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Naim IBL Bass Units?

Discussion in 'audio' started by chris shorter, May 1, 2018.

  1. chris shorter

    chris shorter pfm Member

    I have a pair of Naim IBL's in a second system that we mainly use for watching video streams and DVD's. Also in the room are five cats and, unfortunately, one of them had some great fun destroying one of the bass units!!!

    I'd like to get them working again but Naim original units would be way more than I want to pay, even if they are still available. I believe Naim took something fairly standard (a Mordaunt Short unit???) and modified it. I wondered if the OEM unit might be still available and I could use it as a drop-in replacement. Does anyone know what it was?

    In the context of our second system, I'm not really bothered about ultimate sound quality but would just like to get them working again.

    Many thanks
  2. RJHarker

    RJHarker pfm Member

    From my experience, you can get damn close to original. Know the tolerances of the parts in crossover/speaker drivers, do best/worst case scenario to find tolerances and find something near that.
  3. Whatsisnaim

    Whatsisnaim pfm Member

    If you call Naim’s service dept they should be able to give you the specs you need. They won’t sell you spares for DIY use, but in my experience, they are usually still happy to give advice.
  4. mario

    mario Member

    I think naim used the KEF B110 basket to make both the IBL mid/bass and DBL/NBL mid driver so I think that unit may just drop in. I recall Richard Dane saying this so maybe check with him. I think the mordant short involvement was with the original sbl mid/bass driver.

    YNWOAN 100% Analogue

    Back in the day I recall being told that both the mid for the SBL and IBL were Mordaunt Short designs which were then modified by Naim. When the driver is removed you can find bits of metal glued to rubber and then glued to the magnet and cone as parasitic dampers.
  6. Bob McC

    Bob McC Living the life of Riley

    According to this excellent review on TNT audio bass speakers were originally sourced from Elac, then later Mordaunt Short and finally were manufactured by Naim themselves on a Kef chassis.
  7. chris shorter

    chris shorter pfm Member

    Mine look like those in the picture - the Mordaunt Short ones.

    There is a suggestion about KEF B110 above but they were a completely different beast with plastic cones.

    Many thanks for the suggestions
  8. Craig B

    Craig B Re:trophile

    Those in the tnt pics are the none Mordaunt-Short Mk2 drivers.

    The visual clues are twofold; 1) the shiny black damping ring round the outer edge of the paper cone, and 2) the rubber surround outer flat not being jammed up against the mounting bolts such that it slowly detaches itself from the metal basket flange, as did mine.

    If you zoom in on the bass/mids in this Mk1 pic, you'll notice how the surround had to have been peeled/pushed aside whilst the mounting bolts were being tightened down (mine were considerably worse).

  9. chris shorter

    chris shorter pfm Member

    Mine are exactly like this......except my righthand speaker has had feline attention!

  10. mark121211

    mark121211 pfm Member

    My IBL's use the MS drive unit and as per Craig's observation suffered from the mounting bolts pushing the rubber from the chassis.

    They are apart now for a re-build. I've just dropped a B110 into the baffle and can confirm it's a perfect fit.
  11. chris shorter

    chris shorter pfm Member

    Are there people who could rebuild/repair my damaged drive unit?

  12. Craig B

    Craig B Re:trophile

    Is the paper cone damaged, or is it just the rubber surround?

    Regardless, there exists the possibility that a good cone/surround could be combined with your working voice coil/former.

    Wilmslow Audio's repair and upgrade service comes to mind.

    Perhaps a want ad on here for a fried IBL bass/mid driver?
  13. chris shorter

    chris shorter pfm Member

    It’s both, I’m afraid!

  14. Sergey72vw

    Sergey72vw Active Member

    Very good speakers Naim Ibl, what I even more like the Naim SBL.
  15. chris shorter

    chris shorter pfm Member

    I see that Wilmslow B110 replacements have a paper cone. Looks like a good option for me and at £32 each they are not silly money to get my IBLs functioning reasonably well again.

  16. rontoolsie

    rontoolsie pfm Member

    The IBL 'bass' driver was identical to the midrange driver of the DBL-which was, for lack of a better word-a bit idiosyncratic. It had a an 8dB midrange bump between 800Hz-1.5kHz. This was largely compensated in the DBL by the slotted ('decoupled') mounting plate that effected a similar suckout in that region. I don't think the IBL had this compensatory mounting. Which is to say, if you found another driver of similar basket dimensions and sensitivity-it would sound very VERY different as no audio drivers these days would be so non-linear.

    Here is a sweep of that very driver conventionally mounted (purple trace showing said midrange bump) and a more conventional driver (green trace). I only discovered this irregularity after I had some very high spec drivers custom made in an attempt to improve the DBLs, and found out that since they were linear, they would be subject to a large midrange suckout when mounted in the DBLs.

    And now the DBL midrange in a standard mount (purple trace without the slotted mount) vs a conventional driver (red trace) within the slotted mount-showing the distinct midrange suckout due to the compliant mounting plate to compensate for the midrange bump in the native driver response.
    Last edited: May 5, 2018
  17. hp1

    hp1 pfm Member

    The Ibl units shown above are mk1 versions made by elac uk before they went bump. The mk2 Ibl with the doping around the cone uses units sourced from Mordaunt Short and when they went bump Naim had to make their own.
    Also the Ibl and DBL/NBL units are different as the Ibl unit had an 8 ohm voice coil designed for long throw use and the dbl/nbl have a 4ohm coil for short throw.
  18. rontoolsie

    rontoolsie pfm Member

    Yes, the IBL driver *may* have been different enough from the DBL one to not suffer that low-fi midrange bump. But then again, maybe it wasn't. One thing for sure...the raised lip of the basket would result in unwanted diffractions regardless of impedance and x-max of the voice coil.

    I don't think I ever heard a set of IBLs, but I have heard SBLs on many occasions, both active and passive and have found their midbass to be near unacceptable regardless of the supporting electronics (the best I heard them was with Snaxo/Supercap/4x135, fronted by CDS/52....maybe the CDS3/552/500 added new dimensions).

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