Rhema, the celebrated ministry that caters for thousands of people each Sunday over multiple services, is one of South Africa’s most established churches. Founded in 1979 and revelling in over 40 years of longevity, it has grown from strength to strength over the expanse of its lifetime in such areas as music, television ministry, social work and constantly evolving administration to cater for its ever-growing fellowship.
Considering its constant growth and evolution, getting Rhema’s message out to the congregation in a clear and fidelitous way is of paramount importance. For this reason a comprehensive and “first-of-its-kind in Africa’ upgrade of their audio systems was recently performed, helped in no small part by local audio equipment distributors Wild and Marr and Cristo Hattingh of Sound GP.
If you have ever had the chance to step inside the Rhema sanctuary in Randburg you’ll know that it is simply cavernous. A rough semi-circle in shape with a sloping floor, it, like many indoor venues, presents the difficulty of coverage. Not to mention the fact that the church has got an existing broadcast infra-structure to interface with so signal routing and splitting was also an important consideration. I had a chance to meet Cristo Hattingh and Darren Durbach from Wild and Marr at the Rhema church to take a look at the system, get a feel for the equipment installed there and what makes it significant.
The core system
The core system installed at Rhema centres around JBL’s brand new VTX line array, supplied by Wild and Marr. There are 24 VTX V25s arranged in four hangs of six and in addition to that there are two Vertec 4886 downfills on each hang, totalling eight. The VTX range is a brand new series in the JBL line and is a ’full size, three-way, high-directivity line array element”.
Each box features two 2000W 15′ Differential Drive woofers fixed in die-cast aluminium baffles with four 8′ Differential Drive midrange drivers and three of JBL’s new D2 dual-diaphragm, dual voice-coil compression drivers coupled to a 3rd-generation waveguide. This new HF system also includes a newly patented RBI (Radiation Boundary Integrator) assembly.
While we’re talking about the HF component of the system it might be worthwhile to mention the D2 driver. The D2 is a revolutionary new HF component. As mentioned, it is a dual voice-coil compression driver which JBL claims overcomes the drawbacks of conventional compression driver technology. The two main hurdles when designing a compression driver is the mass of the diaphragm and voice coil which limits high frequency extension and distortion that occurs due to breakup modes of the dome, traditionally titanium. The D2 combines two compression drivers into a single unit with a combined acoustical output. Each of the dual voice-coils are comprised of their own separate, lightweight polymer annular ring diaphragm, their own magnet and their own patented phase plug. The purpose of the phase plugs is to combine the two drivers into a single output by feeding their energies to a single exit point.
There are six JBL VTX S28 subwoofers in cardioid configuration. These subwoofers feature dual differential drive 2269H 18′ drivers and the cabinets are designed to be used in cardioid configuration due to their cabinet design. When asked about whether six subwoofers are enough to cover the needs of the large Rhema sanctuary, Hattingh says: “They more than compensate for this venue. I actually had to remove ceiling tiles that were falling out. It’s quite phenomenal to hear what they do. The distortion ratio is so low that your perception of the low end is totally different to what you’ve ever heard before. It’s really clean low end and the power behind it is amazing.’
Speaking of power, 23 Crown IT-12000HD power amplifiers drive the entire system, which is obviously passive. This includes the delay system which is comprised of eight two-way, passive JBL STX815s, strategically placed at the rear of the room to cover the rear alcoves. Cristo comments on the coverage of the system.
“The main cluster covers the floor and the delays get a full mix with a high pass filter for speech enhancement. So with what you see, we’re covering this room as close to 100% as we can. We’re not hitting the back wall (with the main clusters) on purpose. In other words, we’re hitting the third last row accurately so the last two rows are a little bit in the shade to control the slap back of the esses and the tees.’
An interesting aspect of the setup of the system is that the out-hangs are running in reverse stereo. In other words, the left out-hang gets the right signal from a stereo source, the left in-hang gets the left signal, the right in-hang gets the right signal and the right out-hang gets the left signal. This results in 70% of the audience getting an accurate stereo signal, albeit flipped on the left-hand side of the venue. This works very well since the audience is largely stationary and therefore can benefit from the textural depth of the stereo field.
In terms of consoles, Soundcraft was the preferred vendor, also supplied by Wild and Marr. A Vi6 control surface with a local rack was selected for FOH control along with two Vi1s for on-stage monitoring and broadcast. Two stage boxes, one full size and one compact were spec’d; the compact stage box receiving an Aviom card for the personal monitoring systems employed. The system is entirely digital and uses MADI as the primary audio transport protocol to bus audio to and from the stage boxes and throughout the routing and matrix systems.
A noteworthy and, as mentioned, first-of-its-kind aspect of the system is the implementation of a Direct Out Technologies M.1k2 MADI routing system. The M.1k2 offers 16 MADI ports for a total of 1 024 channels.
“The M.1k2 can handle channel matrixing and not just port matrixing,’ says Hattingh. “So you’ve got your 16 I/O ports which enables you to patch port A to port B but it also goes as far as enabling you to patch individual channels across to any port. For example, we play iPods from FOH, obviously there’s click tracks and stems running for the band and in the back there’s VT running for broadcast. So what we’ve done is, we plug the VT into the Vi1, the iPod, etc, into the other Vi1 and the playback into FOH and then on the M.1k2 we’ve dedicated certain MADI channels as tie lines between us. So, It’s like having a digital version of the old school patch leads but much more flexible and extensive.’
There are a total of 96 channels coming into the FOH Vi6 from the full size and compact ViSi racks and there are 64 channels fed to the Vi1s since they can only handle a maximum of 64 channels. Any further channels are sent from FOH via the MADI bridge as tie lines.
System processing is all run on-board the amplifiers, managed by JBL HiQnet Performance Manager. Performance manager is a hybrid piece of software that combines system architect and line array calculator facilities into a graphic user interface. What is interesting is that any real time changes are purposefully lagged in order to prevent sudden tonal changes. Power shading, system configuration, delays and all other system processing options are available through Performance Manager in real time.
The sound and a walkaround
After I arrived and spent a good deal of time talking to Hattingh and Durbach about the system, a variety of playback material was showcased so we could take a listen to the performance of the VTX system in the room.
My initial impression standing at FOH was the immediately noticeable smoothness of the top end due, I assume, to the D2 compression drivers in the VTX V25 boxes. The tonal balance was clear and unobtrusive. Having had experience mixing on the previous Vertec range, I knew that they could sound a little “bitey’ in the upper midrange, which makes it a good system for rock and which is why the Vertec range has seen huge success in that arena. However the VTX gave me the sense of higher fidelity and a top end that seemed to dance around my ears instead of pierce into them.
The midrange proper was also very polite and seemed to glow or emanate from the arrays. Granted, this was a very large room and from FOH, which is for better or worse in the centre of the room, we were getting a bit of supplementary reflection but it was easy to hear that the fundamental ranges of the instrumentation and vocals were very well reproduced.
The low end was surprisingly full, even from FOH and I was greatly surprised at the power of the six subwoofers that were commissioned to handle low end duties. It wasn’t by any means large bass as you would find in a dance club but they supported the mid/high system just right and added to the feeling of a proper tonal balance. Now, the coverage.
After being encouraged to walk the horizontal and vertical planes by Darren Durbach, I started a semi-circle walkabout towards stage right starting from FOH and following more or less the middle row. Attempting to take note of coverage seams between the coverage of the hangs I only perceived a slight hand-off as I was out of direct line of the HF waveguide of the right in-hang. The right out-hang then took over without much of a drop in level. As usual, I am always interested in hearing what the last person in the last row is going to hear and I am glad to report that there was no loss in fidelity from that position.
What is remarkable about this system is that the bass is consistent from end to end of the venue, possibly only dropping a dB or two from the front to the back. Walking from the extreme right of the venue towards the subwoofers I was also quite surprised to hear a consistent tonal balance not just in the mid/high ranges but also in bass. The bass simply did not get overpowering the closer you got to the subwoofer clusters. The 4 886 downfills covered the front rows perfectly as well.
The wrap
Quite clearly, the VTX system installed by Cristo Hattingh and Wild and Marr at Rhema is a masterfully executed job. Cristo has a long track record of producing quality work for many high profile acts and productions and along with Wild and Marr’s turnkey approach they have really come together in a powerful symbiosis to produce a system that I’m sure Rhema Church will be happy with for years to come.
