I know this is a pretty small minority but here goes.
Does the bass in your Bang and Olufsen Red Line speakers sounds a bit wrong? Maybe it can resonate at higher volumes, you hear rattling when moving them, or the bass just doesn't give that kick you usually had. Or maybe you know the ABR is knackered but don't know what to do without burning your wallet.
If you want an easy way to repair your ABR then read on.
Step 1: Tools and Possible Parts
This could depend on how badly damaged/degraded your ABR is. If the ABR plate has just fallen off the foam/cloth all it needs is glueing on. If the foam/cloth has degraded to nothing you will need to replace the it.
A philips medium sized screwdriver.
Glue for reattaching the plate to the foam/cloth.
Sand paper to ruff up the plate for ease of glueing.
A place to keep screws so you don't loose them, a small pot is ideal.
Tools and parts needed if the foam/cloth has degraded:
A new sheet of foam or cloth similar to the stuff the was there to begin with. I suggest a cloth similar to the cloth on the front of the speakers.
A sharp knife for cutting the foam/cloth.
A clear well lit work area :)
Step 2: Start to Remove the Back of the Speaker.
This can be a little daunting. I know it was for me. Beautiful beovox's taken apart? sounds like a crime. But don't fret, as long as you are careful there is nothing to worry about.
First lay your speaker face down on a large flat work space, with enough room for at least double the foot print of the biggest face of speaker. On the back of the speaker around the edge there are 6 screws. They are all along the top and bottom, 3 at top, 3 at bottom (on the RL 45 anyway). These are hidden a little well. Once you have found them use a medium sized philips screw driver to remove them. You may need to use some force as they not have been turned for over 30 years. But be careful. Don't strip the heads of the screws. Moderate downward force is needed on the screwdriver to keep contact with the screw well. Ease the screw to begin with, once you feel it turn unscrew it, they are quite deep so keep going. Now repeat for the other screws around the edge of the speaker.
Step 3: Removing the Bands Around the Speaker
Now you will need to remove the plastic bands around the speaker (might be a good chance to paint them red as i would love to do). To do this You need to loosen or remove one screw for each band. I prefer to loosen the screw as i know where the screw is and don't get it mixed up with the others.
The bands are held in place with a small plastic block with one screw. Once you have removed the plastic block it will be possible to remove the band. The band will loosen so you can slide it over the top or bottom of the speaker.
Step 4: Removing the Final Screws
Now to Remove the final screws. Remember to keep all the screws you remove in a safe place and to remember where they came from.
First undo the screw next to the signal jacks. This screw is black and at the same level as the jacks.
Now Remove the chrome screws under the band crimps you removed earlier. They are quite recessed so a magnetic screwdriver is a good idea here.
Step 5: Removing the Back
Now its time to remove the rear of the speaker. Be careful here as the signal cable could be damaged if you go ahead and just yank the back off.
After you have removed all the screws on the back (double check) the back should loosen a little. The back is still tightly held on by a foam insulation, so work it off gently. Try to rock it off gently. If you slowly pick up the speaker by the back it should slide out. But be careful, only lift one end an inch or two.
Once the back is free you will need to disconnect the signal cable. This just slides off the clips, but don't tug too hard.
Hold the cable by the metal lug and it should slide off easily.
Step 6: Removing the Sound Absorbent Foam Blocks
Inside are 3 blocks of wrapped sound absorbent insulation. Take not where these go and remove them carefully. Chances are that the block over the crossover will have melted to the capacitor as did on both my speakers. To remove you must peel it away from the capacitor. TAKE CARE!! If these caps are charged (which they shouldn't be) they could still bite. Only handle them by the sides not the end. Also take care not to damage them as your tear away the foam blocks wrapping. Remove it slowly, not like a plaster and in one go.
Once the foam blocks are removed put them somewhere safe. At this point feel free to marvel at how nice these speakers look even from the inside.
Step 7: Assess the ABR Unit
If you don't know how the ABR in your speaker is now is the time to check. Hopefully your ABR should be attached just fine at the bottom of the speaker to the cloth or foam. It should look something like a speaker just without a coil and with a metal plate instead of a cone.
IF your ABR unit looks intact like the second photograph you should asses how well it is joined if at all to the cloth or foam. IF it is not attached at all remove the metal plate and place it aside for now. To asses how well it is attached very carefully lift up one corner. This is made easier if you push very gently on the plate from the front of the speaker. VERY carefully.
If the metal plate is only attached partially then it is up to you if you wish to try to repair it. On one of my speakers the plate had come away completely, on the other the smallest amount of glue remained. I decided to leave the original glue but add more.
If the metal Plate is attached perfectly fine then you should leave it alone. However the glue will not last forever so you may wish to replace the glue/cloth.
If the cloth or foam the plate should be attached to is missing or degraded you will need to replace it.
Step 8: Removing the ABR and Its Bracket
To remove The ABR there are 6 screws around the outside (on the RL 45) they may be covered by the cloth so look carefully. After you have removed each of the screws ease the plate/bracket from the speaker. Ease the topmost part upwards and try to slide it out to the right, from the back of the speaker.
Step 9: Repair or Replace
Now to decide if you are to repair or replace the cloth or foam. If the cloth or foam is in perfect condition then do not worry, my cloth was in fine condition, not bad as its almost twice my age!
If you are going to simply reglue the plate to the cloth or foam, which is what i did, and what i would imagine the easiest repair, you must select a suitable glue. I used spray carpet adhesive, there are probably better glues but it works well for me.
If you are going to replace the cloth/foam then you must select a suitable cloth or foam. I suggest one similar to the cloth on the front of the speaker. Once you have some you must cut it to size, leave excess when you cut it out. leave say an inch and cut around the metal ABR bracket. Then you must glue the cloth/foam to the bracket. Glue it all the way round on the same side as it way before. Leave a while before glueing the plate ideally.
To Glue the plate, I first used sand paper to remove the excess glue residue and rough the plate to help it stick. Once this is done apply Your glue to the plate, and the cloth if applicable, and place the plate on the cloth/foam. I inverted the unit as soon as I applied the place and rested it on the cap of the spray so that it would stick better, and not through the cloth to the newspaper i was working on.
Step 10: Replace the ABR in the Speaker
After your glue has dried and you are happy with the ABR unit (you may wish to repeat) it is now time to replace the ABR in the speaker. Make sure you line up the ABR when sliding it back in, and don't get it caught.
After it is seated Screw it back down, taking care to keep the cloth or foam taught.
Step 11: Replace Blocks and Getting Ready to Close Up
Now it is time to replace those foam blocks. Replace the long one that might have melted to the cap in the same place, rather melt one than two. The smaller block must go over the tweeter and be pressed up against the middle of the speaker. Now place the second long block over next to the smaller block and over the woofer.
Make sure they are all very tidy and neat with nothing hanging out. Get ready to close up, make sure nothing snags. Connect up the signal cable to the inside of the case. Remember the green cable goes to the positive. Once the signal is connected tuck everything inside neatly and slowly and carefully close up.
It took me a few times to close up to get all the blocks just right. Don't rush it and just make sure they all fit.
Step 12: Screwing Back Up
Now it is time to replace all the screws. Got them safe? Know where they go? i hope so. After all the screws have been replaced now replace the bands. Slide them over the top and bottom, make sure they sit in there groves, and screw them back in.
If you wanted to paint them red now would have been a good time.
Step 13: Foot Notes
Clean work space (free of cats)
All your tools ready before hand
Get a pot or somewhere safe for screws.
Take your time
After you have finished, listen to something with a nice bass to it. After i finished i listened to some opeth and liquid tension experiment. Very good sounds there =]
Good luck and enjoy crisp deep music!