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Frequency Shading
Typically, two side-by-side LF transducers operate differently in the LF and HF. At the lower end of a frequency range, the transducers operate in unison to achieve a smooth coverage angle. At the upper end of their frequency range, the transducers transition into operating as a dipole radiator. This results in a significant narrowing of coverage that can adversely affect the consistency of the dispersion pattern between the LF and HF sections.
To solve this problem, EAW uses Frequency Shading to offset the dipole action for desired dispersion of the LF drivers at the LF to HF crossover point. This involves reducing input to one of the transducers as the frequency increases into the region vulnerable to dipole action. This allows control over the LF dispersion pattern so that it can be matched to HF dispersion, providing consitent coverage with frequency. Frequency shading is implemented both in passive crossovers and using digital processing.
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AOS90
Atlanta's Olympic Stadium, now Turner Field, needed a single, passively powered loudspeaker to cover an area from directly below the enclosure to over 100 feet away – a task usually divided between a nearfield and longthrow loudspeaker. No additional powering or external processing could be employed.
The AOS90 uses frequency shading to integrate a high power compression driver/longthrow HF horn subsystem with a lower power nearfield HF subsystem without problematic interference between the two. A single woofer covers the entire area.
Since a constant directivity horn provides pattern control only within a certain frequency range, the concept was to allow the off axis radiation from high power longthrow device in the mid frequency area to cover the nearfield area. Both spectral balance and level were appropriate to the application. The nearfield horn was used only where the longthrow horn’s pattern begins to narrow. As a result, the AOS90 provided high impact, full range response over the entire defined coverage area using only a single amplifier channel.
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Coverage provided by LS832 Column Array™.
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LS Series
EAW's LS Series of line source loudspeaker systems brings the classic column speaker up-to-date. Sophisticated frequency shading and all-pass filtering integrates the drivers, maximizing the benefits of line source coupling while eliminating destructive interference.
The systems provide a well behaved nominal vertical coverage pattern of 20° that opens slowly and holds together into the LF region. With the enclosure baffle defining a gentle arc, the drivers form a curved line source to help prevent the vertical pattern from collapsing in the crossover region.
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Products that utilize this technology:
LS Series |
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