is
why LEWITT chose a more accurate 1/3-octave measurement.
Looking at the corresponding graph on the LEWITT website,
the self-noise is below the threshold of hearing across the
whole frequency spectrum." I have no way of testing this claim
scientifically in my studio... and neither did LEWITT, until their
engineers built a new test chamber of concrete and metal that
looks as if it could safely house the Ark of the Covenant in a

Table of Contents for the Digital Edition of Recording - February 2018