Phase plugs

Discussion in 'Speakers' started by dirt, Jun 22, 2020.

  1. dirt

    dirt Acquaintance

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    My cat, for god knows what reason, left her claw marks on the dust dome of my Fostex FF165K. Maybe she saw a bug or thought the light reflecting off the aluminum dome was a bug. She didn't pierce it but she did make some big creases. I got some of the damage out with a vacuum, but not all. I don't know how much this affects the way the full range speakers sound. Now, the question is, has anybody tried phase plugs after removing a dust cap? Fostex no longer makes these drivers, and there is no perfect substitute.
     
  2. fastfwd

    fastfwd Friend

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    I don't understand, can't you just listen?

    Also, without a photo it's hard to know what the damage actually is, but often a pushed-in dome can be pulled out with adhesive tape -- might improve on what you've already been able to do with the vacuum.
    So if I were in your situation I wouldn't worry about it. Dust covers don't really affect the sound. And certainly, a small crease in the dust cap is a smaller change than replacing it with a phase plug.

    But if the imperfection bothered me aesthetically, I'd call around to see if someone nearby could replace the damaged dust cap with a new one, and if that didn't work out I'd just keep an eye on Ebay, diyaudio, usaudiomart, etc., and wait for a pair of NOS FF165K to show up.

    Good luck...
     
  3. dirt

    dirt Acquaintance

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    Tried adhesive tape first, and got part of the dents out, then tried the vacuum. The remaining damage may not affect the sound. I need to listen more. Some years back, a kid pushed in the dome on a Dynaudio tweeter, in some other speakers I have. I got the dent out and it looked perfect but broke up like crazy on piano. I bought a replacement tweeter. Lucky I did, as Dynaudio quit selling components shortly after.

    And, yeah, aesthetically, the creases in that shiny dust cap disturb my inner peace. :rolleyes:
     
  4. Serious

    Serious Inquisitive Frequency Response Plot

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    That the dust cap doesn't affect the sound is something I highly doubt @fastfwd. Especially with full range drivers I'd expect it to have an effect on the HF performance.
    Anecdotal evidence for sure, but I tried an inexpensive 4" full range. It had some peaks in the treble and I thought it could've been resonances between the dust cap and the magnet. So I carefully cut out the dust cap and tried it without the dust cap. Response was much worse. Even some quick experiments with phase plugs didn't help much. So in the end I put some damping felt between the dust cap and the magnet, which did help smoothen the response a tiny bit, but most of the peaks I saw seemed to simply be caused by cone breakup.
    So @dirt I'd not expect better sound from every driver simply from removing a dust cap. Many drivers have carefully considered dust caps which are essential to their performance and I'd expect the Fostex to be such a driver. However it might be possible to glue the dust cap back on for near stock performance if you don't mind slightly visible glue. A dented dust cap is unlikely to have the same response as a new one anyway.
     
  5. fastfwd

    fastfwd Friend

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    Mmm. Yes, I see that that's what I wrote, although it's not exactly what I intended. What I meant to say was that this kind of damage to the dust cap doesn't really affect the sound. Which we might still disagree about, of course.
     
  6. Cspirou

    Cspirou They call me Sparky

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    Well one is to replace with FF165WK drivers. But might not be worth the $200 if you can save the drivers for far less.

    I would write an email to Planet10 hifi and see if they have done modding on the FF series for phase plugs

    https://www.planet10-hifi.com/pp-info.html
     
  7. purr1n

    purr1n Finding his inner redneck

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    I wouldn’t worry about small creases on the dust cap. Removing it with a phase plug can result in further damage or worse performance than what Fostex intended.
     
  8. squishware

    squishware Friend

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    Where did you bury the cat?
     
  9. Serious

    Serious Inquisitive Frequency Response Plot

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    Oh, in that case I think it's unlikely to make significant differences for a full range speaker. Heck, I managed to cut out and glue back on the dust cap for my driver without really affecting the sound.
    For tweeters I'd side with @dirt. The dented and repaired tweeters I've heard sadly never sounded the same as they did before :(
     
  10. dirt

    dirt Acquaintance

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    The cat is still above ground. She hates my hi-fi, and hides when I use speakers. But she knew she was a bad cat, and stayed in the room when I tested the damaged speaker. Probably thinking, "see Daddy, it didn't hurt it any". On my other system (Tekton Lore), she damaged a whizzer cone, slightly. I was able to fix that. She hasn't bothered my headphones, but she does tap me on the arm for attention when I am listening to my Asgard 3. Cutting into her play time. Thanks for the input. I don't think the FF165WK will work in the Madisound BK16.
     
    Last edited: Jun 23, 2020
  11. Cspirou

    Cspirou They call me Sparky

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