Help for active crossover for 2.0

[pra3718]

I am building 2.0 and building active crossover first time. So how is my schematic ?

[abraxalito]

Filters for HF and LF look a bit low-Q. Oh and the sub seems to have a high-pass characteristic - don't you want low-pass?

<edit> Oh, looking closer seems its band-pass. But also very low Q. Download LTSpice and sim it.

[pra3718]

Thank you, " Filters for HF and LF look a bit low-Q " Should I replace 10nf with 22nf ?

for subwoofer : 4.7uf & 2.7K is high-pass to remove very low frq. 4.7K shelving low-pass resistor. Should I change the values ?

[abraxalito]

No, just changing the cap values won't alter the Q - you need to apply a bit more positive feedback if your aim is to get a Butterworth response. Same with your sub's bandpass - its all first order sections.

You could have a play with this online calculator :

Sallen-Key Low Pass Butterworth Filter Calculator

[pra3718]

Thank you but I am not much expert to run the calculator.

I was copying Project 123

Sub-Woofer Controller

[abraxalito]

Ah but those stages have higher Q because each opamp has those 10k/10k resistors to the -ve input giving a 6dB gain - yours has unity (0dB) gain. So if you're going to copy it, you'll need to copy it more closely.

[pra3718]

Is this as per your advices ?

[abraxalito]

Yep, the tweeter and woofer filters now have the correct Q. You can simplify the sub circuit too if you want as you've made it fixed frequency and the original was variable.

[pra3718]

" you've made it fixed frequency and the original was variable."

If You mean to say VR1 & VR2, I think it is for variable gain. or what ?

[abraxalito]

The article suggests its for customizing the bass response according to your particular system. Its not a gain control as it varies the time constants of the integrators (those are the opamps with 100nF feedback caps).