First-timer speaker refoam - Does size matter?

[Jibe01]

My first time refoaming a speaker. This is the mid-range from a Marantz Imperial 7. I purchased a refoam kit from Midwest Speaker repair - (Item 150417508035) Marantz Imperial 7&9-3.25" Midrange foam speaker repair kit. When I set it on top of the speaker, I see that the inside fits the speaker paper. But if you look at the 2nd pic, to the right, you'll see that the outer edge doesn't quite make it over to the edge of the outer ring of the speaker. It's short about a 1/16" of an inch. I checked the dimension of the foam and it does measure 3-1/4" outer diameter,. The speaker measures 3-5/16" diameter.
What should I do? Should I glue to the inner paper edge first & stretch out the outer flange to fit? Not sure what to do here.

 

[loudnoises]

The wavy outside edge makes me think it's shrunk a bit, and the roll thickness looks smaller in that area as well. You say the Inner fits well?

If it was mine, I'd do as you said, do the inner, let it dry, do the outer - stretching the surround evenly. Looks like it fits naturally in some areas. Many pictures of folks using gentle clips (and a barrier) to hold the surround in place.

Situations like this seem like why folks shim, tho i've only used the tone method myself.

 

[Blue Shadow]

Did you cut out the cardboard ring on the outer edge? Remember these being midrange drivers they don't have to put up with long excursions they just vibrate, not make bass.

That ring of cardboard should be able to cover the surround to keep it in place. I got surrounds for those drivers from Main Electronics, worked fine.

 

[Old Ears too]

Based on your pictures, I'd try rotating the surround around to see if it fits better in another position.
I'd like to see a picture of the surround rotated so that the part of it that is at 2 o'clock is down at the 6-6:30 position.
I just finished changing the surrounds on my CS3008's and didn't use clips or the tone method. If you glue the inner part to the cone first and let it dry, then glue the outer edge to the basket without imparting any stress on the cone you should be OK. Stretching the foam is going to put stress on the cone, pulling it to that side. Getting the surround attached with the cone in a stress-free state is the key.

 

[HTHMAN]

Do not stretch it to make it look centered. You could cause voice coil rub. Either use a test tone to center the cone or push in and out to check for rub. Glue it as it sits. Do not worry if it looks a hair off center. Lots of info and videos around on proper installation.

 

[gadget73]

I recently did an Electro-Voice 15" that didn't quite sit perfect on the basket either. I glued the inner, let it set, then did the tone thing and attached the outer. One edge of the surround overhung by a very small amount. I didn't pull on the cone, the tone was basically verification that it wasn't pulling and rubbing. I used clothes pins as I went to hold the surround in place. Seems to have worked.

 

[Old Ears too]

Proof that centering doesn't need to be perfect.


I used the push method to insure no rub initially, inner edge first. Waited a bit and then did the outer edge. Pushed on the dust cap while rolling a screwdriver handle around the outer edge to help 'spread' the glue under the lip. Stress-free cone, ie allow the magnet to center the cone.

 

[Jibe01]

Thanks for the replies. I've attached a pic of the 2nd midrange with the other foam surround just sitting on it. The speaker's outer diameter is also 3-5/16", not 3-1/4". Looks like if I get it exactly centered, the distance between the edge of the foam surround & the outer ring of the speaker will be 1/32", and should become a little less, once I put glue on the edge and press the foam surround down to seat it in the glue.
It looks to me that the foam surround is exactly 3 1/4" diameter, but the speaker is just a tiny bit larger.

 

[Old Ears too]

That looks a lot better to me than the other picture you showed earlier.
I assume the original foam wasn't glued to the metal part that has the mounting holes in it, correct?

 

[dzkfraser]

Not sure of the issue, looks like the new foam will fit, albeit the outside diameter is a little smaller than the original, are you worried about the cosmetics? If that's the case you can probably shop around until you find ones that have the exact same diameter.

 

[Jibe01]

DZKfraser - No, not worried about cosmetics. The speaker cabinet has a cover, so the driver won't be on display. I was just worried about proper attachment since this is my first time, and I was surprised that the foam did not go all the way out to the edge, esp. since I brought one that stated is was specifically for an Imperial 7 midrange.

Old Ears too - below is a pic of the driver without the foam in place. The foam does not attach to the metal frame. There is a raised., black ring that it attaches to. The ring appears to be of a dense fiberboard. It is very well attached to the metal frame. Thanks to all for the advice.

 

[Oerets]

Was the old surround attached to the top of the outer ring? If not remove it with solvent cleanup and replace on top of new.




Barney

 

[Jibe01]

Yes, The old surround was attached to the top of the outer black ring, where the red arrow is pointing.

 

[dzkfraser]

DZKfraser - No, not worried about cosmetics. The speaker cabinet has a cover, so the driver won't be on display. I was just worried about proper attachment since this is my first time, and I was surprised that the foam did not go all the way out to the edge, esp. since I brought one that stated is was specifically for an Imperial 7 midrange.

Old Ears too - below is a pic of the driver without the foam in place. The foam does not attach to the metal frame. There is a raised., black ring that it attaches to. The ring appears to be of a dense fiberboard. It is very well attached to the metal frame. Thanks to all for the advice.
View attachment 946673

Attaches to the ring? That's weird, would think that it should attach to the frame and the black ring piece is a gasket of some sort. Always something

 

[gadget73]

I was thinking the same thing. I'm not very experienced with speaker refoaming but the ones I have done had the surround glued to the metal basket, and the gasket or ring glues on top of that.

 

[Jibe01]

Actually, in reexamining, I think you may be right. The original foam ring was mostly gone when I got the speaker, and what little was left flaked off at the touch. This was about 2 months ago, some I'm going by memory about how it was fastened. It does make sense that the new foam ring attaches to the metal basket, and the hardboard ring is a gasket that glues down on top of it. If this is the case, why wouldn't the speaker re-foaming kit offer a new gasket, since trying to remove a 40 year old glued-down gasket could result in its damage or destruction? I googled "gasket for Imperial 7 midrange speaker", and nothing comes up but re-foaming kits, none of which offer a gasket. So I'm a little stumped

 

[dzkfraser]

Generally, you would reuse the gasket, that is why the don't come with the foam. There are a number of places that sell foam/gaskets, you'll probably have to google a bit - not having the gasket won't hurt anything, will just look unfinished. You could probably make your own if you are so inclined.

 

[gadget73]

If you're careful with it you can get those off. The E-V I did recently used a cork ring, and I just used a utility knife to get between the basket and the gasket to get it loose.

 

[Oerets]

I have found lacquer thinner will loosen the old glue. Using a razor blade and socked Q tip to open up the gap.



Barney

 

[Blue Shadow]

I have refoamed a pair of Marantz 7 mids and the foam goes UNDER that fiberboard ring. It is simple to remove the ring, just slide a small knife unit it and rotate the speaker around to slice through the old foam. Clean the metal basket, smooth out the ring. If you take chunks out of it, you can glue it back in on top of the foam upside down with the smooth side down. If you do that, paint the other side black so folks don't see the chunks knocked out of it. I used an X-Acto knife, worked great.

Mentioned this ring in Post 3, glad to see you are getting these done properly.

The gasket, reuse it. It gives the surround a bit more strength on the basket edge.

The gasket is for mounting the driver face to the board, to prevent air leaks. It is on all those drivers even though they are used with the backs mounted to the speaker in the 7.