Two B1 and a crossover

[prooptiki]

I want to add a 15" woofer for my OB project so, after reading B5 manual I found the interesting Woofer Equalization.
It looks like a Sallen-Key High-pass Filter at 20Hz plus a bigger Quality factor Q



So my question, using this filter the only way is by an opamp?
In addition is it possible to use it in my schematic after the low pass (post #48 Two B1 and a crossover )?

Here is an online sallen-key calculator:
(Sample)Sallen-Key High-pass Filter Design Tool - Result -

Thanks

[AndrewT]

that filter uses a unity gain configured opamp as the active element.

That's why the filter is known as an S&K unity gain filter.

The jFET used as a source follower can be the active element.

the ratios of the capacitors and the ratio of the resistors determine the Q of the filter. You can create any of a wide range of Q values but the C:R ratios determine the frequency.
Download Ti filter software to avoid the manual calculations.

[prooptiki]

Like this way... (sallen key-buffer)?

[AndrewT]

delete R21 & R22.
The filter elements need to "see" as near infinite load as is possible to get.
That's why we generally use FET input opamps rather than BJT input opamps.

If the filter is placed inside the Power Amp then the output components can be deleted. Maybe retain a lower value of R23

DCB1 graduates to become a 2pole high pass filter !

[prooptiki]

Thanks Andrew!

Thinking loudly :
PLLXO or Sallen Key is better...?