After extensively reading the 4343 crossover thread (more than a few times) and the lengthy 'Capacitor' thread started in 2003, I came to a couple of conclusions. The discussion on Solens, Hovlands, Auricaps, Sonicaps, etc, etc was pretty intriguing. It came down to many of the members having to listen to their mod'd speakers very, very carefully for any nuances that might occur. Some of the mods seemed to jump right out, like the Solen caps adding far too much brightness or the perils of tightly wound wire on capacitor construction.

I wonder how much of audio has become 'black magic' (think Monster cable here)? Does that include caps as well? I'm beginning to think so. While my experience is somewhat limited, my observation of the JBL crossovers from the L-110, L-112, L-150 and L-150A indicates that JBL put pretty good quality components in their networks, but none of it was 'black magic' type of components.

Scott Fitlin had apparently used Xicon Caps to good effect and in going to Mouser Electronics, I found .005 uf Polystyrene film capacitors for 30 cents each. The metallized Polypropylene's are 46 cents each. I ordered 30 of each and I'm going to try them out on one of the L-150's I've modified with the L-112 crossover (mod'd to the 3113b configuration per Giskard). The L-112 crossover has the early .068 bypass caps (later on, JBL went with .01 uf on all their systems)

I downloaded the L-250 schematic and saw the .01 uf/.005 uf bypass configurations on every large cap, including the LF, so I'm going to bypass the LF as well. I'll do an A/B listen to the L-150's and then it will be the L-300's next. The L-150 already has a bypassed crossover, so I'm not expecting a huge improvement as I'm replacing the .068 uf caps with the .01 PP and .005 PS Xicon caps (though there was a tremendous improvement using the L-112 bypassed crossover vs the stock L-150 network, which was unbypassed) and I will bypass the LF cap. The L-300's will be next for an A/B mod/listen as well and I'm pretty sure I'll hear a difference as I have with the L-150's I've mod'd. In my opinion, I don't think you have to spend a ton of money on 'black magic' to make these speakers sound better. They sound very, very good to begin with. The mods any of us perform should be just icing on the cake.