Recording - January 2016 - 28

SPL Iron Mastering Compressor

In use
I should start off by pointing out that I am
not a mastering engineer, but luckily Iron is
equally adept at bus work and individual
instruments, both tracking and mixing.
After a few days of use, the Tube Bias
and Rectifier settings can become second
nature as they relate to the overall grab
and feel of the unit; you will find your own
favorites for many sources. On the other
hand, even after 2+ months with Iron, I
am still coming to grips with the SideChain EQ and what sources and styles of
music each setting is best suited for.
As for AirBass and Tape Roll-off, they
do exactly as advertised. Again, how
and where they are used will be a case
by case scenario.

I had great results with fast Germanium
settings on the drum buss with Tube Bias
at High, AirBass in and the Side Chain
on 2. This gave me tight, big and punchy
drums. On the flip side, setting Iron slow
and gentle with a low tube Bias, the
Germanium setting of 220 nF, and the
Tape Roll-Off on, was great for more vintage drum tones.
On electric guitar on a Ryan Adams
American style song, I favored the Side
Chain off, a Medium Bias, The Rectifier
set to Ge/Si and the Tape Roll-Off on.
My favorite use of Iron was as a pair
of mono vocal compressors. Here I liked
digging in deep with the Bias at High,
the Sil setting for the Rectifier and the
Side Chain off, and really hitting into the

Taking Iron To A Mastering Studio
As I mentioned, I am not a mastering engineer,
so I took the Iron on a field trip to spend some
time with mastering engineer Justin Perkins, who
owns Mystery Room Mastering in Milwaukee, WI.
Justin is a former mix engineer who used to work
at the famed Smart Studios in Madison, WI. His
resume includes work with The Replacements,
Tommy Stinson, Gaslight Anthem, Cory Chisel,
and Screeching Weasel, to name a few.
When I went to visit he was just wrapping
up a mastering job for the forthcoming Miles
Nielsen and The Rusted Hearts album Heavy
Metal, due out in early 2016. (Miles is the son of Cheap
Trick's Rick Nielsen.) We spent an afternoon with Justin getting
familiar with Iron and doing some quick masters of various
material, from prog-metal to ECM-style jazz, Americana-classic
rock, and all things in between.
Justin appreciated how absolutely clean the unit was; we jacked
it up to extreme levels with no signal through it and Iron is all but
dead silent. He also liked its slowest attack and release and found
that those settings worked well for jazz and folkier fare, where
you could dig in nicely for weight and fullness. On heavier metal
styles and hard rock, like many mastering compressors, Iron
worked best when set a little faster, but just tickling the meters.
With regard to the Tape Roll-Off, Justin thought it was well
suited for taming sibilant and screechy sources like soprano
sax. On the flip side, he really like the Air part of the AirBass
28

RECORDING January 2016

gain reduction hard-up to 10 dB on
average. This gave a nice high-fi tube
tone that was not quite LA-2Aish but still
vintage and controlled without being too
squashed.
Oddly, the only application where I
did not use Iron much was on my main
mix bus! Primarily that was because I'm
too used to having a standard highpass
style sidechain as well as a mix/blend
control. In other words, I like a hint of
bus compression sprinkled on the mix,
but I like the ability to dial it back.
Conclusion
All of the work that I did with Iron made
it to my final mixes for the album project I
was working on. I have zero reservations
recommending it as a high-fidelity, versatile dual mono or stereo compressor that
will handle most any compression duties
you push into it. The only thing to be
aware of is that it is not a vibe box in the
traditional sense. It does not get gritty and
driven, and its tube tone is on the clean,
opulent, pristine side.
It is not cheap-like most masteringgrade boxes, it will set you back a
healthy $5000 street. Keep in mind,
though, that at $2500 per channel it's
not much different than many high-end
mono tube compressors... and nothing
else out there really sounds like it.
Price: $4999
More from: SPL, spl.info; dist. in North
America by Audio Plus Services,
www.audioplusservices.com

setting, but wished the Air and Bass could be
split and used individually. He worried that in
mastering it may be problematic to offer such
a big low-end stroke.
Overall he was so intrigued by Iron that I decided to leave it with him for a day, so he could run a
whole new master of the Miles Nielsen album
through it and give the band and producers a
choice. His settings here were: Germanium 1 mF
on the Rectifier, Side Chain off, Attack at medium
fast, Release at one click below Fast, Input at unity,
output +8 dB. Threshold was set to 11 dB and
AirBass and Tape Roll-Off were off.
When I came to pick up Iron, Justin only offered one concern
with the unit: the 2 dB steps on the output side. Like many mastering engineers, Justin does not use a console and patches
direct from compressor to converter. He felt that in mastering vs.
mixing, 2 dB steps may be a bit broad, and more work would
need to be done in the box to make minute final adjustments.
As such he felt 0.5 dB steps would be a wiser choice.
The outcome of the story is that in the end everyone
involved chose to go with the Iron mastered version and you
can check out Miles' website for release info sometime in early
2016. Not a bad endorsement!-PV
Recording would like to thank Justin for his input and expertise.
Learn more at mysteryroommastering.com and milesnielsen.com.

http://www.spl.info http://www.audioplusservices.com http://www.mysteryroommastering.com http://www.milesnielsen.com

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