A new level of intelligibility at Gereja Kristus Yesus Church

Originally incepted 30 years ago, a mission assembly of the Gereja Kristus Yesus (GKY) church decided to locate itself in Puri Indah to the west of Jakarta. Resembling a castle, the GKY was strategically placed in a rapidly growing neighbourhood that has served its new constituents well since 1988. The Presbyterian services are largely non-charismatic in style, relying on the spoken word from a pulpit outfitted with gooseneck microphones and a piano accompaniment. However, the reverberant acoustics of this man-made fortress of the Lord, whose sanctuary ceiling height is 9 m, was singled out as problematic in 2017. As such, several audio suppliers were called upon to tender a solution that would enhance the speech intelligibility. Following a loudspeaker demonstration, PT Hesed Kharis Indonesia was enlisted to supply and install a relatively simple but effective design.

Not only did the church require an audio upgrade that would enhance speech intelligibility, the church committee stipulated that any new speaker system could not distract the attention of their worshippers. “Pastor Musa Saloma desired an audio system that would provide even SPLs throughout the seated areas. But would not distract the worshipper’s eye”, explains PT Hesed Kharis Indonesia’s MD, Dene Dave. “In addition, it was made clear that nothing could be added on stage that would interfere with sight lines – so no monitors or front fills. Therefore, we promoted a ceiling suspended loudspeaker system.”

Having conducted simulations of the fan-shaped room in EASE, Mr. Dene conducted acoustic analysis, where he found the RT60 measured 2.6 s. “The balcony area was the most problematic of all as the seating area rises towards the rear. So the gap tapers from 4.5 m at the lip to 2 m at the rear wall, where a fabric finish absorber has been added.”

The church is relatively modern and architectural drawings were available allowing an assessment as to where loudspeakers could be fixed safely on the ceiling. Loudspeaker cabling and trunking was inserted into the ceiling and rising walls, before being routed to the loudspeaker points. TW AUDiO M8 and M12 speakers were then fixed to the ceiling using a chain on a scaffold tower to hoist them into position. “The M8 and M12 passive cabinets only weigh 10 kg and 20 kg, respectively, so it wasn’t strenuous. The cable lengths from the speaker points to the control room were minimized and did not exceed 30 m, ensuring the signal strength remains high.”

Whilst the main system consists of two TW AUDiO M12 speakers suspended in an L-R configuration from the 9 m ceiling, four delayed M8 speakers are suspended in front for balcony area coverage. Following full configuration, the RT60 reading for the balcony is now below 2 s.

In terms of coverage, the 12-inch M12 is ideal as its low to mid frequencies are focused on the seats with its rotatable 75° × 50° high-frequency horn,” furthers Mr Dene. “In addition, the levels and EQ settings set for the M8 models covering the balcony ensure there is no splash back from the rear wall.”

A Lab.gruppen PLM 12K44 4-channel amplifier was deemed sufficient to provide enough power for the two M12 and four M8 speakers in addition to a B15 subwoofer with a passive crossover below stage. “The M12 speakers operate down to 60 Hz, but the church desired a mild low-frequency extension. A church of this nature doesn’t require a subwoofer, but we equalized this through the low shelf filter at exactly 6 dB at 100 Hz to give them the desired bass. The amplifier is also equipped with Lake processing, so this allowed me to add the delays, EQs, filters and more.”

“Pastor Musa Saloma is satisfied with the result as it has noticeably enhanced speech intelligibility,” adds Mr Dene. “Although the compact loudspeaker system is out of sight during the services up in the ceiling, we were somewhat mystified as to why the church desired the M8 and M12 cabinets finished in black as white is available.” Perhaps GKY is proud to exhibit the newly installed audio system.

Courtesy of Richard Lawn of Worship AVL

Fixed Installation

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