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Tannoy Eaton - Tweeter Failure?

Discussion in 'audio' started by Martian Sunrise, May 16, 2019.

  1. Martian Sunrise

    Martian Sunrise pfm Member

    Hi all,

    I have a pair Tannoy Eatons which have had the crossovers fettled by RFC and i think the tweeter is gone in one of the them. The sound is muddy on the vocal stuff and clearly not right.

    I'd really like some advice/help, as I am not great on understanding the tech side of things.

    Things to note - I have recently acquired a pair of EWA M50P/M50 pre/power amps, which I have rigged up to them, with no problems, until now. Last night was the only time i have put any volume through them (not crazy, mind).

    They also had the slightest rubbing of the voice coil in the same speaker when they came back from Paul, but only with some serious bass being put through them.

    I am assuming that they need to go off to someone (any recommendation?), but I would like to understand the cause, and if there is anything I need to consider (ie - is the SECA M50 too much for them?).

    They are currently playing to a pretty loud volume with some Royd Minstrels and coping (they sound great).

    Thanks in advance

  2. calorgas

    calorgas pfm Member

    Hi Richie, with a bit of experimentation you may be able to re-align the voice coil to stop the rubbing. There are four nuts holding the spider in place, if you loosen them you can tweak the positioning and then carefully push the cone in and out to see if you can get it so it doesn't rub. While the driver is out you could check that the loss of hf isn't a loose wiring/connector issue, clean the pins of the plug etc.

    (Cooky will probably be along shortly with a better suggestion).

    Oh and I previously used a Quad 909 with my Eatons without a problem, though I only listen at moderate volumes at most.
    tuga and cooky1257 like this.
  3. Martian Sunrise

    Martian Sunrise pfm Member

    Hi Dave, thanks. That sounds like a best-case scenario!

    I understood that that was the way to realign the voice coil, from my discussions with Paul. If it is pushed, it doesn't sound like it is rubbing at all. It really needs the massive bass at high volume to get it rubbing - I haven't done that with the new amp. Not really done it at all.

    The plug was replaced two or so years ago, but it may be a connection somewhere - I hope so.

    Am I safe in assuming that parts (if required) will be available?

    I am going to admit to being far more confident to tinkering with old engines than i am with speaker innards, so i will probably take it to someone...
  4. cooky1257

    cooky1257 pfm Member

    Couldn't have put it better myself;-)
    All I'd add is just check the tinsel leads coming off the bass cone aren't fouling against the basket on large excursions-just move them, pinch/bend them a bit if need be.
    It's rare for a tweeter to blow they are 50w comp drivers, so first off I'd swap crossovers over to see if the fault follows the change if so its a crossover issue.
  5. Martian Sunrise

    Martian Sunrise pfm Member

    thanks cooky

    i will have a look inside when i get back from hols.
  6. Martian Sunrise

    Martian Sunrise pfm Member

    I tested the H.F. with a multimeter and got 0.3ohms, which I assume is a shorted voice coil. Is this correct? If so, what is the next step?

    Any help appreciated
  7. cooky1257

    cooky1257 pfm Member

    Did you desolder the wires to the terminals-I've seen a short in the twisted HF wires in the past.
  8. Martian Sunrise

    Martian Sunrise pfm Member

    I haven’t had them open since they were back from RFC. The blue and black twisted wires were squashed under one of the bolts that held the cover down when I opened them. I tried to separate them and test again but it didn’t make a difference.
  9. Mike P

    Mike P pfm Member

    My thoughts:

    • As Cooky has already suggested the two wires which connect the bass cone to the magnet assembly can sometimes touch the cone on loud bass if the wires have been left a bit too long or have been bent in such a way that they are sitting close to the cone. This can be the cause of some horrible buzzing type noise on load bass and is something that caught me out on my Ardens a while ago. I shortened mine a touch but bending them out of the way may be sufficient.
    • It's possible that the blue and black twisted pair may have been damaged/cut when they got pinched under the bolt. Do the wires look damaged at all? It could be worth checking the resistance across the damaged section of wire.
    • The DC resistance across the HF voicecoil should be higher but you need to desolder the wires to measure it properly so that you only have the HF voicecoil in the circuit being tested.
    • The alignment of rubbing coils can be adjusted to stop the rubbing, it's not a big deal but does require a steady hand and a bit of patience.
    cooky1257 likes this.
  10. Martian Sunrise

    Martian Sunrise pfm Member

    thanks guys.

    i will take it out again tonight and see check points one and two. three might be an issue, as i don't know how to solder (it is the next thing to learn, as i need to rewire the racing car!). four can be approached when the speaker is working.
  11. Martian Sunrise

    Martian Sunrise pfm Member

    As an update: it was the tweeter blown and the voice coil rubbing. Nick at Lockwood (hero) sorted it.

    Thanks for the advice.

    Now to work out which amplification I prefer...
  12. cooky1257

    cooky1257 pfm Member

    Great to hear you got it sorted-did Nick replace your tweeter?
  13. Martian Sunrise

    Martian Sunrise pfm Member

  14. Martian Sunrise

    Martian Sunrise pfm Member

    I missed a nos pair on eBay, which were really cheap (!!!) compared to the going rate, but he sourced one.
    cooky1257 likes this.
  15. YNWOAN

    YNWOAN 100% Analogue

    One word of caution, tweeters don’t just ‘blow’, something, some fault, has to have caused it. In my experience a distorting amplifier is the most common cause.
    cooky1257 likes this.
  16. eastone

    eastone pfm Member

    I got the NOS pair you mean which really stung as I paid full whack for a set from mainly tannoy on eBay only a month or two ago. But it’s good to know I’m fully backed up.

    Would be interesting to know where Nick sourced your replacement from?
  17. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    A clipping amp specifically yes but the compression drivers usually have much higher power handling than a typical 1" dome tweeter and what with the high efficiency of Tannoy's you would have to be seriously head banging to get to those sort of levels with 50WPC available and in a typical living room...
    It can happen though as I've repaired several compression drivers in pro PA speakers over the years that have been blown but usually by 500WPC and above amplifiers... hardly the same scenarios I guess!
    It could be worth checking the amps for ultrasonic oscillation though....
  18. YNWOAN

    YNWOAN 100% Analogue

    Fair point - something has caused the tweeter to blow though, perhaps ultrasonic oscillation as you suggest.
  19. Radfordman

    Radfordman pfm Member

    Crossed my mind too.
  20. Martian Sunrise

    Martian Sunrise pfm Member

    that was something that nick brought up.

    I was switching between two amps at the time, so i am not 100% sure what caused it. I was listening loud, but loud in a normal terraced living room, rather than proper hammering it.

    the two amps were: a tube tech unisis (35w/ch) and a EWA M50 (50+).

    What sort of questions do i need to be asking? I can ask colin about the EWA and david coe about the TT. How do i check the ultrasonic oscillation?

    Sorry - I am not an EE - appreciate the help.

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