Apogee APL-10 Spécifications télécharger pdf (Page 18)

Signal Processing

Here’s a hypothetical example of what to look out for. An APL-500

might be set up outdoors in 85°F (29°C) temperature with sunlight shining

partially on the rear panel. Let’s assume it is tested during a 30-minute sound

check and all is well. Later that day, the ambient temperature rises to 99°F

(37°C) and the sunlight is now shining directly on the rear of the loudspeak-

er. The show starts, featuring dance tracks with no pause between song titles.

Under such extreme conditions, it is entirely possible that after a period of

service, the loudspeaker will shut off to protect itself from excessive heat.

Problems, such as the one described above, can be avoided by shading the

heat sink from direct sunlight.

(1) Basic Concept

The APL-220, -500, and -800 use a highly-advanced signal processor con-

tained entirely within the unit. The processor provides the functions of an

eighth-order (48 dB/octave) electronic crossover, fixed equalization to com-

pensate for driver/enclosure anomalies, time delay to acoustically align the

low and high drivers, and advanced protective limiting circuits. It also provides

a low-frequency alignment circuit that acts synergistically with the enclosure’s

ports. This serves to extend the bass response well below that of a conven-

tional enclosure of a similar size. All circuits in the audio path utilize the high-

est quality, most up-to-date semi-conductor technologies available today.

The processor is the key to the extraordinary sound quality of the loud-

speaker system. Unlike generic crossovers, either digital or analog, the APL

processor was carefully designed in tandem with the amplifiers, the drivers,

and the enclosure to provide optimum performance.

(2) Functional Description of Integrated Design Philosophy

One example of integrated design is the deployment of the high-frequency

equalization circuit. Here’s how it works: The loudspeaker’s high-frequency

driver uses a composite diaphragm material that is capable of smoothly

reproducing the extreme high frequencies, but not with the same sensitivity

as that of the lower portion of the spectrum. This is because the material is

highly damped and exceptionally free from resonance, especially when com-

pared to the typical distortion-prone aluminum and titanium diaphragms

used by most manufacturers. This same property, however, causes the driver

to exhibit a linear fall-off in its high-frequency response. The driver would not

be very useful in a two-way, non-processor based system, because it would

require a very specific compensation filter, not available from most generic

equalizers, to restore its response to flat.

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Apogee APL-10 Spécifications Page 18