Bypassing woofer cap -- Value too small?

As part of a crossover upgrade project, I will be changing a couple 125uF Bennic bipolar electrolytic caps in a pair of woofer crossover networks to Mundorf AC RAW bipolar eCaps. In storage, I have a couple unused Duelund CAST PIO CuAg hybrid caps with values of 0.022uF and I’m considering using them to bypass the large value Mundorf electrolytics. (I’m not interested in bypassing any caps on the mids/tweeter networks). That Duelund value is only 0.02% of the larger electrolytic cap value. Is that too small of a ratio? Any downside using a value that small that I should know about? I’m looking for more clarity in the 50hz-300hz range that the woofers’ response spans. Thanks in advance.


(The rest of the woofer cap story, in case it could be helpful... There are two other large value Bennic bipolar electrolytic caps in each of the woofer networks, both with values of 250uF each. I’ve decided to replace them with 200uF Mundorf AC RAW bipolar ecaps and add 47uF Jantzen Standard Z-Caps (metalized PP foil) in parallel on both. This is about 25%, or 1:4 ratio, so very different than the above proposition.)


I think it is too small, but also, keep in mind that caps that go to ground have an important ESR value associated with them. In addition to the Equivalent Series Resistance there is usually a  small value resistor ( < 1 Ohm) in series with the caps and the crossover is unusually sensitive to changes in ESR on even-order filter components. That is, any change to the cap ESR must be compensated for in the adjoining resistor.

You may like to try some of the Axion film caps there, btw. Really inexpensive and good sounding. 

@erik_squires Thanks for the tip about ESR. I was told about that a few months ago, but then I forgot! It sounds like I should leave the woofer caps alone since I can't confirm any ESR values.

Okay nice. I already bought Path Audio resistors to replace all of the cheap cement resistors in the network, including those on the woofer board, so I'll see if that alone gives the woofers a little bit more clarity. I'm pretty hesitant to mess with those woofer caps now. All of the other Bennic caps will be replaced with ODAMs in the next few weeks. Not touching the inductors.

I agree, too small, but I didn't bypass the caps for my woofer on my crossover rebuild.  I only used bypass caps on the mids and uppers.  I used .1uF.

Here is is for reference.  woofer section is bottom.  you can see the bypass caps on middle and upper.