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Replacing foam speaker surrounds

Discussion in 'reference' started by martin clark, Mar 5, 2013.

  1. martin clark

    martin clark pinko bodger

    This has been covered in passing in by several DIY room threads over the years but I thought a quick summary might be good reference material too. So here's a short set of pics driven by necessity, posted by complete amateurs to assure the rest of you it's an easy task if you need to try this.

    H2/ Ta'us Bass driver surround replacement

    My pal StevieD of this parish found the surrounds on the bass drivers of his pair of Impulse H2s had very abruptly expired. The Oh Bugger moment:

    [​IMG]

    No, this really is Not good:

    [​IMG]

    I obtained replacement surrounds from http://www.goodhifi.com/. This site has a downloadable guide and a very helpful short video 'how to' (recommended viewing) so here are a few pics of the Amateur's Night recreation.

    The drop-in replacement part for the Impulse H2 / Ta'us bass unit is the foam surround for the SEAS 21-WBX; cheap at 7euros each (March 2013)

    http://www.speakerrepairshop.com/index.php?action=article&aid=2962&group_id=10000028&lang=EN (Foam ring (8 inch) for SEAS 21F-WBX woofer, article code: F8magCsea5). Since I use H2s also I just bought six - a pair each,and some spares for wastage. Excellent service from GoodHifi, by the way - order email placed on the Friday afternoon, and the parts landed on my desk at work in the UK on the Monday from the Netherlands :)

    Anyway you genrally remove bass driver by unscrewing bolts and desoldering the pair of wires on the back - pay attention to their polarity. Once free - first, carefully turn the driver over and use several pieces of low-tack tape from back of cone to frame to hold the cone outer edge centred in the frame as it is. Removing the surround the cone risks losing alignment in the voice coil gap; the use of 3M magic tape is my own dirty-low-cunning cheat alternative to the usual recommendation to remove the central dust cap and shim the voice-coil. With care tape works just as well, and leaves the dust cap intact.

    Then you can set to the scary task of removing the old surround. Take your time to peel away the remains of the old surround. It's a very soft, sticky, gunge-y mess and cleaning-up may take longer than you expect.

    [​IMG]

    Apply your glue carefully, concentrically, to the cleaned cone edge after trialling your new surround in place - do watch the referred GoodHifi video clip.

    We used Impex Hi-Tack, a PVA glue with very high initial 'stickiness' and guaranteed to dry clear, flexible, and adhere to foam and to metal. You can find speaker-specific equivalents elsewhere at a significant premium. Don't use a contact adhesive - you need a slow drying period to allow gentle manipulation of the surround for seating on the cone, and massaging concentricity of the cone relative to the frame.

    Mr Dempster pays close attention to this first-glue stage with a fine brush:

    [​IMG]

    Once the surround has initially 'taken' to the cone and the glue has grabbed. gently depress and play with the fit to the cone to ensure that the voice-coil does not rub in the gap when the cone moves vertically. You want to set everything so that the surround sits naturally within the area defined by the frame at the outer edge. It's easy, just takes patience and a gentle touch

    [​IMG]

    Leave well alone until the surround-to-cone bond has definitely set - say an hour or more - and then run a bead of glue around the frame to bond to the surround. Nearly there now. Manipulate gently to fully seat the bead and ensure there is no rubbing when you gently depress the cone. If necessary play to ensure the voicecoil is centred and not the slightest rub/scrape is felt - we had no problems at all.

    [​IMG]

    Mr. Dempster bakes exceedingly good drivers!

    [​IMG]

    Allow the surround bond to dry thoroughly, another hour or two, and re-fit the drivers. We played a low tone I'd written to file, a full-scale 7Hz sine 'wobble', as a final check for excursion and audible scraping noises. Result - none. Job done - play tunes!

    [​IMG]

    (I'm happy to share the 7Hz aiff file - PM me if interested)
     
  2. Tenson

    Tenson Trade: AudioSmile

    Nice shots Martin. It's a good thing surrounds are easily available, many woofers that age are out of production.
     

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