When we started the draft on this project we knew that we had to pursue a different approach to mainstream venue PA. First, our customer had very high demands towards sound quality. The system had to have transparency at all sound levels, zero distortion, and surplus headroom on the amps - something you would expect from a high end studio monitor system. Second, the system needed to be as ”green” as possible.
We had the great fortune of working with some of the best manufactures in the industry and their interest for this design has been overwhelming. Since we knew what was in the pipeline from Pascal (Denmark) we started building up a signal path based on their X-pro 3 digital amp and a custom developed DSP together with Ohm (England). We choose to build two ”amp farms” in separate 20U racks, each rack providing 52,000 Watts into 4 Ohms – 104,000 watts in total! The PA is a modified Ohm HD arena system with the freshly developed Pukk-218 Subwoofer by Pasi Kokkonen chief designer at Ohm, and the specs are through the roof.
The LightViper Series 32 system from Fiberplex (USA) was an obvious choice because it would enable us to accommodate a very complex data flow utilizing a single 4 core fiber, thus reducing the multicore from stage box to FOH to a single 100 meter tactical fiber on a single drum,
keeping the setup simple and intuitive for the user. The stage crew and the sound engineer must feel secure and at ease, especially with a system as complex as this.
The response from the users of the system has been quite interesting. The speed and ease of set-up has taken everybody by complete surprise. At one concert we had to change the monitor send configuration from FOH to a Monitor-mixer backstage - before sound check for the 3rd band! I must say that the crew looked a little pale thinking that the sound check of the 2 prior bands would have the levels all wrong due to the introduction of a monitor split at this late stage, not to mention delaying the sound check. However, we had prepared the LightViper Series 32 system setup not only to utilize a 64 channel optical split from the stage rack, but also delivering a 16 channel monitor send that could access the amp farm by moving a single fiber connection in the Neutrik fiber-optic patch bay, allowing the 16 monitor mix channels to be switched from FOH to the Monitor split. Changing this set-up takes 5-10 min if the monitor mixer is in the house.
The total system set-up is quite intimidating, but with only one fiber from FOH to stage rack and one fiber from the stage rack to the each of the Amp racks creates a slick underplayed “stealthy-look”.
One of the many techniques used is the introduction of Wave Division Multiplexers. These allow different light frequencies to travel in the same fiber. This allowed us to put our 8 data streams in a 4 core fiber by coding half the streams in 850nm and the other half in 1310nm.
It is a challenge to migrate to the digital domain. Understanding the fundamentals within the digital domain is still a work in progress, and not quite common knowledge yet as one would hope for. One should always remember that the sample rate is a constant value used to register a non-constant frequency representation, so the higher/faster the frequency the fewer sample points and therefore less resolution.
For live PA we need at least 24Bit/96Khz to have enough resolution to do filtering and DSP. We have chosen to use the clock in the LightViper VIM-1832 as master clock. The LightViper clock is rock solid delivering 96Khz to FOH (Midas Pro 3) and the entire system, synchronized between units by Super Clock (24.576Mhz) outputs for unsurpassed stability. All connections to the Midas Pro 3 are done through AES/EBU. All signals are available simultaneously as analog and digital, so that the PA system can work independently of the Midas Pro 3. As one may have spotted, the entry level Midas Pro 3 can handle 48 Channels of input and we have a 64 channel stage box. The deal is that we actually have 64 inputs so routing can be easily done within the Pro 3. The information is stored within your scene snapshot making it a smooth ride changing between different stage setups. If a band wants to bring another mixer, the LightViper Series 32 system will still prevail, although we made the decision that only 96khz is available as the house-clock to slave external equipment to ensure absolute signal quality and minimum latency.
The Mic-preamp on the LightViper VIS-1832’s perform impressively. The design reveals that the developers at Fiberplex have taken a step into the future that not many have the vision for yet. With 3 steps of gain +26 +12 and line (0), the setup is very simple and intuitive. Each channel has an overload LED which will indicate analog overload prior to the A/D converter. From this point all signals are line levels and should be treated accordingly. The input levels on the Pro 3 should be targeted to 0 db before fader. We have recorded many live shows already, and I am continuously amazed by the sound quality of the LightViper Series 32 system.
I believe that we have opened Pandora’s box with this project. Using the LightViper Series 32 system we have created a LEGO like set of rules, and cleared the way for new possibilities in sound reinforcement. We found it difficult to stop the design process and finalize the system design due to an abundance of new ideas that the system brought to light the further we went. With this system design complete, we will continue to work with Fiberplex to implement many more new ideas for the next project.