We have taken
room with all the inherent problems (12 dB peek at 221 Hz being
the worst) and given it the performance of much larger room. How
do you make a tiny 13 x 15 room larger? The Zen technique would
indicate that you make the room smaller and believe it or not
we actually did just that!
The "listening room" before
enlightenment... There was a reason for this at the time. Until
the Zen amp came along, I was a dedicated speaker designer and
well aware of the acoustical problems most rooms present so I
tried to make sure I had an "average room" to use as
a reference. The irony of that was in consistency. A room like
this one will never sound the same way twice because your head
will never be in the exact (to within a 1/2") spot twice.
That presents a continuous level of frustration that many of
you share I'm sure.
As you can see,
the couch or listening position was near the back wall, the speakers
are only a foot or so away from the front wall, although I always
DID pull them out to listen. Notice the TV in the window? When
you're done chuckling about that take a good look at the wall
around it, and realize how hard this surface is. Also the coffee
table just in front of the listening position. THIS IS ALL BAD!
doing some model response plots for our room - after the painful
decision to sell the couch and loose the TV I might add - we found
the ideal speaker placement and listening position for the room
and used that as a starting point.
We applied the
WASP technique to observe
the differences. After doing the Wilson Audio Setup Procedure
we averaged in the suggested computer modeled locations and re-did
the last steps of the WASP. This
we agreed gave the best sound/imaging we could obtain and tried
many other ways just to confirm it.
on the correct setup of all the equipment ( well speakers anyway)
we measured the response of the room from the listening position
seven ways from Sunday. The results were terrible but typical.
There was a large 12 dB problem in the mid bass, a huge 9 dB hole
at 80Hz and several high frequency problems as well. At this stage,
and armed with this knowledge we still couldn't help but judge
the stereo equipment harshly. I remember in particular I grew
to hate Dynaudio's new little 6.5" woofer and thought there
hundred dollar tweeter was the worst sounding damned thing I ever
had to put up with. (Even on tube gear mind you.)
this is what is happening in this now ideally set up "small"
listening room: The speakers are about 6 feet apart and the listening
chair centered about 6 or 7 feet back, speakers toed in directly
at the listener. The distance to the side walls from the speakers
is about 40 inches. Since this is the closest surface, it is considered
the 1st reflection point. Sound hits that from off axis radiation
patterns emitted by your speakers. It then hits the next surface,
the rear wall behind the listening chair. From there it hits the
opposing side wall on the other channel and the finally hits the
front wall behind your speakers where it is now aligned once again
to travel directly at the listening position.
with all this is simply that the direct energy from your speakers
hits your ear in just a few milliseconds. The same sound that
goes past your ear, and around the room to finally reflect back
to you from the front wall is delayed in time by so much that
it creates confusion in the brain. The brain hears both sounds,
one slightly delayed on top of the original and has a hard time
deciding where the source of the sound actually is. This is often
referred to as cloudy, smeared, flat, etc.
To handle these
reflections, we used quadratic prime number sequencing to create
diffusers that would spread sound out in a 180 degree fan instead
of a direct reflection that a wall brings. By doing so, we diffuse
the sound energy at that reflection point dramatically, so the
reflections that leave it on their journey to the next wall, are
substantially lower in energy. This diffusion also adds a delay
to the energy that will help widen the gap between the direct
energy and reflected energy our mind tries to interpret.
we had to put these diffusers on every wall at the major problem
points, and we had to design diffusers that worked in a linear
fashion across a wide frequency band from 200 Hz to at least 4
kHz. We concluded that the needs of the side walls were different
than the needs of the front and rear walls so we designed two
sequences for the diffuser wells.
is the side wall sequence. (S.W.A.L.) Note: Pictured during construction.
What you see finished is the back of the wells and the diffuser
blades only. This assembly will go into a frontless coffin (for
lack of a better word) which will allow it to be a free standing
(portable) unit and give us plenty of space for the other half
of the product - the absorber.
Here is a picture
of the sequence used to treat the front and rear walls. These
deeper wells offer results lower in the frequency band. These
were a particular project to design and build because of the tension
between an engineer who couldn't operate a screw gun (Dan) and
myself, the more artistic craftsman type. The bottom line is that
the tension was worth it in the end. Without both of our strong
headed wills these products would have been non ergonomic and
All this diffusion
will be wonderful for handling higher frequencies from 200 Hz
on out to 8 kHz, but in our room the lower frequencies were the
big problem. Remember a huge peek a 220, a giant dip at 80 Hz
and then a 60 Hz swell (I forgot to mention that one.) To handle
these issues we had to first recognize that the bass energy our
system produces was abundant (even though it sounded thin and
sloppy) And to effectively get flatter bass and MORE bass in the
room we had to somehow get rid of most of it! and
to do that we needed to absorb it.
Since we learned
and measured for ourselves how the low frequencies always find
the corners of the room and stay along the walls and floor, those
are the areas that we have to deal with. By drinking the energy
that accumulates in these areas we can reduce the reflection and
thereby reduce the cancellation that creates the holes in your
room where there is no bass. Because we know we will effectively
be wrapping the entire room with these diffusion units, we knew
it would be a perfect opportunity to incorporate absorption into
the back of each unit and along the bottoms.
This will do
a couple of things. One it will absorb the air space between the
unit and wall that will certainly be concentrated with bass energy.
Two it will absorb resonance's from the diffuser wells created
by low energy and lastly it will give a nice even blanket of controlled
absorption throughout the room creating a nice barrier between
you the listener and the crappie sheet rock walls of most homes.
they only had these as C.E.S. non of the manufacturers would have
had a escape-goat for why their stuff sounded bad. (grin)
along these lines when we got to the corners where we knew there
would be no diffuser units placed, we really got serious and created
a HUGE diaphragmatic linear absorbing structure designed to by
the mere act of placing it into a corner, eliminate the corner
and it's associated side effects. These corner units (C.W.A.L.)
absorb clear down to 23 Hz and weigh a 151 pounds! Wanna know
a secret... that's exactly what it took to correctly treat the
problem. Anything less is a placebo.
At one point
we compared one of these units to the more popular light weight
tube traps. To make a long story short, we had to make a 300 mile
radius to borrow enough of the darn things to match the absorption
of this CWAL. It took 22 of them, and naturally there was no place
to put the speakers when we were done. This is for real, so please
consider it a wake up call, and realize that this is what it takes.
When all was
said and done, we ended up with three finished products.
From the left
to right is a side view of the CWAL, the SWAL, and without a fabric
sock is the DWAL. We built 8 DWAL units, and 4 SWALL units, and
2 CWALL units for the room. Actually we built more than that,
but the treatment was so effective some of it had to come back
The process of
installing these units and doing before and after listening tests
was wonderful because unlike before and after listening tests
with pillows, dots, and tubes, we could actually hear a very obvious
The first item
was one CWAL unit placed in one corner of the room. Then a week
of listening. The model issues of the room changed and you could
hear it. The bass was tight now, WAY MORE DETAIL and speed was
apparent. Some say it dry cleans the bass! The huge dip at 80
Hz was now a mere glitch, and the 220 Hz peak was reduced noticeably.
Then we brought in a second unit and repeated the process of listening
and measuring. It doesn't matter which corner the units are in
for low freq. absorption, however we found having them on the
front wall corners behind the speakers offered a tighter sounding
mid bass which the CWAL is also controlling.
I had to take five photos and paste them all together to get this
shot, and now I can't even find the Big version of the picture..
No wait, here it is, I found it. This shows almost everything
but the rear wall.