I want to chat a little bit about my personal approach
to low frequency control that may not be everybody's approach,
but let's try this on for size.
We're all in agreement that our goal is to have
the responsiveness in the frequency domain
particularly be as non-colored or as even, not necessarily
flat, but non-colored and as even as possible
in our critical listening position.
This is more or less the goal, particularly for control rooms.
How do we get to that goal?
Well the first way for me is always with geometry.
Now maybe that's because my career starred as an architect,
but I would suggest for your consideration
that this be your first goal.
The more low frequency control you can introduce in your design
by simply having the correct geometry, the easier
it will be to deal with the remaining issues of low frequency control.
By that I mean specifically squashing certain eigentones.
Let's drill down a little bit further.
So when somebody approached us with a room
in their basement that was 20 foot by 20 foot, the first thing that occurs to me
is to see if we can get rid of the 20 foot by 20 foot dimension.
It's obvious that there's going to be problems in that room.
Two of the three dimensions are the same.
They're not even built from the same multipliers, they're exactly the same.
So obviously modes they're associated with a 20 foot
dimension which are now in two of the three axes will be piling up.
So this is a bad room to start off with.
I guess the only worse room would be one that had a 20 foot height.
Now you'd be in a cube, might be very interesting architecturally
but it certainly wouldn't be interesting from a low frequency modal buildup
issue.
So if we can first step is to solve the problem geometry,
we have a number of tools that allow us to do that, room ratios is
what it's commonly called.
There are some advanced computer tools to do it,
but there are some also very, very simple graphic tools
and we're going to explore those.
That's the first step, try to get the geometry right.
Well you might say to yourself, well, why
don't we always get the geometry right?
Well there's lots of reasons why you might not
be able to get the geometry right.
One, you may not be able to based on the site that you are given.
You may not be able to get the height ratio exactly
proportionate to the width and the length.
In fact, that's a common problem, never seem to have enough height.
A second reason could be a programmatic reason, a reason that you're causing,
like the nature of your seating or the nature of the console configuration,
or the nature of where the door has to be
and where the windows want to be because of viewing, exterior viewing,
viewing into a live room, et cetera, et cetera,
are causing the room to take a certain shape, by that I
mean x, y, and z proportions.
And even though you want it in your heart to have correct ratios,
you're just not able to get them.
You won't be able to get everything to fit into the room the way you want.
So there are a lot of reasons why you might not
be able to get an ideal room ratio configuration.
In fact, most of the time you don't get an ideal room configuration.
On top of that, what also is important is
of course location of the monitors and location in the listening position.
If left alone, most studios seem to want to have the listening
position in the middle of the studio.
This is more of an ergonomic feature.
You seem to want to be sitting in the middle.
You have equipment and monitors towards the front and people
and gear towards the back.
And the next thing you know, you're in the middle of the room.
And you don't have to study room modal analysis very long
to realize that the middle of the front-to-back dimension
is not a very good place to have a listening position.
So right off the bat, there's a conflict there.
So room geometry is our first step.
Then analysis of which modes will be problematic.
We can do that either graphically or we can do that with computer programming.
We're going to show you one program that we use,
it's a little cumbersome but at least you'll have an understanding of it.
Then we attack the problematic eigentones, which eigentones,
or room modes, or standing waves as we used
to call them are peaking causing valleys and how do we squash them?
We can't bring up the valleys, we can squash the peaks.
How do we squash the peaks?
With targeted low frequency absorption.
So first geometry then specific targeted low frequency absorption.
That's the basic philosophy of how we deal with low frequency
or modal analysis usually up to about 200 or 300 Hertz.
After 200 or 300 Hertz, we don't really have low frequency or modal
issues anymore, now we have reflection control, it's a whole other subject.
So that's the general philosophy and we'll explore both approaches.
But first geometry.
The more accurate and the better your room ratios, the much easier
it'll be as far as targeted low frequency absorption.