Crossover networks: essential for speakers to achieve a clear sound
A comprehensive guide for DIY enthusiasts, loudspeaker developers and DIY beginners
Just imagine, you are at a concert. The band is playing and you can clearly hear every note. The bass makes your chest vibrate. The guitarist is hitting the high notes and the vocalist is filling the room with a powerful voice. The thing you hear is a perfect separation of frequencies.
Now, we are going to transfer this concert into your living room. Without a crossover network, every cone in every speaker system would try to simultaneously reproduce this complex sound mixture. The vocalist’s voice would probably not be as clear, the bass not as rich and the high frequencies would rather be dull, depending on the speakers. Thanks to crossover networks, each cone in a multi-way speaker only delivers the sound which it is designed for.
Why are crossover networks important?
Without crossover networks, every speaker would try to reproduce the complete frequency spectrum. This would result in distortions and a poor sound quality. Crossover networks optmise the power capability of individual speaker components by ensuring that only frequencies will be reproduced which they are designed for. This
- results in a clear and well-balanced sound and
- also protects the components due to reduced wear and tear.
How do crossover networks work?
Just imagine the audio signal as a river which flows through a network of channels in the speaker system. The crossover network operates as a lock-keeper, diverting the water (in this case, the signal) to different channels.
- Low-pass filter: the bass speaker provides low frequencies. The low-pass filter only allows for low frequencies to pass through and blocks the high ones. This is achieved by means of inductivities (coils) which develop a higher resistance to high frequencies.
2. High-pass filter: the high-pass filter requires high frequencies. A high-pass filter only allows for high frequencies to pass through and blocks the low ones. For this purpose, capacitors are used to develop a higher resistance to low frequencies.
3. Band-pass filter: the midrange speaker requires a certain range of frequencies. A band-pass filter combines high-pass filter and low-pass filter to allow for the midrange to pass through only.
2. High-pass filter: the high-pass filter requires high frequencies. A high-pass filter only allows for high frequencies to pass through and blocks the low ones. For this purpose, capacitors are used to develop a higher resistance to low frequencies.
3. Band-pass filter: the midrange speaker requires a certain range of frequencies. A band-pass filter combines high-pass filter and low-pass filter to allow for the midrange to pass through only.
Display of 3 crossover frequencies of a 3-way speaker
Types of crossover networks
There are 2 main types of crossover networks: passive and active ones.
Passive crossover networks | Active crossover networks |
These feature passive electronic components, e.g. capacitors, coils and resistors. They do not require an external power source and are easy to implement. However, they may be less flexible and precise. | These feature active components such as operating amplifiers and require an external power source. They divide the signal prior amplification and can therefore provide more flexibility and precision. This results in a much more precise operation. |
Important aspects of crossover networks – particularly for speaker DIY enthusiasts
1. Selection of components
The right choice of components is essential for your crossover network. High-quality capacitors and coils ensure an improved sound quality. For example, you could use film capacitors instead of electrolytic capacitors because they are more robust and durable.
Important aspects of crossover networks – particularly for speaker DIY enthusiasts
1. Selection of components
The right choice of components is essential for your crossover network. High-quality capacitors and coils ensure an improved sound quality. For example, you could use film capacitors instead of electrolytic capacitors because they are more robust and durable.
2. Calculating the filter
You should carefully determine crossover frequencies, i.e. frequencies at which the signal is split. For this purpose, online equation calculators can help you. The equation for calculating a basic low-pass filter, for example, is as follows:
3. Layout and setup
The layout of the crossover network can influence the sound. Please pay attention to correct dimensions of the components and proper soldering. Avoid unnecessarily long wires. Place the components in such a way that they cause only minor electromagnetic interference.
4. Testing and adjusting
After assembly, you should test and adjust the crossover network, if required. For this purpose, use measuring equipment, e.g. oscilloscope or a frequency generator in order to check the crossover frequency and response of the crossover network. Small changes made to the components can have a huge effect on the sound quality.
A practical example: building a 2-way crossover network
Assuming, you want to build a 2-way crossover network for a speaker with a bass speaker and a tweeter. The crossover frequency should be at 3,000 Hz.
- Low-pass filter: use a coil with 0.27 mH in parallel to the bass speaker. This coil is blocking high frequencies and allows for low frequencies to pass through.
- High-pass filter: use a capacitor with 5.3 µF in parallel to the tweeter. This capacitor is blocking low frequencies and allows for high frequencies to pass through.
Mount the components onto the circuit board and solder them properly. Please ensure that the connections are stable and the components positioned correctly.
Types of crossover networks: Butterworth, Linkwitz-Riley, etc.
There are different types of crossover networks with respective characteristics for different ranges of application:
- Butterworth crossover networks: these crossover networks feature a flat amplitude response and are easy to calculate. They provide a good balance between phase and amplitude linearity.
- Linkwitz-Riley crossover networks: these crossover networks feature a steeper slope and provide an excellent phase at the crossover frequency. They are a very popular with high-quality speaker systems.
- Bessel crossover networks: these crossover networks are known for their excellent phase linearity. Thus, they are ideally suited for applications which require a precise phase reproduction.
- Chebyshev crossover networks: these crossover networks feature a steeper slope. However, at the expense of the rippled amplitude response. These are useful if a sharp separation of frequencies is required.
Find out more about interesting and helpful aspects of audio technology in our magazine
Matching the crossover network to the room
Room acoustics greatly influence the sound of a speaker system. Therefore, please note the following useful suggestions:
- Room concepts: certain frequencies are emphasised in a certain room while others are attenuated. Test your speakers in the room to be applied in. Match your crossover network accordingly.
- Listening position: the position at which you normally listen to the music determines which frequency should be emphasised. Match the speaker setup and crossover network, if required, to achieve the perfect sound at your listening position.
Application of DSP (Digital Signal Processing)
Digital signal processing (DSP) is increasingly applied in modern DIY projects to optimise the performance of crossover networks:
- Fine tuning: with DSP, you can precisely adjust crossover frequencies, phase and level matching.
- Correction of room acoustics: DSP allows you to solve problems occurring with difficult room acoustics, e.g. standing waves or reflections.
- Flexibility: you can try different configurations for the crossover network without having to carry out physical changes to the circuit.
Double or triple amplification: bi-amping and tri-amping
Bi-amping and tri-amping are techniques where separate amplifiers are applied for different frequency ranges:
- Bi-amping: 2 amplifiers drive bass speaker and tweeter separately. This can improve control and dynamics of the system.
- Tri-amping: 3 amplifiers drive bass speaker, midrange speaker and tweeter separately. This provides even more precision and control.
Impedance and crossover networks
The impedance of speaker components affects calculation and functionality of the crossover frequency:
- Impedance matching: please ensure that the impedance of the speakers match the values for which the crossover network is designed for.
- Series resistors and parallel resistors: use resistors to match the crossover network’s impedance. This ensures a perfect performance.
Cabling and layout
Layout of the crossover network and cabling affect sound quality and efficiency:
Avoid crosstalk: place your coils at an appropriate distance. This minimises electromagnetic crosstalk.
High-quality cables: use high-quality cables with a low resistance. This minimises signal loss.
Clean connections: please pay attention to clean and tight solder joints. This prevents contact problems and signal loss.
Conclusion: crossover networks are the exciting part of speaker building
Building speakers is a rewarding hobby which combines technical know-how and craftsmanship. Crossover networks are an essential part because they ensure a clear and differentiated sound reproduction. With the right components, careful calculations and a little eagerness to experiment, you can achieve impressive results. Come and enter the world of crossover networks and discover the joy of a perfect sound.
Headergraphik: AdobeStock Stefano Pepperino
