[Metfit77@gmail.com]

Are the 3.6uf caps worth upgrading on the nx-otica tweeter circuit? I don't know much about crossovers. Since the 3.6uf, 0.27mh and 8.0ohm parts connect the positive and negative, do their quality affect the sound?

[Hafgrim]

All the parts in a crossover affect the sound. Parts in the tweeter circuit affect them the most. If you want to start small, you could simply add a high end bypass cap to both capacitors in the tweeter. Bypass caps only have to be .1uf or lowers. Bypass caps are wired in parallel with the base cap.

[Hafgrim]

Miflex are popular
https://www.soniccraft.com/product_info.php/miflex-kpcu-010uf-600vdc-copper-foil-polypaper-in-oil-p-5288?osCsid=jq1ml2nt2v2nkffsrkekffndj1

Sonic cap platinum I've heard good things about.
https://www.soniccraft.com/index.php/sonicap-platinum-c-301_49_52?osCsid=jq1ml2nt2v2nkffsrkekffndj1

I used Duelund 0.01uF 600Vdc JDM Series Silver Foil & Wax/Oil Precision Capacitor   

[Tyson]

Oh yeah.  I'd get a Miflex copper foil cap for that spot if the budget allows. 

[Metfit77@gmail.com]

Thanks for the suggestions. I already added a 0.1uf miflex with the 9uf sonicap on the tweeter circuit. Does the 3.6uf cap need to be 250v? Looking to spend about 100$. The miflex would be way outside my budget.

[Tyson]

I'd just get Miflex (or Duelund) bypass caps for all the caps in the circuit.  Or at least as many as $100 would buy

[Metfit77@gmail.com]

Thanks for the recommendation. I went with Duelund Capacitor 0.1uF 630Vdc CAST-PIO-Cu Pure Copper Foil Series

[Hobbsmeerkat]

Thanks for the suggestions. I already added a 0.1uf miflex with the 9uf sonicap on the tweeter circuit. Does the 3.6uf cap need to be 250v? Looking to spend about 100$. The miflex would be way outside my budget.

Just an FYI, that 3.6uF cap is used in a notch filter.
That's probably the last place I would use a copper foil capacitor.
It's main purpose is to reduce output within a narrow frequency band.
So while a signal is technically passing through it, you're not going to gain anything by going with higher quality capacitor
As it's intended use is both narrowly focused and "subtractive"

Personally, I would put the money into upgrading the main resistor to a path or Duelund CAST resistor.
Alternatively, adding a high quality bypass capacitor to the midrange bundle, and bypass to the cap in shunt at the end of the network where the effect will be most beneficial as they affect the main cap provides is additive.

[Metfit77@gmail.com]

Thanks for your advise Hobbs. I will not bypass that 3.6uf cap.

I currently have a 0.1uf miflex on the 9uf cap in the tweeter circuit and on the 100uf on the midrange circuit. Is that what you meant by bypassing the cap in shunt at the end of the network?

[g3rain1]

Is there any rule for sizing a bypass cap?

[Tyson]

Is there any rule for sizing a bypass cap?

The rule of thumb is the small cap should not be more than 10% of the value of the big cap.  Personally I almost always use .01uF or .022uF caps.

[g3rain1]

The rule of thumb is the small cap should not be more than 10% of the value of the big cap.  Personally I almost always use .01uF or .022uF caps.

Is there a lower bound also? Like if it's too small it won't make a difference?

[Hobbsmeerkat]

Thanks for your advise Hobbs. I will not bypass that 3.6uf cap.

I currently have a 0.1uf miflex on the 9uf cap in the tweeter circuit and on the 100uf on the midrange circuit. Is that what you meant by bypassing the cap in shunt at the end of the network?

There are 2 caps in the mid circuit, the 100uF bundle then another single cap between the 2 coils. I would add the bypass to that capacitor.

[Hobbsmeerkat]

Is there a lower bound also? Like if it's too small it won't make a difference?

Generally we recommend staying within 0.22 and 0.01uF too much smaller and it becomes inneffective.
It really just depends on how much of an influence you want the caps to have on the main cap.