Capacitor

Indeed. One substantial difference, if the drivers are upgraded they will almost certainly be different response and therefore require at least some crossover changes. If the upgraded driver is a known commodity, like adding a Be tweeter to Moab for example, something the manufacturer actually does and knows how to do, that is one thing. But to just pick a superior driver that fits, well that is almost certainly going to call for a lot of crossover tweaking.

As opposed to not really changing anything in the design at all, but merely implementing it with superior quality parts. That is what I did.

Also keep in mind, not only the caps, resistors and inductors. Also the inductors are now oriented better, their axes all at 90 degrees to each other. Also they are mounted on Omega eMat. They are no longer mounted on a wafer thin bit of fiber board, they are now on massive dense carbon fiber BDR Shelf. They are no longer hot-glued to a brace, but isolated on Townshend Pods.

Each and every one of these changes would be a pretty decent improvement on their own. All of them combined is why this upgrade elevates these speakers to such a high level. The beauty of this approach is that by being so careful to use all the same electrical values this means all Eric’s original work is retained and nothing needs to be trimmed or adjusted or experimented with.

That's a big value and can get pricey, I've had good luck with Claity Cap CMR, Jantzen Aumin Z then for a smoother rich sound copper foil, Juniper, Miflex the copper foil are great for bypass also. Sonicaps aren't bad for the money certainly if you bypass them with a copper foil. If you have sand cast resistors pull all those out and add Mills or a little expensive the Path are nice. Re wire the cabinet can make a big difference. If changing out caps gets to expensive the little things like resisters, wire change, cabinet bracing does make a difference. Even with very expensive we'll know speaker company's once you open the speaker up you will be shocked the cheap crap they put in there.

One of mine needed to be 125uF. That is pretty big and real expensive. So to save money I used 122uF Jantzen Premium ELKO with a 3.3uF Alumen Z as a bypass cap.   

I view this as similar to the way I used Duelund JDM Silver .01uF bypass caps with the Alumen Z.  

Looking at doing the wire, but with 17 drivers per speaker that is a big project for a Moab! Might still do it but really need to do some planning first.

+1 rodman 
George I think you are probably correct for the main purpose of THAT cap, especially if the circuit has it going to ground. Not super important and Auydn is darn good. If you want to spend $$, my choices are Jantzen and Juniper for capacitors really used in the L/C frequency circuit. More expensive, not worth the $.

@paulcreed - thanks, I'd never looked at Miflex components before, thanks for bringing it to my attention.