In the early days of recording, it
was all about making live mono recordings of acoustic bands, a bunch
of mics wired direct to tape. Next came the multitrack and recording
evolved into click tracks, isobooths, post processing and mixdown
sessions. Then the digital age showed up. Acoustic recording was
out, sampling and DI was in and everybody’s cousin had a home
But times keep changing. The home studios
have evolved into more sophisticated studios and the bands themselves
have evolved. Now days there are more mic companies than ever. That’s
because studios are doing more micing and less direct. Studios and
bands want to do live, ensemble recording. Even rapping is going
in this direction. Today’s studio is actually recording more
real music, air breathing acoustic sound, than ever before.
But some things never change. Open
up a mic we get two kinds of sound. The first is exactly the sound
we wanted to get, the direct signal from the talent. The second
is exactly the sound we didn’t want to get, the sound from
the room. We usually end up needing a cleaner signal at the mic
and so our goal, as recording engineers, is to figure out ways to
boost the direct signal and cut the room signal.
By following in the footsteps of the
last few decades of recording, we try to get an acoustically dry
signal, as close to an acoustic DI as possible and then perform
the familiar post processing on it to get it into the mix. To do
this, we have to build acoustically dead spaces. To do that, we
have to kill reflections, all reflections.
But, in so doing, we are also throwing
the baby out with the bath water. Who’d have guessed that
some of those hated, hunted and hammered room reflections actually
help make real sound, sound real? Well, in the olden days, recording
was full of this type of “real sound” and today, by
implementing a few acoustic tricks, recording can once again, sound
Mic is a 2 Channel Acoustic Premix
In any room, the mic acts like a two
track acoustic premix: The direct signal is acoustically mixed right
in with the room signature; reflections, echos, reverb and general
room noise. And most of the time, the room signature track is too
loud. Our job is to boost the Signal to Noise Ratio, the (SNR).
To do that we need to either boost the direct signal or fade the
room noise, but usually it is some combination of both. What we
want is an acoustic fader but air faders, like air guitars, don’t
do much for sound.
We boost the direct by getting the
talent to eat the mic and reduce the mic gain back down to zero
VU. But now our talent sounds like a radio DJ and that just might
not be the sound effect the producer wants. In addition, we lose
control on dynamics, plosive and proximity effects. To regain control
we add the wind ball, dial in EQ, compression and limiters and hope
for the best.
Another way to increase the direct
to room signal strength ratio is to change the mic pattern. Start
closing it down, narrow the focus pattern of the mic, stopping somewhere
between cardiod and shotgun. But the tighter the pattern, the more
colored the voice, like singing into a mail tube, and we go back
to EQ, compression and limiters to try to doctor the track into
a semi-real sound. Also moving the mic around the room can come
up with some spots that don’t sound as bad as the others.
But they usually are no where near the studio window.
And all this time, the talent is locked
in a head halo, with the producer saying sweetly: “That was
great, but this time, a little more emotion and a little less movement”.
Despite the best of everyone’s efforts and tricks of the trade
applied to boost the SNR at the mic, all too often the desired effect
for the song is either lost or destroyed.
The other way to get a better SNR at
the mic is to just dump the room. Kill the room and get pure sound
flowing into the mic. Forget EQ, compression and limiters. Just
set the mic up in a soundproof anechoic chamber and one would think
we have the ultimate recording space, essentially it’s acoustic
DI, all direct signal with a -80 dB noise floor. Later, this very
dry signal can be revived by post processing, add some warmth and
depth with a little delay reverb and some sparkle with a spank from
When working in dry rooms, any reflection
is audible and sounds bad. All it takes is one reflection and the
sound we are trying to get picks up a hollow effect. It’s
the Comb Filter effect. This is when the desired signal is combined
with a lower level and time delayed signal, in other words, an early
reflection. The combination imposes a harmonic set of cancels and
adds onto the original signal spectrum which sounds like the direct
signal was recorded at the bottom of a drinking glass. Dry acoustic
recording is very sensitive to the presence of early reflections
(comb filter effect), late reflections (echo), fast repeating reflections
(flutter echo), boundary loading, mode coupling and finally reverberation.
Still, dry recording seems to be the primary tool for today’s
The rule of thumb in a dry recording
studio is “the best room is a dead room.” Engineers
are trained in AE schools and the school of hard knocks to hate
reflections. Engineers hunt them down and kill them (reflections)
with fervor, whenever and where ever possible. One might say that
recording engineers suffer from a mental condition called reflecto-phobia.
It started somewhere in the 60’s when multitracking and post
processing became available. Highly infectious, this impaired judgment
condition reached epidemic levels in mid 70’s spread to nearly
every recording engineer, producer and audio instructor in the industry.
Today, reflecto-phobia is rampant.
Music is proudly recorded in acoustically sterile environments.
Fueled by fears of comb filter coloration, every single reflection,
near or far, that might ever hit a mic has been systematically exterminated
over the last 30 years in recording studios. Most of today’s
so called “live rooms” are now completely “reflection
With the purge of reflections nearly
complete, today’s studio music is now completely composed
out of separate, sterile, acoustically dead tracks. Preparing these
tracks is not much different than being the make up artist in a
sonic funeral director, where dead tracks are fluffed and stuffed
and somewhat brought back to life by the paint and sparkle tools
found in the FX rack.
When people listen to sound, in contrast
to microphones, they generally just listen to what they want to
hear and pretty much dial out the rest. People can be located pretty
far from the talent, compared to a mic, and not even notice the
sound of sound in the room. They just hear the talent. People are
able to naturally tune the room out and focus in on the talent.
The engineer with a mic has to work hard to tune the room out and
focus in on the talent.
A person (as well as other critters)
is a biological signal processor, not an electronic one. We use
a different mechanism to hear than what is built into microphones.
A by-product of our hearing system is that we automatically mix
all early reflections right into the direct signal and end up hearing
one composite “direct” sound. Early reflections are
those that arrive within about 1/30 second following the direct
signal. It doesn’t matter where those early reflections come
from, they just add together (correlation signal detection) in a
way that makes the perceived sound be significantly louder than
the direct signal. This sound fusion process creates a composite
direct signal which has easily more than twice the sound power than
the direct signal alone.
Although it doesn’t matter to
the sound fusion process where the early reflections come from,
we aren’t confused by where the direct sound comes from because
of something called the Precedence effect. We cue in on the direction
of where a sound comes from by tracking and locking on where the
original sound signal comes from. The process of knowing where a
sound comes from is called echolocation.
There is one adjustment to echolocation
that has to be mentioned here; the Haas effect. Very early reflections,
those arriving within 5 ms of the direct signal, will distract us
from knowing exactly where the direct signal is coming from. The
perceived direction of the direct signal is somewhere between the
location of the direct signal and the location of the very early
People like early reflections. Just
step outside, into the middle of a large grassy field, and we can
barely hear ourselves, let alone carry a tune or talk to anyone
else. That’s what the DI (direct inject) version of life sounds
like. Go back inside the house and everything sounds fine and you
can carry a tune or a conversation. We’re made to hear direct
+ early reflections, and to mix them together into one “direct”
sound. And this process helps us hear more easily what is going
The traditional, studio-dead sound
tracks lack life, the quality of sound that makes sound seem to
sound real, natural. Yes, there’s always the “fix it
in the mix” perspective to dry recording. That means lots
of time and money gets spent trying to bring back to life, dead
sounding tracks. But studio recording was not always done like this.
In the early days of recording, the
luxury of dead studios didn’t exist. Engineers had to record
live, entire acoustic bands. They made good records in those days
too. Part of their recording process inadvertently included the
sound fusion process. Their mono mixes were chuck full of delayed
early reflection type signals and there lies the reason they sound
so whole, so much like a real recording of a real sonic event.
In the early days of live band recordings,
1950’s, they had one, maybe two takes and then the session
was over. The idea was to use a number of mics distributed throughout
the group, adjust their position and gain and get a live, hard wired
mix down direct to tape on a mono track. Their goal was to capture
enough signal to recreate the sound that was heard when sitting
in the room. Those days are far from the idea of recording separate
tracks in isobooths at various times and in various parts of the
country and then mixing them together a few months later.
good example of the tail end of the early days recording technique
was in the RCA Victor StudioB in Nashville back in the 50’
and early 60’s. This topic came up during an AES Sectional
presentation on the Quick Sound Field (QSF) recording technique,
held there in 2003. The QSF is a modern way to acoustically capture
sound fusion at a mic. StudioB had finally been renovated but it
wasn’t open to public yet. The room was full of engineers,
a lot of new ones who hadn’t even been in the studio since
it closed and some ole timers who worked there when they were young.
After the QSF presentation was over, the question and discussion
time quickly lead back to the recording techniques that used to
go on in that room.
StudioB is a shrine. It’s enough
to just stand there, inside that room and wonder upon all those
hallowed vibrations. The ones that hit the floor tiles and bounced
off and those that lie buried still in the wall and ceiling tiles.
So many early greats worked and played there. Elvis and the Jordanairs,
Roy Orbison, Everly Brothers, Chet Atkins and many more recorded
in this old RCA Studio B.
The QSF lecture reminded the ole timers
about recording in this room. They talked about the mic setups and
how the band played all together, at one time, one song from start
to finish, direct to tape. And that was how they made records.
This was all well before multi tracking
and mixing capability became available in recording. When multi
tracking came, in the 70’s, StudioB accomodated the growing
interest in this “new sound” of music. The room was
deadened and hosted a small village of iso sound shacks lining the
walls. Eventually Nashville was overrun with recording studios and
StudioB closed. Now it has been renovated back to the glory of its
former years. All the sound shacks are gone now and the room has
been returned to it’s original, one big recording room, configuration.
Back in the early days, the room had
a 3-mic gain and mix to tape Ampex. Later, more mics were added.
There was no isobooths. At best, there were gobos. In this environment,
each mic got signal from every instrument. For example, if there
were 12 mics and 6 talent sources, there would be at least one direct
signal from each talent source arriving at each mic. That means
that there were at least 12 different signal path versions of each
talent source after mixdown. And then the early reflections have
to be added in; floor bounce, glass bounce, other instruments and
The net result after mono mixdown would
be that each talent source would have at least 12 direct signals,
with time delays ranging from 4 ms out to 25 ms, and levels ranging
from zero VU down to -16 dB on the track. And then there would be
the reflections, off instruments, floor, glass and what not, filling
in the mix with even more random time offset signals. In a 12 mic
setup there would actually be captured up to 30 or 40 distinct time
delayed signal paths for each talent source. That qualifies as a
Sound Fusion effect recording.
QSF Takes Shape
It all started in 1983, shortly after
the TubeTrap was invented. A cylinder shaped bass trap was designed
to stand in the corners of rooms. It came with a built-in treble
range diffusion panel covering the front half to keep the room brightness
up. Rotating the Trap acts like a treble control and changes the
brightness of the corner. Bass traps are usually located in corners
because that’s where the bass builds up the most. The TubeTrap
was the first factory built, UPS shippable bass trap.
It didn’t take long before the
bigger studios across the country, always looking to try something
new, started buying pallet loads. The seasoned engineers in those
days didn’t ask questions. Their ears would tell the truth,
if these tubes worked or not. These big studios already had lots
of built-in bass traps and didn’t really need much in the
way of tuning up, except in a few iso or drum booths.
Curiously, it was the treble range
panel that caught their ear. The engineers fooled around with these
acoustic cylinders and eventually set up in a semi-circle pattern,
a Stonehenge, with the dead side of the Tube facing in. They got
what they expected, the room dialed out and inside, that all so
familiar, Studio-Dead. Then they rotated the traps and set the bright
side in, and all of a sudden, they got a sound they didn’t
expect: Studio-Live. The room disappeared and the spotlight hit
The engineers called the factory to
report their discovery and each engineer discovered the same thing.
They discovered an acoustic space they hadn’t heard before
and that sounded good, very good. They dropped a mic inside and
it still sounded good, very good. Eventually the factory replicated
these set ups, measured and analyzed what was going on and reported
it in a series of AES papers. The Quick Sound Field was born.
The first QSF I saw was in a local
studio located near the original TubeTrap factory in Eugene, Oregon,
run by relocated LA engineer, Steve Diamond. We had about 30 Tube
Traps and were busy tuning his live room when I noticed Stonehenge
in front of the window and Steve saying “Check, check, testing
one , two…”. He bolted those Tubes down right then and
they stayed there till the city tore the building down, some 1000
BiMart commercials later.
A short time later at Pierce Arrow
Recorders, in Chicago, engineer/owner Sam Lynn Halonen was experimenting
with his first load of TubeTraps. He called in about how he could
get great horn sounds. Later, he got more instruments mic’d,
including drums, inside the Stonehenge pattern. More recently Sam
used the QSF to remic a dry studio recording of an opera singer
to add life and dimension.
Reports keep coming in, describing
new ways to use the QSF effect to get good sound. The QSF setup
created a Haas saturated track. It created a boost in the direct
and produced a great signal to work with. It cut room so effectively
that it wiped out the need for room acoustics. The QSF produces
the acoustic gain adjustment needed at the mic without destroying
the desired effect for the song. In fact, the effect for the song
is enhanced and can be dialed in. The QSF seems to be a natural
for any engineer who has the chance to work with it.
Finally a cure to lifeless sound has
been found. Inoculation process requires that tracks be recorded
in a Haas Saturated signal, the exact opposite from a Haas Sterile
Signal. With some 30 to 60 random time offset Specular Reflections
accompanying each direct signal, there is no comb filter effect
and the track is completely full of acoustical life, ie, music.
Formerly dead mixes can be remixed through an acoustic process of
sweetening by playing the dry mix through an acoustic package that
creates a plethora of early reflections. Caution, the RT-60 of the
early reflection package needs to be in the range of 1/10 second
and a very early time gap is recommended to be set at about 3 ms.
This cure was discovered when big studio recording engineers started
fooling around with TubeTraps in the mid 80’s, endorsed early
on by Pete Townshend (Eel Pie Sampling Room) and for the last 10
years with Studio Traps by Bruce “You’ve got to hear
on Sound Fusion Effect Recording
During this early period, the ASC TubeTrap
factory got a few calls from engineers who heard about the QSF sound.
One had been doing a radio for many years. He said he developed
a magic black box that was his trade secret. It gave him a voice
edge over everybody. He put a whole bunch of amplitude adjusted
time delays into the box. Fed his mic into one end and got a synthetic
QSF sound (direct + a whole lot of random time offset signals) out
the other end. The time delays matched exactly the QSF window of
about 25 ms. He welcomed us to the club and figured it was time
to let the secret out of his magic “voice-box.”
Another engineer contacted the factory
and told his story how he had hooked 30 some mics up over the top
of a classic opera singer. Each mic was located at a different distance
and angle from the talent. He just added them all together and ran
it out to the house sound system. He said the sound was fantastic
and used the technique many times. He effectively collected some
30 random-time off set signals, all within the 25 ms time window.
Each signal was basically the same signal except for the acoustic
EQ due to the off axis coloration of the voice. And, as the talent
moved around, the sound package didn’t change. The total sound
remained the same even though the signal fed into the different
mics did change. The listener’s brain can’t tell which
reflection is where inside the Sound Fusion effect time window.
Digital reverb was starting be affordable.
The reverb plate was being replaced with a 4 adjustable delay/reverb
returns. When ambience was set tight (300 to 500 ms) and the delays
set shorter (30 to 100 ms) it produces a synthetic ambience, much
like a room. By setting it even tighter and shorter, the Sound Fusion
effect could be generated. But the big advantage with the acoustic
version, the QSF, is that it controls the presence of natural ambience
in the room at the mic while adding close and natural flush of early
reflections into the acoustic mix at the mic position.
Townshend, NED and sampling booths
little while later digital sampling got started. Synclavier was
looking for a Sampling Room and they knew it had to be something
different than a vocal booth. ASC built a QSF sampling booth and
Synclavier loved it. That booth and the Synclavier followed AES
around the world more than once.
Pete Townshend (Who) had heard about
TubesTraps was at a session in LA and ran into Bruce Swedien (everybody)
and asked him about TubeTraps. Bruce had already checked them out
and thought they were all right, he liked them. Pete called the
factory a little while later and before long, he had outfitted his
Boathouse, a small sampling room with non-parallel walls and round
windows at Ell Pie Studios, into a world class sampling room.
was blown away by the sound he got in that room. He wrote the factory
and told us his story. It went something like this: “The Boathouse
was so smooth that no one could hear which fader ran the nearfield
or farfield mics. They sounded the same. For the first time ever,
I had to tape along side the faders, labeling the two mics, so my
engineers could remember which fader was the nearfield mic and which
was the ambient mic.”
The factory asked if he’d consider
endorsing the QSF Sampling Room and he said “normally, no”
but in this case, he’d be glad to, because recording engineers
needed to know about the QSF. And so, three rolls of Hassleblad
negatives later, Pete Townshend became the first star to endorse
the QSF recording technique.
space vocal booth
little later, Rockwell Corp contacted the factory. They were doing
voiceprints for training astronauts. They were working with something
like a 10 open mic studio talkback system, where everybody could
be heard, all at once. Only one problem: There was just one send/receive
channel, in order to keep the weight down. They decided to chop
and sequence the open mic signals so that one transceiver could
carry all signals. Chopping the signal train was not a problem,
but reconstruction was. How to recreate someone’s voice when
you only have 1/10 sampling of the signal? They needed a hot vocal
booth to help them develop a voice reconstruction algorithm.
They chose the QSF system. The ASC
factory built, shipped and even set up the booth. This room was
made out of alternating half round TubeTraps and Plexiglas strips.
The see-through walls created a very open feeling. Rockwell engineers
used the QSF Sampling Booth to get the most room-free, information-filled
version of a person’s voice that was possible. They chopped
it up and figured out an algorithm to reconstruct a person’s
voice chop sequence into a reasonable facsimile of the voice. The
plan worked and the rest is space history.
the QSF space
high performance QSF Sampling Rooms worked great for sampling but
they were a little too fast for live talent work. A standard iso
booth might have an RT-60 of 0.4 seconds and have as few early reflections
as possible. These sampling rooms were running an RT-60 in the range
of 1/10th second and sported diffusion rates of 1000 random, time
delayed, early reflections (distinct specular reflections) per second.
This means the room was very dead and at the same time, very bright.
The acoustic gain produced by a QSF sampling room was about +10
dB above the direct signal. It was a bright anechoic chamber. QSF
vocal or iso booths are still bright but the reverb time is set
slower, in the range of ¼ second, so it is a comfortable
space to work in.
The QSF Stonehenge package was becoming popular and to get the price
down and usability up, ASC developed the StudioTrap, a small diameter
(voice range) TubeTrap mounted on an adjustable shaft with a tripod
base, like a mic stand. There have been improvements over the years.
A hand synch grip was added along with a quieter internal slide
clutch. The diffusing reflector sheet was moved forwards to increase
the top end reflectivity from 6k to something above 7k Hz. But overall,
the StudioTrap remains pretty much today, as it was originally conceived
and is the cornerstone of the QSF effect.
Ed McMahon has probably the best known
voice in the country.And he travelled a lot all over the country.
In between scheduled public appearances, he had to do commercials.
Swedien discovers the QSF sound
During this time we noticed an interview
with Bruce Swedien. It was clear that Bruce was so acoustically
in tune that he probably watched sound run around the room in slow
motion. I wrote him, explained a little about the QSF effect and
invited him to audition it. “Why certainly,” he’d
love to. He’s always looking for new sounds and ways to get
them. He tried it and loved it. After a bit, he volunteered to endorse
the QSF. He said and still says: “I wish everybody could hear
this” because Bruce wants other engineers to get to know the
power of the QSF sound and discover for themselves this new recording
little later, the factory sent a truck load of StudioTraps to join
Bruce at René Moore’s large home in Studio City to
help Bruce make his first mic training video. At the end of that
tape Bruce and I kibitz a while about the QSF Effect. It’s
a great tape and a lot of good QSF techniques are demonstrated.
Bruce continues to ship Red Rocket
his original set of 14 StudioTraps, from session to session, back
and forth across the US just to be sure he’s always ready
to add that little kiss of life, the QSF effect, into his tracks.
The Studios got so beat up, shabby actually, over the years that
the factory offered to replace them, no charge. But Bruce wouldn’t
have it. Nobody touches his tried and true, vintage gear. Eventually,
a fork lift changed his mind and we were able gently repair, update
and refinish his set of original StudioTraps and return them, good
Bruce gets to work in the best live rooms in the world. Like a master
chef, he adds just a pinch of the QSF effect to the already nearly
perfect live room sound. He uses wide spacing of the StudioTraps
and randomizes the reflector positions. He dials in a number of
specular Haas reflections to bring forward and capture the essence
of a live performance.
of us don’t get a chance to work in the best live rooms in
the world. Most of us are lucky to be working in small, home or
barn studios, something less than perfect rooms. Here, we set the
QSF pattern not open, but tight. The smaller the room, the tighter
the pattern, the more intense the Haas reflections, which boost
the live effect and at the same time, the room is blocked even more.
Typical small room recording does very well with only 8 StudioTraps
in a semicircle setup, 4 to 5’ in diameter. The tightness
of the QSF setup is proportional to the strength of the “Haas/direct”
to room reverb ratio.
Recording with the QSF is good for
everybody in the studio. The engineer gets the desired sound while
the talent doesn’t get worn out trying to make it. It’s
easy to find sound you want and the sessions go fast. And there’s
a bonus. The halo clamp got tossed. No more: “That’s
pretty good, but this time, let’s try to emote just a little
more and move just a little less.”
While working in QSF, talent is free
to groove to the music without causing a shift in the sound at the
mic. As the talent moves, all that’s changing is the arrival
time of the various Haas reflections. However, the ensemble package
of direct + early reflections remains at the same level and sounding
the same. As with the early sampling booths, you can’t tell
which signals arrived when, just as long as they are all inside
the Hass time package, it’s all just one sound.
produces a track that needs no riding gain, no limiters, no compressors
and no equalization. Just dig out your favorite omni or ribbon mic,
back away from the proximity effect and go direct to tape, pretty
much no matter what room you are in. And there’s another bonus.
What the talent hears inside the QSF field is exactly what they
hear later in the control room. There are no surprises when recording
with the QSF effect. A QSF track can be processed and mixed just
like a regular dry track. And yes, it will amplitude and delay pan
And so, Jennifer Lopez stopped to say
thanks on her last album cover to the whole crew at ASC. It was
for staying the course and delivering “where’s those
round things?” the breath of live sound, the QSF effect, into
her vocal tracks on the last 3 albums.
Orriel Smith, coloratura, uses a QSF
setup in her home for practice and demo work. She hauls her QSF
to the recording studio to make sure she gets the sound she wants.
aware that the “voice” is mostly air, I like the idea
that StudioTraps create a bright atmosphere to reflect or absorb
the air/tone in a way that is controllable and consistent. The
standard “recording booth” can seem overly absorbent
and airless to me, not to mention claustrophobic. Operatic singing
is based on overtones that are large, full with a ringing high
presence. The feeling of singing within the StudioTraps is that
of being within a “live and active” atmosphere and
is extremely predictable.