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SBL tweeter replacement

Discussion in 'd.i.y.' started by Stenne, Nov 30, 2019.

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  1. Stenne

    Stenne Active Member

    I bought secondhand Naim SBL speakers with mk2 bass driver a while ago.


    My plan is to get them in the best possible shape;
    New gaskets; I have ordered 5 mm neoprene, 0.3 mm aluminium sheet and veneer pins.
    New crossover; Les at Avondale has built a pair of crossover for me that are ready to be shipped.

    Replace the old tweeters with new ones.


    I just removed one of the tweeters and discovered that it is Scan-speak D2008/8512 (with ferrofluid).
    The leads have only been wrapped/tied to the terminals, not soldered.

    There is also no brass/rubber or any sign of any hotglue on the back of the tweeter.

    There is a peace of metal attached to some kind of damper material onto the bottom of the box.
    Is this original?

    I had expected original Scan-Speak D2008/8511 (no ferrofluid), hotglued around the edge at the back and a brass/damper attached to it. Correct?

    My plan is to replace the tweeters with Scan-Speak D2008/8511, Hiquphone OW2 (compatible according to another thread about SBL) or similar.
    But as I don't have the brass/dampers I wonder what to do.
    What is the function of it?
    Would I need it also for Hiquphone OW2?

    I noticed that the nominal sensitivity SPL at 1W/1m is not the same:
    Scan-Speak D2008/8511: 89 dB https://www.lautsprechershop.de/hifi/scanspeak_tweeter_en.htm
    Scan-Speak D2008/8512: 88 dB https://www.lautsprechershop.de/hifi/scanspeak_tweeter_en.htm
    Hiquphone OW2: 90 dB http://www.hiquphon.dk/page1.html

    Now I'm not sure what to do.
    Looking for advise please
     
  2. colasblue

    colasblue pfm Member

    Sounds like the tweeters have been changed in the past and with the wrong thing.

    I don't think it's likely to be cost effective to get a new pair of Naim factory matched tweeters these days, though actually there was a brand new pair for sale in classifieds not long ago, but at a fairly eyewatering price.

    Whether it's even really worth changing the 12's for the 11's is a bit questionable since they aren't actually very much different in sound.

    My original SBL's had 12's in for a while (many years ago) because I couldn't get the 11's. It really wasn't a big deal at all when I did get the correct 11's (in fact I'm not sure there was any significant difference other than that of knowing I had the correct thing).

    It's easy enough to glue round the edge of the cardboard back panel and reinforce the cable connections when soldered with glue but the dampers will be a bit of an issue if absent if your'e seeking perfection. In reality I suspect they make virtually no difference but it's just a bit of brass with some similar neoprene to the gasket material so easy to get something made.

    If you ask in DIY classifieds (or just classifieds) somebody probably has a set salvaged from some dead tweeters.
     
  3. Stenne

    Stenne Active Member

    Thanks for the advise!
    I have found a donor; original Naim sbl tweeters from the 90ies. They look as good as new. Will test how they sound compared to the 8512 (will solder the connections) and then decide what to do.
    So the 1 dB SPL difference between 8511 and 8512 didn’t cause a problem? I’d expect you would hear that.
     
    Last edited: Dec 5, 2019
  4. a.palfreyman

    a.palfreyman pfm Member

    Typically 1dB is recognised as about the limit of audible difference. The impedance plots of the tweeters (if different from model to model) are likely to have the biggest effect on sound as these work with the cross-over impedance to give the desired output at different frequencies. Certainly won't help that the wires are just twisted to the terminals and not soldered. Intermittent contact could cause all sorts of nasties in the HF
     
  5. Loz828

    Loz828 pfm Member

    Just for fun, here is a web page with a test to see if you can detect different dB level changes, I can't vouch for it's accuracy but it's interesting.

    https://www.audiocheck.net/blindtests_level.php?lvl=1

    And just FYI the Hiquphons are sold in matched pairs and have a much flatter freq response but they are much more expensive than the ScanSpeaks, as for the 1dB between the 8511s/8512s -you probably wont be able to tell any difference and even if you can tell in a direct a/b comparison I would bet you could not tell in a blind test under normal music listening, so it really comes down to the weakest link - your ears and what they prefer If you own SBLs you're probably over 40 so your HF hearing is rubbish already, but you can't go far wrong replacing with original tweeters seeing as you have a donor pair, and yup..... I highly recomend soldering the wires - can't believe someone would replace tweeters in any speaker and not solder them - that's ridiculous!!!!!!
     
  6. bluearcher

    bluearcher Member

    I've also had a tweeter die in one of my SBL Mk.IIs so am in process of replacing both.
    I thought about "upgrading" to the Hiquphon OW2 92, but at ~£200 more than a pair of Scanspeak D2008/851100s (~£135 from Falcon Acoustics) decided to stay with the original spec.
    Lifted out the original tweeters by carefully screwing bolts (2BA?) into the holes in them which pushed them clear of the box. Came out easily; I found they'd had only the tiniest spread of Blue Hylomar applied to seal them in.
    What is puzzling me however is the sticky black stuff holding the brass damper onto the back of each tweeter. Each tweeter has a piece the same size (5/8" wide x 1" long by 3/16" thick) as the brass block it holds. It is definitely not sponge and is thick, squidgy and tacky. Does anyone know what it is made of??
     
  7. colasblue

    colasblue pfm Member

    It's a dense foam rubber.

    What you need to do is separate the damper and rubber from the back of the old tweeter as one part. The tweeter back is made of cardboard so this isn't too difficult and a sharp chisel will do it easily.

    It doesn't really matter if the top layer of the cardboard comes with it.

    You then stick it to the back of the new tweeter, which can be done with carpet tape, evo stick or pretty much anything else which will give a decent bond.

    You also need to glue round the back of the new tweeters with hot melt glue to better secure it as will have been done on the originals.
     
    bluearcher likes this.
  8. bluearcher

    bluearcher Member

     
  9. bluearcher

    bluearcher Member

    Thanks.
    Might have been once i suppose but definitely not foam any more! Looks and feels like something left at the bottom of a cauldron!
    I have ended up losing some of the black stuff in trying to remove it. Any thoughts on how critical that may be? Perhaps i need to replace it with dense foam from somewhere, or maybe some thick rubber sheet?
     
  10. Fatmarley

    Fatmarley "It appears my intelligence circuits have melted"

    Does anyone know what the brass damper is supposed to do? I've got to admit, it sounds like marketing bull to me, a bit like when Naim used to test LM317 regulators and reject about 75%. Or the Naim Snaic shaking machine.
     
    bluearcher likes this.
  11. MJS

    MJS Technical Tinkerer

    On the SBLs I believe it's sorbothane rubber. It's been a while since I had one apart and it's probably 5mm thick.

    Re: LM317s. They were rejected for one of 3 reasons. A very small number of them didn't regulate at all. A few of them were out of voltage spec from the nominal in the test jig, and the remainder (most of the failures) had too much high frequency or shot noise. I think it was something like about 5% of them that got rejected. Literally thousands of them passed through my hands (and others).
     
    bluearcher likes this.
  12. colasblue

    colasblue pfm Member

    Could well be.

    Just had a look on the back of my spare pair of tweeters. 5mm looks right and its fairly squashy (ie much more than a shoe sole) but much less so than the SBL gasket.
     
    bluearcher likes this.
  13. Oneandtwo

    Oneandtwo pfm Member

    I refurbished my mk1 upgraded to mk2 SBL’s a few years ago, including replacing both the tweeters (both plastic surrounds had cracked which seems to be quite common). When removed it appeared my tweeters had already been replaced previously as there was no glue around the rear of the tweeters, and the brass blocks were glued directly to the tweeters without the damping foam. To replicated I used double sided closed cell adhesive foam 5mm thick to attach the brass blocks to my replacement Scanspeak tweeters, along with hot melt glue around the edges which seemed to work well.
     
    bluearcher likes this.
  14. bluearcher

    bluearcher Member

    Excellent advice and info, thank you all. I have ordered small samples of 5mm Sorbothane, Neoprene sheet and closed cell neoprene foam, then will use whichever comes closest to the original in squishyness
     
    MJS likes this.

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