Hi everyone, Dennis Foley from Acoustic Fields.
Today we're going to talk about sound diffusion. We get a lot of questions
about diffusion.
It's one of the four main room distortions that we always discuss
and people that experience diffusion for the first time are just
completely, their musical experienc is changed and
we're going to be doing a whole series of videos with Bruce Hallberg, one of
our customers who's
made a big commitment to diffusion and
we're going to talk about his discoveries in sound. He calls me every
night, and
tells me how much it's changed. So it's going to be an interesting video.
How a sound diffuser works.
There's a lot of devices on the market place, in the marketplace, that call
themselves diffusers, I even saw some foam the other day that said it was a
diffuser.
Just simply not true. These are marketing names given to products.
Those of us in the business, understand how diffusion works and a
quadratic diffuser is a true diffuser.
We've all seen these quadratic diffusers around. Maybe you didn't know quite
how they work or understand the function but we'll talk about that
today.
A Quadratic Diffuser is based on
prime numbers; 3, 5, 7,
9, 11, these are all examples of prime numbers. It's a formula that
you
plug in a constant and work through
the end and get residuals, a little bit too complicated for this video
but let's just talk about quadratic because it's the real true diffusion, it's the
one we use because it's predictable
and it's consistent and it's available in two dimensions. So you have vertical
and horizontal so you can get
two dimensions of diffusion in your room. How does it work?
Let's talk about that. It's a series of wells
or troughs with horizontal dividers in them.
We've all seen these examples of these.
This is a P seven right here. So it's based on prime 7 like we discussed.
It has actually more than six. We took out the and wells because
it's not really necessary, it's not audible, just a flat surface for a
reflection anyway.
So our first well depth starts at 1 inch. The next well depth is four.
The middle two are two inches, four and one. So the series kind of repeats itself.
Runs one way in the beginning and then repeats itself in the end.
Okay? These numbers were derived by using that formula that we talked about
and getting residuals,
which we'll discuss in another video, that's more of math related.
Each one of these well depths is based on quarter wavelength rule
and we'll talk about the quarter wavelength rule in another video. So each one of
these well depths is based on the quarter wavelength rule.
The distance across or horizontal dimension is half wavelength.
So let's just stick with the vertical
ones for right now and look at the quarter wave rule.
So our first well is one inch,
times four, because its 25 percent remember, quarter wave length.
So that gives us a total wavelength of four inches.
We want to find what frequency that is at.
Speed of sound, lets just call at 1,132
feet per second so we have to change our inches to feet,
it's a third of a foot so about 3400 cycles.
So this one inch depth, is standard on
quadratic diffusers for the end wells and
therefore our quadratic diffuser really will have an upper limit
of around thirty four hundred cycles. Now
we'll go the other way, we can always go lower or we can go down to even eigthy
cycles.
The wells obviously get very deep, you can have
a prime 43 diffuser with a 41 inch well depth
So you can have a lot of distance and a lot of space
that these the devices can take up. This particular one obviously is
about four and a half inches deep.
So that's our top frequency and then
we get the same calculations here,
running for these.
Okay I went
ahead and ran the calculations for us so we don't have to spend the time doing
it.
3,385 as we work through our first example on the
end wells. The next well at four inches 847.
1,691 for the middle and then
847 repeating. So what's our bottom? Our bottom is 847,
and our top is 3,385.
So that's the frequency response of the diffuser.
Predictable, consistent so you know what you're working with.
So obviously frequencies
that are all higher than this will be defused also. This is kind of our upper
limit for each well.
So keep that in mind as you're working through this so we have a
curve that starts at 847 for diffusion and it ends at 3,385.
What is that range right there? Well that's right in our middle range. It's
actually the high middle range. So
very important. It adds a lot of space, a lot of dimensions
to our presentation. So I'm gonna go out into the studio and bring one in and
we'll look at a real one in person.
OK, here's our prime 7 based quadratic diffuser that we were just discussing.
You can see the series of wells. Here's our first well. That's the one
and then our second one is the deep one which is the four.
The middle two are two, repeating sequence again at four
and one. So this is what a quadratic diffuser looks like.
When you position them verically like this,
in a room, you get a horizontal
diffusion. Sound energy enters the diffuser and then spreads out in this
fan like array.,
180 degree array. So it doesn't
reduce any amplitude, it doesn't take any energy away from the signal, and it
doesn't change the time signature.
It just takes that reflection and spreads it out
in a nice 180 degree array. It's amazing what that sounds like.
If you ever haven't heard it, you really should. If you change the diffusers
orientation and you put it horizontally,
then you defuse vertically. So there's an inverse relationship between position
of the product
and the performance. So horizontally we get a vertical diffusion.
So with vertical and horizontal
you get two dimensions of a possible three within your room. So
a very, very important tool; predictable and consistent. Those are the two words I
like to use for it and if you've never heard
a room with diffusion,
especially quadratic, you just got too,
I mean you're just missing out on such an important part of your
musical presentation in small rooms. It can,
well done and positioned correctly, it can take a small room and make it sound two
to three times larger.
I hope you enjoyed today's video. If you did give me a thumbs up so I know that it
had value to you,
and please, if you have any questions leave them in the comments section
and I'll be more than happy to answer them for you. Alternatively if there are
other topics that you wish to discuss
or see discussed in a video presentation,
send me an email info@acousticfields.com
and we'll get them on our list and get it done for you. I release a new
video about every week so stay tuned to our YouTube channel
and keep updated on our new videos.