RC vs RL Filters: Power Loss & Which is Better?

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Discussion Overview

The discussion revolves around the comparison of RC and RL filters, particularly focusing on power loss and efficiency in audio applications. Participants explore the implications of using resistive components in these filters and how they affect performance in practical scenarios.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants note that while ideal inductors and capacitors do not dissipate power, the series resistor in an RC filter can lead to significant power loss when driving audio signals.
  • Others argue that the resistance in the RL filter, represented by the loudspeaker's drive unit, can be more efficient as it converts electrical energy into sound energy, especially when properly enclosed.
  • One participant emphasizes that the power loss in the RC filter occurs due to the capacitor shunting audio signals, which requires a series resistor that dissipates power.
  • Another participant clarifies that the terminology used in describing the components may lead to misunderstandings, particularly regarding the roles of the drive unit and amplifier output impedance.
  • Some participants express confusion about the definitions and roles of components in the filters, leading to a need for clarification on terms like "drive unit" and "resistance."

Areas of Agreement / Disagreement

Participants express differing views on the efficiency and power loss associated with RC and RL filters. There is no consensus on which filter is definitively better, as multiple perspectives on the implications of resistive components and their roles in audio applications remain present.

Contextual Notes

Participants highlight the importance of context in understanding power loss, particularly in relation to the specific configurations of filters and the characteristics of audio amplifiers. There are unresolved assumptions regarding the definitions of components and their interactions in practical scenarios.

iScience
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this guy on youtube said "if you try pushing more than a few miliamps through an RC filter then you get significant power loss" and that therefore the RL filter was more preferable.

@ 2:40:


i thought L & C components don't dissipate any power, so what's the difference between running the same amount of current through either filters?
 
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WOW --- conclusion with no explanation. There is no power loss in in an ideal inductor or the capacitor. But, that is not the issue. He quickly showed a low pass filter with a capacitor, which is a shunt low pass filter. Pause at the last schematic, at the very end (2:49). The power loss is in the series R (he shows heat radiating from the R).
A lot of what he says makes me cringe, but it's not outright wrong. And, demo-ing a woofer with no enclosure --- wow.
 
I think the point he is trying to make is that the R in the RL filter is the drive unit itself and (particularly when the unit is in a proper enclosure ) the Resistance component in the RL, actually consists of the acoustic load, pushing sound out into the room. That is more efficient than with an RC filter with a series, dissipative resistor which, even near DC, will be dissipating a significant amount of the amplifier power.
 
I think you are a bit confused. He is describing an RL and RC crossover network driven by a low impedance amplifier.
Audio amplifiers do not have 8 ohms out. The point he is making is that the R in the RC filter drops power when the C shunts audio.
 
meBigGuy said:
I think you are a bit confused. He is describing an RL and RC crossover network driven by a low impedance amplifier.
Audio amplifiers do not have 8 ohms out. The point he is making is that the R in the RC filter drops power when the C shunts audio.
Not confused. For the C to work, there needs to be a series R first. A Low Impedance (Voltage Source) will not be affected by a shunt C; it needs a series R. That will waste power. The dissipated power in the RL arrangement is partly (if not totally) in the form of radiated sound energy (radiation resistance - to use an antenna term). In the right enclosure, the resistance of the voice coil will not be the only 'R' element involved.
 
meBigGuy said:
I think you are a bit confused. He is describing an RL and RC crossover network driven by a low impedance amplifier.
Audio amplifiers do not have 8 ohms out. The point he is making is that the R in the RC filter drops power when the C shunts audio.
Ahh. I see what you are saying now and it makes sense. In my vocabulary, the 'drive unit' is the moving part of the loudspeaker - and a loudspeaker consists of the box, ports, damping and the drive unit etc. etc.) I did not mean the Amplifier had a poor output impedance. Not an 'understanding' problem - just the use of terms. :)
 
I think we are in sync. I misunderstood "drive unit". We just call it the driver. You are correct that the driver is the R in the RL filter, which is an important point.
He certainly leaves room for misunderstanding in his last paragraph, though.
 

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