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Need some educated help with speaker surrounds.

Jim West PA

Jim West PA

Well-Known Member
I have a pair of Marrantz SP-1250's that I need to re foam.
I have searched high and low for replacement surrounds to no
accurate avail.
I need 8.75 I.D. X 11.5 O.D.
My cones are 9.25", angled.

This is what I have to choose from from Rick Cobb.


#1 Foam surround dimensions - p/n #610-155A
Inside diameter: (edge to edge) 9"
Outside diameter: (edge to edge) 11-1/2"
Inside attachment lip: 7/32" (low profile, angled attachment lip)
Outside attachment lip: 1/2"
Roll: 9/16"
For 9.25" - 9.5" diameter angled cones


#2 Foam surround dimensions - p/n #610-1285
Inside diameter (I.D. edge to edge): 8-5/8"
Outside diameter (O.D. edge to edge): 11-9/16"
Inside (inner) attachment lip size: 3/8" (angle attachment lip)
Outside attachment lip size : 1/2"
Roll size-Unmounted: 11/16"

For 9.25" - 9.4" diameter angled cones

Can anyone give me an educated answer to which I should choose ?
Thanks
 
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Buy both and see what fits best when you offer them up. I'm sure he'd take the other ones back, just ask him.

Lee.
 
I think it would depend on whether the foam is glued to the front or the back of the cone. If it's the back, and the roll is positive (convex), you have to get foam that is large enough for the cone to fit inside the roll. If its on top, you can have a bit of the cone out past where the roll is, and no one will see it.
 
Nothing against Rick but he is not the only game in town.

SimplySpeakers is an AK sponsor and has come through for me numerous times with unpopular sizes.
 
Nat said:
I think it would depend on whether the foam is glued to the front or the back of the cone. If it's the back, and the roll is positive (convex), you have to get foam that is large enough for the cone to fit inside the roll. If its on top, you can have a bit of the cone out past where the roll is, and no one will see it.
Click to expand...

It attaches to the back Nat. And the roll is convex.
I suppose I'm wondering if it's ok to have more foam than necessary attached to the cone. Would it have any adverse effect on the speakers performance.
 
wmgwizard said:
Nothing against Rick but he is not the only game in town.

SimplySpeakers is an AK sponsor and has come through for me numerous times with unpopular sizes.
Click to expand...

I already checked with SS to no avail.

EDIT: I just checked with them again and it seems that they do have a pair designated for the SP-1250's.
The question tho. Will they sell me the foams alone without the kit .
I asked. We'll see.
 
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I have often gone on the assumption that a little bit of extra flat or angled foam will have little effect, ditto a little bit less of the cone (if the surround covers over the outer lip). When the driver is actually working, its alignment is very largely electromagnetic, so the spider and surrounds' job is to keep the voice coil centered in the magnetic gap, and to keep the front and back wave isolated from each other. I don't see how either role would be affected by a bit of flat foam. It is true that there might be a little bit more distortion -- supposedly trained ears can hear the difference between positive and negative roll surrounds. If this is a concern, you can always cut the surround and overlap it to take up the extra size. Not ideal, but it's often done.
I'd be hesitant to replace foam surrounds with cloth or rubber since the design and parameters of the speaker is premised on a specific surround type since they offer different resistance to motion, and different amounts of damping.
On the other hand, EPI seems to have switched from foam to rubber on the surrounds of some of their speakers (whatever the model was that had forward and upward facing drivers) with out otherwise changing the design. So it may not always matter that much, but the point may be moot since the cloth ones suggested don't fit.
 
I've recently re-foamed a pair of marantz woofers, and the foam was a little smaller in diameter, like 1 or 2 mm in a 10" woofer, seemed not important when I tried the foam on top of the cone, at the speakers shop. The seller also told me that little difference will disappear when glueing the foam. (glueing in front of the cone would work)

But the foam had to be glued at the BACK of the cone, so that difference made it very difficult, since the foam was smaller, and didn't adhere even pressing the cone. I've ended glueing it with contact cement after the first glue was dry and the cone and surround were centered, what allow me to bend the foam a bit and follow the cone shape.

So, if in doubt, choose a little larger, not smaller.

I suppose I'm wondering if it's ok to have more foam than necessary attached to the cone.
Click to expand...
I don't think this will do any difference.
 
I would bet that any of the foams or the cloth surround will work. I would buy the one that best fits into the basket. There will be enough flex to make it fit the cone.

I once bought a surround for an Optimus Pro X77 without measuring because I had done a Minimus 77 and thought it was the same woofer. Turns out there is about 1/4" difference in the cones and the foam was a little too small. I tried to install it anyhow and it worked just fine. If you look closely you can see the edge of the cone just a hair past the foam.
 
Jim West PA said:
I have a pair of Marrantz SP-1250's that I need to re foam.
I have searched high and low for replacement surrounds to no
accurate avail.
I need 8.75 I.D. X 11.5 O.D.
My cones are 9.25", angled.
Click to expand...

With 9.25" cones it seems you need angle-lipped surrounds with a 9" inner dimension.
I purchase my surrounds only from vendors that include inner dimensions in their descriptions.
 
Well, turns out that Simply Speakers had exactly what I needed in stock.
Ordered 'em up. They sent me an e-mail saying they are sending me an invoice so I can PayPal 'em. That was about 30 hours ago and so far no invoice.
attachment.php


Also got me enough surrounds to re foam all the Mini Advents I got layin around here.:thmbsp:

We're in the process of buyin a house and I can't wait to get it all wired for sound and put all these old speakers back to good use.:D:banana:
 
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Jim West PA said:
Well, turns out that Simply Speakers had exactly what I needed in stock.
Ordered 'em up. They sent me an e-mail saying they are sending me an invoice so I can PayPal 'em. That was about 30 hours ago and so far no invoice.
attachment.php


Also got me enough surrounds to re foam all the Mini Advents I got layin around here.:thmbsp:

We're in the process of buyin a house and I can't wait to get it all wired for sound and put all these old speakers back to good use.:D:banana:
Click to expand...

I've had great results with using Simplyspeakers for my many past speaker projects.
Last week i refoamed my Dahlquist DQ-10's and their kit fit perfectly.

Al. Wise
 
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