How would you complete this refoam?

[swechsler]

I'm currently refoaming a trio of Boston 555x THX speakers, a total of 6 4.5" mid-woofers. Purchased the foam from Rick Cobb. The surround was a tight fit in the frame (see pics); since there was no adjustment possible (I think the surround might actually have been ever so slightly, like under 1 mm, larger than the interior of the frame) I decided to glue that in first rather than to the cone which is typical. I'm now trying to determine the best way to glue the cone to the surround. Should I play a bass signal and then try to press the surround evenly down on the cone? Should I use a battery to force the cone to hit the surround (there's currently a small gap)? And should I use contact cement for immediate attachment, or Aleene's that would allow it to move around somewhat before it cures? The cone is polypropylene or some other plastic.

Thanks!

 

[andy]

I usually use contact cement to bond the surround to the cone since it's instant, and it's next to impossible to properly use clamps for that. I like to gently push down on the cone with a weight on something hollow like a roll of tape while I position the surround. Then, carefully raise the cone into position and press it into the surround to form a tight bond.

To bond the surround to the frame, I use Aleene's so I can adjust it as needed. I use a low frequency tone and gently press on the edges of the cone to test for rubbing. Adjust the position until the force needed to cause rubbing is even all the way around, and clamp it. It can't hurt to check it again after about 15 minutes before it's completely dry. If the surround is too big to allow adjustment, I would trim the outside if needed.

Since you've already glued it to the frame, I would probably remove the dust cap and shim the voice coil and glue with contact cement. I like to carefully cut almost all the way around the cap with a sharp blade where it meets the cone so it forms a flap. A thin bead of Aleene's all the way around will reattach it and be practically invisible. With a poly cone, it's sometimes possible to cut the adhesive between the dust cap and cone, but this is more risky.

 

[Oerets]

The larger the driver the easier to align up is my experience. Doing the inner and adjusting on a smaller driver may be difficult.

Did you just do the one this way?

As to the adhesive, I like contact cement over water based ones.
Does set quickly so have to be ready for that.

 

[RTally]

The problem with gluing the surround to the basket first is that there is no way to adjust the surround to fit on the cone when the cone's VC is centered in the gap. That is, the cone has only one perfect position and that position will likely not line up with where the surround is now positioned. If the driver has a large gap for the VC, you may get away with a slight misalignment.

I would use a tone to force the cone to its magnetic center. Increase the amplitude of the signal so that the cone is just barely vibrating against the inner lip of the surround. If the cone seems to be evenly spaced around the inner edge of the surround, I would glue it. If there is a gap between the cone and the surround on one side, then there is a misalignment of the surround. In that case I would remove the surround and glue it to the cone first, then glue the surround to the basket. If the surround does not fit in the basket, trim it and then glue it.

 

[ghamilton]

I had the best luck using clear gorilla glue.

 

[swechsler]

The problem with gluing the surround to the basket first is that there is no way to adjust the surround to fit on the cone when the cone's VC is centered in the gap.

I understand that, but remember that there was no way to adjust the surround on the frame anyway, as it is a tight fit in the frame (see my first pic, abov

Since you've already glued it to the frame, I would probably remove the dust cap and shim the voice coil and glue with contact cement.

This idea has merit, and I may consider it, but I think I'll try @RTally's method first.

 

[PhooBar]

Just making sure I understand this correctly.

The low freq tone will keep the cone centered properly?
Crank up the volume, until it touches?

 

[GD70]

I’d carefully and slowly trim the surround edges to fit in the basket. Then glue to the cone, then glue to the basket.
Use an Xacto with a #11 blade. Shouldn’t take more than a minute for each. Far easier than having to unglue the surround from the basket to realign. I always use Aileens tacky glue. Apply to both surfaces, let it tack up, approx 5-7 minutes then press together while using the test tone at very low volume. Or cut the dust cap around the base, leaving just a little still attached, flip it open like a can, and shim the cone. After the surround glue has dried, apply a light coat of glue and flip the dust cap back to its original position.

 

[goodolpg]

I’d carefully and slowly trim the surround edges to fit in the basket. Then glue to the cone, then glue to the basket.
Use an Xacto with a #11 blade. Shouldn’t take more than a minute for each. Far easier than having to unglue the surround from the basket to realign. I always use Aileens tacky glue. Apply to both surfaces, let it tack up, approx 5-7 minutes then press together while using the test tone at very low volume. Or cut the dust cap around the base, leaving just a little still attached, flip it open like a can, and shim the cone. After the surround glue has dried, apply a light coat of glue and flip the dust cap back to its original position.

That's what I was thinking, trim the outer edge of the surround. Then glue the inner edge first.
BUT
It appears there is not very much outer edge to trim in the first image which might result in part of the roll being on the basket?
Since it's already glued might as well go ahead and try to center and glue the inner edge.

 

[Quadman2]

Personally, I don't think I would attempt this procedure. Just my take. Like some gear, I think they have a lifetime of use and just need to be replaced.

Wonder if there's been any study to determine if there was much of a change in production of sound after a "refoam"?.

Curious.

Q

 

[Doug G.]

I glue the surrounds to the frame first on all-metal Advent woofers and it works every time. The same situation there. No leeway in positioning the surround flange on the frame, anyway. There is always some leeway in positioning on the cone.

Is the inner surround flange supposed to be in front of the cone edge or behind? How was it done in the factory? Regardless, use a medium-setting glue and apply. Then, as the glue sets but you can still move the cone, press down on the cone all the way around the outside edges. If there's no rubbing at any time, you're OK. If there's rubbing at any point, move the cone slightly so there isn't.

Doug

 

[colohiker]

I would usually use urethane or some left over Simply Speakers glue for something like this. I wouldn't trust to Aleene's to stick to the "plastic" cone. Contact cement would probably work since it is adjustable while still wet. As suggested, weight the cone while gluing and then run a 30hz tone loud enough to be able to gently press the surround to the cone. It may take some patience until it starts to stick. The problem with using a battery is I find sometimes it tends to push the cone off center at full extension.