Since I could't find any information on this online, here is some information for anyone else who might be attempting to replace their Vivid Audio B1 tweeter.
The Vivid Audio B1's use the D26 tweeters; these are tweeters made by Vivid themselves and used in a range of their speakers. Information can be found here:
I consider it a design flaw of the Vivid B1s that the speaker grille attachment holes are perilously close to the driver cones. The top grille hole in particular is about 2 inches away from the tweeter - which itself is well known for being extremely sensitive to accidental damage. Add a strong magnetic force into the mix (from the tweeter), and miss the grille pin hole by a cm or so and the force will pull the sharp grille pin right into the tweeter. This happened to me a couple weeks ago and caused a significant dent in the tweeter dome, which was irreparable.
Anyway, onto the repair. I was unable to find any D26's for sale myself and so I had to order one through my vivid dealer. And they're not cheap at £210 each. This is just for the tweeter dome unit itself and not the tapered tube loading unit that it attaches to. Worth noting - the B1 Decades (and some of the Giyas) use an updated tweeter dome, though the only difference appears to be the dome protection; the tweeter itself seems to be the same. The original tweeters use a "cross hatch" protection (which leaves 4 quadrants of the tweeter dome exposed), whereas the updated tweeters use "integral" protection, which leaves less of the dome exposed. I also received some instructions, which were helpful though did not seem to be fully accurate. These are attached below for info.
First, here is a picture of the damaged tweeter in situ:
Now, on to the repair.
STEP 1: remove the old tweeter assembly
The first step is to remove the old tweeter assembly. This is done by removing the locking nut at the rear of the speaker:
Looking inside the hole, I was expecting to see the back of the tweeter, as the instructions say to push it forward so that it pops out the front for removal. However, the back of the tweeter I did not see. Instead, I saw this:
The light is not great, but the back of the tweeter isn't there. What happens when you remove the locking nut is that the back of the tweeter drops down due to gravity onto the wooden supporting beam inside, as the unit is only held in place at the front and the back. So you have to put your finger (or another suitable implement) inside the hole, locate the back of the tweeter and gently push it forward until the front of the tweeter stars to protrude from the cabinet, like this:
It is then a straightforward job to gently pull the tweeter assembly forward and out, until the electrical connection block pops out:
Care must be taken not to drop the unit at this stage, as it could swing down and perforate one of the other drivers, which is not part of the intended procedure. Care must also be taken not to bump or scratch the driver enclosure.
Anyway, the next step is to disconnect the electrical connection block, which requires pressing down on the plastic level on one side and gently wriggling and pulling the 2 sides apart. An extra pair of hands is helpful here, or alternatively you can use your knee to balance the unit on:
Once the block has been disconnected, the entire tweeter unit (dome and tapered tube loading unit) can be pulled out of the enclosure. Here is is removed:
From right to left we have the tweeter assembly (comprising cross-hatch plastic dome protector, the aluminium diaphragm (dome), the magnet system, electrical connectors and securing nuts) and the tapered tube unit. Note the elastic band (now broken) which was used to secure the cables to the edge of the tube unit.
Looking inside the hole in the enclosure, we can see the foam, the wooden support for the D26 tweeter, and the D50 mid band driver which sits below:
STEP 2: Disassemble the old tweeter assembly
First, the elastic band (sometimes tape is used) securing the wires to the edge of the tube unit must be removed. Then, the front-mounting o-ring must be removed. Note of caution: similar to elastic bands which degrade with age and become friable, the o-ring similarly loses elasticity with age. Mine broke, and I had to use a little super-glue to glue the 2 broken ends back together:
Next, the securing nuts must be unscrewed; one part of the nut is part of the tweeter unit, the other part is loose. Note that you have to give it a tug, due to the pull from the magnets. Once done, the tweeter assembly unit can be removed from the tapered tube:
Here you can see the protrusion at the end of the tube which links in to the tweeter unit:
Also, note the ring of magnets in the tweeter unit:
Each tweeter unit should have a sticker on it too, denoting the testing date for the tweeter quality control, the tester's initials, and confirmation that sound pressure level, PHS and VIS (I'm not sure what the latter 2 denote):
STEP 3: Reassemble the new tweeter assembly:
Now, we are ready to do this all in reverse with the new tweeter unit:
Fitting the new tweeter unit to the tapered tube and securing with the locking nut:
I would suggest practicing this with the damaged tweeter first so that you get used to the magnetic pull (as any unexpected sudden movements might lead to damage to the dome). Also note that the tapered tube is able to rock a little within the tweeter unit; this allows both the unit and the read of the tube to be correctly aligned with the cabinet.
Next, put the o-ring back at the top of the tweeter, and then secure the electrical wires back down to the top of the tube below the locking nut:
Now we are ready to insert the assembly back into the enclosure.
STEP 3: Insert the repaired assembly back into the enclosure
Place the repaired assembly back into the enclosure, carefully pushing the assembly in until the tweeter unit is about flush with the speaker enclosure. Finally, from the rear of the speaker, locate the back of the tweeter tapered tube. You might have to angle the locking nut down to "pick up" the back of the tube, then lift it up and screw it in. No need to over-tighten, just needs to be snug. Final product:
Hope this is helpful for anyone attempting a similar endeavour!