I did some looking around concerning this speaker today. Didn't find a lot.
I found some discussion concerning this one and some other concurrent speakers about removing the back panel. They boil down to what has been discussed above.
0) The backs are sealed with probably the same Bostik sealant used in the later Braun models to seal both drivers and panels. It dries hard over time and can be a pita to remove.
1) Using a putty knife or such to pry the back panels free, starting at a corner. The danger here is damaging the side flanges.
2) Measure the size of the back panel (to fab a replacement) and then use a saw and cut through the back panel 1/2" or so from the outside edges. Then it is possible to use a putty knife or such to work from the inside to cut through the sealant and remove the rest of the back panel. Then make a new panel.
3) Some people have apparently tried the heat gun method of softening the sealant but didn't have good results with that. The back panel is too thick and dissipates the heat.
Based on info that I found concerning similar Braun speakers from the same time period, the screws through the middle area of the back panel attach to stand-off posts attached to the front baffle and act as cabinet bracing to reduce resonance.
I tried to think of a way to make use of that to assist with removing the back panel. Would be somewhat complicated.
1) Screw a long rod into the standoff through the back panel.
2) Make a pulling bar or piece of angle iron with a center hole and 2 side holes.
3) Thread a nut over the rod.
4) Lay the pulling bar over the rod.
5) Screw some long wood screws through the outer holes of the pulling bar, into the back panel.
6) Use a wrench to turn the nut under the pulling bar, thus pulling on the back panel.
7) Then see if that in combination with a putty knife prying up on the back panel, with something laid over the side flanges to protect them from damage, will successfully remove the panel.
8) My guess is that it will be easier to cut through the back panel and replace it than to do the above. If it works one will still have to fill in the holes in the back panel caused by driving screws into it.
The crossover is attached to the back side of the front baffle.
The cabs aren't very deep, so I wouldn't use a very long sabre-saw blade if cutting through the back panels.
The front grills are apparently glued in place and can't be easily removed.
The drivers are installed from the inside, mounted on threaded studs pressed in from the front. Therefore the back panels must be removed to remove the drivers.
Concerning the tweeters, I found next to nothing. Starting in about 1967(?) there was a L 450/1 series. I can't find what the difference was from the early version but apparently they still had cone tweeters. In 1968 there was a 450/2 series that switched to a dome tweeter. From 1969 the 450 was replaced with the L 470.
Posting direct ebay links in the open forums is against the regs. But if you search ebay.de with "Braun L 450 Lautsprecher" you will find what's current. At the moment there is only a single orphan speaker listed that comes due on Sunday 13 Oct.
Sorry that I can't find more useful info, that's the best that I can do at the moment. If I see any L455-33 tweeters listed I'll PM and inform you.
Cheers,
James
