Why Large Sound Systems Need to Go Vertical - Page 2
Although the HDH enclosures are trapezoidal, when you pack them tightly with the horns side by side, the horns still overlap considerably, which causes cancellations and interference. In the system that I devised, I placed an HDH-3 enclosure between each HDH-4, which resulted in a nearly ideal arraying of the system. The real key to the performance of this system was the multiple PC4-XL digital electronic crossovers I used to calibrate the system. In this case, I employed two per array to calibrate the near- and far-field components. Since then, I have conducted further experiments with multiple PC4-XLs on smaller systems and have come up with some very interesting applications, where I would use one PC4-XL for each bandpass.
The vertically arranged components easily out-performed the same number of components spread out horizontally. The point of critical distance, where the direct field and the reverberant field become equal in level, was extended far beyond my predictions. I thought we would get at least a 50% increase in critical distance. Well, we increased the point of critical distance by a factor greater than 200%. Of course, the vertically arrayed system had been aligned using the digital-delay capabilities of the PC4-XL. We experimented with other versions of vertical arrays, but the one outlined here was the most efficient.
I would like to thank Ibrahima Ndiaye, the owner of Studio Demille in Yoff, Senegal, for giving me the opportunity to configure his Peavey stadium-sound reinforcement system. After returning from Africa I was contacted by our distributor in Barbados, A&B Musical Supplies. Norman Barrows, the owner, was thinking of updating his concert-level sound system. I gave him the proposal and told him to look it over and get with me if he had any questions. Well, he liked what he saw and ordered the exact system. When he took delivery of the system, he arranged for a conference call between his sound engineer and me. I had his engineer in Barbados sit with the PC4-XL digital crossover in his lap while we spoke on the phone. I also had a PC4-XL in my lap. In the course of about a ninety-minute phone call, I told him everything I knew about the digital crossover and helped him set it up for their system.
In December, I did a presentation on the digital crossover at the week-long Peavey Advanced Sound Reinforcement dealer seminar. It took more than three hours to cover the new PC4-XLA. Norman has been using this system for a couple of years now. He enhanced the original system by doubling up on the UDH(TM) Subwoofers and adding two more vertical rows to expand the horizontal coverage.
That is the story behind the R&D involving the system that I am now going to outline. This proposal includes the components that I would use if I were building the system today. The drawings of the racks and the signal flow of the crossovers are from the original system used by both Ibrahima Ndiaye and Norman Barrows.