Event Acoustics baffles Tivoli

28 january 2011

Event Acoustics, the audio consultancy division of the Ampco Flashlight Group, has completed its first job since its name change from Team Projects in June by transforming the notorious acoustics of Utrecht's 1,000-capacity Tivoli live sound venue, a staple of the Dutch touring circuit since 1980.

The project, which is one of the largest permanent installations of TexLnt sound absorbing baffles to date, follows a long working relationship between Erik Mans, the Tivoli's facilities manager and head of technology, and acoustician Peter van der Geer of Event Acoustics.

Mans had been a touring sound engineer (listing Mudhoney among his clients) prior to joining the Tivoli. He comments: "I always hated the sound here; it was totally unfit to do a show, but the atmosphere was superb. We had a great big two second reverb at all frequencies and we measured 12 to 14 seconds at around 70Hz at certain points under the balcony. It's a beautiful art deco building, but sound-wise it was just wrong for amplified music. The result was that every band played really loud on stage, and their FOH engineers would do their best to try to make something out of it. You could get a reasonable sound if the room was sold out, but with less than 500 you had no chance." He adds: "Yet last year we had over 230,000 customers - it's one of the most popular venues in Holland."

A major obstacle to improving the acoustics was the building's status as a protected historical monument, making architectural changes impossible. The venue's location compounded the problem: the building, originally a church, later a theatre, occupies a downtown block with housing barely a metre from its rear stage wall.

With increasingly tough national sound level controls the prospect of exceeding the 105dBA limit for live music over five minutes brought with it the threat of legal measures. Says Mans: "In a venue with good acoustics that's no problem, but here it was a big problem on a daily basis. For example, trying to keep Therapy?, in this reverby room, at under 105dBA, that's a problem. Bands always wanted to go louder. We record the levels every day so the government can check afterwards, so we are seriously under control, and every show was a problem." The stage had a very strong reverberation field, naturally amplifying the on-stage volume, which in turn meant sound levels in the hall needed to be raised further.



Attempts had been made to improve the acoustics using standard sound absorbing panels, which proved unable to deal with the Tivoli's seven-second bass RT in the rhythmically critical 40-90Hz range.

In 2009 the decision was made to opt for a substantial refurbishment, intended to both eliminate the noise spill issue and improve the room's natural sound. Event Acoustics measured the reverberation at 30 different locations in the venue and designed acoustic treatment for each specific location, including problematic areas such as under the balcony.

Mans: "Event Acoustics had already done acoustic design for De Helling, our other venue in Utrecht. I've got about 20 freelance sound engineers who tour a lot nationally and internationally, and they all say De Helling is the best sounding room in Holland. So Peter came in to talk to me about how their sheep wool baffles called TexLnt had improved acoustics, mainly for festival tents at that time, which sound horrible too, and at the North Sea Jazz Festival at the Ahoy, to improve the acoustics of several rooms in that venue.

"I trusted his knowledge and capability because he's the only person I know who combines acoustical knowledge with knowledge of amplified music. Most people who design acoustics only know classical music and very little about rock music, and the result has been some big mistakes - venues which have bad low end, because the acoustics weren't done by experts in amplified music. I liked the sound of Peter's solution, and also the fact that the wool comes from Texel, an island in the north of Holland, where there's a sheep farmer looking for new markets who's found himself in acoustics!"

A complication was the Tivoli's lack of a ceiling grid from which to hang the TexLnt baffles. Engineer John ‘Kabel' Essing designed and fabricated a hanging grid, a complex job among the old building's convoluted geometrics. The panels were hung high up around the walls, on the wall over the stage opening and on the large back wall over the bar, each positioned at varying distances in front of the wall to give double absorption of both direct and reflected sound. The baffles extend from ceiling height to two metres from ground level to minimise physical contact with the audience. The final touch was to hang a layer of TexLnt on the rear stage wall. Installation took two weeks, heralding an overnight change in the acoustical situation.

The measures improved stage acoustics to a level that Mans says the Tivoli team has been "overwhelmed" by compliments from performing bands, including top Dutch rock band De Dijk, who have played more than 50 shows at the Tivoli. The band's FOH engineer, Rene Botman, commented: "Tivoli is one of the most popular stages in Holland, but while the bands know about the acoustic problems they love to play there because the crowds and ambience are great. Now the sound is great as well - not too dry; I like it very much."

Mans adds: "We have a small smoking room, which still has the original acoustics. Some people with a good ear have asked what the difference is, so I take them into the smoking room where you can still enjoy the horrible two-second reverb. The audience gets a better deal and the bands get better shows. It's a win-win situation."