We're a couple years out on this thread admittedly, but I have some feedback on the boomy bass issue and other thoughts for anyone else (like me) still enjoying these speakers. I have the Braun L-810A. They're a wonderful speaker. We had an incident a couple years ago where some of the paper woofer cones became torn. To match up, all four woofers were sent away to Richard So. He reconed them with a more rigid paper material and installed new surrounds.
The two original 50uF ROE/Elko Platt electrolytics in each crossover were replaced with two 47uF Audyn Q4 MKPs. The inside of the L810 cabinets are completely open and the reverberations from both woofers can make it a little boomy inside. I fixed this by adding some additional insulation behind the upper midrange and tweeter drivers, and around the back of both woofers to create a (relatively) form fitting cradle around them -without actually touching them- which isolated them from each other as well as the upper drivers, to increase the dampening. It took three tries to get the amount of fill right, but in addition to recapping the old electrolytics which made LFs sloppy and loose, this dampening and the more rigid cones also helped tighten the lower end up a bit as well.
Also, the mid and tweeter sticky domes benefit from being re-doped by VintageAR's product on the auction site if they appear dry. Finally, I wanted to mention that if you've recapped them (like me) using two 47uF mkp per crossover because 50uF mkp may be harder to find and that 47uF was "close enough", they do indeed benefit from reaching the original 50uF value. I got a double-dose of added performance enhancement when I paralleled a 3uF cap across each one so it equaled 50uF. Not only that, but I used paper-in-oils, which complimented the polypropylene quite well and filled in any deficits of just using the Audyns.
Last night, I re-recapped just one the two speakers by incorporating the two PIOs, now 50uF x 2. I left the other speaker with just the Audyns 47uF x 2 and reconnected them to my stereo to compare in real-time. The difference is not subtle. The 50uF PIO speaker has more impact to its sound with higher gain. It is better defined with more detail, the soundstage is a little more open, forward and convincing. The bass impact has increased without losing focus. These are highly recommended upgrades for any pair of L810s to help tame and tighten the bass while increasing fidelity and performance over what a simple 47uF x 2 mkp recap (per crossover) had delivered.
