Help with Bass drivers for SBLs

I’ve just bought a pair of SBL’s and the aluminium (I believe that makes them Mk1s) phase plugs are detached from the bass drivers. I can’t imagine its a difficult fix but Naim haven’t got the parts and still haven’t answered my question regarding fashioning a DIY fix.
I’m looking for a pair of replacement drivers with no luck. I understand they are on the endangered species list but if anyone could point me in the direction of someone who can help either with a repair or with replacements I’d be very grateful.

Are you sure they are the original Mordaunt Short drivers? Can you post a picture, including the detached phase plugs?

IIRC, the M-S driver just had the phase plug fixed into place - some carefully applied adhesive should suffice I would have thought.

Otherwise, have you considered upgrading to Naim mid/bass drivers? If Naim can no longer supply these then it’s a case of finding good condition secondhand drivers from the usual places online. Or else look for a pair of Credos with poor cabinets but good drivers and salvage them from there. They won’t be specifically selected or matched, but after so long and at this level that’s probably not going to be a deal breaker.

Many moons ago I used Wembley Loudspeaker Co a number of times for band cab & PA systems.
Although called Wembley they are now at Shepherds Bush. They’ve been around for years & offer a complete rebuild & repair service that includes re-cone & re-foam, I’m sure a driver refurb to include refitting a phase plug is well within their abilities
You’ll find them at wembleyloudspeaker dot com & give’em a call

I once sent them a pair of Royds, and they returned them months later, no repair done, no explanation, covered in large dents, so I would strongly recommend avoiding them. I would guess they are more used to dealing with PA type speakers that are designed to take some abuse.

I’ve never seen SBLs with cones that colour. My mk1s were black. I wonder if they have already been replaced with something else.

With secondhand (or perhaps even more hands) speakers anything is possible. The driver cones are certainly some of the palest I’ve seen on early SBLs - they’re usually various shades of grey. Maybe just the photo? The glue around the rubber surround looks a bit messy too.

What does the seller (original owner?) say about them?

On the M-S driver the phase plug should just glue back into place. Best done with the drivers lying on their backs. Be very careful though to get it perfectly centred (a trick is to wrap thin card around the piece so it just fits easily into place and forms a perfectly even gap - then just remove card once the glue has set) and not get glue anywhere else in the driver, otherwise the drivers are ruined. Use just a tiny single central drop of superglue would be my advice.

My Credo drivers were once black but the sun faded them to similar to the OPs SBLs.

I found that Wembley firm excellent, but that was some years ago, and a pro speaker - whether they can help with a domestic driver like that would need checking with them first, and I think the’re more into voice coils and replacing cones, surrounds and dust caps than phase plugs that if not a stock spare part would need machining, with a mechanical specification to follow. And if they can I guess they would likely only want to receivers the drivers, not cabinets,

The other people worth speaking to are Falcon Acoustics, whose proprietor us very knowledgeable and helpful.

Hi snaphappybob,

Your picture does not show a complete phase plug - each one consisted of two of those mounted back to back secured with a plastic core & self adhesive gasket between them.

Richard is correct, the original phase plug repair kit contained of a bespoke sheet of thin plastic (similar to a piece of cola bottle) to wrap around the plug & some cyanoacrylate glue.


Out of interest do Naim still have stock of SBL MK II mid/bass drivers?

Hi Alley Cat,

Now that, I am not sure about. I will check for you as soon as I can.


Thanks I blew both tweeters some years ago but my dealer successfully replaced them.

I can confirm that Naim can currently supply the bass units & tweeters. Without divulging exact stock figures, I will say that stocks are VERY limited indeed!!


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Many thanks NeilS.

Wow, Naim want £345 for each driver.
I cannot see how they can possibly justify that price for old stock!

Well, if you had seen Naim building the drivers and the amount of hours that went into their build, the price might be better understood. You have to also think of the drivers in the context of a pair of speakers that would today have a retail cost somewhere around £5-6k.

As for old stock, space (i.e. valuable factory space taken up) and time only add to the overall cost.

If you want Naim (Mk2) drivers cheap, then find a good pair of Credos going cheap (£100-250) and salvage the drivers from there.

I would snap them up if i still had my sbl,s…they would give you another 20 years of music. Nothing really like the Naim speakers such as sbl,s made anymore.

Well protected SBL drivers:

I’m pretty sure they will survive the kids and visiting friends and pets.

Since they are against the wall, they are also pretty safe. Kids won’t run into them (fingers crossed).

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Just needs a mains live feed in to be perfect :slight_smile:

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