View towards screen, illustrating soffit FlutterFree®, custom black anodized BAD™ panels, and Opti-Step™ - Diffractals®

When examining the context of a surround environment, it is evident that the five main channels are oriented in different directions. We assumed that to provide accurate and matched reproduction from these channels, the acoustic environment would have to be similar along each speaker axis. By extension, we concluded that how the speakers were coupled to nearby boundary surfaces, and how the directivity was loaded into opposing surfaces would have to be matched to expect matched reproduction. This led to a specific approach to room geometry which began with placing an identical wall of given size at a fixed distance behind each speaker so as to match boundary effects.

Next, to achieve matched room loading, custom made RPG Diffractals® were embedded into the room shell on the rear wall, and both sidewalls between the front and rear speakers. In this way each speaker is directed into a wide band diffusor on its opposing room surface. The RPG Diffractals®consisted of custom modulation of the room shell geometry and RPG OptiStep™ diffusors made with cherry wood.

View showing custom black anodized BAD™ panels (left) and Opti-Step™ - Diffractals® with glass dividers

As this approach yields a geometry that begins to approximate a circular plan, each room corner incorporates a custom built low frequency trap to control modal conditions. This trap consists of a 12" deep composite diaphragmatic panel with surface mounted 3' deep anechoic wedges.

To control specular reflection within the space, custom made RPG Bad™ Panels were applied to the wall surfaces. These panels were 3" thick and incorporated a brushed black anodized aluminum reflection mask custom manufactured by RPG.

The concrete floor surface also received 2 foot deep absorptive traps covered with heavy gauge perforated steel, with geometry derived from the speaker directivity. This geometry is also matched with an 18" deep ceiling trap. These surfaces control all specular reflections from the floor and ceiling between the speakers and the listening area.

The space is hydronically heated through the concrete floor slab. Cooling is provided by an integrated air-conditioning system. The ductwork for the air handling is contained in a ceiling perimeter bulkhead. The surfaces of the bulkhead are treated with RPG Flutter-Free of solid cherry wood.

Close-up of Opti-Step™ - Diffractals® with glass dividers built into concrete block wall opening

The execution of the plan was masterfully carried out by the contractor Arcademia Group. Each aspect of the construction was closely monitored and built with an overall tolerance of less that 3/16". The complex room geometry was constructed of solid concrete block with all necessary mitres cut by the manufacturer. As the block wall was the finish surface, the workmanship had to meet exacting standards in placement and finish quality.

Upon testing the acoustic performance of the end result, we note that the decay time within the space is a uniform 0.43 seconds across eight octave bands. All specular reflections are down -15 dB from each speaker location to the listening area. The frequency response of each speaker is within 2 dB of each other.

Subjectively, the sound performance is impressive. The RPG Diffractals® do a masterful job of reducing the wide band specular energy and filling the listening area with a uniform diffuse sound field. All twelve seats sound identical, with even response and excellent sound stage development. The surround envelopment is very immersive. The client, an experienced audiophile, is absolutely thrilled with the outcome."

System Components:
Wilson Audio Watt Puppies
Krell Power amplification
Theta Digital Processor
Theta Digital DVD/Laser Disk
Transparent Cable
Whise Subwoofers
Runco VX-3 Projector
Stewart Micro-perf Screen
RPG Diffusors

RPG to exhibit at AES in New York
We invite you to visit us in Booth 467 and also visit the SONY SACD demonstration room, where RPG's Variscreens and Skylines will be in use. RPG will exhibit its full line of products and software and will introducing several new additions to the acoustical palette. Dr. D'Antonio will be at the booth to answer any questions you may have.

BASWA®phon used for ceiling treatment in Lake Shore Casino
The Lake Shore Casino on Lake Zurich, Zurich, Switzerland was recently refurbished using BASWA®phon acoustic plaster on all ceiling surfaces. A combination of whites and yellows was used to create a truly vivid and exciting visual statement. The Lake Shore Casino is a site for dining, conferences, meetings, entertainment and a wonderful view of the lake.

Ceiling treatment in front of wall mural

Ceiling treatment above raw bar area illustrating
lighting and loudspeaker mounting

Application of BASWA®phon on ceiling and
cloud structures in bar area

Ceiling application in restaurant area

RPG introduces new slotted FlutterFree®
Now FlutterFree® can be used to provide low frequency absorption along with high frequency diffusion. RPG is developing an expanded line of products that absorb sound below the diffusion frequency cutoff and diffuse sound above it. These important new surfaces define a new class of what we call diffsorptive surfaces. BAD™ panel was the first offering in this class and it is enjoying significant interest as a complement or replacement for purely absorptive panels. To provide diffsorption using a wooden finish, RPG offers a slotted version of its popular FlutterFree planks. We invite you to consider using slotted FlutterFree when you want to absorb low frequency sound and diffuse high frequency sound. Since this is a common desire, we expect acousticians and architects to find slotted FlutterFree a very popular acoustical finish. The absorption data for a surface and cavity mount are now available.

Photo of slotted FlutterFree® showing ¼" slots on 1" centers

Reverberation time, diffuse reflection, Sabine, and computerized prediction - part I
RPG offers a tutorial to explain the effect of diffuse reflections on reverberation. RPG is frequently asked what the effect diffuse reflections have on reverberation time. Since acousticians are used to using Sabine, Eyring, Fitzroy and Arau-Puchades to calculate reverberation time using absorption coefficients, it is natural to ask if there is an equation that can incorporate diffusion. The short answer is that all of the above mentioned equations already assume a totally diffuse sound field, so the real question is "How does one calculate reverberation time correctly when the sound field is not diffuse or mixing?". One answer to this lies in the use of computer prediction programs, which properly take into account diffusion. One of the initial findings of round robin experiments comparing experimental measurements with computer predictions was the absolute need to include diffuse reflections. Today, diffuse reflections are attempting to be modeled in commercial programs. CATT Acoustics has been on the forefront in diffusion modeling and so we have asked the creator of CATT Acoustics, Bengt-Inge Dalenback, to write a tutorial that we will run in two parts on our website. RPG has been doing its part to experimentally measure and theoretically predict the diffusion coefficient and there have been significant advances in the creation of a method to measure the random incidence diffusion coefficient, specifically to be used by the computer modeling programs. Therefore, with these data close at hand, I encourage all acousticians to read this tutorial to advance the accuracy of the computer prediction of reverberation time and the other objective parameters.

Read Article

Dr. D'Antonio publishes continuing series on new architectural acoustical tools in Archi-Tech magazine.
Welcome to ARCHI-TECH. Subtitled, "Bridging the Gap Between Design & Technology." This magazine has been created specifically for architects, systems designers and integrators for commercial and residential buildings. The purpose is to provide critical information surrounding the all-important business of integrating technology into building design and architecture. With an emphasis on commercial and residential buildings, the editorial purpose is to inform, educate and help establish a comfort level among architects with systems integration. Each issue provides cutting-edge feature stories, state-of-the-art product and industry information, news, trends, advice and success stories in the areas surrounding commercial and residential building design and technology.

The first installment of Dr. D'Antonio's serialized contribution appears in the Residential issue September 2001 issue, Volume 4, No. 5 entitled New Acoustics: Sound Diffusors. in the new ArchiTech Residential. Subsequent articles will cover New Optimized Surfaces, New Absorptive Materials, Desktop Auralization.

RPG add reverberation chamber and impedance tube measurement capabilities at headquarters

RPG adds absorption measurement capabilities down to 10 Hz to its diffusion measurement capabilities With the publication of the AES-4id-2001, the acoustical community is now aware of the various measurement goniometers RPG has developed and the many years of research that have gone into creating a measure of scattering. Acousticians can now utilize this diffusion coefficient to evaluate potential diffusing surfaces. RPG also uses the diffusion coefficient in our Shape Optimizer, which combines an architectural motif with desired scattering performance, to create custom shapes for performance facilities. Please consult our website for more information.

RPG is also very much involved in bringing innovative absorptive and diffsorptive products to the acoustical community. These products include our new absorptive plaster called BASWA®phon, absorptive Topakustiks® and Topperfo® wood systems, diffsorptive slotted FlutterFree® (described in Diffuse Applications) and the binary amplitude diffsorber (BAD™ panel). To assist in the development and testing of these new absorptive and diffsorptive products, RPG has recently added a reverberation chamber, several impedance tubes providing absorption coefficients from 10 - 5000 Hz and a flow resistance apparatus to complement its diffusion testing goniometers.

The reverberation room measures 10' x 14' x 19', which is capable of providing good statistical absorption coefficients down to roughly 200 Hz. To extend our capability to measure absorption coefficients down to 10 Hz, we have also added a 7 ton, 2'x2'x24' impedance tube using the two-microphone method according to ISO 10534-2 and ASTM E1050-90. This new impedance tube gives us the capability to document the performance of materials in the sub-100 Hz region, not accessible currently using the reverberation room method. This information is sorely needed in recording studios and home theaters, where subwoofers are routinely used. We are also developing additional impedance tubes to study small homogeneous samples over the rest of the audio spectrum. This approach will be used to study and continually develop BASWA®phon. Since we get so many questions on the applicability of various fabrics to cover our BAD™ panels and diffusive products, we will also be adding a flow resistance tube to quantify fabric performance.

We invite the acoustical community to visit us for our Diffuse Seminars and use these facilities for research.

Dr. D'Antonio to address NCAC at ASA meeting in Ft. Lauderdale
Dr. D'Antonio will present a 2 hour lecture beginning at 10 AM at the annual NCAC meeting in Ft. Lauderdale. The title of the presentation will be "Expanding the Acoustical Palette: New Absorptive and Diffusive Surface Treatments and Pending Diffusion Standards". We invite you to also read Diffuse Reflections: The News Letter for Progressive Acoustics Research which contains additional information on topics covered in this talk.

Diffuse Seminars
RPG offers regular educational seminars for acousticians, sound contractors, home theater system integrators, architects, and other specifying consultants to apprise the industry of our research, new products, application assistance, and an introduction to RPG's Room Sizer, Room Optimizer, Shape Optimizer, CATT Acoustics software and Lake Technology convolution platforms. The press is also welcome. RPG is applying for AIA Continuing Education credits. The response to these educational seminars has been very enthusiastic. The 2001 seminar calendar will be posted next month.

If you are interested in attending, please e-mail to info@rpginc.com, contact your local rep or call Jeff Angel at 301-249-0044.