[WGH]

Together again for the first time, eleven white papers written by Floyd E. Toole, Ph.D., Vice President of Acoustical Engineering at Harman International Industries, two papers by Todd Welti, Research Acoustician, and a Room Mode Calculator from Harman International.

Due to the fluid nature of the web, previous links to these papers no longer worked. Though still available on the Harman web site, these papers are hard to find so I consolidated them in one location.

Excellent reading for beginners and seasoned audiophiles. Enjoy.

Wayne


A New Laboratory for Evaluating Multichannel Audio Components and Systems**
By Sean E. Olive, Brian Castro and Floyd E. Toole, Harman International Industries, Inc.
http://www.wghwoodworking.com/audio/HarmanWhitePaperMLLListeningLab.pdf
The design criteria, features and acoustic measurements of a new listening laboratory designed specifically for listening tests on multichannel loudspeakers and components are described.

Designing a dedicated listening room? This white paper will get you started with formulas to determine the perfect room including sections on room proportions, background noise, reverberation time, and control of early reflections.


Direction and Space – the Final Frontiers**
By Dr. Floyd E. Toole, Vice President Acoustical Engineering, Harman International Industries, Inc.
http://www.wghwoodworking.com/audio/HowManyChannels.pdf
How many channels do we need in order to be able to believe that we are "there"


Audio - Science in the Service of Art
by Floyd E. Toole, Ph.D.
http://www.wghwoodworking.com/audio/AudioScience.pdf
"… it turned out that most people, most of the time, liked and disliked the same loudspeakers."


Loudspeakers and Rooms - Working Together
by Floyd E. Toole, Ph.D.
http://www.wghwoodworking.com/audio/LoudspeakersandRooms-WorkingTogether.pdf
"Problem is that there are no industry standards for either loudspeakers or rooms. In this paper we
will attempt to make the best of this imperfect system by identifying the major variables in the
loudspeaker/room system, and discussing methods for their measurement and control."


Loudspeakers and Rooms for Multichannel Audio Reproduction, Part 1
by Floyd E. Toole, Ph.D.
http://www.wghwoodworking.com/audio/LoudspeakersandRoomsPt1.pdf
"Here we look at the basic theory of multichannel audio systems, leading us to understand why certain loudspeaker designs and room arrangements work better than others."


Loudspeakers and Rooms for Multichannel Audio Reproduction, Part 2
by Floyd E. Toole, Ph.D.
http://www.wghwoodworking.com/audio/LoudspeakersandRoomsPt2.pdf
"Making a good loudspeaker - Imaging, space and great sound in rooms.
Loudspeakers can be designed to be “room friendly” so that they can sound good in a variety of different rooms. Controlling reflections can optimize imaging and spatial effects."


Loudspeakers and Rooms for Multichannel Audio Reproduction, Part 3 – Getting the Bass Right
by Floyd E. Toole, Ph.D.
http://www.wghwoodworking.com/audio/LoudspeakersandRoomsPt3.pdf
Choosing the number and locations of subwoofers, and determining where to sit, are fundamental to good bass. Multichannel
audio should be shared, so we try to get good bass at several locations. Acoustical knowledge is essential, but EQ can help.


Subwoofers: Optimum Number and Locations
by Todd Welti, Research Acoustician, Harman International Industries, Inc.
http://www.wghwoodworking.com/audio/multsubs.pdf
"Intuition tells us that putting a large number of subwoofers at different locations in a room is likely to excite room modes in a more “balanced” manner, as compared to a single subwoofer. This idea has potential where there is not a single listening location, but rather a listening area."


Low-Frequency Optimization Using Multiple Subwoofers*
by Todd Welti and Allan Devantier
http://www.wghwoodworking.com/audio/low-frequency_optimization_using_multiple_subwoofers.pdf
At low frequencies the listening environment has a significant impact on the sound quality of an audio system. Standing waves within the room cause large frequency-response variations at the listening locations. Furthermore, the frequency response changes significantly from one listening location to another; therefore the system cannot be equalized effectively. However, through the use of multiple subwoofers the seat-to-seat variation in the frequency response can be reduced significantly, allowing subsequent equalization to be more effective.


Maximizing Loudspeaker Performance in Rooms - Part 1
by Floyd E. Toole, Ph.D.
Why Loudspeakers Sound the Way They Do.
Maximizing Loudspeaker Performance in Rooms Part 2 - The Acoustical Design of Home Theaters
by Floyd E. Toole, Ph.D.
Acoustical Design and Equalization
http://www.wghwoodworking.com/audio/MaximizingLoudspeakerPerformanceInRooms.pdf
This overview in four steps is intended to set a context within which readers can apply the more detailed technical information in the accompanying paper: “Loudspeakers and Rooms - Working Together”.
Getting good sound in a room. How is it done?

• Step One: Start with a good room
• Step Two: Start with good loudspeakers – ones that are “room friendly”
• Step Three: Improving Bass Performance – working with standing waves
• Step Four: Improving Bass Performance – equalization does work!

Understanding Room Acoustics and Speaker Placement
by Floyd E. Toole, Ph.D.
http://www.wghwoodworking.com/audio/UnderstandingRoomAcousticsAndSpeakerPlacement.pdf
The room is the final audio component and, as such, it can make or break a truly satisfying listening experience.


Loudspeakers and Rooms for Sound Reproduction—A Scientific Review*
by Floyd E. Toole, Ph.D.
http://www.wghwoodworking.com/audio/loudspeakers_and_rooms_for_sound_reproduction.pdf
James Moir: “Finally, in my view, if a room requires extensive treatment for stereophonic listening there is something wrong with the stereophonic equipment or the recording. The better the stereophonic reproduction system, the less trouble we have with room acoustics.”

[This paper] is a review of acoustic and psychoacoustic research from disparate fields, put into a framework that is familiar to the audio community. The result is intriguing. It turns out that some of our common practices are less than optimum, and some popularly held notions might need to be revised.


The Harman Room Mode Calculator
http://www.wghwoodworking.com/audio/RoomModeCalculator.zip
A tool to play with after reading the above articles. Part 2 of "Maximizing Loudspeaker Performance in Rooms" has detailed information on how to interpret the graphs.

The calculator uses Microsoft Excel or compatable spreadsheet for the calculations.
Toggle betwen WAVES and MODES at the bottom left of the spreadsheet.




*Articles added 7-04-10
**Articles added 5-15-12

[opaqueice]

Thanks very much!  Those are great articles.

[satfrat]

Being that I'm a multichannel fan and am interested in trying multiple subwoofers in a small rectangular room, I'm appreciative of these articles. Thanks a lot!

Cheers,
Robin

[youngho]

There is also Loudspeakers and Rooms for Multichannel Audio Reproduction, Part 3: Getting the Bass Right. Apparently, it isn't available on the Harman website anymore, but if you PM me with your e-mail address, I can send you a copy. Also, Toole is retired, from what I understand.

[satfrat]

There is also Loudspeakers and Rooms for Multichannel Audio Reproduction, Part 3: Getting the Bass Right. Apparently, it isn't available on the Harman website anymore, but if you PM me with your e-mail address, I can send you a copy. Also, Toole is retired, from what I understand.

Why not just PM me the copy? If not, my email addy is at the bottom left here,,,, looks like an envelope. Thanks.

Cheers,
Robin

[whubbard]

Loved this part.

E=MC² +/- 3dB

-West

[WGH]

There is also Loudspeakers and Rooms for Multichannel Audio Reproduction, Part 3: Getting the Bass Right. Apparently, it isn't available on the Harman website anymore, but if you PM me with your e-mail address, I can send you a copy. Also, Toole is retired, from what I understand.

Found Part 3 and some other stuff too.
I'll get it up soon as I have a chance to look it over.

Wayne

[WGH]

Added 3 more white papers by Floyd Toole:

Loudspeakers and Rooms for Multichannel Audio Reproduction, Part 3 – Getting the Bass Right

Maximizing Loudspeaker Performance in Rooms - Parts 1 and 2

Understanding Room Acoustics and Speaker Placement

Thanks youngho

Wayne

[youngho]

Thanks for putting up the "Understanding Room Acoustics and Speaker Placement." I hadn't run across that one before. Short and sweet.

[Don_S]

Wayne,  Thanks for all the hard work.  I nominate this thread for "sticky" status.

[satfrat]

Thanks Wayne & youngho, I've bookmarked this thread incase it doesn't earn sticky status. 

Cheers,
Robin

[MaxCast]

bump.
Rob, please consider making this a sticky.

[poseidonsvoice]

Agreed. This has to become a sticky. So much excellent info, and completely debunks a lot of the crap out there in the internet, such as this. The theory seems marginally okay, but the implementation? Egg crates? An example of what NOT to do!

Anand.

[DanTheMan]

Thanks for posting these Wayne!  I only wish I knew they were here earlier.

This should be a sticky.

Dan

[Nyal Mellor]

Everyone on this forum should read Floyd Toole's book. It is written in an accessible manner with minimum of math. It is the best 'if you are going to only read one book on acoustics make it this one' book there is.

http://www.amazon.com/Sound-Reproduction-Acoustics-Psychoacoustics-Loudspeakers/dp/0240520092/ref=sr_1_3?ie=UTF8&s=books&qid=1270660492&sr=8-3

[Nuance]

Great thread!

[K Shep]

Great thread!

Thanks for the bump Nuance...although now I have a bunch of reading to get to this weekend.

[youngho]

A few additional papers:

This paper is essentially a preview of Floyd Toole's book:
http://www.harman.com/EN-US/OurCompany/Technologyleadership/Documents/Scientific%20Publications/13686.pdf

This paper explains the theoretical basis behind the JBL BassQ device and also Sound Field Management in the some of the upper end Harman products, as mentioned in Toole's book:
http://www.harman.com/EN-US/OurCompany/Technologyleadership/Documents/Scientific%20Publications/13680.pdf

[WGH]

Thanks again youngho, I added the papers to the list.

I liked this quote from Floyd's paper:

James Moir: “Finally, in my view, if a room requires extensive treatment for stereophonic listening there is something wrong with the stereophonic equipment or the recording. The better the stereophonic reproduction system, the less trouble we have with room acoustics.”


Wayne

[WGH]

I just added two more white papers by Floyd Toole to the top of the list.

A New Laboratory for Evaluating Multichannel Audio Components and Systems is the most interesting. The paper describes the steps taken to build a new listening laboratory. The techniques and formulas in the article could be used to design the perfect dedicated audio room and include sections on room proportions, background noise, reverberation time, and control of early reflections.

Direction and Space – the Final Frontiers is a good primer on multi-channel sound.

Wayne