Good question. I’m afraid I’m not the one to elaborate on it, Kevin, even though I’m the one who said it. I’m quite sure that the depth of sound and resonance needed in bass would be lost without it. But I’m lacking in the technical knowledge to explain why. If I thought the bladder was unnecessary, I would have replaced it with a hard cover a long time ago, and my Suzuki would get used rather than sitting on the shelf.
We have discussed this before. I think the A-34C has the little bladder, and I think it’s a previous A-34 I have with the bladder opening covered over. I may be misremembering which model. When I compared the two instruments, I thought the low notes were easier to play on the bladderless number but that the sound of those notes was shallower, noticeable when the note was sustained.