Recording - October 2013 - 50
Dr. Peter D’Antonio is the Chairman/CEO and Founder of RPG Diffusor Systems, Inc., in Upper Marlboro, MD, which is celebrating its 30th year in business. Since 1983, he’s been applying hard science to the often murky world of room acoustics. It’s
difficult to accurately assess the impact his work has had on the recording industry; virtually every commercial studio in the world,
whether the designers know it or not, incorporates at least one of the principles he’s helped develop over the years.
In this candid and enlightening interview, Dr. D’Antonio covers some basic principles you might not know or appreciate about
room acoustics, offers strategies for getting your best sound when you’re working in a room you can’t build from the ground up,
and talks about what you can expect from commercial acoustic treatments... and what you can’t.—MM
First Principles
In your Technical Presentations, you draw a line
between problems that one encounters at low
frequencies vs. problems one has at middle and
high frequencies. Can you lay those out for us?
Peter D’Antonio: I’m a musician, but I’m also a
physicist. So when I first got involved in the recording industry, I wanted to approach it from a scientific point of view. We came up with the idea of
“acoustic distortion;” everybody’s familiar with
electronic distortion, and we wanted to put acoustic
distortion on a very scientific level, but with easily
understood principles. For example, we say, “Listen
to the music and not the room.” Another slogan that
reinforces that is: “If you can’t take your room out
of the mix, then you can’t take your mix out of the
room.”
We’re trying to make the point that if you’re mixing in a room that has acoustical deficiencies, you
can’t play that mix anywhere else, because when
you play it outside that room it will have the opposite
of the room’s deficiency. For example, if the room is
bass-heavy, when you take the mix out of the room it
will be bass-light.
In these days of active surround sound (i.e. multiple speakers), we have a
control room design that has been the de facto standard since the early ’80s...
with some kind of absorption in the front, some kind of diffusion in the back,
and some kind of bass trap in the corners. But there isn’t an appreciation of
how this standard came about and how it has evolved as we moved from
mono to stereo to surround playback. It all comes down to those four basic
metrics and how you create a neutral listening environment. That’s why we’re
doing the things we’re doing in control rooms today.
Low-End Problems
Let’s start at the low end. Can we begin by talking about modes?
We can talk about modes first, as long as we understand that we can’t
attack the problem of modes by itself. There are modal issues and there are
speaker boundary interference issues. To treat them separately is just folly,
because they’re interrelated.
In our software programs, especially our speaker placement program,
Room Optimizer, we deal with both simultaneously, because you can have a
good solution for modal issues that’s bad for speaker boundary interference.
Conventional wisdom states that choosing the right ratio of room
dimensions, length to width to height, can spread out resonant frequencies (room modes) so that they don’t reinforce one another at a
particular frequency—and that ratio is, if not the best you can do,
perhaps all you can do. Is there more to it than that?
Interview by Mike Metlay
A founding father of modern studio design separates acoustic myth from reality
We examined rooms and tried to determine and
catalog the potential problems. On the low end you
have modal distribution and speaker boundary interference, and in the mid and high frequencies you
have comb filtering and poor diffusion. Everything that
we’ve done has been based on solving those four
problems; we set out to design products to attack these
four acoustic distortion issues. (See Figure 1)
Figure 1. The four types of acoustic distortion and how
they’re treated. The last column lists specific RPG products
for each application.
50
RECORDING October 2013
There are a lot of myths out there about room ratios; one says that you
want to get the greatest modal distribution. Well, we don’t hear the distribution of the modes! What we hear is the frequency response. It’s been
proven over and over again that the flatter the frequency response, the
more preferable the listening experience is. So we developed a way to predict the frequency response in the room.
The axial modes are resonances that develop between opposite walls or
between floor and ceiling; they’re easiest to calculate. Most of the spreadsheets that you see, all they want to do is space the axial modes out.
However, there’s a lot of discussion as to how prominent the axial modes
are vs. the tangential and the oblique modes. The tangential modes involve
sound waves bouncing between four surfaces, and the oblique modes
involve six—all four walls plus your floor and ceiling.
But if you don’t have a smooth modal distribution, isn’t that going to
have an effect on your frequency response?
Distributing the modes is important, but the key is how it affects the frequency response—the point being that, people look up these ratios and
they don’t realize that a ratio that works best for a certain room volume
doesn’t work for another volume. [Here we’re discussing “volume” as in
the overall size of the room in cubic feet or cubic meters, not “volume” as
in sound level.—MM] The ratios are not Heaven-sent; they depend on
how large or small your room is. Our approach takes into account the volume of the room.
We used to sell a software program called Room Sizer that did this, but
it’s all basically online now; basically you give it your maximum and minimum room dimensions and the program automatically gives you your most
appropriate dimensions.
Recording - October 2013
Table of Contents for the Digital Edition of Recording - October 2013
Recording - October 2013
Fade In.
Contents
Talkback.
Fast Forward.
AEA R88 mk2 Stereo Ribbon Microphone.
Live In The Studio.
The Mixing Workshop: Spectral Balancing.
Apogee Symphony I/O 8x8 + 8 MP and Symphony 64 | ThunderBridge.
Radial Engineering Gold Digger and Cherry Picker.
Echo Digital Audio Echo2.
Gear Shootouts—A Home-Brewed Personal Guide.
Twenty Questions On Mics And Miking: A Chat With Shure’s John Born.
ADAM Audio A77X Powered Monitors.
Plug-In Outlet: Slate Digital Virtual Buss Compressors.
From Room To Studio.
iOS Music Tools: iMusicAlbum Audio Mastering Studio.
Talking Acoustics With Peter D’Antonio.
Recording Fundamentals. Chapter 22: Compression—Part 1.
How To Edit.
Readers’ Tapes.
Advertiser Index.
Fade Out.
Recording - October 2013 - Recording - October 2013
Recording - October 2013 - Cover2
Recording - October 2013 - 1
Recording - October 2013 - 2
Recording - October 2013 - 3
Recording - October 2013 - Fade In.
Recording - October 2013 - 5
Recording - October 2013 - Contents
Recording - October 2013 - 7
Recording - October 2013 - Talkback.
Recording - October 2013 - 9
Recording - October 2013 - Fast Forward.
Recording - October 2013 - 11
Recording - October 2013 - 12
Recording - October 2013 - 13
Recording - October 2013 - AEA R88 mk2 Stereo Ribbon Microphone.
Recording - October 2013 - 15
Recording - October 2013 - Live In The Studio.
Recording - October 2013 - 17
Recording - October 2013 - 18
Recording - October 2013 - 19
Recording - October 2013 - 20
Recording - October 2013 - 21
Recording - October 2013 - The Mixing Workshop: Spectral Balancing.
Recording - October 2013 - 23
Recording - October 2013 - 24
Recording - October 2013 - 25
Recording - October 2013 - Apogee Symphony I/O 8x8 + 8 MP and Symphony 64 | ThunderBridge.
Recording - October 2013 - 27
Recording - October 2013 - 28
Recording - October 2013 - 29
Recording - October 2013 - Radial Engineering Gold Digger and Cherry Picker.
Recording - October 2013 - 31
Recording - October 2013 - Echo Digital Audio Echo2.
Recording - October 2013 - 33
Recording - October 2013 - Gear Shootouts—A Home-Brewed Personal Guide.
Recording - October 2013 - 35
Recording - October 2013 - 36
Recording - October 2013 - 37
Recording - October 2013 - 38
Recording - October 2013 - 39
Recording - October 2013 - Twenty Questions On Mics And Miking: A Chat With Shure’s John Born.
Recording - October 2013 - 41
Recording - October 2013 - ADAM Audio A77X Powered Monitors.
Recording - October 2013 - 43
Recording - October 2013 - Plug-In Outlet: Slate Digital Virtual Buss Compressors.
Recording - October 2013 - 45
Recording - October 2013 - From Room To Studio.
Recording - October 2013 - 47
Recording - October 2013 - iOS Music Tools: iMusicAlbum Audio Mastering Studio.
Recording - October 2013 - 49
Recording - October 2013 - Talking Acoustics With Peter D’Antonio.
Recording - October 2013 - 51
Recording - October 2013 - 52
Recording - October 2013 - 53
Recording - October 2013 - 54
Recording - October 2013 - 55
Recording - October 2013 - 56
Recording - October 2013 - 57
Recording - October 2013 - 58
Recording - October 2013 - 59
Recording - October 2013 - 60
Recording - October 2013 - 61
Recording - October 2013 - 62
Recording - October 2013 - 63
Recording - October 2013 - Recording Fundamentals. Chapter 22: Compression—Part 1.
Recording - October 2013 - 65
Recording - October 2013 - 66
Recording - October 2013 - 67
Recording - October 2013 - How To Edit.
Recording - October 2013 - 69
Recording - October 2013 - 70
Recording - October 2013 - 71
Recording - October 2013 - Readers’ Tapes.
Recording - October 2013 - Advertiser Index.
Recording - October 2013 - 74
Recording - October 2013 - 75
Recording - October 2013 - 76
Recording - October 2013 - 77
Recording - October 2013 - 78
Recording - October 2013 - 79
Recording - October 2013 - Fade Out.
Recording - October 2013 - Cover3
Recording - October 2013 - Cover4
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