Now you CAN refoam your minimus-77 speakers. Here's how....
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MarkAnderson
Addicted Member
Feckin' tease.
OK! Here we go.
You've probably at some point in your life run across some minimus-77 speakers that were pretty cheap and though to yourself "I'll just refoam them and see what happens." However to your dismay you can't find anyone with surrounds that work. So you're screwed unless you buy into one of those expensive "upgrade kits" which has you changing crossover components and installing a new woofer....
I say f$*& that! Here's how to do it:
The dimensions of the woofer are indeed strange. The required surrounds have to have an ID of 2.6 and an OD of 4.75, which simply do not exist (are the manufacturer's listening? --doubtful)
Since they don't exist, you have to make them. This is done by affixing two surrounds together of different sizes. Here's what you need:
The smaller surround should have an ID of 2.5-2.6" and an OD of 3.875"
The Larger surround should have an ID of 3.5" and an OD of 4.75-4.8"
The two combined produce the correct surround and still allows for proper excursion and support. You'll have to hunt around for the surrounds between various suppliers but the surrounds do exist. If you have a speaker repair business, you're probably familiar with MWA speaker parts, but they only sell to repair businesses.
On with the repair:
1. Clean off all the old surround crap from your woofers. This can be done with a knife, solvent, or whatever you chose. I would personally stray from chemicals because the soften the cone and smell terrible. You can remove the old cardboard trim ring if the glue is coming loose, but if its tight, it provides a more even adhesion surface for your surround. The glue that "simply speakers" sells is really good, and "global adhesives" surround dampener is good glue as well - it just takes much longer to dry. I wouldn't recommend Elmer's or tacky glue here. It didn't work well at all under high excursion.
2. Apply a bead of glue to the top of the outer edge of the smaller surround. Now lay the larger surround on top of the smaller surround. Tamp the two together until the glue gets tacky. Allow it to dry overnight before going any further.
3. Apply a bead of glue to the back of the cone where the surround will attach. carefully work the inner lip of your surround and make sure it evenly contacts the cone and glue. Tamp it down until it gets tacky, then wat a few hours for the glue to set.
4. At this point you notice something. The outer lip of the surround you made sticks up about 3-5mm from the basket. You're going to find it tricky to keep the surround glued to the basket while the glue dries unless you shim the woofer..
5. cut 90% of the dust cover away so you can easily re-attach it. At this point you need shims. Old photographic film is a great source here. Cut off the feed holes, and cut lengths about 1.5" You'll need six total. Fit the 3 pair of 2 lamination film in a delta formation and you'll have the VC perfectly centered while still allowing you to move the cone down slightly while you attach the surround.
Continued in the next post.....
You've probably at some point in your life run across some minimus-77 speakers that were pretty cheap and though to yourself "I'll just refoam them and see what happens." However to your dismay you can't find anyone with surrounds that work. So you're screwed unless you buy into one of those expensive "upgrade kits" which has you changing crossover components and installing a new woofer....
I say f$*& that! Here's how to do it:
The dimensions of the woofer are indeed strange. The required surrounds have to have an ID of 2.6 and an OD of 4.75, which simply do not exist (are the manufacturer's listening? --doubtful)
Since they don't exist, you have to make them. This is done by affixing two surrounds together of different sizes. Here's what you need:
The smaller surround should have an ID of 2.5-2.6" and an OD of 3.875"
The Larger surround should have an ID of 3.5" and an OD of 4.75-4.8"
The two combined produce the correct surround and still allows for proper excursion and support. You'll have to hunt around for the surrounds between various suppliers but the surrounds do exist. If you have a speaker repair business, you're probably familiar with MWA speaker parts, but they only sell to repair businesses.
On with the repair:
1. Clean off all the old surround crap from your woofers. This can be done with a knife, solvent, or whatever you chose. I would personally stray from chemicals because the soften the cone and smell terrible. You can remove the old cardboard trim ring if the glue is coming loose, but if its tight, it provides a more even adhesion surface for your surround. The glue that "simply speakers" sells is really good, and "global adhesives" surround dampener is good glue as well - it just takes much longer to dry. I wouldn't recommend Elmer's or tacky glue here. It didn't work well at all under high excursion.
2. Apply a bead of glue to the top of the outer edge of the smaller surround. Now lay the larger surround on top of the smaller surround. Tamp the two together until the glue gets tacky. Allow it to dry overnight before going any further.
3. Apply a bead of glue to the back of the cone where the surround will attach. carefully work the inner lip of your surround and make sure it evenly contacts the cone and glue. Tamp it down until it gets tacky, then wat a few hours for the glue to set.
4. At this point you notice something. The outer lip of the surround you made sticks up about 3-5mm from the basket. You're going to find it tricky to keep the surround glued to the basket while the glue dries unless you shim the woofer..
5. cut 90% of the dust cover away so you can easily re-attach it. At this point you need shims. Old photographic film is a great source here. Cut off the feed holes, and cut lengths about 1.5" You'll need six total. Fit the 3 pair of 2 lamination film in a delta formation and you'll have the VC perfectly centered while still allowing you to move the cone down slightly while you attach the surround.
Continued in the next post.....
Attachments
6. Apply a bead of glue to the adhesion point, tamp down and let dry. After the glue has dried, pull the shims while supporting the cone (so you don't accidentally pull the surround loose from the basket before its completely dry.) Now lightly pus the dust cap back down and apply a small bead of glue. You'll need to hold it there while it dries enough to let go.
Once everything dries, reinstall and enjoy. Now you know how.
[[[
Once everything dries, reinstall and enjoy. Now you know how.
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Attachments
vegabass25
Awesome AK member.
Neat! And the woofers will have more travel now 
The easy method...
..is to get standard 5" foams from MAT electronics.
OK so the roll isn't as big, but they do work. I've done it a couple of times now....:yes:
..is to get standard 5" foams from MAT electronics.
OK so the roll isn't as big, but they do work. I've done it a couple of times now....:yes:
ymarko
Super Member
But what to do if the outer foam is too large?
I like your concept of 2 foams to refoam non-standard size woofer.
But what is the outer foam is to large? Can I reduce its diameter (cut it around)?
Some suggest I simply have to use one larger foam and cut a small part of it out, so reduce the diameter. But then I have to deal with anb across cut on the surround. What do you think?
I like your concept of 2 foams to refoam non-standard size woofer.
But what is the outer foam is to large? Can I reduce its diameter (cut it around)?
Some suggest I simply have to use one larger foam and cut a small part of it out, so reduce the diameter. But then I have to deal with anb across cut on the surround. What do you think?
On this particular woofer, the outer edge where the surround attaches to goes pretty much to the edge of the basket frame. Trimming the diameter would compromise the surface area to adhere to, but on other drivers it might not be a problem.
You can trim down a larger surround, but you run into two difficulties. One of them is that when you trim down the surround, the end opposite the area cut will be compressed making inside of the suspension slightly tighter than the other side. The other difficulty is the part of the surround that overlaps due to the cut may develop air leaks or break apart unless a large amount of glue is used.
Just my thoughts. Here in this scenario everything is completely linear and no sacrifice is made in time, labor effort, cone travel or durability. It just works.
You can trim down a larger surround, but you run into two difficulties. One of them is that when you trim down the surround, the end opposite the area cut will be compressed making inside of the suspension slightly tighter than the other side. The other difficulty is the part of the surround that overlaps due to the cut may develop air leaks or break apart unless a large amount of glue is used.
Just my thoughts. Here in this scenario everything is completely linear and no sacrifice is made in time, labor effort, cone travel or durability. It just works.
Curious what you're using for glue. It looks clear on your pic of gluing the DC back.
I've been thinking that I'd like to use a clear rubbery type of glue that I've found on some speakers, rather than the white glue type that dries hard like Aleen's Tacky Glue which I and many others use. I'm looking ahead to the *next* refoaming, and I can hear persons of the future cursing white glue.
So, what are these products like? Solvent based clear rubber cements?
[Edit: I just Googled globaladhesives and it appears the WD-32 is a water based white glue they say to use for bonding surrounds to cones. They also have rubber type adhesives on the same page that look like what I'm talking about. Ever used any of these? http://www.globaladhesives.net/surround_adhesives.htm
The Simply Speakers MI-3035 looks like a solvent based adhesive. Is it flexible and rubbery when dry? http://www.simplyspeakers.com/2doityourself.htm ]
So, what are these products like? Solvent based clear rubber cements?
[Edit: I just Googled globaladhesives and it appears the WD-32 is a water based white glue they say to use for bonding surrounds to cones. They also have rubber type adhesives on the same page that look like what I'm talking about. Ever used any of these? http://www.globaladhesives.net/surround_adhesives.htm
The Simply Speakers MI-3035 looks like a solvent based adhesive. Is it flexible and rubbery when dry? http://www.simplyspeakers.com/2doityourself.htm ]
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Haven't used anything but the standard white stuff until recently. I got a small tube of the simply speakers stuff to try out. The 3035 glue dries clear and is VERY flexible while still maintaining a strong bond.
The global adhesives WD glue also gries clear and is very flexible, but it is more of a contact glue meaning it works best if both surfaces have glue on them. The Ss glue doesn't seem to mind what surface its on and it bonds to just about anything.
The global adhesives WD glue also gries clear and is very flexible, but it is more of a contact glue meaning it works best if both surfaces have glue on them. The Ss glue doesn't seem to mind what surface its on and it bonds to just about anything.
I think the 3035 may be what I'm looking for. Thanks!
Surprisingly, I did not notice any difference between the modified pair with new surrounds and the one working original I had that was starting to deteriorate. Its not any stiffer, nor is it loose and flabby. I can imagine it will only get better with time and use.
Unless someone comes up with a pre-fab surround for these things, I don't see too much of an alternative. Yes, you can stretch a standard 5" from MAT to work, but the travel is hindered and when you crank it you can hear the flapping when the excursion limit allowed by the surround is reached.
So far its turned out to be a good outcome. Of course, your mileage may vary, not available in all states, does not include tax, liscense and docking fees, etc.
