Adding bypass capacitors correctly to a crossover?

[solderdude]

It seems these bypass caps have helped in that the attack has gotten quicker - not by a lot but noticeable.

Some sobering numbers (at 20kHz).
2uF = 3.9 ohm
0.015uF = 530 ohm

This means the current through the 2uF cap is 133x higher than what flows through the 15nF.
And not just 20kHz but for every frequency this is the case... a factor 133.
In other words the signal passing through the 'bypass' cap is 42dB lower than what goes through the 15nF.

As an experiment remove the 2x 1uF cap and only use the 15nF. You will hear nothing coming out of the tweeter... well perhaps with your ear against it.
That's what the 15nF 'adds'.

Using bypass capacitors can help with decoupling capacitors (big time even for high speed circuits > 1MHz) but does absolutely nothing for coupling caps (filter caps) other than change the filter frequency minutely lower.

 

[Randolf]

I think the idea of bypass capacitors in crossovers is to get the eventual positive effects of high price boutique capacitors for a lower price, since it is usually cheaper to combine a bigger "average" capacitor with a small high end capacitor than using just one big high end capacitor. How much benefit high priced capacitor really have I don't know, I typically struggle to hear these differences as long as you stay away from cheap electrolytical capacitors (with high tollerance and poor ESR, 2 obvious reasons to avoid these). For me reasonable quality is just good enough. Anyway many people really took a lot of effort to find the best matching capicator. E.g. in a recent german video in Franks Werkstatt der Lautsprechertechnik Frank tried various options for 3,3uF capacitor including 2 combinations (2,2uF+1,0uF and 2,7uF+ 0,47uF) and ended up picking a single expensive 3.3uF Mundorf MCap EVO SilverGold Oil (50 Euro) for the Mundorf AMT U60W1.1 he used in his project. Anyway I would assume the capacity of the bypass cap needs to be in some range of the other cap otherwise no audible signal at all would go through it.

 

[Randolf]

When looking at your crossover picture it looks like you already use some decent / expensive Janzen Superior Z-cap, so there is probaly little/nothing a bypass cap can improve here and it should be significalty better than an original vintage AA crossover. Looks like the original schematic of the AA crossover can be found here.