24 3月 2016

Crystal clear speech inside protected Birmingham church

Large, open spaces, hard walls and high ceilings make it difficult to amplify speech effectively in historic church buildings. To ensure that sermons and other spoken elements of the service are crystal clear, one Birmingham church has deployed innovative d&b audiotechnik loudspeaker technologies.

As light streams in through stained glass windows it can transform the appearance of floors and walls. So often made from stone or brick, these imposing slabs tend to be enclosed by an exceptionally high ceiling, which invites people to look upwards. Visually, the result can create a sense of spiritual occasion and wonder.

While pleasing to the eye, these physical characteristics can make churches less engaging from an acoustic point of view. A large open area with hard surfaces will always result in the same problem: multiple reflections and an extremely reverberant space. This creates a particular church sound and brings out the best of the organ and choir. However, it can also compromise the clarity of speech during sermons and other spoken addresses.

These were some of the issues facing St Stephen’s, a late 19th century church in Selly Park, Birmingham, in the UK. As part of a multimillion pound redevelopment of its structure and facilities, this Grade II listed building recently decided to tackle its acoustic challenges head on.

The brief was clear; St Stephen’s needed an audio system that would vastly improve speech intelligibility but could also be mounted out of the congregation’s line of sight. It was d&b audiotechnik installation partner, Southby Productions, based in High Wycombe, who recommended a sound reinforcement solution from d&b. This was based around the 24C column loudspeakers from the d&b xC-Series.

The 24Cs house six 4” low/mid drivers along with a HF array comprising of six 1.1” soft dome tweeters. While all column loudspeakers exhibit pattern control in the vertical plane, the xC-Series feature a unique passive cardioid setup. This results in a broadband attenuation towards the rear of 18 dB, greatly reducing reflections, and increasing gain before feedback when working with open microphones.

Chris Jones, a director at Southby Productions, says, “Because the xC-Series combine directionality and pattern control based on passive cardioid technology, we have been able to keep reflected sound to an absolute minimum in St Stephen’s reverberant building. The d&b system has significantly increased the clarity of spoken parts of the service, which is excellent news for church leaders and for the congregation who don’t miss a single word. What’s more, when combined with a 27S subwoofer, the system has the necessary headroom for contemporary worship reinforcement.”

With clarity of speech in hand, St Stephen’s also had to comply with the strict Diocesan Advisory Committee for the Care of Churches (DAC) guidelines for sound installations in church buildings. To ensure the cabinets would aesthetically integrate with the gothic-style interior, the slender columns were mounted high up on the walls. To reduce the excitation of the reverberant field even further, the entire HF array was mechanically adjusted to target the audience listening area exactly.