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

Nagata Acoustics News 00-07 (No.151)
Issued : July 25, 2000

"Kitae-e-ru," Hokkaido's New Public Athletic Center

by Akira Ono and Katsuji Naniwa (sound systems)

Interior of main arena
<< Project Overview >>

The Hokkaido Public Athletic Center project was planned and developed as a replacement and upgrade facility for the Sapporo Nakajima Athletic Center in Hokkaido Island's largest city. The project began with a design proposal competition in 1994. The firm Kume Design won the competition, and the project entered the programming stage based on Kume Design's proposal and a working consortium of Kume Design, Atelier Bunk and Nakahara Associates. Construction began in October 1996 and, by the completion of the project nearly four years later, included participation by some 70 companies. Hokkaido Public Athletic Center officially opened in February 2000.

<< Location >>

Hokkaido Public Athletic Center is located directly across from1 Toyohira Park Station on the Sapporo Municipal Subway Toho Line. The site is next to the rich greenery of Toyohira Park, and is an unusually prime location for a publicly funded facility. An underground passageway connects the Center and Toyohira Park Station, making the short walk between the two pleasant even during Hokkaido's cold and snowy winters. Hokkaido is Japan's northernmost main island, and the city of Sapporo was host to the 1972 winter Olympics.

<< The Center's Nickname >>

Japanese halls, cultural centers and other buildings often have two names: one is the official name that describes the building's purpose and funding source; the other is more poetic or symbolic, and is usually the name that individuals, the media and advertisers use in day-to-day references to the facility. Hokkaido Public Athletic Center's nickname is "Kitae-e-ru." The elongated "e" in the middle of the name makes the name a colloquial pronunciation of the Japanese word that means "to strengthen" or "to polish." In addition, "kita" by itself means "north" in Japanese, so hearing the sounds of the first two syllables of the center's name immediately brings to mind the word "north" and the center's location in Hokkaido, Japan's most northern main island.

This kind of nicknaming logic may sound convoluted to readers outside Japan, but it has been used successfully before, most notably for another Nagata Acoustics project, Sapporo Concert Hall, completed in 1997. Sapporo Concert Hall's nickname is Kitara, which also uses the "kita" syllables, and literally refers to the place name where the hall is located. Now, after three years of hearing "Kitara" used as the hall's nickname, Japanese speakers immediately recognize it and use it as a more succinct and fond way of referring to Sapporo Concert Hall.

<< Kitae-e-ru's Facilities >>

The new athletic center is outfitted with a robust suite of facilities, including a multipurpose main arena, a sub-arena with a free-climbing wall, a martial arts "dojo" for kendo, jyudo, and kyudo (Japanese archery), training and workout rooms, audio-visual studios, reference rooms and a full complement of related and ancillary rooms. While one important objective of the structure is to serve as a venue for competitive sporting events, the center also aims to be available to the local and regional community for any activity or endeavor that has to do with sports. This includes training athletes and sports enthusiasts of all ages, providing space for sports-related studies, research and implementation of sports-related scientific and technological developments and sports medicine-based athletic training.

<< The Multipurpose Main Arena >>

Architecturally and acoustically, the most significant space of the new center is its main arena. This very large, enclosed space was designed not only for sports events, but also with the assumption that it will be used for a variety of musical events as well. To this end, for the flooring system of the main arena we adopted a system that has both the appropriate springy quality required for sports competitions and can support the arena's deployable stage and stage apparatus, as well as the heavy weight of a seated audience and event-related equipment across the entirety of the arena's expansive floor.

The main arena has a fixed seat count of 4,500. An additional 2,072 seats can be added using a pneumatic deployment mechanism and more temporary seating can be placed in the arena to bring the maximum seat count to 10,000.

<< Building Exterior and Sound Isolation >>

It is common everywhere for large-scale sports arenas to be used as the venue for rock concerts and other popular music events. However, in the architectural design of the average sports arena, the roof structure over the arena's large open space often tends toward a lightweight design. Because lightweight roofing provides weak sound isolation, when popular music events raise the decibel level in a sports arena, the surrounding neighborhood usually raises its voice to complain.

For the Kitae-e-ru project, we performed our design work under the assumption that the main arena will be used for rock concerts and other popular music events. We provided sound isolation to address the needs of the surrounding neighborhood by selecting 90 mm (23") thick concrete panels for the arena's roofing material. These panels' weight equals the weight of standard steel-reinforced concrete slabs, so the roofing framework built to support the roof is as thick and strong as a steel bridge. As a result of implementing this design, when the arena's sound system is raised to its maximum output, the sound can be heard only slightly at the perimeter of Kitae-e-ru's grounds, and should certainly be quite enough to prevent any complaints from the surrounding neighborhood.

Interior of sub-arena
<< Room Acoustics: The Arenas' Reverberation Times >>

The main arena, which has a room volume of 120,000m3 (424,000 cu ft), has a reverberation time of 2.4 seconds, at 500 Hz, in the empty, 4,500-seat arena (no supplemental seating deployed). The sub-arena, which has a room volume of 26,000m3 (92,000 cu ft) and no fixed seating, has a reverberation time of 2.7 seconds at 500 Hz. We consider these values appropriate for athletic facilities and for the multipurpose use of the main arena. In our opinion, the sound absorption in the respective rooms also achieved appropriate levels.

<< Sound System Characteristics >>

In large-scale spaces such as Kitae-e-ru's main arena, one of the important functions of the sound system is clear amplification of announcements and other spoken communication. Because the main arena is a large-scale space measuring 92m x 86m (990 ft x926 ft) with a ceiling 20m (215 ft) high, we opted for a speaker system that uses center cluster speakers and supplemental ceiling speakers for the arena's audience seating areas.

The use of center cluster speakers in the center of an arena is prevalent in large-scale arenas such as the Kitae-e-ru main arena. The reason for this configuration and placement is that it enables the speakers to be placed equidistant from both the audience seating and the arena floor. However, due to the dual constraints created by sporting competition requirements and architects' design visions, speaker systems can often be scaled down to compact, semi-circular configurations. When this compact configuration is used and multiple sets of speakers emit sound simultaneously, the center of the arena may experience a "booming" phenomenon of low-register sound, or many parts of the arena may hear a long-path echo.

For the Kitae-e-ru project, we eliminated the possibilities of both low-register booming and long-path echoes by using a large number of cluster speaker units, dividing the clusters into precisely determined groups and applying a delay to the timing of the respective groups. In this way, we eliminated listeners' perceptions of any long-path echoes. We implemented the same methodology for the ceiling speakers installed to support the sound quality in the audience seating areas.

<< Find Tuning the Main Arena's Sound System >>

Because the main arena's ceiling speakers are both numerous and installed throughout a large-scale space, we ran repeated listening tests to adjust the delay, volume level, and other parameters of each speaker to achieve optimal clarity in both the audience seating areas and on the arena floor. This fine tuning work was also effective in abating low-register booming from the center of the arena. The adjustments to eliminate booming require not only fine tuning the timing of sound reflections, but also precise modifications to a number of sound parameters. By performing these adjustments, both long-path echoes and low-register booming were abated to low enough levels that they no longer pose any impediment to the clarity of amplified speech in the main arena.

The fine-tuning adjustment process proceeded with ease thanks to our use of a digital control console, the control console's remote control hardware and a remote output control device operated using a personal computer. The main arena's sound booth is located on the arena's top floor in order to maximize visibility over all parts of the area, so for our fine tuning work we used the announcers' booth located at one side of the arena instead. For our purposes and for uncomplicated events that may be held in the arena, the use of this booth provides an excellent vantage for checking the arena's acoustics. The fine tuning work afforded me the joy of experiencing directly how easy and smooth acoustical testing and adjustments can be when one is not burdened with having to physically move about a space to hear and try various modifications.

The Kitae-e-ru project's fine tuning period and our successful abatement of both low-register booming and long-path echoes reconfirmed for me the importance of providing time for detailed and intensive fine tuning of the sound system immediately prior to the final completion of a room's construction. Without fine tuning, it is impossible to achieve the high level of sound reproduction and voice amplification that can be so satisfyingly realized when fine tuning is properly scheduled and performed diligently.

"Listen to the Latest Loudspeakers," an Sound Engineers and Artists Society of Japan Seminar

by Motoo Komoda

One of the most important activities of a sound system design consultant is to listen to loudspeakers and grasp each loudspeaker model's and each brand's overall sound quality, peculiarities and approach to sound reproduction. On June 23, 2000, the Sound Engineers and Artists Society of Japan held a one-day technical seminar entitled "Listen to the Latest Loudspeakers" that provided an opportunity for both society members and the general public to hear 17 companies' loudspeakers one after the other. The event was held in Hokutopia's Sakura Hall (this facility's large hall, with a seat count of 1,300), located in Oji, Kita Ward, Tokyo.

Each participating company presented one set of loudspeakers to the audience. Virtually all of the major manufacturers of professional loudspeakers were represented. By order of appearance, the companies were: Sony, JBL, HK, Mackie, EV, Apogee, EAW, Voss, Bose, Ramsa, Turbosound, d&b, outline, Nexo, L-Acoustics, Community, and TOA. The breakdown by country of origin was: seven U.S. manufacturers, four Japanese, two French, two German, and one manufacturer each from England and Italy.

<< An Overwhelming Prevalence of Enclosed Loudspeaker Sets >> Almost all of the participating companies demonstrated enclosed loudspeaker sets comprised of a sub-woofer at the bottom and 2-way or 3-way loudspeakers clustered on top. One manufacturer presented a model styled in what the manufacturer called a "line array." This model arrayed 32 small loudspeakers mounted one above the other and enclosed in a slim, rectangular enclosure. The objective and result of this unique design is to make the directionality of the loudspeakers' output limited to the vertical direction (the direction parallel to the line-up of the loudspeakers). Another unique model incorporated the power amplifier within the loudspeaker enclosure.

<< The Seminar's Program and Stage Set-up >>

Each of the participating companies was allotted 20 minutes for the salesperson to demonstrate the company's loudspeakers and speak to the audience. A procession of loudspeaker models "waiting their turns" was visible at both wings of Sakura Hall's stage. The musical sources for the demos were a combination of live performance and recorded CDs. The Sound Engineers and Artists Society hired rock music drummer Eiichi Ishikawa and bass guitarist Hojin Egawa to play for part of each company's demo, adding an element of entertainment to the seminar and alleviating the tedium attendees might otherwise have felt from listening to multiple sales pitches. In addition to the live sound source, the presenters played several CD selections and/or used a microphone to demonstrate voice reproduction. The demos, as well as the sound volume during each presentation, were entirely at the discretion of each company's presenter.

<< Comparing Loudspeakers Means Comparing Other Variables Too >>

The objective of the seminar was to provide an opportunity for the attendees to compare different loudspeakers. But while the demos all used the same CD player and sound mixer, each company used its own processor and power amp in-between the mixer and the loudspeakers. Almost all of the professional-use loudspeakers on the market today use their own processors, since this part of the system greatly affects the quality and characteristics of the loudspeakers' sound.

<< Adjusting Loudspeakers to the Hall's Acoustics >>

When these kinds of loudspeakers are used in a real-life situation, an equalizer would also be used to adjust the sound output for the reverberation and other acoustical characteristics of the room. However, for the purposes of this seminar, in which each loudspeaker set was used for only a brief period of time, the use of an equalizer was omitted, so we heard the "raw" loudspeaker output without matching the sound to the hall's specific acoustics.

While the loudspeaker output was not adjusted for the hall's acoustics, some adjustments were made to the hall for the seminar. The walls of Sakura Hall, where the seminar was held, have mechanisms to rotate portions of the wall to decrease the hall's reverberation time. For the seminar, the walls were all set to their absorptive sides, thereby suppressing the hall's reverberation characteristic and making the seminar more pleasant for the attendees' ears.

<< My Peripatetic Listening Strategy >>

In order to make the most of this listening opportunity, I turned my attendance at the seminar into a day of exercise. I made my "home base" a seat in the middle of the main audience section. Then, I walked around to different sections of the audience seating, all the while concentrating on listening carefully for how the sound from the loudspeakers might sound differently when I changed my location. I climbed the stairs to the balcony and listened there as well. Repeating this strategy every 20 minutes gave me quite a workout by the day's end, leaving me much more tired than I imagined I could become from a single day of listening to audio speakers!

<< Evaluating the Loudspeaker Sets >>

There are so many parameters one could discuss in evaluating one brand of loudspeakers as compared with another that the bottom line is really whether the loudspeakers' overall sound is appealing and comfortable for the ears to hear. Some of the parameters considered are volume, the sound balance from low to high registers (the frequency response), directionality, degree of definition, responsiveness to changes in rhythm and tempo, naturalness of sound and distortion. Choosing loudspeakers might be compared with choosing food recipes: individual preferences, likes and dislikes cannot be discounted. My impression of each of the 17 brands I heard at the seminar differed slightly one from the others, but overall, I did not sense any huge differences. To my ears, one of the brands stood out as better than the rest, and two of the brands seemed clearly inferior.

Reviewing my notes from the seminar, my positive comments include adjectives such as "subtle," "well-rounded," "clear" and "clean rhythm transitions." My negative comments included "no lilt in the modulation," "jerky," "artificial," "unpolished," "aggravating," "lack of presence" and "seems to disappear into the woodwork." Maybe it was Tokyo's summer heat outside, but my choice of adjectives somehow reminded me of the kinds of words I expect to hear in TV beer commercials.

The differences that I recorded in my notes are not the kind that would correlate to any numerical measurements I could gather with even the most precise acoustical measuring tools. In earlier iterations, loudspeakers were simply mechanical devices that converted electricity and air vibrations into sound. Today, however, it may be more appropriate to consider loudspeakers as a category of musical instruments, since evaluating them is becoming an increasingly subjective exercise.

<< Giving Each Brand a Fair Chance >>

As I made my evaluations, I questioned whether certain brand names predisposed me to favor or disfavor the loudspeakers presented. However, when I later discussed my impressions with other seminar attendees, I learned that there was a general consensus of agreement about the loudspeakers we heard. Certainly, I would like the opportunity to hear a variety of loudspeakers without knowing beforehand which brand I was hearing, and it would be valuable to hear a more rigorous one-to-one comparison, but setting up such a demonstration would be much more work for a seminar's sponsors. It would also be less entertaining and therefore more tiring for attendees, and we would then have to try to figure our levels of fatigue or distraction into our evaluations.

<< This Seminar's Value >>

This seminar, hosted by the Sound Engineers and Artists Society of Japan, was a fine way to grasp the big picture in loudspeaker development today and each company's main strategy or focus. The sound level during the entire program was consistently loud. In actual concert and event situations this may be the norm for these kinds of loudspeakers' use. Nevertheless, I found myself wishing that I could hear the loudspeakers at more quiet sound volumes.

That each presenter was allowed to supply different CDs as the music source made comparisons between the models presented difficult, and some of the musical selections used were more appealing to the audience than others. The live drum and bass guitar performances were excellent in and of themselves, and also provided a sound source that made the differences among the loudspeaker models easily distinguishable. In my opinion, this feature of the seminar was a great success.

It is a rare opportunity to be able to compare so many different models of professional loudspeakers in this kind of setting. Not only was the event of great intrinsic value, but in addition, it was open to the general public for a mere \500 ($4.50) per ticket. I am glad that I had the chance to attend it.

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Nagata Acoustics News 00-07iNo.151j
Issued : July 25, 2000

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