Basic knowledge in loudspeaker selection, part 2: How to find the right loudspeaker.

Welcome to the second part of the loudspeaker guide. After we introduced you to the different designs different designs of available loudspeaker drivers and their areas of application in the first part, this part will explain the different enclosures and other important parameters. We will also give you a checklist for your choice of loudspeaker.

Enclosure types

Loudspeaker drivers are dipoles, i.e. the sound produced is emitted in two directions: the useful signal to the front via the diaphragm and the opposite signal through the diaphragm swinging back. Since the rear signal is shifted by 90° to the front signal, in the worst case both signals can cancel each other out. In order to be able to channel the sound appropriately, each driver must therefore be installed in one of the three basic enclosures.

Open baffle

The first type is the open baffle: the loudspeaker chassis is mounted behind a wooden board with a matching hole. The board prevents an acoustic short-circuit, i.e. a cancellation of the signals, by delaying the time of flight. An open baffle is often used in radios or guitar amplifiers – and for some years now it has also been used again in hi-fi speakers.

Exponential horn

The exponential horn is even older than the open baffle. In its original form, it was used as an acoustic amplifier in gramophones, wax cylinders and Edison phonographs. Even today, it is mainly used in high-frequency loudspeaker chassis, amplifying the sometimes low sound power. You can find inspiration for this in the reichelt online shop.

Closed box

The most common design for loudspeakers is the closed box. In contrast to the open baffle and the exponential horn, the closed box ensures a good bass reproduction and is also available in different sizes. Usually, these speakers are equipped with two or three drivers. Either a tweeter and a midrange driver, a midrange and a bass driver or all three are combined. In addition, there are other possible combinations with full-range drivers, especially in the cinema/surround range. However, since these combinations are more for commercial use, they will not be discussed in detail here.

Physical evaluation criteria

Even without a university degree in physics, you should know and be able to evaluate the four most important parameters of a loudspeaker driver. They are presented below and explained in an easily understandable way.

Frequency response

The frequency response of a loudspeaker chassis describes the operating range in which the chassis provides optimum sound transmission. It lies in the frequency range audible to the average listener from 20Hz to 20kHz. The sound transmission should be as linear as possible and without level deviations. In practice, however, this cannot be guaranteed one hundred percent – that is why the frequency response often has to be corrected with electronic filters and loudspeaker cabinets.

Impedance

The impedance of a loudspeaker is an important selection criterion for matching it to an amplifier. If the impedance does not match the power amplifier, there may be a loss of power – in the worst case, the speaker and power amplifier may be damaged. The most common values for impedance are:

• 2 Ohm bass chassis
• 4 Ohm midrange, broadband chassis
• 8 Ohm midrange, broadband, tweeter chassis
• 16 Ohm midrange, tweeter chassis

Power

The power of a loudspeaker chassis is given in watts. It is important to note that the number given does not describe the sound power, but the electrical power to which a chassis can be subjected. About 99 percent of the power input is converted into heat and only one percent reaches the listener as sound. The stated power therefore refers either to a continuous sine wave signal at 1kHz or to a mixed signal or pink noise, measured in True RMS (Root Mean Square). However, the continuous sine wave signal is now obsolete as it can feed more energy into the speaker than is beneficial. Caution: Frequently seen specifications of 1000W for a PC’s mini-speakers are PMP or PMPO values, which may only be applied to the speaker for a few milliseconds.

Efficiency

The efficiency of a loudspeaker, given in dB, describes what proportion of the input power can be converted into sound power. It is decisive for the selection of the amplifier power amplifier. The value is usually between 83dB (low efficiency) and 99dB (high efficiency). Speakers with an efficiency of less than 90dB are often used in multi-way speakers. Even a low efficiency speaker can produce a reasonable sound level when used with a low efficiency amplifier.

Electrical systems

The complete frequency spectrum of a song reaches the loudspeaker via the amplifier of a stereo system. To ensure that each loudspeaker chassis receives the optimum frequency range for its design, filters are used in front of it. They are also called crossovers and are combinations of coils, capacitors and resistors. A distinction is made between three basic circuits: A low-pass or a high-pass filter directs only the corresponding low or high tones to the chassis. A low-cut circuit, on the other hand, is a combined high-low filter that suppresses or emphasises certain frequency ranges. A wide variety is available in the online shop.

How do I find the right loudspeaker for me?

Although choosing the right speaker system is often subjective, there are a few factors that should be considered when making a decision: Size of the room, possible furnishings, seating position and musical taste. Especially the size of a room is crucial for the right system – a one-room flat has different requirements than a disco. Depending on the room size, more compact solutions must be used accordingly. In addition, both the seating position and the furniture have an influence on the listening experience. If you are not sitting centrally to the speakers, speakers with a pronounced directional characteristic such as horn speakers or an open baffle are not advisable, as otherwise the stereo effect is lost. Speakers with a wide dispersion, such as two- or three-way speakers, are recommended. The more the acoustics can be damped, the stronger the sound output can be. When purchasing larger systems, it is advisable to test the speakers in your own rooms to make the right choice. After all, you test shoes for fit before you buy them. If you want to build your own speakers, you are spoilt for choice. The range is huge and sometimes confusing. The industry offers the right driver for every taste. The following matrices should help you to make the right choice for your own musical taste.

Especially the size of a room is crucial for the right system – a one-room flat has different requirements than a disco. Depending on the room size, more compact solutions must be used accordingly. In addition, both the seating position and the furniture have an influence on the listening experience. If you are not sitting centrally to the speakers, speakers with a pronounced directional characteristic such as horn speakers or an open baffle are not advisable, as otherwise the stereo effect is lost. Speakers with a wide dispersion, such as two- or three-way speakers, are recommended. The more the acoustics can be damped, the stronger the sound output can be. When purchasing larger systems, it is advisable to test the speakers in your own rooms to make the right choice. After all, you test shoes for fit before you buy them. If you want to build your own speakers, you are spoilt for choice. The range is huge and sometimes confusing. The industry offers the right driver for every taste. The following matrices should help you to make the right choice for your own musical taste.

Conclusion

After describing the different types of drivers in more detail in the first part of our guide to loudspeakers, we have now clearly explained the decisive parameters. With this knowledge, nothing stands in the way of a perfect sound experience.