Slicing and dicing
Dividing sound into separate areas of frequency in the hopes of seamless reproduction, is like trying to make a 4-wheel car out of two motorcycles. Possible, yes, seamless, hardly. The reasons we divide reproduction duties between different drivers is to optimize performance. Tweeters are best for high frequencies, woofers for bass. The problem of this slicing and dicing of sound is found at the point where they crossover. Were it possible to draw a hard line between the tweeter and the woofer, we'd have an easy go of it. Instead, each driver eases into the other's territory with much overlap. The device used to separate highs from lows is appropriately called the crossover. Crossovers are typically passives devices with capacitors, resistors, and coils of wire that range from the simple to the complex. Crossovers perform their task by rotating the acoustic phase of each driver around the crossover point set by the speaker designer. In a two-way system, that point is typically in the 1500 Hz to 2,000 Hz range. Interesting data, but who cares? We do. Our ear/brain mechanisms use phase to locate sound and we are very sensitive to small changes. In fact, the frequency areas where we are most sensitive starts at about 300 Hz and extends a magnitude, 3,000 Hz. Which, unfortunately, is right in the middle of where tweeters meet woofers. The fact that acoustic phase angles are mangled, relative to music played back without a crossover, makes it rather apparent why multi-driver loudspeakers are problematic. Yet, single driver loudspeakers offer no E-ticket ride either. They, like everything else, come with plenty of baggage. We'll open that suitcase tomorrow.
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