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.
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