Willy
They look rather good, but did you try to take them out too? J found two different foamings one more greenish and one more gray. The greenish one was really bad an fell to dust merely by looking at it. The grey one was in better shape but crumbled as well. Maybe naim used better foaming with the earlier speakers … 
Charlie,
Think I prodded it and there was still some bounce left in it. Never explored much beyond that. Certainly never noticed anything greenish. Maybe re-foaming is a future project after I’ve cleared the current backlog of “to do” lists. In that respect this furlough lark is a bit of a godsend. If it extends to about October I might just be hunting down some foam! 
Regards,
Willy.
Hello Charlie
Just wondering what led you to dismantle your bass drivers, did you know the foam inside was collapsing and if so how ?
My speakers are much older 92 and although not shabby but certainly not as immaculate as yours look although mine are black which won’t have the same wow factor
My bass drivers seem absolutely fine with no apparent degradation other than a loss of shine
Seeing the inside of yours does concern me especially given the age difference but I’d rather not dismantle the drivers just to see
Each recent upgrade has always been noticeable with a marked clarity in the bass especially 135 - 500 and then again with DR
lyndon
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Good morning Lyndon,
So what made me suspicious? Mostly curiosity und a certain gut feeling. On the other hand since going active on the DBLs I always had some kind of a bass issue. Since I have exchanged my 552 with the S1 which probably was the biggest improvement of all tweaks I have taken so far, these issues were seemingly resolved. A grain of uncertainty nevertheless remained. So I guess the wish to be 100% sure with a maxed out front end and the fact that I had to dismantle my system completely and relocate it temporarily because we had the room painted came as an occasion to finally take the knife and have a look into the bass cabinets. But mind you I did not come unprepared but have checked before all necessary prerequisites, ie organizing the reconing of the drivers with ATC and finding a source for the foaming pads in case I needed them.
As you see my suspicions were well justified. I was surprised myself by the extent of the decomposition of the inner foamings considering that my DBLs are reasonably young with 16 years.
To be continued …Must dash…
Charlie
Are there any other NBL owners anxiously reading this thread…? The NBL bass drivers are rather inaccessible.
In my case there seemed to be two types of foam with differing levels of desintegration. Here the “better” ones which just crumble. They are from the middle section of the bass cabinet. The same type seem to be in the mid range cabinet which I haven’t taken out so far but plan to exchange as well. The more greenish foaming which I found in the bass cabinet in the top and bottom section and in the pillars of the L shaped bass corpus pretty much returned to dust upon touching …
Another off-topic question, but somewhat related.
Can anyone tell me the distance (in cm) of the DBL spikes from the borders of the base (front/back and side)?
Stefano
They are 4cm in from the side both front and back. Hope that helps.
Charlie
As I finally ordered the foaming today I thought I post the measurements/quantities required for all inner foamings for 1 pair of DBLs. It’s made from reticulated Polyurethane 80 ppi acoustic foam all 25mm thick.
Bass cabinets:
390x130 (4x) middle sections
460x130 (8x) upper and lower sections
Midrange cabinets:
400x190 (4x)
Bass corpus pillars
550x340 (4x) according to naim data sheet
550x240 (4x) actual measurement taken from my own speakers
Hope it helps 
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big thankyou for this, I’ll print it out and keep it with my manual. Was it hard sourcing the foam?
Mario,
Ben Lilly from ATC referred me to customfoams
I expect to receive the foamings in about two weeks time. The lady at custom foams I was in contact with -Michelle Smith- was very helpful.
I guess I know more once I got the stuff here then.
Meanwhile I have some 808 to play around with
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I think I remember @Richard. Dane posting that the NBL bass drivers didn’t suffer from foam surrounds, nor do SBLs, allaes etc.
No one has mentioned what the stuffing is in the various NBL nested boxes or whether it deteriorates. I assume the speakers will become a tad more characterful should it collapse but the only mention I remember of the bass module in the manual is a warning not to mess with it.
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The foam lining inside the NBL top, where the top box is “nested” most certainly deteriorates. My pair certainly need this foam replaced but I have not yet worked out how to remove the banana terminals from the top box in order to remove the nested box with the flying leads following out behind it.
I believe that this foam breakdown is more related to the environment that the speaker lives in. It looks like damp conditions, with cold wet walls being the main culprit as I have seen at least some older SL2’s and DBL’s for that matter, that have no real signs of this deterioration. SL2’s also have acoustic foam in the top box where the tweeter resides. This is easy to replace.
After reading the various posts on here (I suspect I know Charlie by another name ) I thought I should check my DBLs. Well, the drivers anyway, which I seldom look at because they’re out of sight behind the foam covers which, despite being the originals and very old, are immaculate. Or so I thought, until they more or less disintegrated in my hands. Luckily, I had a spare set I’d bought from Tom-Tom a few months ago.
Checking the bass units, they and their surrounds are still fine, and look like new. As regards the internal foam, it can quietly disintegrate to itself in the dark whilst I remain blissfully ignorant.
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Message understood loud and clear. Thank you.
Hi Tony
Yep you do anyway, I don’t want to wake sleeping bears here but mine looked immaculate too from the outside including the bass drive units. Not until I dismantled the drivers from the bass cabinet I realized how fragile the foam circumferences of my bass drivers actually are. One disintegrated while removing the bass unit from the cabinet while the other one miracously remained intact. The material merely upon slightly touching would tear apart. So it was high time to have the bass units sent to ACT for a reconing job. Now with the inner foaming of the cabinets most were in really bad shape and fell to dust upon touching with the best ones in the cabinets of the mid range drivers.
So I conclude from that that my bass issues I did have lately -although they seemed to have been resolved once I introduced the S1 may well be due to deteriorating drivers/foaming. I assume I did not hear my DBLs at their true full poteintial particularly now with S1 /active 500DR. I am really curious how they will perform with new drivers and new foaming also then in a fair comparison then with the 808s I currently have on trial.
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