Any advice regarding replacing foam surrounds on rare Fostex F220a speakers ?

I have a pair of Fostex F220a Full ranger drivers; big brother to the F200a. Sadly the foam is completely rotted :(.

I spent a while looking for aftermarket foam surrounds, however, I didn't find anything off the shelf that was close in size. From what I could tell most placing that sell replacement surrounds, don't actually manufacture them and naturally only cater for more common models. Fostex International were no help either. Perhaps I could try cutting down some 10" foam surrounds, but I don't see that working well. I did create an MDF form to size and created a leather surround, but the 1st attempt didn't quite work. Fs measured about 30hz higher inspite of the added weight; I think I got the surround curve too steep and should have made it shallower, I also didn't consider the variation in leather's elasticity. Still the leather did look nice for a first attempt.

I've no idea how foam is made, but I'm guessing it's beyond the average diyer's abililty unless the the sheet material can be reformed using heat and pressure ?

I've started experimenting with paper soaked in latex, but don't hold much hope of that working.

Also, I'm not sure what I should be looking to attain, the surround will block/reduce the rear wave cancellation and ideally should be light for a FR driver, but beyond that I am unsure, perhaps it should be elastic, deflecting with little force and returning dead stop to the center position.

Thanks for reading
Dave
 
sounds like you might be able to repair the speaker yourself eventually. I looked up Fostex Oceana site and they do have a repair service if you want to go down that route to see if possible/affordable, see https://www.fostex.com.au/pages/parts-service-repair-fees-charges

Another option could be a third party repair service. In my location we have Queensland Speaker Repairs who have diy parts for a range of speakers or they can do the whole repair. There might be a similar service in your region.

I once had Pro9TL units including a Peerless sealed midrange with a foam surround that deteriorated after 20 years or so. Somehow QSR found the part, whether OEM or compatible I'm not certain. That midrange was never that great IMO anyway but sounded just the same after the repair. Hope you find a practical solution.
 
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Thanks,

I contacted Fostex.au , and they got back to me but sadly they don't have a solution.

I wonder how accordian would perform. I'm guessing there is a reason(s) they're popular (limited to) with guitar drivers.... thinking about it I can think of at least 4 FR drivers that use accordian style including the Visaton B200 being well regarded and not ancient an design, so perhaps it would work alright. When wet the paper allows a little stretch so I'll try replicating the original curve for now.

The latex liquid (natural rubber) once dried is quite stretchy in itself but the inelasticity of the paper negates that; but it does seem to make the paper somewhat tear resistant and damped.

Here is the leather version installed; it was formed from a single piece:

Leather.jpg
 
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Fostex 206ES-R use a doped cloth accordion style surround as well. (Pic)

I wiuld think that might be a good solution fir your drivers.

I bought what was supposed to be a NOS pair of the ES-R.

No real issues with the surrounds, but there is mildew and mold on the back of them and the cones that show through in some spots.

Only managed to get half my money back and the seller didn’t want to pay for return shipping…so I guess I’m stuck with them.

Haven’t had the motivation or time to see if anything can be done to restore them.

I had wondered if it was possible to recone them.
 

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