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Crossover and Speaker Settings in Relation to Bass Management
Most, if not all AV amps and receivers now incorporate some form of bass management. In many instances this management allows a user to determine the point at which lower frequencies are sent to the speakers and subwoofer via crossover settings.
This topic isn't intended as a tutorial for specific models of AV amp, but is intended to give some general guidance and dispel some of the misconceptions associated with the 'LARGE' and 'SMALL' speaker settings found on AV amps and receivers.
The Basics
Not all speakers are capable of handling the full range of frequencies associated with audio reproduction. The range of frequencies a speaker will reproduce (lowest to highest) is in many cases limited. The optimal range is 20-20,000Hz – this is generally accepted as being the range of human hearing. Speakers that can handle the full optimal range are referred to as "full range". Limited range speakers are far more common than full range units. While limited range speakers will more often than not be capable of handling the full gamut of high frequencies associated with treble, they're unlikely to be able to reproduce the lowest audible frequencies associated with bass. Some full range speakers go beyond what is accepted as the range of human hearing, but this is beyond the scope of this post and has little relevance to the topic being addressed in its context.
Crossovers are filters, made up of coils and capacitors, that direct specific frequency ranges to the appropriate speaker components such as the drive units associated with bass and treble (the low and high frequencies). This means that the drivers do not strain to reproduce notes out of their intended range and beyond the speaker's capabilities.
Most speakers incorporate passive crossovers, designed for the components within that speaker, such as the drive units etc.. A passive crossover is placed post amplification and the full range of frequencies are present in the amplified audio signal the passive crossover has to filter. During the filtering, if the crossover finds frequencies beyond the speaker's frequency range, it discards them. The discarded frequencies are lost forever and will not be passed on through to the drive units. These lost frequencies will therefore not be reproduced by the speakers. The passive crossover incorporated into the vast majority of speakers are fixed and non adjustable. Some speakers do incorporate adjustable crossovers, but again, this is beyond the scope of this post.
Active crossovers divide the frequency range before amplification, and can be adjusted to adapt to any speaker setup. They allow you to set the point at which the frequencies are divided before the audio signal is amplified and allow for certain frequencies to be directed to either individual power amps, for different drive units (bi-amping), or away from the amplifier(s) altogether. This form of crossover arrangement is generally regarded to be the cleanest and most effective. It does away with the amplification stage having to amplify frequencies that may not be acceptable by speakers that would otherwise be discarded. An active crossover also takes the strain away from the speakers onboard crossovers (if present). Basically, both the amplifier and the speakers are having to do less work.
AV Amps and Receivers (in general)
AV amplifiers and receivers incorporate their own form of active crossover filtering, allowing a user to determine where lower frequencies are sent and at which point (cut-off) the division of frequencies occurs. The cut-off point you enter within an AV amplifier's settings determines where low frequencies should be directed and at which frequency the redirection/split occurs.
Speakers you wish to apply crossover settings to must be set to 'SMALL'. This is usually done within the amplifier's speaker settings.
The size of a speaker (LARGE/SMALL) is determined by its low frequency handling abilities and not by its physical size. The full range of frequencies are sent to those speakers set to "LARGE', even if those speakers cannot handle the full frequency range (20-20,000Hz). If a speaker is set to 'LARGE' and incapable of handling the full range, the speaker's crossover will discard the frequencies the speaker cannot handle and those frequencies are lost.
In a setup who's speaker configuration lacks a subwoofer, at least one speaker or pair of speakers must be set to 'LARGE'. You get little if any say in this and the receiver will automatically designate the front left and right speakers as being 'LARGE' if a subwoofer isn't detected. Without the presence of a subwoofer, you cannot set all the speakers to 'SMALL'.
In configurations lacking a subwoofer, where at least one or more of the speakers must to be set to 'LARGE', the crossover setting of speakers set to 'SMALL' determines that frequencies below the setting be redistributed to those speakers set to 'LARGE' . This occurs even if the 'LARGE' speakers cannot handle the lower frequencies. In configurations lacking a subwoofer, you should try to use the speakers with the widest frequency range as the speakers set to 'LARGE'. Such an arrangement is more practical in configurations where the front pair are more capable than the accompanying satellite speakers. Such a configuration would be one where the front two speakers are floorstanders (full range or wider than normal) and the remaining speakers are bookshelf speakers (limited range).
In speaker configurations that incorporate an active subwoofer, connected to the dedicated LFE sub out of an amplifier, all the speakers connected to the amplifier's speaker terminals can be set to 'SMALL'. In such a configuration, the crossover settings determine at which point or points frequencies are split and sent to the speakers and subwoofer. All frequencies below the crossover setting are directed to the subwoofer and the frequencies at and above the setting are sent to the speaker or speakers the setting or settings directly relate to.
In configuration incorporating a subwoofer along with speakers set to 'LARGE', the results are much the same as those outlined above, but the full range of frequencies are still sent to those speakers set to 'LARGE', except for the dedicated LFE channel (if present). The LFE channel is output to the subwoofer via the dedicated LFE sub out. In order to send low frequencies other than those associated with the LFE channel to the subwoofer, speakers must be set to 'SMALL'.
It is generally better practice to set all speakers to 'SMALL' and use custom crossover settings when a dedicated active subwoofer is present. In cases where speakers are full range and or able to deal with frequencies at or below 80Hz then it is still suggested that a crossover no lower than 80Hz be used. You can get some of the reasoning behind this from this Audyssey article:
Determining The Crossover Setting(s) to Use
Several factors need to be taken into consideration when determining the crossover setting. You need to know both the frequency range of the speakers and that of the subwoofer in order to determine the acceptable range of frequencies you can use for the settings. If you buy a speaker package then guidance on what settings to use will more than likely be outlined within the documentation that accompanied the package. In other instances then the following rules apply. The highest frequency a subwoofer is capable of handling is the highest frequency you should use for the crossover settings. The lowest frequency a speaker is able to handle is the lowest you should set its crossover to, but it is generally advised that you set ctossovers at least 10Hz higher than the lowest rated frequency handling capability of the speakers..
EXAMPLE 1
Subwoofer frequency range: 20-130Hz
Centre speaker frequency range: 70-20,000Hz
Therefore the acceptable crossover settings range for the centre speaker would be: 70-130Hz and preferably 80 - 130Hz
This means you can use a setting of 70, 80, 90 etc., up to 130Hz for the centre speaker. If you use settings above or below the acceptable range then frequencies outside of the acceptable range will be lost and not reproduced by either the subwoofer or the associated speaker.
EXAMPLE 2
Subwoofer frequency range: 35-120Hz
Rear speakers frequency range: 120-18,000Hz
Therefore the acceptable crossover setting would be: 120Hz
The above example gives no leeway for adjustment and a setting of 120Hz must be used for the rear speakers.
EXAMPLE 3
Subwoofer frequency range: 24-175Hz
Front floorstanders frequency range: 48-20,000Hz
Centre speaker frequency range: 75-20,000Hz
Rear speakers frequency range: 68-20,000Hz
Therefore the acceptable crossover setting ranges would be:
Front floorstanders frequency range: 50-170Hz (preferably 60 - 170Hz)
Centre speaker frequency range: 80-170Hz (preferably 90 - 170Hz)
Rear speakers frequency range: 70-170Hz (preferably 80 - 170Hz)
When you know what the acceptable crossover range is, there is no optimum setting that suites all situations and listening tastes. It is up to the individual to determine which setting best accommodates their listening environment and tastes. As far as the settings go, one person's nirvana may be another's hell on earth, but 80Hz is more often than not suggested as being the frequency that should be used for the crossovers if the speakers are able to handle frequency as low as this. This is because this is the point at which the human auditory system starts to localise frequencies and some individuals may be able to start detecting where the subwoofer is located if sending frequencies above 80Hz to it?
Reasons For Adjustments
There's a practical advantage to redirecting the bass to a dedicated subwoofer channel with its own amplifier. This improves the headroom in the main channels in association with the frequencies still being amplified by the AVR and being output to the passive speakers. Redirecting the bass to the subwoofer relieves the receiver's amplifiers from having to work on reproducing the low frequencies and this greatly improves the headroom.
You may ask, "why not simply use the lowest acceptable frequency a speaker can handle for that particular speaker's crossover?". In at least two of the examples above, you have a choice as to what figure you use for the crossover setting(s). If the sound is distorted, or you feel a lack of surround effects, you can redirect more bass away from a speaker or speakers in order to try clean the sound up. When dealing with dialogue and the centre speaker, you can use the crossover setting to make adjustments to the mid range frequencies associated with speech. Apart from sending low frequencies to a subwoofer that can better produce bass, the objective is to get a smooth transition of bass from the speakers to the subwoofer while also cleaning up the midrange. Note that your room's acoustics may even play a part in determining where you set crossovers. A room may effect speakers in a way that creates lulls in association with certain frequencies at different location within that room so you;d want to try portraying those frequwnciesat those locations.
I hope this brief explanation is of use to someone and thank you for reading
Further Reading:
The Crossover - Brain of your Loudspeaker System
The Crossover - Brain of your Loudspeaker System | Audioholics
Bass Management Basics; Settings Made Simple
Bass Management Basics – Settings Made Simple | Audioholics
Bass Managwmwnt and The LFE Channel
Most, if not all AV amps and receivers now incorporate some form of bass management. In many instances this management allows a user to determine the point at which lower frequencies are sent to the speakers and subwoofer via crossover settings.
This topic isn't intended as a tutorial for specific models of AV amp, but is intended to give some general guidance and dispel some of the misconceptions associated with the 'LARGE' and 'SMALL' speaker settings found on AV amps and receivers.
The Basics
Not all speakers are capable of handling the full range of frequencies associated with audio reproduction. The range of frequencies a speaker will reproduce (lowest to highest) is in many cases limited. The optimal range is 20-20,000Hz – this is generally accepted as being the range of human hearing. Speakers that can handle the full optimal range are referred to as "full range". Limited range speakers are far more common than full range units. While limited range speakers will more often than not be capable of handling the full gamut of high frequencies associated with treble, they're unlikely to be able to reproduce the lowest audible frequencies associated with bass. Some full range speakers go beyond what is accepted as the range of human hearing, but this is beyond the scope of this post and has little relevance to the topic being addressed in its context.
Crossovers are filters, made up of coils and capacitors, that direct specific frequency ranges to the appropriate speaker components such as the drive units associated with bass and treble (the low and high frequencies). This means that the drivers do not strain to reproduce notes out of their intended range and beyond the speaker's capabilities.
Most speakers incorporate passive crossovers, designed for the components within that speaker, such as the drive units etc.. A passive crossover is placed post amplification and the full range of frequencies are present in the amplified audio signal the passive crossover has to filter. During the filtering, if the crossover finds frequencies beyond the speaker's frequency range, it discards them. The discarded frequencies are lost forever and will not be passed on through to the drive units. These lost frequencies will therefore not be reproduced by the speakers. The passive crossover incorporated into the vast majority of speakers are fixed and non adjustable. Some speakers do incorporate adjustable crossovers, but again, this is beyond the scope of this post.
Active crossovers divide the frequency range before amplification, and can be adjusted to adapt to any speaker setup. They allow you to set the point at which the frequencies are divided before the audio signal is amplified and allow for certain frequencies to be directed to either individual power amps, for different drive units (bi-amping), or away from the amplifier(s) altogether. This form of crossover arrangement is generally regarded to be the cleanest and most effective. It does away with the amplification stage having to amplify frequencies that may not be acceptable by speakers that would otherwise be discarded. An active crossover also takes the strain away from the speakers onboard crossovers (if present). Basically, both the amplifier and the speakers are having to do less work.
AV Amps and Receivers (in general)
AV amplifiers and receivers incorporate their own form of active crossover filtering, allowing a user to determine where lower frequencies are sent and at which point (cut-off) the division of frequencies occurs. The cut-off point you enter within an AV amplifier's settings determines where low frequencies should be directed and at which frequency the redirection/split occurs.
Speakers you wish to apply crossover settings to must be set to 'SMALL'. This is usually done within the amplifier's speaker settings.
The size of a speaker (LARGE/SMALL) is determined by its low frequency handling abilities and not by its physical size. The full range of frequencies are sent to those speakers set to "LARGE', even if those speakers cannot handle the full frequency range (20-20,000Hz). If a speaker is set to 'LARGE' and incapable of handling the full range, the speaker's crossover will discard the frequencies the speaker cannot handle and those frequencies are lost.
In a setup who's speaker configuration lacks a subwoofer, at least one speaker or pair of speakers must be set to 'LARGE'. You get little if any say in this and the receiver will automatically designate the front left and right speakers as being 'LARGE' if a subwoofer isn't detected. Without the presence of a subwoofer, you cannot set all the speakers to 'SMALL'.
In configurations lacking a subwoofer, where at least one or more of the speakers must to be set to 'LARGE', the crossover setting of speakers set to 'SMALL' determines that frequencies below the setting be redistributed to those speakers set to 'LARGE' . This occurs even if the 'LARGE' speakers cannot handle the lower frequencies. In configurations lacking a subwoofer, you should try to use the speakers with the widest frequency range as the speakers set to 'LARGE'. Such an arrangement is more practical in configurations where the front pair are more capable than the accompanying satellite speakers. Such a configuration would be one where the front two speakers are floorstanders (full range or wider than normal) and the remaining speakers are bookshelf speakers (limited range).
In speaker configurations that incorporate an active subwoofer, connected to the dedicated LFE sub out of an amplifier, all the speakers connected to the amplifier's speaker terminals can be set to 'SMALL'. In such a configuration, the crossover settings determine at which point or points frequencies are split and sent to the speakers and subwoofer. All frequencies below the crossover setting are directed to the subwoofer and the frequencies at and above the setting are sent to the speaker or speakers the setting or settings directly relate to.
In configuration incorporating a subwoofer along with speakers set to 'LARGE', the results are much the same as those outlined above, but the full range of frequencies are still sent to those speakers set to 'LARGE', except for the dedicated LFE channel (if present). The LFE channel is output to the subwoofer via the dedicated LFE sub out. In order to send low frequencies other than those associated with the LFE channel to the subwoofer, speakers must be set to 'SMALL'.
It is generally better practice to set all speakers to 'SMALL' and use custom crossover settings when a dedicated active subwoofer is present. In cases where speakers are full range and or able to deal with frequencies at or below 80Hz then it is still suggested that a crossover no lower than 80Hz be used. You can get some of the reasoning behind this from this Audyssey article:
Small vs. Large
Do you have a subwoofer in your system? Great. Then your speakers are small. Before you get all upset, read on. This is one of those audio myths whose time has come to be busted. To understand why, we need to talk about Bass Management.
In the early days of home theater it was thought that in order to reproduce the full movie surround experience at home it was necessary to place 5 large loudspeakers in the room. The reason for the size was the woofers. To play at theatrical reference levels and reproduce the deepest bass available in the content requires each speaker to have 12” or larger woofers. Let’s just say that this theory didn’t get very far in the real world.
A better and more practical approach came after studying human perception. The mechanisms that we use to determine the direction of arrival of sound depend on the frequency. At high frequencies the wavelength of sound is small and so sound coming from the side is shadowed by our head. That creates a level difference between the sound reaching the ear closest to the source and the ear on the other side. Our brain analyzes these level differences and produces an estimate of where the sound is coming from. But at lower frequencies, the wavelength of sound gets longer and our head is not large enough to produce a level difference at the two ears. Instead, we analyze the difference in time of arrival of sound at the two ears. Sound arrives first at the closest ear and we use that to determine the direction. But even that ability fails us below about 80 Hz. The wavelengths get very large and it was found in listening tests that 80 Hz is the frequency below which most people can not localize the direction of sound.
Taking advantage of this apparent “deficiency” in our hearing was what made home theater practical for millions of homes. Five satellite speakers of reasonable size could now be used because they no longer required large woofers. A subwoofer (or two) can reproduce the lower octaves and it can be placed out of sight since its content is not directional.
But there is also a practical advantage: directing the bass to a dedicated subwoofer channel with its own amplifier greatly improves the headroom in the main channels. The idea behind this was proposed in a Society of Motion Picture Engineers (SMPTE) meeting in 1987. The participants could not agree on the minimum number of channels required for surround sound on film. Various numbers were being shouted out until a voice was heard from the back: “We need 5.1”. Everyone’s head turned around to look at Tom Holman. He proceeded to explain what he meant: Take the low frequency content from all 5 channels and redirect it away from the satellite speakers to the subwoofer. If we do the math, then the content below 80 Hz is 0.004 of the audible 20,000 Hz bandwidth. But 5.004 didn’t sound as catchy so Tom rounded up to 5.1. By the way, don’t make the amateur mistake of calling it 5 dot 1. It is a decimal: 5 point 1.
Fast forward to the early 90s when the first DSP powered home theater receivers started to appear. Along with progress came complexity. Some industry forces believed that Bass Management should be an option that could be turned on and off by the consumer. That’s not necessarily a bad idea, but to make an informed decision requires much more knowledge about the system than what was available to the typical consumer. So, the Large and Small rule of thumb was established. The idea was to look at the size of your speakers and decide whether their woofers were “large enough” to reproduce the lowest octaves at the required levels. It was a noble thought, but looking at it 15 years later I believe that it has led to nothing but massive confusion. The poor consumer was led to believe that Large is somehow a good thing and was then left wondering why there was nothing coming out of their subwoofer.
Redirecting the bass to the subwoofer relieves the receiver amplifiers from having to work on reproducing the low frequencies and this greatly improves the headroom. If you happen to be using Audyssey MultEQ for room correction, you will achieve much better low frequency performance because the MultEQ subwoofer filters have 8x higher resolution than the filters in the other channels.
Here is a better rule: All speakers are Small. In today’s complicated AVR lingo that just means: If you have a subwoofer you should always turn bass management on. Always. Even if your receiver clings to the past and automatically sets your speakers to Large.
Determining The Crossover Setting(s) to Use
Several factors need to be taken into consideration when determining the crossover setting. You need to know both the frequency range of the speakers and that of the subwoofer in order to determine the acceptable range of frequencies you can use for the settings. If you buy a speaker package then guidance on what settings to use will more than likely be outlined within the documentation that accompanied the package. In other instances then the following rules apply. The highest frequency a subwoofer is capable of handling is the highest frequency you should use for the crossover settings. The lowest frequency a speaker is able to handle is the lowest you should set its crossover to, but it is generally advised that you set ctossovers at least 10Hz higher than the lowest rated frequency handling capability of the speakers..
EXAMPLE 1
Subwoofer frequency range: 20-130Hz
Centre speaker frequency range: 70-20,000Hz
Therefore the acceptable crossover settings range for the centre speaker would be: 70-130Hz and preferably 80 - 130Hz
This means you can use a setting of 70, 80, 90 etc., up to 130Hz for the centre speaker. If you use settings above or below the acceptable range then frequencies outside of the acceptable range will be lost and not reproduced by either the subwoofer or the associated speaker.
EXAMPLE 2
Subwoofer frequency range: 35-120Hz
Rear speakers frequency range: 120-18,000Hz
Therefore the acceptable crossover setting would be: 120Hz
The above example gives no leeway for adjustment and a setting of 120Hz must be used for the rear speakers.
EXAMPLE 3
Subwoofer frequency range: 24-175Hz
Front floorstanders frequency range: 48-20,000Hz
Centre speaker frequency range: 75-20,000Hz
Rear speakers frequency range: 68-20,000Hz
Therefore the acceptable crossover setting ranges would be:
Front floorstanders frequency range: 50-170Hz (preferably 60 - 170Hz)
Centre speaker frequency range: 80-170Hz (preferably 90 - 170Hz)
Rear speakers frequency range: 70-170Hz (preferably 80 - 170Hz)
When you know what the acceptable crossover range is, there is no optimum setting that suites all situations and listening tastes. It is up to the individual to determine which setting best accommodates their listening environment and tastes. As far as the settings go, one person's nirvana may be another's hell on earth, but 80Hz is more often than not suggested as being the frequency that should be used for the crossovers if the speakers are able to handle frequency as low as this. This is because this is the point at which the human auditory system starts to localise frequencies and some individuals may be able to start detecting where the subwoofer is located if sending frequencies above 80Hz to it?
Reasons For Adjustments
There's a practical advantage to redirecting the bass to a dedicated subwoofer channel with its own amplifier. This improves the headroom in the main channels in association with the frequencies still being amplified by the AVR and being output to the passive speakers. Redirecting the bass to the subwoofer relieves the receiver's amplifiers from having to work on reproducing the low frequencies and this greatly improves the headroom.
You may ask, "why not simply use the lowest acceptable frequency a speaker can handle for that particular speaker's crossover?". In at least two of the examples above, you have a choice as to what figure you use for the crossover setting(s). If the sound is distorted, or you feel a lack of surround effects, you can redirect more bass away from a speaker or speakers in order to try clean the sound up. When dealing with dialogue and the centre speaker, you can use the crossover setting to make adjustments to the mid range frequencies associated with speech. Apart from sending low frequencies to a subwoofer that can better produce bass, the objective is to get a smooth transition of bass from the speakers to the subwoofer while also cleaning up the midrange. Note that your room's acoustics may even play a part in determining where you set crossovers. A room may effect speakers in a way that creates lulls in association with certain frequencies at different location within that room so you;d want to try portraying those frequwnciesat those locations.
I hope this brief explanation is of use to someone and thank you for reading
Further Reading:
The Crossover - Brain of your Loudspeaker System
The Crossover - Brain of your Loudspeaker System | Audioholics
Bass Management Basics; Settings Made Simple
Bass Management Basics – Settings Made Simple | Audioholics
Bass Managwmwnt and The LFE Channel
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