Speaker Specifications: What They Mean and How to Choose the Right Audio System
When selecting a speaker system, one of the biggest challenges is understanding the specifications of different models. Terms like frequency range, sensitivity, impedance, or recommended power can be overwhelming. How do these characteristics affect the performance of a speaker? In this article, we will explore the key specifications and provide recommendations for choosing a speaker system. Let's begin!
How Does a Speaker Work?
A speaker is a device that converts one form of energy into another (electrical into mechanical). To produce sound from a speaker, it must first be connected to a source of electrical signals (such as an amplifier) using appropriate cables.
The speaker receives these signals and passes them through a coil of wire called the voice coil, which moves freely back and forth between two poles of a large magnet.
Acoustic systems:
Brand: Bowers & Wilkins
: 46
Connection method: stereo
Brand: Focal
Connection method: stereo
Diameter of the woofer, mm: 165
A round diaphragm attached to the voice coil moves forward and backward, creating changes in air pressure that move in front of the speaker. Our ears recognize these waves as sound. Most speakers are housed in an enclosure, which helps focus the sound waves emitted from the front of the speaker.
Types of Drivers
To understand some of the specifications we'll discuss, it's important to know the common types of drivers. Each type is optimized for a specific frequency range and has unique characteristics.
Cone Drivers
These are the most common type of speakers, typically used for reproducing mid and low frequencies. The cone shape effectively moves air, generating sound waves across a wide frequency range. These drivers are versatile and can be found in various speaker systems, from small bookshelf speakers to large subwoofers.
- Application: Low-frequency (LF), mid-frequency (MF), and full-range drivers in speaker systems.
- Key Characteristics: Size and material of the diaphragm, frequency response, impedance, sensitivity, and power handling.
- Materials: Affect sound quality, durability, and efficiency. Common materials include paper, polypropylene, Kevlar, and aluminum.
Dome Drivers
These are typically used for high-frequency reproduction. The dome shape provides wider sound dispersion compared to cone drivers. This type of driver is effective at reproducing high frequencies due to its ability to handle fast-moving waves. However, it is not suited for bass reproduction.
- Application: Tweeters (high-frequency drivers) in speaker systems.
- Key Characteristics: Size and material of the diaphragm, frequency response, impedance, sensitivity, and power handling.
- Materials: Influence high-frequency performance and durability. Common materials include silk, fabric, metal (such as aluminum or titanium), and composite materials. Silk and fabric domes often produce smoother, more natural sound, while metal domes offer greater detail and precision but can sound harsh. Each material has its pros and cons and its unique sound character.
Horn Drivers
Typically, these are dome drivers housed in a specially sized horn. The horn amplifies and disperses sound from the driver. This design increases efficiency, making it ideal for high sound pressure levels. Therefore, horn speakers are often seen in concert venues, but they are also popular in home audio. For example, Klipsch extensively uses horn drivers. These drivers cover a wide frequency range depending on the design but are usually used for mid and high frequencies.
- Application: Mid and high-frequency drivers in home, studio, and concert speaker systems.
- Key Characteristics: Horn shape and size, driver material, frequency response, sensitivity, impedance, power handling.
- Materials: Like other types, the material affects performance and durability. Horn drivers often use compression drivers with diaphragms made from materials such as titanium, aluminum, or phenolic resin.
These are the most common types of drivers, but there are other options, such as planar magnetic, electrostatic, and ribbon drivers. We will leave those aside for now, as we're focusing on "classic" speakers.
Frequency Range
This indicates how effectively a speaker can reproduce different sound frequencies. The frequency response refers to the range of frequencies a speaker can reproduce, from bass notes to the highest treble notes. This range is measured in Hertz (Hz). There are two common ways to display frequency range in manuals and descriptions:
- Textual: Most manufacturers specify the range as a boundary, defining the frequencies the speaker can reproduce without significant distortion.
- Graphical: A description showing how the speaker reproduces specific frequency regions, usually displayed with a dB scale on the Y-axis and frequency on the X-axis. A graph is much more informative than just a boundary, as it shows how the speaker will behave depending on the frequencies being played. Not all manufacturers provide graphical data for users.
Recommendation: A flat response within the operating range is preferred, as it indicates that the speaker can accurately reproduce sounds across the spectrum without favoring or neglecting any specific range. In headphones, a "smile" graph is often seen, where bass and treble are elevated for a more vibrant and emotional sound presentation.
Recommended and Peak Power
Let's clarify that speakers don't have a "power" rating. Instead, it refers to the power a speaker or specific driver can handle without damage. Power is usually specified in two ways: RMS (Root Mean Square) and peak. This characteristic is expressed in watts (W).
- RMS (Root Mean Square): Often referred to as continuous power, this is the amount of power the speaker can handle continuously without overheating or damage. This specification provides a realistic assessment of the speaker's capabilities, as it reflects the power they can handle during prolonged listening. RMS is usually specified as a range between the lowest and highest values. Exceeding the recommended power range can cause the driver to operate in extreme conditions, leading to failure.
- Peak Power: Refers to the maximum power the speaker can handle in a short burst (less than one second) without damage. This characteristic is less indicative than RMS. Manufacturers often use it to make a model appear more "impressive." Operating a speaker at peak power will lead to overheating and damage.
Impedance
Impedance refers to the resistance the speaker provides to the electrical current from the amplifier, measured in ohms (Ω). Unlike regular resistance, impedance changes with frequency due to the nature of audio signals (alternating current).
Manufacturers specify the nominal impedance or average value in the manual. Common values are 4Ω, 6Ω, 8Ω, and 16Ω, which are crucial for compatibility between speakers and amplifiers.
- Lower impedance (e.g., 4 ohms) allows more current to flow, resulting in louder sound. However, this imposes special requirements on the amplifier, increasing the risk of overload and overheating. A speaker with low impedance should be well-controlled so the amplifier can handle the load without damage. Some speakers have impedance that drops to 2 ohms or lower, which can be problematic for weak amplifiers.
- Higher impedance (e.g., 8Ω) limits the current, making it easier for the amplifier to operate, reducing the risk of overload and overheating. This typically leads to more controlled and stable performance. There's a common misconception that speakers maintain their nominal impedance across all frequencies. This is not true. The actual load on the amplifier depends on the minimum impedance, not the average value. That's why it's crucial to ensure the minimum impedance matches the amplifier's capabilities.
Note: The international standard (IEC 60268-5) provides a certain level of consistency: the speaker's minimum impedance should be no less than 80% of its nominal value. For example, an 8-ohm speaker should not drop below 6.4 ohms.
Impedance Matching Recommendations
Impedance is a key factor affecting the performance and stability of a sound system, so precise matching is crucial. When purchasing components, be sure to study the impedance specifications and match them accordingly.
- Generally, the amplifier's output impedance should match or exceed the speaker's impedance.
- Avoid connecting low-impedance speakers to a high-impedance amplifier, as this can overload the latter. However, connecting high-impedance speakers to a low-impedance amplifier usually does not cause problems, but it may result in the speakers not utilizing the amplifier's full potential.
- Many amplifier and speaker specifications include impedance matching recommendations. Pay attention to them. Some audio systems have an impedance-switching feature for adaptation.
Sensitivity
Sensitivity measures how efficiently a speaker converts electrical power into sound. It is expressed in decibels (dB) and indicates how loud the speaker will be at a given input power, usually measured as 1 watt of power at a distance of 1 meter.
High sensitivity means the speaker will produce more sound with less power. This is advantageous, especially when you want to achieve high volume without needing a more powerful amplifier. Most home speakers have a sensitivity range of 87-92 dB, but there are exceptions. Note that speakers with low sensitivity, such as 84 dB, are not suitable for weak tube amplifiers but are more manageable for some transistor amplifiers. We recommend choosing speakers with high sensitivity, as they are less demanding on amplification.
Distortion
Distortion occurs when a speaker alters or changes the original sound during playback. This is an undesirable effect in audio that reduces sound quality and clarity. Distortion occurs in various ways and is often reflected in the specifications of a particular model. For example, harmonic distortion is a type of non-linear distortion that occurs when the signal passing through the device is distorted in such a way that new frequency components appear in its spectrum, multiples of the original signal's frequency.
Directivity
Directivity refers to how a speaker's frequency response changes at angles off-axis. A speaker with wide directivity maintains consistent amplitude (sound pressure level, SPL) between on-axis and off-axis sound. Conversely, a speaker with narrow directivity shows significant differences in amplitude.
Using the image above as an example, you can see that after about 2 kHz, the off-axis response (red) of the speaker begins to diverge significantly from the on-axis response (blue). This means that if you listen to the speaker slightly off-center at frequencies above 2 kHz, the sound will be less pronounced and detailed. When designing a speaker, the manufacturer aims for it to sound consistent both on and off-axis. However, the driver is not the only factor influencing directivity. Other factors include the enclosure design, crossover network, and driver placement. All these elements affect how evenly sound is distributed in different directions, impacting the overall listening experience.
Thiele-Small Parameters
These represent a set of electromechanical specifications that define a driver's performance characteristics. Named after engineers A. Neville Thiele and Richard H. Small, these parameters include values such as resonance frequency (Fs), total Q factor (Qts), equivalent compliance volume (Vas), and others. They provide important information about how a driver will interact with an enclosure and the surrounding space.
These parameters are primarily important to speaker system designers. They accurately predict the driver's behavior in various types of enclosures, allowing the speaker system to be tuned for the desired sound quality and performance. In this article, we won't delve into their details. However, it's important to understand that Thiele-Small parameters allow designers to simulate the driver's behavior using software before it is even built.
Acoustic systems:
Brand: Pro-Ject
: 37
Connection method: stereo
Brand: Focal
: 37
Connection method: bi-amp, bi-wiring
Conclusion
We've covered the key characteristics you should consider when choosing a speaker system. Now, when you open a manual with specifications, you'll have a better understanding of what terms like frequency range, impedance, and other parameters mean. This topic is too broad to cover in one article, but now you have the basics. At Dr.Head stores in Dubai, our experts are immersed in the world of audio and will guide you toward the perfect sound for your home or professional setup.
