If you read the previous blog post, you know that there is a LOT of back-and-forths of all kinds going in a speaker system, even if you didn’t read the last blog post I’m pretty sure majority of you already knew that. The purpose of this blog post is to talk about the major factors that determine how a speaker system manages all that. These factors include: bass, efficiency and enclosure Size, placement, bass and other wavelengths and lastly moving up the scale.
Let’s starting off by talking about the first factor which is bass, efficiency and enclosure size. In order to reproduce really low frequencies (60 Hz and below) you have to move plenty of air and the louder you want to play those low frequencies, the more air you have to move. The most obvious expedient for moving the most air is a BIG speaker cone, which obviously takes a bigger bite of air than a small one. But there are penalties involved, especially if you’re talking about a full-range system. One is that the cabinet involved must be of an appropriately large size, another is that the behaviour of the speaker at frequencies above the lowest one being pretty quickly to leave something to be desired. This can be overcome by crossing over to a midrange speaker, which dictates at least three-speaker system.
So what almost all speakers designed to be heard in rational living spaces do to produce bass involves manipulation of four factors: the size of the cone, the mass of the moving system (mainly cone and voice coil), the strength of the magnetic “motor” driving the voice coil and the volume of air enclosed in the cabinet used. Increase or decrease any one of those and you affect what’s required of the other three for a given good level of bass performance. Increase speaker size and you need a bigger enclosure for the same low-frequency limit at the same efficiency. Increase magnet size and you’d better increase the mass of the moving system to prevent a peak in response from happening at or near the limit. Increase the mass of the moving system and you’ll have to increase the weight of the magnetic motor for the same efficiency.
Moving on to the next factor, a good way to represent the “fluid” nature of sonic radiation is with the illustration to the right, which depicts how the radiation of sound waves from different basic points is enclosed spaced affects its sonic output, especially at lower frequencies. As you can see, sonic output is increasingly reinforces as a sound-source such as a speaker moves away from a central position in space and toward boundaries. The greatest focusing occurs in a room corner and the greatest effect happens with low-frequency waves.
Our last factor is moving up the scale, above the bass region, the physics of sound involves less brute force and more subtlety. One of the big considerations is making sure various wavefronts arrive at your normal listening position together, without cancellations and additions. The other main and interrelated one is how high frequency powers response and dispersion, and the matching if speakers off the production line affect definition and imaging. There is a jumble of sounds reflected in different ways; near-by reflections from cabinets affect response with tiny “echoes” at higher frequencies. Close by reflections from walls affect response by in-phase additions and out-of-phase cancellations. Good speaker designers give enormous consideration to minimizing diffraction effects on high frequencies on the front surfaces of their speaker enclosures. What happens with sonic reflection s after the designers get through depends mainly on you. If you’re among the many speaker owners whose first placement of speakers in a listening room sounds so satisfying that the thought of repositioning them never occurs to you, wonderful. But if things don’t sound quite right, either at the beginning or later on, very small changes in speaker placements sometimes only a few inches may make a major difference. If room and cabinet reflections are as important as we say they are, you might see why we have some reservations about bi-polar speaker designs that radiate sound in two (or more) directions at once for an increased sense of spaciousness. They make perfect sense for surround speakers in a home theater system, which are meant to create a diffuse soundfield, but we find them undesirable for use in the main speakers of music. The artificial spaciousness produced by deliberately bouncing sound around also tends to produce effects, like the ten-foot-wide soprano singing form everywhere in sight. Real spaciousness depends not only on the ambiance of the original recording and the positive or negative nature of your listening room, but on extreme precision in the factors discussed above. And besides the midrange and high-frequency difficulties, we’re also not fond of the fact that placing full-range bi-polars even a trifle off from the suggested relation to the rear wall tends to bring bass boominess.
Let’s starting off by talking about the first factor which is bass, efficiency and enclosure size. In order to reproduce really low frequencies (60 Hz and below) you have to move plenty of air and the louder you want to play those low frequencies, the more air you have to move. The most obvious expedient for moving the most air is a BIG speaker cone, which obviously takes a bigger bite of air than a small one. But there are penalties involved, especially if you’re talking about a full-range system. One is that the cabinet involved must be of an appropriately large size, another is that the behaviour of the speaker at frequencies above the lowest one being pretty quickly to leave something to be desired. This can be overcome by crossing over to a midrange speaker, which dictates at least three-speaker system.
So what almost all speakers designed to be heard in rational living spaces do to produce bass involves manipulation of four factors: the size of the cone, the mass of the moving system (mainly cone and voice coil), the strength of the magnetic “motor” driving the voice coil and the volume of air enclosed in the cabinet used. Increase or decrease any one of those and you affect what’s required of the other three for a given good level of bass performance. Increase speaker size and you need a bigger enclosure for the same low-frequency limit at the same efficiency. Increase magnet size and you’d better increase the mass of the moving system to prevent a peak in response from happening at or near the limit. Increase the mass of the moving system and you’ll have to increase the weight of the magnetic motor for the same efficiency.
Moving on to the next factor, a good way to represent the “fluid” nature of sonic radiation is with the illustration to the right, which depicts how the radiation of sound waves from different basic points is enclosed spaced affects its sonic output, especially at lower frequencies. As you can see, sonic output is increasingly reinforces as a sound-source such as a speaker moves away from a central position in space and toward boundaries. The greatest focusing occurs in a room corner and the greatest effect happens with low-frequency waves.
Our last factor is moving up the scale, above the bass region, the physics of sound involves less brute force and more subtlety. One of the big considerations is making sure various wavefronts arrive at your normal listening position together, without cancellations and additions. The other main and interrelated one is how high frequency powers response and dispersion, and the matching if speakers off the production line affect definition and imaging. There is a jumble of sounds reflected in different ways; near-by reflections from cabinets affect response with tiny “echoes” at higher frequencies. Close by reflections from walls affect response by in-phase additions and out-of-phase cancellations. Good speaker designers give enormous consideration to minimizing diffraction effects on high frequencies on the front surfaces of their speaker enclosures. What happens with sonic reflection s after the designers get through depends mainly on you. If you’re among the many speaker owners whose first placement of speakers in a listening room sounds so satisfying that the thought of repositioning them never occurs to you, wonderful. But if things don’t sound quite right, either at the beginning or later on, very small changes in speaker placements sometimes only a few inches may make a major difference. If room and cabinet reflections are as important as we say they are, you might see why we have some reservations about bi-polar speaker designs that radiate sound in two (or more) directions at once for an increased sense of spaciousness. They make perfect sense for surround speakers in a home theater system, which are meant to create a diffuse soundfield, but we find them undesirable for use in the main speakers of music. The artificial spaciousness produced by deliberately bouncing sound around also tends to produce effects, like the ten-foot-wide soprano singing form everywhere in sight. Real spaciousness depends not only on the ambiance of the original recording and the positive or negative nature of your listening room, but on extreme precision in the factors discussed above. And besides the midrange and high-frequency difficulties, we’re also not fond of the fact that placing full-range bi-polars even a trifle off from the suggested relation to the rear wall tends to bring bass boominess.