Boston Acoustics A40 Refoam Project

he11fire

he11fire

Decidedly Budget
Hello. I've been lurking for a while, but I'm a brand new member. I love it here, this place has a wealth of information.

I've owned a Technics SA-505 receiver (1980) for almost 20 years, using it for about 6 or 7 of those, and have recently jumped right back into vintage audio. Just in the past few weeks, I've purchased a near mint Kenwood KA-7100, a pair of KLH Model 20s with tweeters that don't work, and a pair of Boston Acoustics A40s that are in dire need of a refoam. I'm using them as my first attempt because the basic consensus is that they're a relatively easy refoam and are nice little speakers. Here is the before picture:



My first (of probably many) question is: Have I removed enough of the adhesive from the speaker cones?




I got almost all of it off of the metal basket with alcohol and elbow grease, but there is still a visible amount left on the cones. It's getting more and more difficult to remove, even with a little alcohol and cotton swabs and all of the recommended methods. I'm starting to worry that I'm going to damage the cone if I'm too rough with it. If it's necessary to remove every last bit for a good bond, I'll stick with it and keep trying different solvents. Should I just proceed with the refoam when the kit arrives and hope it sticks? Any recommendations for an easy way to remove it that won't trash the cone? Thanks in advance for your help.


EDIT: OK, I think I got the picture thing all figured out.
 
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I'm not seeing any pictures.

To answer your question, a small amount of residue is ok on the cone. Normally that's better than trying to get each and every last bit off the cone as the more you mess with it, the greater the chance you could damage something.
 
Ohighway said:
I'm not seeing any pictures.

To answer your question, a small amount of residue is ok on the cone. Normally that's better than trying to get each and every last bit off the cone as the more you mess with it, the greater the chance you could damage something.
Click to expand...

I'm working on the pictures right now. :)

And thank you for your input. That's the way I was leaning, but having never done this before I wanted to get as many opinions as I could.
 
he11fire;6764169Should I just proceed with the refoam when the kit arrives and hope it sticks? Any recommendations for an easy way to remove it that won't trash the cone? Thanks in advance for your help.[/QUOTE said:
For every pair of Boston speaker I've done, I take a greeen scotch-brite pad (or the Menards equivalent) and lightly rub it against the area where it sticks to the cone. It should come off quite easily. Occasionally it gums up on the pad but then you just switch to a clean spot (I recommend wearing gloves or your fingers will end up black/tarry). I've done 4 sets of speakers and NEVER ruined a cone yet. It's easy, go light, and you'll be fine.

Congrats on the A-40's, some great little speakers.
Click to expand...
 
On that style of Boston A40 woofer, you might have to trim the outer edge of the surround to get it to fit correctly.
 
Ohighway said:
On that style of Boston A40 woofer, you might have to trim the outer edge of the surround to get it to fit correctly.
Click to expand...

That's what I've heard. The kit I ordered (from MidwestSpeakers I think;
on eBay), says it's specific to the Series 2 woofers, so hopefully that doesn't happen. If so, I feel I have a pretty steady hand, so I'll just have to make it work.
 
dodog said:
For every pair of Boston speaker I've done, I take a greeen scotch-brite pad (or the Menards equivalent) and lightly rub it against the area where it sticks to the cone. It should come off quite easily. Occasionally it gums up on the pad but then you just switch to a clean spot (I recommend wearing gloves or your fingers will end up black/tarry). I've done 4 sets of speakers and NEVER ruined a cone yet. It's easy, go light, and you'll be fine.

Congrats on the A-40's, some great little speakers.
Click to expand...

So just a regular green-side coarse sponge? Like a dish washing sponge? Yeah, I've already had the black/tarry finger issue when I did the bulk of it yesterday.

Thanks for the congrats! I've never even heard them, but they came highly recommended here, both for their ease to repair and resulting sound quality. What kind of bass do they put out? The cabinet seems a little larger for a 6.5" woofer, so I'm hoping for the best.
 
he11fire said:
Thanks for the congrats! I've never even heard them, but they came highly recommended here, both for their ease to repair and resulting sound quality. What kind of bass do they put out?
Click to expand...

Boston A40 speakers are nice. You'll enjoy them. They put out plenty of bass for their size.
 
Ohighway said:
Boston A40 speakers are nice. You'll enjoy them. They put out plenty of bass for their size.
Click to expand...

Have you ever heard them compared with the Pioneer SP-BS22? I bought a pair of those and like them ok, but still have a few days left on my return window. So, if the A40s stomp them, they may go back.
 
I refoamed mine last year and trimming the surrounds was easy. Just make sure to leave enough margin so they stick to the basket. You may want to buy 2 sets of surrounds in case you mess one up. Use the 9V battery technique to center the cone when attaching the foam.

They're nice little bookshelf speakers. I have tried others since and the A40s always win out.

Good luck!
 
You'll enjoy these guys a lot. I refoamed mine and stripped the old vinyl veneer (was ripping off) and replaced with real walnut veneer. They're currently in my 10-year olds room and he uses them to play his tunes. They sound great for their size. Here's a link to the thread:

http://www.audiokarma.org/forums/showthread.php?t=346444

My A-40's had the paper cones but I've had A-60's and A-70's with the poly cones. BA's are some of the easiest speakers to refoam and have very newb-friendly gaps for centering the voice coil. Use a test-tone and you'll be golden.
 
I've thought about using the test tone, but the AA battery technique seems to be very popular. I'm a little confused on the specifics of how it works (IE which way you want the cone moving when you applying to the cone and then the basket), but that was how I had planned to do it.
 
Quick update: I've been swamped with work and life in general, but I plan on picking up Scotch-Brite pads this evening. I'll post updated photos after I get the rest of the gunk off. The kit shows up Monday, so hopefully by Tuesday morning I'll be rocking my "new" a40s.

Any input on the AA battery technique? Anything to avoid or watch out for?
 
Success....?

OK, so the kit showed up early. Right after I got home, I got to work.



Unfortunately, I did end up having to cut the surrounds down. This is after I did that, which was terrible, and glued the surround to the cone. Everything went pretty smoothly with that part and I was really happy with the results. While I was doing that, I also noticed this:



I thought that was kind of cool, since I was 10 when these speakers were made. I decided to use the AA battery method as opposed to a test tone or shims (which I am scared to death to do), and I used a RadioShack AA battery holder, since it already had leads on it. I had to strip them down a bit, but I made it work. I also used a rechargeable AA, because I read that 1.2 volts is better than 1.5 for this application.





After hooking up the battery, I ran a strip of glue around the basket, which magically became much more narrow once I had the surround glued to the cone. I managed to get glue all the way around and get the surround somewhat in place around the edge of the basket with the cone pushed out (but it was much harder than I thought it was going to be). After disconnecting the battery, I went around the edge of the basket with a wide stick and pushed the surround down all the way around, repeating the process periodically for about 15 minutes to make sure everything was held down where it needed to be. I put the drivers back in the cabinets after hooking the wiring back up, and here we are:







I tested the drivers by pushing the cones in slightly, and I feel there might be some rubbing on one of them. I'm going to be really disappointed if I have to redo it, but I'm reserving judgement for another couple of hours until they dry and I actually hook them up. $25 won't be the end of the world (if I have to order another kit), but I really wanted to succeed at this. Plus, then I'll have to modify my eventual "And even with the repair kit, I'm only out X dollars!" statement. Wish me luck!
 
dodog said:
You'll enjoy these guys a lot. I refoamed mine and stripped the old vinyl veneer (was ripping off) and replaced with real walnut veneer. They're currently in my 10-year olds room and he uses them to play his tunes. They sound great for their size. Here's a link to the thread:

http://www.audiokarma.org/forums/showthread.php?t=346444

My A-40's had the paper cones but I've had A-60's and A-70's with the poly cones. BA's are some of the easiest speakers to refoam and have very newb-friendly gaps for centering the voice coil. Use a test-tone and you'll be golden.
Click to expand...

By the way, thank you for the link. It was an enjoyable read, and yours ended up looking quite nice. I don't think I have the confidence for a job of that scale quite yet. I'm, so far, too intimidated to even re-cap my Model 20s.
 
Ok, so I had a couple of problems. I did screw up one of the refoams, as when I hooked up a bassy song, it was rubbing and sounded like it was bottoming out. I'm going to order another refoam kit and fix that, obviously. Discouraging, but not the end of the world.

However, I think I also have a bad tweeter. I was getting little to no output out of one of them. I tested it, and it tested at 5.7 ohms, which is pretty close to normal, so now I'm not sure. Next I'm going to hook it up in the other cabinet to make absolutely sure it's the tweeter and not part of the crossover network.

Any advice on how to check the woofer to make sure it's not damaged as opposed to a refoam issue? It tested at right about 4 ohms, but I don't know if there is anything else I can do to make sure it's ok internally.
 
Another update (even though it seems at this point that nobody is listening): I ordered a replacement tweeter and more foam. Even if the old tweeter isn't bad and it turns out it's the crossover, for $15 it'll be good to have a backup.
 
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