||Once upon a time there was an empty
The room we chose for Sub Central is approximately 2/3 below groundlevel.
The window's bottom is just about at the outside groundlevel. Due
to this underground location, the room is very well isolated to noise
transmission. The size of the room is 100 m2 (square meteres) or 12.5
x 8.0 m, height is 3.4 m. (492" x 315" x 134" LxWxH).
The name "Sub Central" was created on our way home from
a German Home Theater expo. "Central" is based on the German
word "Zentrale", because the theater is built in the basement
of a phone company building, called "(Telefon-)Zentrale"
in German. As it is in the basement and therefore below the "Zentrale"
itself, we added the latin term for "below" in front of
"central", resulting in "Sub Central". Of course,
the "Sub" is also an hommage to the two 18" subwoofers
we have in use...
This again shows the room as it was when we started.
On Wednesday, January 17, 2001 at 8 a.m. we first set foot
in the almost empty room:
"One small step for mankind, one giant leap for us..."
A lot of construction material had to be unloaded from several trucks
||At the end of the first day, we already
had constructed the outline of our new home theater. We built some
artificial walls in order to create "a room within a room".
The outer wall was made of heavy 6 x 10 cm (2 3/8" x 4")
wooden planks as was the bottom and top lining. Construction went
fast due to the air-pressure driven "wave nailer" tool we
After two days, the outline of the new room was almost
finished.The spaces between the planks had been previously calculated
and measured and could now be filled with the damiping material.
Standard fiberglass wool from our local store did just fine. Of
course, there still was a lot of cutting to do... a work that can
be pretty icky sometimes and the glass splitters in the air easily
make you cough. We highly recommend wearing protection devices when
working with fiberglass wool.
||The artificial walls had to be covered
with Fermacell, a material similar to and with the acoustic advantages
of gypsum, but much more durable (reinforced) and easier to work with.
Slicing was done with an electric saw and an attached vacuum cleaner.
Still, this work was a very dusty one... as you can see. What was
to become the "Foyer" in the future has served as the "cutting
and slicing" area during the construction of the main room of
the home theater.
The Fermacell plates have been firmly attached with
lots of screws to the planks. The narrow gap between two Fermacell
plates were filled with a silicon rubber to completely seal off
any air hole there might have been. The idea was to have the room
completely sealed from the outside as any unwanted leak could lead
to distortion or noise reverberations.
||Carefully applying the silicon rubber
on the top row of Fermacell plates...
Final cuts had to be made in order to have space
for electrical wiring as well as lighting cables. As mentioned before,
it is highly recommended to wear a protection device when cutting
the fiberglass wool.
||Within one week, the "room within
the room" was finished. The walls had all been covered, the gaps
were sealed and everything looked fine. The main entrance to the home
theater was still without any doors, but other than that, we quite
liked the results after only one week of work.
This picture shows the interior of the inner room.
There is no front baffle wall yet, but a frame around the main entrance
had been constructed. It had the exact same depth as the fake wall
would have behind which we would cover the loudspeakers and all
the acoustical treatment. The outer wall had also been treated with
acoustical damping material in order to absorb any sound that might
come from the baffle wall. The intention was that the room behind
the screen (baffle wall) was as dead as possible with no reflections
or reverberations whatsoever. Any of these could diminuish sound
quality in the home theater.
||Once everything had its final shape,
a fake front baffle wall was mounted to seal off the main listening
room. With the help of WSDG-e and their professional acoustical equipment
we measured the room and its resonances (eigentones, room modes).
A speaker and microphone were placed at different locations in the
home theater and recordings were analyzed on the computer using special
software. A professional test tone generator was hooked up to the
installation providing reference quality test signals.
Here's a picture of a test setup. Speaker, microphone
and test tone generator were hooked up to the computer. Both outgoing
and incoming signals could then be compared and based on the variations,
calculations were made. The results were then analyzed at WSDG-e's
office and a detailed report containing simple and understandable
countermeasures was mailed to us a few days later. We used different
types of acoustical treatment to even out the eigentones of the
||The crossing planks of the elevated
floor were ideal to have all the wiring installed in between the spaces.
We used tubes for loudspeaker cables, stair light, back light (our
favourite!) and some for additional purposes (USB, power, etc.) Special
pre-cautions were taken in order to have power, light and loudspeaker
cable with a minumum distance of 20 cm (approx. 8") from each
other in order to avoid intereference between them all.
Once all the tubes were in their place, the floor
could be mounted. We used some heavy layers of chip board and screwed
it tightly to the ground. Gaps were again glued to be sealed tight.
The middle and back rows are elevated 30 cm (12") from the
main floor, with steps on each side of half this height.
||Opposite of the main entrance we built
a "twin" of it. This helps to keep the room absolutely symmetrical
and does therefore not add any problems due to uneven reflections
from the side walls.
The front side of each level shows a special-sized
space (based on the calculations of the room mode measurement) filled
with special damping wool, soon to be covered by a custom made cover
with an exact number of drill-holes giving a calculated surface
of air leakage to eliminate one of the formerly measured room modes.
On the right side, you can see the stairway steps being half as
high as the level. Also, you may have noticed the short overlapping
edge of the steps under which the indirect stairway lighting will
soon be installed.
||A black baffle wall was mounted on
the front side of the room, or at least half of it was mounted when
this picture was taken. Fully mounted it will provide housings for
all three front channel speakers, two subwoofers and also serves as
mounting plate for the large and micropreforated Stewart Luxus Deluxe
ScreenWall with ElectriMask. On the left side is an adjustable rack
for all the electronic equipment (accessible from both front and back!),
on the right side we have the shelf for some hundreds of DVDs.
This is an image from outside the home theater with
view through the main entrance. The black covers on the front side
of the levels have been attached and some damping material has been
mounted on the left wall. Between the two black planks you can see
an empty space where the side surround channel will be mounted soon.
On the right leads a door behind-the-screen in the equipment room.
Speakers and all electronic equipment is easily accessible from
the backside. This room is very convenient when servicing or changing
something in the configuration.
||The high left rear corner shows the
supports we mounted on the ceiling. They will soon carry the fake
and slightly downwards angled ceiling. The spaces between these supports
are soon to be filled with more sound absorbing material, resulting
in no reflections or no added bass activities from the ceiling. The
back wall is also completely covered with damping material, leaving
spaces only for special acoustical treatment and back surround speakers.
Above the fake ceiling we run more than 1000 meters
of fiber optics for the starlight ceiling. The "stars"
are still hanging from the ceiling in this picture, but a few days
later they will be cut down. Also, you can see the huge tube
(4.9 cm / 2") we installed to the projector. It will have to
provide enough space for RS-232 control as well as a high quality
||This picture shows again the finished
starlight ceiling with hanging stars. The fake angled ceiling is now
finished and the indirect shining light that offers this beautiful
ambient light has been turned on for the first time (and worked ;)
The nearly finished back wall shows one of a
total of 6 JBL Professional 8340A THX surround speakers. On both
the left and the right side of this back surround speaker, we installed
a SKYLINE panel in order to get a diffuse surround sound and almost
no direct reflections from the front speaker sound waves. Below
the diffusor panels there are two white boxes. They are MODEX panels
and absorb bass at a certain frequency and help to even out another
peak of a room mode we measured before. After all the acoustical
treatment was made, the room responded pretty much linear to all
||The TRIAD Gold LCR/10 InWall fit perfectly
in the holes of the baffle wall. On of the great advantages of this
speaker besides its exceptional sound qualtiy is its ability to tilt.
We were able to aim it and point it directly to the main listening
area and thus get superb overal tonal balance and crisp and clear
dialog reproduction. The front Left and Right speakers were not only
tilted vertically, but also toed in horizontally in order to exactly
meet the specifications of the THX installation manual.
This picture shows the front wall with all its speakers
in place and some more absorbing material next to the two 18"
SMART subwoofers. The Stewart Luxus Deluxe ScreenWall Horizontal
ElectriMask was mounted without the projection surface yet. We wanted
to keep it protected from the dust during the construction of the
home theater. We also left the plastic covers on the frame to protect
the stylish velux finish of the Stewart screen.
||Then it was time to color up the room
a bit. The guys of FAHRNI laid a beautiful dark blue carpet and did
quite a good job regarding the edges and steps and special wishes
we had. The carpet was glued in and had a special back to absorb unwanted
noise from the floor when walking on it.
The chairs in Sub Central were custom made by the
French seating company Quinette. Our main goal was to get more leg
space and larger seats than most public theaters do. Quinette custom
made such a chair for us with an XL arm rest (so you don't have
to fight over it with the guy next to you!), a matching cupholder
and an adjustable width of 60 cm (23.6") or more at a reasonable
price. The only "bad" thing about Quinette was that they
produced them only in quantities of 16, plus a sample. This is why
Sub Central has 17 seats...
||The first two rows of our beautiful
chairs... aren't they neat? The outer chairs were slightly angled
towards the center of the screen, offering a perfect view from any
seat. Ah... just wonderful!
This is our favourite - the backlight! Every speaker,
damping material and acoustical treatment has been hid behind a
fake wall that is acoustically transparent. Blue and black acoustically
transparent fabric has been pulled over several panels and tacked
on in the back. The panels have been attached with pushbuttons and
can not be seen through from inside the room. At the touch of a
button we can turn on spots behind the fake wall and the acoustically
transparent fabric then gets see-through, making the crowd go "Aaah!"
and "Oooh!" every single time. This is always fun!
||Here's another shot from the Foyer
with view through the main entrance. The door is now in place, featuring
heavy duty emergency exit handles. An emergency exit sign - fed with
a special power source - automatically turns on when the main power
to the room gets cut and all other light and/or equipment falls out.
There is also a small step on the outside to bring the entrance level
to the same height as the elevated floor inside the home theater.
The nearly finished front wall now has the microperf
projection surface installed and dimmed stage lights. The red curtain
we installed in the meantime is not yet mounted, when this picture
was shot. The Screen has a width of 3048 mm (120") in 16:9
HDTV format (1.78:1). The horizontal masking system allows us to
mask any aspect ratio from 1.78:1 to 2.66:1 and is a great benefit
to picture quality as the black bars can be really masked black
instead of only black projection on a white surface. Ask anyone
who has seen the difference or come and find out for yourself!
||Relax... Boy, was it time to just
sit back and relax after the endless number of hours we spent constructing
this home theater and still there was no end in sight (there never
will be an end... no matter how good your components are you will
always find something to tune around, change a detail here, add something
there). It was the first time we had a picture and just enjoyed watching...
and remember: every seat is the best seat in the house!
"Hand me that wrench over there"
CRT adjustment is one of the most complicated things there is...
not to get a picture, but to get the best picture you can get! If
"Scheimpflug Adjustment" or "Astigmatism" does
not ring a bell, you probably should have re-adjusted your CRT by
We used the Burosch DVD Discovery to setup the CRT projector for
the different PAL resolutions.
||And then finally, somewhen in May
2001, we did it... sound and picture were calibrated, all the seats
have been mounted, all the panels stuck in place, all the equipment
was connected... and the AMX system was programmed. POWER ON, PLAY
MOVIE, VOL REF... just sit back and enjoy the ride!
Well, the best movie is only half as good if you
can't have popcorn and a coke with it... that's why we decided to
add a little counter with a 6 oz. popcorn machine, a Coca-Cola refrigerator
and a Pierrot-Lusso deep freeze and some candy bars.
That's all Folks!