As has been mentioned the woofer shunt caps are not directly in the signal path, so the "quality" of the cap is less critical than a series midrange or tweeter cap. I tend to use good quality non-polar electrolytics (NPE) as woofer shunt caps, but have on occasion used a film cap when I can get the correct value and it's not too big or expensive. Since my time is valuable, I don't use the really cheap, generic NPEs, but use high quality NPEs from Mundorf, Elna and Nichicon. I figure good quality NPEs will likely last longer than cheapies and I don't want to have to re-recap any of my speakers in my lifetime.
I did use an 18uF Axon True Cap as the woofer shunt in a pair of JBL L19A crossovers I rebuilt. It was the correct value, inexpensive and small enough to fit in the same location as the original NPE. Here's a photo that shows the original crossover (left) and the recapped crossover (right). You can see how much larger the Axon is than the original NPE, but since there was plenty of room, that's what I went with.
The JBL 4301B Control Monitors have almost identical crossovers (the only difference in the woofer shunt is 16.5uF vs. 18uF). In that case, I used a pair of 8.2uF Murdorf E-Cap NPEs. The Mundorfs are good quality NPEs, they are affordable, and reasonably small. I use them a lot for woofer shunt caps.
JBL 4301B before:
Lol! These REALLY needed a recap. They had been improperly stored in an uninsulated attic and had gotten so hot the glue holding the inductors failed and the wax filled caps had melted.
JBL 4301B after:
A pair of 8.2uF film caps would have been much larger, more expensive and unnecessary.
Here's a photo of a Rapid Rectilinear Highboy crossover I recapped, again with a Mundorf E-Cap. In this case, the woofer shunt cap was 100uF. Even the E-cap was tight in this value. A film cap would have been the size of a Coke can and MUCH more expensive (4x the volume and 3x the price).
Sorry to post so many non-Klipsch pics in this forum. I hope it's not considered sacrilegious. To steer things back on track, my current project is a pair of 1st generation Klipsch Fortes. I will be using a 47uF Nichicon DB NPE cap in place of the original 47uF NPE. The reason I went with Nichicon over Mundorf is the original is a radial lead NPE mounted on a PCB. The Mundorf E-Caps are axial lead. I may have been able to shoehorn in a Mundorf E-Cap, but it would be larger than the original, and wouldn't have directly fit the original PCB. So, I went with the Nichicon DB radial lead 47uF NPE. It was specifically designed for use in crossover networks, is actually slightly smaller than the original, and like the original, has radial leads. This makes it an easy drop-in replacement for the original.
So, yes replace the original NPE woofer shunt caps, they are the most likely to drift out of spec over time. Replace them with whatever is the correct value, affordable and fits. No need to spend too much on caps that aren't directly in the signal path.
