Do you happen to know how many SBLs and SL2s were made?
Sorry, I donât, Jim. Iâd guess many, many more, particularly the SBL. It would be great to see the official production volumes for all these classic speakers.
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I forget the numbers but I think SL2s were well under 200. Many more Sibbles and I would estimate over 1000? Perhaps Richard has the numbers somewhere?
Hi Charlie, not sure with the exact number, but it was under 200 pairs, I recall something like 190 so 173 may be correct.
Short answer - not many!
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It has been a few weeks now since my refurb of the internal foam and what a difference it has made. I will change the Tweeters at some stage and hopefully Charlie will be able to find a replacement for the Mids. When I built my Sons Recording Studio I used Backer Rod in all the joints for sealing and anyone that uses the Studio comments on how clear the sound is. Obviously other treatments were used as well. I wonder how well it would work on the Bass Cabinet rather than using the Sealant.
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Did you replace the internal foam in isolation of any other changes?
Can definitely recommend new tweeters. Has been transformational on my DBLs. 5 months in and I think theyâre (nearly) there. I donât recall the SL2 tweeters taking so long, or changing so dramatically, during burn-in, however they were Naim matched, maybe the Naim process involves a degree of burn-in?
Willy.
Great to read itâs been worth while an effort for you too 
I could not have done it without your help and advice Charlie.
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Hi Charlie
Interesting to see you changed the tweeters too. Did you find they made a big difference to the sound over the old? I see Falcon Acoustics sell them for circa ÂŁ77 each. Considering modern beryllium tweeters cost towards ÂŁ1000, a bit of a cheap tweeter design by todayâs standards.
It will be interesting to see if Scanspeak can see if a more advanced midrange driver will work with the DBLs.
Having listened to a few new speakers I realise how much detail and resolution I am missing from the DBLs and that is mostly down to the drivers rather than cabinet design. A lot of that will be down to the midrange unit of the DBLs. I donât think the ATC bass drivers have changed that much over the years.
Still waiting for the bass drive units to come back from ATC. They have been focused on their new ordersâŚ
Hi delft
Been out of touch somewhat lately. I assume you got your dbls back together meanwhile. Hope you are satisfied with the result. No further news on my end here, except playing around a bit with some of the ineffable cables.
Taking the mids to skanspeak eventually is still on my agenda, just donât know when âŚ
Playing around with more modern drivers in dbl cabinets might be interesting yet a completely different endeavour that probably would need a second pair to fool around with 
Itâll be interesting to see what Skanspeak suggest? I will follow your updates with interest.
Hi Charlie
I did indeed finally get them back from ATC. Everything went fine putting them back together. However my 500 is still with Naim waiting for DR upgrade - another long delay it seems. So havenât been able to test them with music.
I am currently running the DBLs through my AV amp - no real test at all - but comparing the sound before using them in AV setting there is already a notable improvement in the sound out of the DBLs running them in stereo on movies etc. So I am hoping for a notable improvement on music once 500 is back. Perhaps I wonât need to change them after all .
I have also âinvestedâ in better cabling. Chord sarum t from 552ps to 500 and speaker cables.
I think the DBL design is sound with separate boxes etc (like Wilson Audio ) but if Scanspeak can fit a better midrange then that would be fantastic. I see on Falcon Acoustics website they make a few light midrange units that might fit. I think it would need to be fairly light to sit on the suspended plate. Fingers crossed.
Many thanks to you and all the other contributors on this thread. I wouldnât have had a clue otherwise.
Karl
awaiting your impressions then with the newly DRed 500. My guess is that youâll be quite overwhelmed .
Think itâs time then to come up with a picture gallery of all the newly refurbished DBLs here on the forum âŚ
Short update: Pilgrimage with the mid drivers to Scanspeak scheduled around March/April. I am optimistic
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Wow, thatâs very interesting news. Good of them to have a look, theyâre hardly going to be making a mint out of it, but of course it will benefit NBL owners too.
Pilgrimage with my DBL mids to Scanspeak scheduled for early April.
I will just need to desolder the wires, and then remove and pack the drivers veery carefully to take them on a 7h ride. The plan is to determine their exact specifications, as naim unforunately can not provide these anymore. I hope for a solid assessment on their current status, with the option of a reconing job to be done and/or a recomendation for matching alternatives. Lets just hope corona is not getting in the wayâŚ
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Hi
I finally received my 500 back from Naim with the DR upgrade. So this was my first opportunity to
hear the refurbished DBLs. I also upgraded cabling 552 ps to 500 and speaker cables to Chord Sarum T (from standard cables and Naca 5).
I usually hear improvements âstraight out of the boxâ. This time I didnât, so initially disappointed. So I left it on a system burn in disc for a few days. I was staggered by the improvement!
All together the changes are immense. never heard my system sound so good. I can now listen to my DBLs at low volumes and get a lot of pleasure from them. I attribute that to the lower noise floor of 500dr. Sound staging was always a good feature on DBLs. This has been further enhanced. Depth, bass dynamics, clarity and detail have all improved significantly.
Thoroughly enjoying it all.
Many thanks to all those I have learnt from in refurbishing the DBLs. Couldnât have done it without the forum. 
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This is pretty much what I heard when I got my 500DRâd on DBLâs. However, I can happily report that the amp continued to improve over several more months with remarkable clarity and realism. I thought it so good It convinced me to get my 552DRâd.