Speakers come in all sizes, from compact “bookshelf” models, to big floorstanders that take up valuable floor space in your living room. As the name implies, a bookshelf speaker is compact enough to sit conveniently on a bookshelf, which accounts for its enormous popularity ever since the 1960s. Before then, most speakers that claimed “hi-fi” status and that had authentic deep bass output were big, heavy, obtrusive and expensive. Then an American inventor, Edgar Villchur, of AR in Boston, devised the recipe to get decent low frequencies from a compact box. The result, dubbed the bookshelf speaker, caused a major revolution in home entertainment (besides making Edgar Villchur and his partner, engineer Henry Kloss, wealthy men).
To create, say, a convincing illusion of a jazz group playing in your room, a compact speaker must reproduce a staggering range of musical sounds — from the low tones of a grand piano or electric/acoustic bass (41 Hz) to the delicate harmonics of a cymbal (15,000 Hz and higher). How accurately and smoothly a speaker approaches that goal is called the frequency response.
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Most compact speakers use a “woofer” for the deep bass tones, typically a paper, plastic or metal cone of about 3.5 inches to 7 inches in diameter. For delicate high frequencies, a titanium-dome “tweeter” barely 1 inch in diameter is used. Remember, it has to vibrate 15,000 times per second to create the sound of a cymbal!
Other things being equal, the larger the diameter of the woofer or the more woofers that are used and the bigger the enclosure, the more deep bass the speaker will produce. And although compact speakers have definite lower limits in bass output, the best ones, which use 6.5-inch and dual 5.5-inch woofers, respectively, do a fine job of delivering bass to about 40 Hz. If you want ultra-deep bass sounds (bass drum, pipe organ, bottom octave on a piano), you have to go to a bigger floor-standing speaker or add a subwoofer, a large separate speaker dedicated to just producing the bottom few octaves of deep bass tones, from about 25 Hz to 100 Hz.
But you can start small, with a modest pair of compact bookshelf or “satellite” speakers and, later on, combine them with a subwoofer (for deep bass that the small satellites can’t deliver). Add three more satellite speakers and you’ve got a surround sound home theater system!