Recording - March 2016 - 44

Reviews by Mike Metlay
Fostex is not necessarily a name that novices in the recording world
would think of immediately amid the constant bombardment of new products from other firms, but experienced engineers know better. The greatsounding and nearly indestructible T20 has been famous for over 30
years, and many of the best studios in the world have a trusty set of Fostex
T50RP cans sitting in the place of honor at the console.

The mk3 RP phones all feature low-profile earcups
that swivel a small amount for a comfortable fit, sliding on exposed metal rails to accommodate different
head sizes, with a wide and well-padded headband.
Those exposed rails are a Fostex trademark, along
with the exposed fabric-covered earcup cabling in
contrasting orange: there's no mistaking an RP phone
for anything else out there. While they're technically
circumaural phones, the very low profile and oval
shape of the earcups means that they rest ever so
slightly on the ears in use. They're not at all uncomfortable, but might be a little odd to engineers who
are used to "ears floating somewhere inside a big
hemisphere of air" earcup designs.
The spec sheets of the three phones are almost
identical. The T40RP mk3 has a sensitivity of 91
dB/mW and a frequency response of 20 Hz to
35 kHz, while the other two models are rated at
92 dB/mW and 15 Hz to 35 kHz. As is common
with headphone specs, the frequency responses
are listed without tolerances, and it takes only a
little bit of listening to hear that the 20 and 50

Fostex RP Series mk3: T20RP, T40RP, T50RP
Similar looks-beautifully different sonics
Over the 14 years since its introduction, Fostex has continuously revised
the T50RP, and added other headphones to the RP lineup. RP stands for
Regular Phase, and refers to the unique drivers in Fostex cans. Rather than
a conventional dynamic driver (essentially a small speaker and voice coil),
the RP driver is a film of polyimide plastic that's been etched with copper
foil and stretched across a rectangular frame with neodymium magnets.
This idea of metal-etched plastic film as a transducer has been around for
decades, in ribbon tweeters (not to be confused with the AMT transducers
in speakers by ADAM Audio and others) and even in ribbon microphones
by Shure and Sandhill. Because polyimide is so light yet sturdy, it has good
transient response and exceptional power handling capability without being
as fragile as a conventional pleated-metal ribbon. At least in theory, this
should make it a excellent mechanism for headphone drivers, and theory
has been borne out for decades in the RP phones' excellent track record.
I was lucky enough to be sent a set of three different RP phones that
make up the new mk3 lineup, and not having used a set of T50RPs myself
in over a decade, it was quite the treat.
Alike and different
Some companies out there differentiate between headphones by subtle
voicing tweaks-this headphone is voiced very flat, while that one is a bit
heavier in the bass or more forward in the mids. Others set up product tiers
by offering different external options and accoutrements-perhaps one headphone will have a non-detachable cable, while a more expensive one will
have a detachable cable, and a still costlier one will come with a selection of
cables for different uses, as well as replaceable earpads or headband cushions. The RP mk3 series leans much more toward the former; the three phones
sound quite different, but are virtually identical in appearance and features.
How identical is identical? The only way to tell them apart is by their product numbers, or by a very close look at the outside of the earcup underneath
the headband swivel. At first glance, the horizontal louvers there look alike,
but a bright light reveals differences between the three models' designs. On
the T20RP mk3, the louvers are open and you can see the back of the RP
transducer inside; on the T50RP mk3, they're open but have some kind of
opaque internal screening; and on the T40RP mk3, they're sealed shut.
By the simple expedient of molding the louvers in place, then either cutting
holes there or not, Fostex can turn one earcup mold into three very different
headphones. The T20RP mk3 is called "Open for Deep Bass", the T40RP
mk3 is "Closed for Focused Bass", and the T50RP mk3 is "Semi-Open for
Flat and Clear Sound".
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RECORDING March 2016

sound very different within those limits; more on
that later. All other listed specs are identical: 50Ω
impedance, weight of 315 grams (about 11
ounces), and an absolutely insane 3000 mW
maximum input power; while Fostex cautions
against high listening levels, RP phones are
famous for laughing off levels that would shred
any other headphone.
All three headphones come with two cables: a 3meter black cable ending in a 1/4" TRS plug, and a
1.2-meter orange cable that ends in a miniplug. The
cable connects to the left earcup with a miniplug that
has a 90º twist-lock collar; the orange cable has this
on both ends for simplicity's sake. The phones don't
come with carrying cases or other accessories, but if
I had to choose the best possible extra to include, a
pair of interchangeable cables would be it.
Oh, and this is a good place to mention another thing that's identical between the three mk3 RP
phones: the price. These phones are not intended
to be "entry-level/mid-level/pro-level"; they're
three different flavors of the same quality ice
cream to suit different palates and needs. So let's
get tasting, shall we?
The T20RP mk3
The T20RP mk3 is an exception to the widely held
belief that "closed means more bass and open means
less". Despite being an open design (not obtrusively
so, but you wouldn't want to use it in a tracking room
near open mics), it has by far the most bass punch of
the three headphones. The low end is powerful yet
clear, not at all woofy, and quite seductive.
On modern mixes that have had their dynamics
noticeably limited, the T20RP mk3 presents a believable balance, but when you go back to older albums
with softer mixes and a lot more dynamic range, you
immediately notice how far forward the low end is
with respect to the mids; lead vocals can sound positively distant in comparison to the bass and kick drum.

Table of Contents for the Digital Edition of Recording - March 2016