Title means "Quietness", "Comfortable Sound" and "Excellent Acoustics"




Nagata Acoustics News 98-12iNo.132j
Issued : December 25, 1998





Kitakyushu Mediadome Opens

by Keiji Oguchi

Inside View of Kitakyushu Mediadome
A beautiful new, gently curving, hi-tech-looking rooftop recently added its presence to the Mihagino Section of Kitakyushu City on Japan's southwestern Kyushu Island. Named "Mediadome," the new structure replaces Kokura Stadium, a bicycle racing venue formerly located on the site. In replacing the stadium, the city decided to build an enclosed facility that can seat 10,000 people and serve as a multipurpose venue for a wide range of events. To this end, Mediadome implements the notably innovative architectural technique known as "Compression Dome ( MK Dome) " developed by architects Kiyonori Kikutake and the late Gengo Matsui, professor emeritus of Waseda University.

The design of the new Mediadome includes a banked floor for bicycle racing, which will occupy Mediadome's schedule for 100 days of the year. Professional bicycle racing is a popular betting and spectator sport in Japan, yet Japan has only one other fully enclosed bicycle racing facility, Maebashi Greendome, not far from Tokyo.

For the two thirds of each year that Mediadome will not be used for bicycle racing, state-of-the-art equipment will enable quick "makeovers" to a more versatile venue. These include: pneumatically-assisted movable grand-stand seating; a large-scale video screen (9mH x 24mW); a "fly tube" catwalk; booms for lighting and other stage equipment; and electrical outlets, lines, and other apparatus to support whatever electrical gear may be used in an event or performance.

Mediadome's architectural design is the work of Mr. Kiyonori Kikutake and Kikutake Architects; Fudo and Maeda contractors shared responsibility for the project's construction. Of particular note on this project was the planner's novel approach to taking bids. While it is not unusual for a client to request that architects make their proposals together with a general contractor, in the case of Mediadome, the client also required that bids for the project include post-completion use planning and operations proposals.

<< Innovative Loudloudspeaker Distribution Arrangement >>

Ballparks and arenas are often equipped with a combination of a large center loudspeaker cluster and satellite loudspeaker clusters to augment the sound energy. Unfortunately, however, sound from the center cluster tends to bounce off the far walls and create a long path echo. Instead of this traditional loudspeaker set-up, at Mediadome we distributed loudspeakers along the fly tube, which was hung from the ceiling inside the perimeter of Mediadome's banking. Using this arrangement means that it is easy to limit the area that each loudspeaker needs to cover; and the area covered by each loudspeaker is close enough to the loudspeaker that the output does not need to be made too high. Consequently, the likelihood of extreme path echoes is eliminated.

Another innovation we implemented in the electrical acoustical design of Mediadome is the use of a large "co-axial one-box" loudspeaker containing both the horn and woofer loudspeakers on axis. We measured this set-up for clarity at the time of completion of the project, and obtained a favorable speech intelligibility of STI=0.46~0.62.

Reverberation Times at Large Spaces
<< Designing the Space for Very Short Reverberation Time >>

Because public address and sound reproduction inside Mediadome relies overwhelmingly on the facility's electrical sound system, we aimed to design the space with a short reverberation time. Specifically, with the hall empty, we aimed for a mean absorption coefficient above 0.35 (measuring at mid-frequency range). The only way to achieve such conditions is for all of the space's surfaces to have absorptive finishing, except for the flooring, which is a sound reflecting surface. We covered the ceiling with glass-wool board finished by perforated sheet, with an air space behind. This treatment absorbs even low-frequency sounds.

For the walls of Mediadome we used the light steel stud material usually reserved for the supports of finishing board. We added perforations to this material and treated it as a design element, giving it an eye-appealing finish appropriate for the visible side walls of the arena. When set up for bicycle racing, the arena's reverberation time is 3.7 seconds (at mid-frequency range, with empty seating). Above 125Hz, we were able to achieve the special characteristic of virtually flat reverberation.

<< Mediadome's Opening Ceremonies >>

Opening ceremonies for Mediadome were held on October 4, 1998, starting at 10:00 in the morning. The program included a tape-cutting ceremony, tour of the new facility, and a special live guest appearance by the Japanese pop stars "TRF." Excitement filled the air throughout the day as the program changed tone several times from joyous yet serious moments to pop music, to scenes charged with the competitive energy of a racing sport. I found the bank-riding stunt demonstration of pro cyclists an especially apt and thrilling attraction.

The performance part of the opening day's ceremonies including the formal inauguration and the TRF concert. These program items could be viewed on the large video screen, in real time, as they took place on a temporary stage built along the length of the arena. For the spoken part of the program, extra loudspeakers were set at both ends of the stage and were used together with Mediadome's own loudspeaker system. In the past, when ceremonies of this kind were held in arenas, acoustical problems typically caused dismal consternation. However, Mediadome's inaugural welcome address and congratulatory speeches were heard loud and clear, with only the faintest hint of an echo that did not in any way impede audience understanding. This positive effect of drastically shortening the arena's reverberation time was the major contributor to the excellent level of clarity we achieved. In my opinion, we pushed the boundaries of the possible with the clarity we achieved in this enclosed arena, and I doubt that greater clarity can be achieved in a domed space of this scale and size.

<< Mediadome's First Pop Performance >>

For the live TRF concert, Mediadome's own loudspeaker system was turned off and only the extra loudspeakers set at the ends of the stage were used. The group's promoters and others involved with this part of the event had no complaints about the arena's acoustics. Rather, they expressed satisfaction that the artistic intentions of the performance had been achieved smoothly with a minimum of preparation time. As the person responsible for Mediadome's acoustical design, I am grateful for the positive feedback I received from all who participated in the opening ceremonies. I congratulate the arena on its successful opening and look forward to hearing about many more successful events that will make use of all of the possibilities that Mediadome offers.

More information about Mediadome can be found at www.kikutake.co.jp, as well as at www.mediadome.co.jp.



Backstage at the Berlin Philharmonic

by Suzuyo Yokose

This past mid-September, I accompanied the planners of a new concert hall on an observation tour of Berlin Philharmonic Hall. Having long heard about this hall's dressing room area from people in Japan, I was especially interested to see the hall's backstage with my own eyes.

From the hall's stage door, I climbed the staircase and entered the artists' foyer, where lively activity was in progress as I arrived just before the start of a season concert's dress rehearsal. The foyer was filled with orchestra members as well as a crew of Japanese broadcasting personnel on hand for transmission of the performance to audiences in Japan. In the midst of the hub-bub, my nose caught the distinctive smell of fish cooking. Looking around the elongated rectangular room, I discovered kiosks at the center. They sold all kinds of beverages and light fare. One corner looked exactly like a scene from a neighborhood cafe.

Coffee Shop at Backstage of the Berlin Philharmonic
<< The Relaxing Artists' Foyer >>

In recent years in Japan, increased focus has been given to halls' backstage dressing room areas, and our newer halls often have much larger artists' foyers than older halls. However, this extra space is used mostly for such mundane purposes as a place to leave instrument cases. I therefore found it most refreshing to see the relaxed atmosphere of the Berlin Philharmonic's foyer. When I voiced my delight of the foyer, however, the acoustical operator who served as my guide replied that "people who remain here during the concerts continue to speak in loud voices and it is quite a problem." His response gave me a bittersweet feeling, as he underscored how thoroughly at ease people felt in this backstage space.

<< The Artists' Dressing Rooms >>

From the Berlin Philharmonic's stage, the dressing rooms are on the far side of the artists' foyer, laid out around the circumference of the stage. Each of the dressing rooms certainly has enough space. Nevertheless, I was amazed to discover how dark and windowless the conductor's dressing room is (the artistic director's dressing room was much better). The other dressing rooms were all bright and had windows. In reply to my question about the reputation of the conductor's dressing room, I was told with great confidence that "the hall is the design of the famous architect Scharoun, so who would dare to complain?" Whether this reply reflects everyone's feelings I have no way of knowing, but the fact that even the hall's dark conductor's chamber is protectively cloaked in the fame of the hall's reputation is enviable indeed!

<< A Place for Every Instrument and Every Instrument in its Place >>

The Berlin Philharmonic's backstage area is well-designed for the storage of instruments. There is storage space for large instruments such as the contrabass at both stage wings, and the piano can be lowered from the stage to a holding location that leads directly to more long-term storage space. There is also a room for long-term instrument storage on a level below the dressing rooms. I was told that an unused spare room was turned into storage space because there was not enough space for the instruments. When the control room's mixing board grew old and needed replacement, it too was not discarded, but moved to a room above the sound room.

<< An Amazing Maze >>

Visiting the Berlin Philharmonic made me imagine that the concert hall was built first and then, once completed, that the spacious land around the building was used to tack on myriad other appendages of rooms. The layout of the backstage rooms is so complicated that people who come to work in the hall need a year's employment before they have fully mastered the ins and outs of each room's location. Even the stairway of the concert hall's spacious foyer gives the impression that the doors to the audience seating came first and the staircase was constructed thereafter, rising freely to meet the already waiting doors.

During my visit, of course, I also toured the audience seating and the control room, and I was even shown the space above the ceiling. I saw the ceiling that was reconstructed after a piece of it fell down, and the organ pipes that have been added around the stage. In sum, I learned anew how the hands of many have added to this structure in order to bring it to where it is today. I also realized the link between this hall's reputation and the very visible and ongoing efforts of those who care for it to not only use it but continuously improve it as well.



Sound system for Concert Halls -- Part 2 in a Series

by Makoto Ino

Continuing last issue's discussion of speakers, first I will enumerate the four characteristics that are to be considered in evaluating amplified speech in a concert hall setting. These are sound quality, volume, tone,source-localization and clarity. To some extent, each of these characteristics can be individually controlled through the use of sound system. Of course, speaker selection is especially important. The type of speakers, their operating conditions, location, and how they are adjusted affect the four characteristics of amplified speech.

<< Some Considerations in Speaker and Related Equipment Selection >>

Fundamentally, the most significant consideration is the kind of speakers used, including whether they are 2-way or 4-way speakers. Also of great importance are considerations of how many speakers are used, whether they will be clustered together or distributed throughout the hall, and the disposition of the front sides of the speakers (covering materials, whether the speakers are exposed, etc.).

There are also considerations which affect speaker performance, but are separate from the speaker units themselves. These include the degree to which an sound system can be adjusted and fine-tuned, whether the output of the power amplifier has remote control capability, and whether the system has a graphic equalizer or not.

<< Adapting to Unanticipated Contemporary Music Performance Needs >>

In designing a hall's sound system, it is most desirable that the acoustician know what genres will be performed in the hall and what will be the objectives of amplification. Realistically, however, it is very difficult to anticipate the frequency of various kinds of performances for most halls. In Japan, at least, it is much more common for the genres performed in a hall to reveal themselves over time after the hall opens, or for a hall's owner to seemingly serendipitously decide to promote some previously unconsidered kind of performance that was not part of the hall's plan at the time it was being designed. Therefore, the sound system must be able to adapt to unanticipated performance needs and expectations.

One recent example of an extreme adaptation occurred at the September 1998 concert by Ensemble Modern, performed at Opera City's Takemitsu Hall, in Tokyo. The program for this concert was Frank Zappa's work of contemporary music, entitled: American Classics. The sound system for this concert included speakers set at both sides of the stage on temporary additions to the stage built for this purpose, and a mixing console set in the center of the audience seating area. It was the kind of sound reinforcement set-up one expects to see at a rock concert. According to the concert's Sound Reinforcement Chief, Masamitsu Miyazawa, his first plan was to hang speakers on wires from the ceiling, as this would have taken the least amount of time to install before the concert and knock down thereafter. But the hall would not let him suspend the speakers, leaving him with the sole alternative of spending extra hours to build temporary supports for the speakers at the stage's sides, and then spend the better part of the entire night after the concert knocking down his work.

Certainly, concert programs featuring works on the scale Frank Zappa's composition are rarely performed in Tokyo. The question is how to balance the limited need for large scale sound reinforcement equipment against the huge burden of the sound reinforcement expert who must build the artists' desired stage against tight deadlines. Listening to Zappa's composition, it is clear that this work is not meant to be heard in a hall designed for the performance of popular music, but in a hall rich in reverberation time. There are many other works as well which, while differing from the orchestral form that prevailed until the early years of the 20th century, nevertheless should be performed not in sports arenas and popular music venues, but more properly in concert halls. The difficulty in performing these kinds of works in concert halls is that they are either scored for electric instruments, use a mixture of electric and non-electric instruments, or they require some kind of sound reinforcement. The issue is not simply whether the music can or cannot be heard without a speaker; it is rather a question of how the music is to be correctly or best expressed. From an artistic perspective, the determination of how a composition's sound is (re)produced should remain in the hands of composer, conductor, and musician.

In readying a hall for the performance of contemporary music, the challenge is even greater because compositions continue to be in a state of flux at the rehearsal stage, where "cut and try again" is an accepted convention of the rehearsal process. This makes it very difficult for an acoustician or other outside expert to prepare sound system in advance for a contemporary music performance. For this kind of musical endeavor, either the hall's owner and management, or the concert's audience and promoter must take responsibility for ensuring the availability of proper equipment so that the musicians, conductor, and composer can fulfill their artistic intentions.

<< The Need for Speakers for Non-speech Use in Concert Halls >>

Returning from my tangent on hall sound systems and contemporary music performance, I wish to suggest that concert halls do have an obligation to provide at least portable loudspeakers designed for the reproduction of sound other than the spoken word. To this end, it is most convenient to install pipe-battens above the stage that is both electrically wound and can sustain the suspension of sufficient weight that a main speaker can be suspended above the stage. If this is not possible, at the very minimum, halls should provide means to suspend a 2-to-3 ton speaker above the stage area. In addition, concert halls should install several battens above the audience seating area or other means that enable the suspension of speakers as dictated by performances' needs. Halls should also consider where a mixing console can be located in the audience seating area, and should install telephone lines, intercom capability, electrical outlets and power for audio equipment, connections to-and-from the hall's control and recording rooms, and a video link to-and-from the conductor.

<< A Final Word on Speakers for the Spoken Word >>

Returning to the topic of concert hall speakers to amplify the spoken word, there is a great divide between those purist architects who staunchly claim that concert halls do not need speakers and the pleas of the administrators of--in particular--publicly funded concert halls who clamor for the installation of a speaker or speakers that will allow audiences to hear what is said clearly. Public announcements must of course be easily understood, but there are also public ceremonies, award presentations, social gatherings, lecture concerts, and music seminars, all of which require clearly amplified speech. These kinds of events occur more often than one might think.

Concert halls have long reverberation times. Under these conditions, sound system designers should not force themselves to cluster speakers together. Rather, we should learn from the successful distribution of speakers in convention halls and sports facilities, many of which have achieved excellent levels of clarity. In these venues, clarity is achieved at some sacrifice of source-localization. It is time that concert halls also realistically assess their speakers' reach and implement layouts with speakers distributed throughout a hall. This can be accomplished with a variety of excellent design schemes that will be both visually aesthetically pleasing and enable audiences to really hear what is being said.



Nagata Acoustics News 98-12iNo.132j
Issued : December 25, 1998


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