Planar sources radiate uniformly for low frequencies, but as the frequency increases, the directivity narrows and becomes directional. This phenomenon is known as diffraction.
Loudspeaker Design Speakers
Loudspeakers are complex audio-frequency transducers, and their performance depends on a host of design factors, from the choice of drivers to the structure of the cabinets. A well-designed speaker will have a smooth transition between how a large driver, such as a woofer, plays a note and how a smaller driver, such as a tweeter, plays the same note. If the transition is not smooth, there will be discontinuities in the harmonic structure of a note and a loss of clarity. This is what is referred to as phase distortion.
The crossover network is one of the most important components in a loudspeaker. Its function is to interpret the signal from the media device and direct the appropriate frequencies to the corresponding drivers. It should also include a low-pass filter to keep the highs from reaching the woofer and a high-pass filter to prevent the lows from entering the tweeter. Unfortunately, some manufacturers use very steep slopes in their crossovers, which can cause the acoustic centers of the woofer and tweeter to be misaligned. This can result in a noticeable delay between the acoustic centers of the two drivers, and it can create a harsh sound. In addition, steep slopes increase the amount of noise in the signal and can cause distortion in both the woofer and tweeter.
In addition to a thorough understanding of the theoretical elements of loudspeaker design, a sound engineer needs to be able to perform accurate measurements and make subjective listening evaluations. This combination of technical data and hands-on testing is essential in delivering a high-quality product that will be musically rewarding for the listener.
In addition to a unique acoustic signature, every brand has its own specialized engineering and manufacturing processes that shape the listening experience in subtle yet impactful ways. These differences help establish each manufacturer’s esthetic preference, and at many points throughout the design process, esthetic choices merge invisibly with engineering decisions. The result is a unique product that will have its own distinct sonic character. This is what makes the difference between good and great speakers.
Drivers Speakers
A speaker driver is the component of a loudspeaker that converts electrical current into sound waves. When an electric current passes through a conductor, it creates magnetic fields that can be detected by the voice coil in the speaker. This causes the voice coil to move back and forth, producing sound. The driver also has an enclosure that can be ported or sealed to create different sound characteristics. Understanding how these components affect the performance of a speaker is crucial for creating high-quality audio systems.
The voice coil in the speaker sits inside of an annular gap formed by the cone and the magnetic pole piece. This gap can be vented to reduce the highly non-linear spring effect caused by air trapped behind the dust cap or to dissipate heat and prevent damage to the voice coil during high excursions. The woofers and midranges of high-performance drivers also employ phase plugs, which reduce on-axis beaming and provide additional venting and cooling.
When selecting the diaphragm material for a driver, cost, manufacturing complexity-uniformity issues and performance considerations must all be considered. The choice of diaphragm material can dramatically impact the performance of a speaker. For example, paper formulations are inexpensive and have good performance but are sensitive to humidity. On the other hand, polypropylene has a very controlled break-up and is durable, but it requires much more careful manufacture to maintain unit-to-unit consistency.
The frame, top plate, and magnet are known as the speaker’s “hard parts.” It is expensive for small speaker companies to tool and produce these components so they tend to buy them ready made. However, the “soft” components such as the cone, surround, voice coil, and spider are where a lot of differentiation is created by speaker manufacturers.
Infinite baffle designs eliminate rear wave interference by using a large enclosure. This ensures that the waves generated by the speaker never interfere with each other, which can cause diffraction and resonances. While this type of design is impractical for most applications, it can be very effective in a home cinema setup.
Enclosures Speakers
The enclosures (also called cabinets) of loudspeakers play a major role in their performance. They can influence factors such as frequency response, efficiency, and power handling. They also determine how well the speakers blend in with the acoustics of the room they are placed in. In addition, enclosures protect the delicate internal components of the speaker from dust, moisture and physical damage.
The first thing to consider when selecting a speaker enclosure is the size of the room in which they will be used. Larger rooms require larger enclosures to fill them with sound, while smaller spaces may be best served by a smaller enclosure. The size of the driver and its physical characteristics also have a direct impact on enclosure size. For example, woofers with larger cones need bigger enclosures to achieve adequate bass output.
In order for a speaker to function properly at all frequencies, it must prevent the pressure wave created by the back of the driver from canceling out the wave produced by its front. This can be accomplished by mounting the driver in a large, rigid sheet of material called a baffle. However, this is impractical in most applications and would impose a significant weight penalty. Instead, a closed box is usually used. A closed box can be designed to reduce unwanted resonances, which color the sound, by using low-resonance materials for the enclosure and internal absorption materials such as wool or synthetic fiber batting.
Some speakers are designed with a ported enclosure to enhance their bass output. These designs use a tube or vent that extends from the rear of the enclosure to provide extra space for air to escape. A ported enclosure is ideal for lower-frequency sounds, such as bass, guitars and drums.
Other types of enclosures include the transmission line and dipole. A transmission line enclosure consists of an infinitely long tube that is stuffed with absorbent material and then vented at the end. This type of enclosure is effective at reducing reflections from the back of the driver and can improve sound quality, especially in the mid to high frequencies. The amount of stuffing and the type of material is critical, as too much can cause resonances that degrade sound quality.
Power Amplifiers Speakers
Power amplifiers are the heart of any audio system, turning low-level electrical signals into high-level sound waves. They play an important role in enhancing sound quality by boosting the amplitude of the audio signal and driving speakers at higher volumes without clipping or distortion. Power amplifiers are also capable of delivering consistent performance across different frequencies, improving clarity and detail for a richer listening experience.
Choosing the right power amplifier for your speakers is essential to achieving the highest levels of sound quality. The power output of the amplifier must match the impedance rating of the speaker to prevent over- or under-powering the speakers, which can cause significant distortion and reduce audio clarity. In addition, higher-powered amplifiers offer more headroom, allowing sudden peaks in the audio signal to pass through without distortion.
Impedance ratings of speakers are measured by putting the speaker through a test signal that is usually wideband and fairly steady over the frequency spectrum. This gives a fairly accurate result for the power required by the speaker, but it is not necessarily indicative of how the speaker will behave in real-life use. In fact, two speakers can have very different impedance ratings if one has major dips in its response or is very reactive at certain frequencies.
The frequency response of a speaker is a curve that tells you how much SPL (sound pressure level) it can produce when driven at various levels of power. It doesn’t tell you what the speakers will sound like at those reference levels though – that would require knowing the speaker efficiency and distance from the listener, among other things.
Wrapping It Up
The most common type of power amplifier is the Class AB, which uses a feedback loop to increase its efficiency. This increases the power handling capacity and allows the amplifier to operate at lower temperatures, which improves long-term reliability. Moreover, the symmetrical output of Class AB amplifiers ensures a balanced performance, making them ideal for home and pro applications. In addition, the separate preamp and power amp designs provide versatility in adjusting audio signals before they are amplified, resulting in a customized listening experience.