See how a bad 20W amplifier design destroys the entire speaker system
Time:2022-06-30
Views:1977
Many engineers who work with speakers and amplifiers will tell you the same thing. If the amplifier is operated excessively, the speaker driver will be damaged more or less. This process usually involves gradually increasing the bass knob or sharply increasing the volume knob. What are the consequences of this?
It may damage the tweeter driver of the speakers. But why did this happen? Most tweeter drivers are designed for the 10W to 15W power range. Driving them at high frequencies requires very little energy. The rated power of midrange and bass speakers is generally the average power of the entire speaker (50W, 100W, etc.).
Think about what happens when you add gain to a sine wave in a limiting system (using a fixed power rail to play music). At this time, the signal starts limiting. If you drive a signal beyond the limit, the waveform begins to look more like a square wave. In the frequency domain, we begin to obtain the input signal harmonics. Due to the appearance of a large number of amplitude limiting, the harmonic has a higher amplitude. Now, if you use a passive divider, many higher-order harmonics can easily go from the mid bass drive divider to the treble.
Because the driver power of high audio is very low, the damage probability is much higher. This is a real problem in many systems, especially those that use simple analog processing (e.g., Op Amp) or numerical control analog EQ systems. Two better solutions are:
1. dual power amplifier system
If you are in a closed system, such as an active speaker, please consider using dual power amplifiers in your system. Dual amplifier allows you to use a separate amplifier to drive the treble. The separation between treble and bass is completed before the low-frequency gain, which can prevent the treble from damaging the high-frequency part of the limiting bass channel.
The dual power amplifier system allows you to run most analog systems with highly flexible digital adjustment functions. The disadvantage is the high cost of adding amplifiers. However, we must make a compromise between a good passive divider and the cost of additional amplifiers. Using digital frequency divider in digital to analog converter (DAC) or multimedia digital signal codec (codec) can alleviate this problem to some extent.
It is much easier to fine tune your frequency divider digitally than to replace various passive components. This also allows the same PCB design to be used repeatedly for speakers and speaker drivers of different sizes. Note that this system only works if you have direct access to both drives individually.
2. Intelligent post-processing amplitude limiting bass signal
Some developers use soft clipping. This is a very simple method, but it is rare in home audio systems. Generally speaking, we will increase the low-frequency bass frequency to the highest. Some developers will remove the 24 dB bass boost to compensate for the low frequency response of small 2-inch drives.
If the frequency increase frequency is generally low, try adding a low-pass filter after the gain stage to reduce the high frequency caused by clipping. In analog systems, a multi-stage filter is usually required to construct such a low-pass filter with a sufficiently high cut-off rate, which makes the system bulky and expensive. However, it can be easily implemented in a digital processing system if there are enough effective MIPs in the audio processor.
Figure 2 shows an example of a processing flow for soft clipping.
Fig. 1 processing flow of high gain DRC and low pass filter
From portable audio amplifiers such as tlv320aic325x series devices to the updated pcm514x home audio minidsp DAC, these programmable minidsp products can achieve soft limiting. Some more intelligent implementation methods depend on the innovation of the majority of system developers. Each device is integrated with a fully programmable minidsp kernel, so that developers are no longer bound by the fixed processing flow and do not have to copy other people‘s audio system design methods.
Figure 2 use plimit to limit output and ensure no high frequency harmonics
For some, this may not be new. But for others, after reading this article, they may suddenly understand that "this is the reason why my speaker is damaged!"
It may damage the tweeter driver of the speakers. But why did this happen? Most tweeter drivers are designed for the 10W to 15W power range. Driving them at high frequencies requires very little energy. The rated power of midrange and bass speakers is generally the average power of the entire speaker (50W, 100W, etc.).
Think about what happens when you add gain to a sine wave in a limiting system (using a fixed power rail to play music). At this time, the signal starts limiting. If you drive a signal beyond the limit, the waveform begins to look more like a square wave. In the frequency domain, we begin to obtain the input signal harmonics. Due to the appearance of a large number of amplitude limiting, the harmonic has a higher amplitude. Now, if you use a passive divider, many higher-order harmonics can easily go from the mid bass drive divider to the treble.
Because the driver power of high audio is very low, the damage probability is much higher. This is a real problem in many systems, especially those that use simple analog processing (e.g., Op Amp) or numerical control analog EQ systems. Two better solutions are:
1. dual power amplifier system
If you are in a closed system, such as an active speaker, please consider using dual power amplifiers in your system. Dual amplifier allows you to use a separate amplifier to drive the treble. The separation between treble and bass is completed before the low-frequency gain, which can prevent the treble from damaging the high-frequency part of the limiting bass channel.
The dual power amplifier system allows you to run most analog systems with highly flexible digital adjustment functions. The disadvantage is the high cost of adding amplifiers. However, we must make a compromise between a good passive divider and the cost of additional amplifiers. Using digital frequency divider in digital to analog converter (DAC) or multimedia digital signal codec (codec) can alleviate this problem to some extent.
It is much easier to fine tune your frequency divider digitally than to replace various passive components. This also allows the same PCB design to be used repeatedly for speakers and speaker drivers of different sizes. Note that this system only works if you have direct access to both drives individually.
2. Intelligent post-processing amplitude limiting bass signal
Some developers use soft clipping. This is a very simple method, but it is rare in home audio systems. Generally speaking, we will increase the low-frequency bass frequency to the highest. Some developers will remove the 24 dB bass boost to compensate for the low frequency response of small 2-inch drives.
If the frequency increase frequency is generally low, try adding a low-pass filter after the gain stage to reduce the high frequency caused by clipping. In analog systems, a multi-stage filter is usually required to construct such a low-pass filter with a sufficiently high cut-off rate, which makes the system bulky and expensive. However, it can be easily implemented in a digital processing system if there are enough effective MIPs in the audio processor.
Figure 2 shows an example of a processing flow for soft clipping.
Fig. 1 processing flow of high gain DRC and low pass filter
From portable audio amplifiers such as tlv320aic325x series devices to the updated pcm514x home audio minidsp DAC, these programmable minidsp products can achieve soft limiting. Some more intelligent implementation methods depend on the innovation of the majority of system developers. Each device is integrated with a fully programmable minidsp kernel, so that developers are no longer bound by the fixed processing flow and do not have to copy other people‘s audio system design methods.
Figure 2 use plimit to limit output and ensure no high frequency harmonics
For some, this may not be new. But for others, after reading this article, they may suddenly understand that "this is the reason why my speaker is damaged!"
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