I've burned in the Wima film cathode bypass caps and my impression is that the film caps have a smoother sound, less dynamic than with the lytics I had before, not as much textural detail and a tad boring if I'm honest. I was a bit surprised because I thought that film caps would provide the most changes, more so than the WCF caps that I had just increased to 1uF recently, but the opposite is the case. With that change the difference was quite striking, more weight and body to the sound and therefore more dynamics and also a more pronounced soundstage with all that going on. So I've decided to change back to the lytics because I'm really missing the sound I got after the last change. I'm slightly surprised because I'm not that much of a bass head but I've missed that lively sound.
The film caps were 150uF and it's possible that 200uF would have made more of a difference but I don't think so going by the frequency curve from the cathode bypass calculator which is virtually identical for the 200uF. Maybe it might have affected the cutoff and let in more bass but I don't think so. I feel that this might be a characteristic of film caps that they have a flatter, more seamless sound.
The reason I wanted to try the film caps in that position was to see if the sub bass could be tightened up a bit with the increased speed and lower ESR but I couldn't really tell any difference.
The upshot of this is that maybe an extended chassis isn't necessary for top level sound so it might be preferable to save all that effort


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Edit: I also tried the dynamic test and as with the WCF caps this was the same as before, ie. there were still bass dips as shown on the meters so no increased power handling capability with the Wimas.