It has a similar effect to a ported enclosure, creating a resonance to boost a narrow band and frequencies, and cutting all frequencies below this. The difference is that it is an electrical resonance rather than mechanical acoustic resonance.
The main 'problems' are that the capacitor is subject to large ripple currents, which leads to internal heating and shorter lifespan in electrolytics. Secondly the driver is subject to higher excursion over the boosted frequencies and lower excursion below this - this is the opposite to a ported enclosure.
The main 'problems' are that the capacitor is subject to large ripple currents, which leads to internal heating and shorter lifespan in electrolytics. Secondly the driver is subject to higher excursion over the boosted frequencies and lower excursion below this - this is the opposite to a ported enclosure.
I managed to simulate the issue. The speaker can be placed in a small enclosure with Q=1.0 and fc=50Hz (green).
With the series C it is now linear until 34.4Hz (brown). It falls off with 18dB/oct.
Amazingly the capacitor increases the driving voltage above the amp output (red).
With the series C it is now linear until 34.4Hz (brown). It falls off with 18dB/oct.
Amazingly the capacitor increases the driving voltage above the amp output (red).
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You also get the voltage gain when a suitable driver is measured in free air (with a large value cap)
And if you add a large value inductor (like you would for a low F crossover for OB use) you also get the voltage gain on the other side of the resonant impedance peak.
So you end up with a passively assisted boost on either side of the drivers resonant F
cheers
And if you add a large value inductor (like you would for a low F crossover for OB use) you also get the voltage gain on the other side of the resonant impedance peak.
So you end up with a passively assisted boost on either side of the drivers resonant F
cheers
For the second-order topology, I notice that there are 2 different types. One is a cap in series and an inductor in parallel to the drivers as a common style in every section of the crossover. The other is a cap in series and a resistor in parallel, if I’m not wrong it’s called passive line subsonic crossover or PLSX. What’s the difference between them? And why the latter is not popular in other crossover sections — used in tweeter, midrange circuits or even woofer for the low-pass filter?
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