Adding this to the DIY forum too
A month or so back, I ran across a set of Bang & Olufsen RL 60 speakers on craigslist. These things looked to me like something out of Star Wars. I got them for $50, including the metal speaker stands. The speakers had the original "straps" around them, also in good condition.
The guy who sold them to me said that the "woofers need to be re-foamed." I was up for a fun project anyway. I have now learned a lot about these weird but nice little speakers with a very odd design.
Here they are:
There is no true "woofer." As you can see, each speaker has three "panels." If you put them on the stands vertically (they are designed to be put on the stands horizontally or vertically, or mounted to a wall or a ceiling, even…pretty useful concept), then the top panel is two 16cm "woofers."
In the middle panel is one 2.5cm tweeter. The bottom panel is an ABR, or Auxillary Bass Radiator. Repairing the ABR was the issue with these speakers.
The ABR is an oblong opening that was totally covered in thin foam. There was also a rectangular piece of metal suspended in the foam. However, when the foam rotted away, the rectangular piece of metal would just fall into the box of the speaker and rattle around.
A lot of folks were trying to figure out what type of foam would replace the old foam. I spoke with an authorized B&O service dealer out of Atlanta. He immediately knew the issue and told me how to build a different type of "fix" and assured me that his was the best solution.
The first thing I did was open up the speakers. First remove the straps by loosening the screws that are tightened down to hold the straps in place. With the straps off, you remove all SIX screws around the exterior rear of the speakers.
Then you remove THREE MORE screws, one in each of the slots where the strap holders were and one in the center just behind the speaker connections.
Open the speaker and disconnect the green/black wire from the speaker connection. The green wire goes to the positive connection. It will look something like this:
You will see some insulation blocks and the rotted foam everywhere, especially down around the opening where the ABR was. You will see the metal frame around the ABR opening. You will see the ABR plate that had been suspended by the foam and is most likely rattling around inside.
Remove the insulation blocks and the ABR if it's still in there. Remove the metal frame around the ABR opening using a screwdriver and SAVE THE SCREWS. Clean out all the rotted foam. Once clean, it will look something like this:
The idea behind this fix is that you cut a thin piece of fiberboard to fit and seal off the ABR opening. However, you also build a port in the fiberboard using PVC pipe. This was essentially the "fix" that B&O released and ultimately it replaced the ABR in later versions of this speaker. However, it supposedly cost $75 per speaker.
First I traced the outer ABR metal frame, cleansed of any extraneous old foam with a flat razor knife, onto the thin fiberboard:
Then I cut out the fiberboard tracing carefully, using a dremel tool. I also picked up some 1.5" PVC pipe with 90degree connector pieces. I glued the 90degree connector to the end of the PVC pipe and then cut the PVC pipe to length. Here's the fiberboard cut-out and the PVC pipe:
Dry fit the fiberboard over the ABR opening. Trim the fiberboard slightly here or there, especially around the notches and holes where the screws will go when the fiberboard is screwed down.
The next step is tracing the end of the PVC pipe 90degree connector and cutting out the resulting circular hole with the dremel tool. I just clamped the fiberboard down:
After the circle was cut out, I trimmed it very slightly until the PVC pipe fit the opening. I cleaned the circular cut-out on the fiberboard and also around the end of the PVC pipe. Then I used a little PVC pipe glue to glue the PVC pipe into the circular opening of the fiberboard. It doesn't have to be solid, it just needs to hold the pipe in place. I suppose you could also use a little super glue. It looked like this after the glue:
Once the glue was set up a bit, I then started in with the clear silicone. I know, I know, it looks messy. But it worked fine and it will never be seen, so…
The next day, the silicone was set and the entire fiberboard / PVC combo felt pretty solid. I dry fit it into the ABR opening and it fit pretty well. It was flat against the ABR opening.
Now, the question was, how to get this thing permanently installed and screwed down, but to have the fiberboard be airtight against the ABR opening? I just figured I would use silicone, but my caulk-gun sucked and it's kind of a tight squeeze. So, I just ran a bead of gel superglue all the way around the ABR opening and then put in the fiberboard / PVC combo. Again, it fit great, but I wanted it to be airtight around the edges. Once it was installed, I screwed it down using the same screws that held the original metal ABR outer frame in place. Worked like a charm. It looked like this (this photo was taken before I put in the screws but the screws worked and fit great):
I should add, that once the fiberboard was glued down, you can see a couple of unavoidable gaps and also some gaps that were probably avoidable but hey, I'm no pro with the dremel tool. I hit those with silicone and let them cure up a bit.
This next part was kind of funny to me. I had seen an infomercial not too long back about a spray-rubber sealant substance. Looks like a can of black spraypaint but it essentially sprays liquid rubber that will seal up just about any crack or crevice. I got a can of it at Home Depo for $10. That brought the total price of this project (not including the speakers) up to around $20.
I used the spray rubber sealant all around the outside edges of the fiberboard where it connected with the ABR opening. I also sprayed it around the PVC pipe joints and over the silicone. It looked kind of messy but you could really tell that it was sealing up any cracks that might have remained and made it airtight. Looked like this:
Once the spray rubber was sufficiently dry, it was time to put the speakers back together. I put the small square insulation block over the tweeter, where it was initially. Then I put one of the long insulation blocks on each side of the box.
I hooked the speaker connections back up and closed up the speakers. I replaced all the screws. The straps were carefully put back on and tightened down. Then I let them sit for a while on the speaker stands and continue to cure up.
I should have spent a little more time listening to them prior to doing this refurb, but really they did not sound very good. They did not sound damaged, but they did not sound full and there was not a lot of bass response. I don't think these speakers were designed to be particularly bassy in the first place (please forgive my novice writing and terminology). I think they were more designed to be versatile in where they could be placed. The design was pretty interesting to me and I love that they look how Han Solo's personal stereo speakers would look.
With that, I will say that this modification drastically improved these speakers. The bass is clearly not overwhelming but it is clear, clean, and resonant. The clarity is nothing short of lovely and the detail is very nice. To my untrained ears, these quirky little speakers are kind of like a big set of headphones. I have been joking that they might be the best set of computer speakers of all time. Placement is key with these speakers, as is the angle at which they are mounted and directed.
I gave them a good listen for several days straight, powered by my B&K amp and pre-amp. I am impressed at their sound and VERY impressed by how much better they sound with this modification. I would venture to say that if you run across a set of these speakers, they WILL need to be fixed and I highly recommend this method as described above. Thanks for reading!
--Mitchell Byrd, March 2012