I think [cpole~] and [rpole~] based filter is still expensive.

Is there any way to build one only using [lop~] and [vcf~]?

If I have to build one this way, what would be the best method to create one?

If you just want a 2 pole lowpass, you can simply use the second outlet of [vcf~].

You can make a 4 pole resonant lowpass (like a Moog filter) using 4 [lop~] filters in series inside a feedback loop, but this has to be in a subpatch with a block size of 1, and some other stuff needs to be added to make the resonance behave correctly, add nonlinearities, etc. It's too expensive, so it's better to use the [moog~] or [muug~] externals.

>If you just want a 2 pole lowpass, you can simply use the second outlet of [vcf~].

is this even in the docs yet? yes it works.

I kinda doubt that the second outlet of [vcf~] is a lowpass filter.

When I checked it through the spectrum analyzer, low frequencies were not completely passed and cut out as I increased the frequency which is the second inlet of [vcf~].

So I thought both outputs of [vcf~] are all bandpass filter.

Can somebody confirm if I'm wrong about this?

Miller wrote [vcf~] with two outlets for real and imaginary components because he seems to like complex numbers. He realized later that this is equivalent to bandpass/lowpass, but only mentioned it informally on the PD list. I don't think it's officially documented anywhere.

And any resonance will attenuate low frequencies. This is true of any standard lowpass filter, if it's not specifically designed for constant passband gain. I think minimum resonance should be q = 0.707, which shouldn't attenuate low frequencies. But I haven't tried this for myself.

[cyclone/svf~] has a low pass output. A state variable filters does not attenuate the pass band when resonance is set to higher value. Theoretically it can be very efficient, however the cyclone version recalculates coefficients for every signal block, even when not required.