Sony APM 700's Need New Foam-Home Fix?

Discussion in 'Speakers' started by SweetDoug, Nov 1, 2009.

  1. SweetDoug

    SweetDoug Member

    Messages:
    82
    These are great speakers and don't sound too bad even at my cottage with the foam rotted out on the bass and midrange.

    There's a nimshe fix out there using chamois cloth and starch spray to make your own "foams".

    I don't seem to be able to locate the replacement custom foams and frankly, I don't think the speakers are worth $90 to fix just the bass speaker.

    Suggestions?

    Doug
     
  2. goanlisten

    goanlisten Active Member

    Messages:
    412
    Location:
    Fremont, CA. 94536
  3. chasaboo

    chasaboo Active Member

    Messages:
    474
    Location:
    Easy Street
    I'm not sure what the hell it is but these speakers just fascinate the hell out of me. I've been looking for a cheap pair that have the foam rotted out so I can effort a fix. No luck as of yet but I'll keep looking.

    I hope someone who has done the fix can post his experience here. Curious to see how it went.
     
  4. SweetDoug

    SweetDoug Member

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    82
    Yeah, I brought them down to the house for the fix over the next couple of weeks.

    Wish I could identify the other "foam" replacements in the fix-site. I've got some super thin foam sheet that I might try to fake in, as I'm not so sure about chamois.

    Doug
     
  5. SweetDoug

    SweetDoug Member

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    82
    Hey! I just took the Sony APM apart, and did somebody rip me off?! There's no speaker coil on the big speaker/woofer?!? It's just a floating front?! What!?

    How does this work?

    Doug
     
  6. WilsonCreek

    WilsonCreek Active Member

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    290
    Location:
    SW Idaho
    From the sound of it the big speaker/woofer is actually a passive radiator rather than an active driver. I have the model 707 and, if yours is like mine, it is just a silvery sheet of cardboard with a little weight attached in the middle on the back. No rip-off, it's supposed to be that way. Are you sure you have the 700 though, as pictures on the internet of the 700 show a two-way speaker--one tweeter, one woofer?
     
  7. goanlisten

    goanlisten Active Member

    Messages:
    412
    Location:
    Fremont, CA. 94536
    The model tags on that speaker could be lying - The APM-700 is a two way design and a bookshelf size cabinet.

    The APM-x250 & APM-x270 are larger (floor) 2 way systems with an additional passive radiator - i.e. a flat thingy with a weight on it, as "WilsonCreek" has already pointed out. I'm wondering if you have one of these two models perhaps.
     
    Last edited: Nov 9, 2009
  8. SweetDoug

    SweetDoug Member

    Messages:
    82
    Oops. Sony 717 APM.

    But yeah, it's just the silvery sheet. So what does this really do? There's no breathing hole, so doesn't this sheet vibrate in an anit-sympathetic movement to the movement of the active speakers?

    Wow. From the above, it might sound like I know what I’m talking about, but don't let that fool you!

    Doug
     
  9. tmad40blue

    tmad40blue "I can hear forever!"

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    Location:
    Ann Arbor, MI
  10. SweetDoug

    SweetDoug Member

    Messages:
    82
    Sony APM 717's

    Here's the pic's.

    SD
     

    Attached Files:

  11. SweetDoug

    SweetDoug Member

    Messages:
    82
    I've been giving this issue a bit of a think. What does that passive radiator do? I'm thinking the mid-range, the one in the middle, would be more better to fix and just cover the big hole of the P.R.

    And instead of the chamois fix as suggested in the fix solution, what about some thin rubber membrane?

    SweetDoug

    I checked the web site for the cost and it's about $100 Canadian for the foam. Too pricey for me. I'll try the fix.
     
  12. goanlisten

    goanlisten Active Member

    Messages:
    412
    Location:
    Fremont, CA. 94536
    Search this forum for "passive radiator" and you'll find many links.

    or try "google" for more info.
     
  13. SweetDoug

    SweetDoug Member

    Messages:
    82
    Lots of info, thanks guys.

    BUT! Here's a thought: Am I wasting my time refoaming the passive radiators? The foam that came on them is so thin it's only got one side (Da-Da-Dunt!) and since nothing's driving them except the air moving from the main mid, is it really worth my while, unless I use a super-duper thin membrane, like maybe a rubber from something like a medical dam, like the one your dentist would use?

    SD
     
  14. goanlisten

    goanlisten Active Member

    Messages:
    412
    Location:
    Fremont, CA. 94536
    SweetDoug, I'm no expert on these things but noticed on mine that the APM's need a way of centering the VC and the foam surround does that, and more importantly isolates the rear of the speaker panel from the front - i.e. since you have a passive radiator, the cavity must be airtight. So, any air leak will affect the low frequency detail and steal sound quality.

    Beyond that any material with comparable rubber/elastic properties of the original foam surround should work.

    BTW what you've been calling the mid-range is actually the woofer (low freq. driver) - the larger panel at the bottom, is only a helper in that, it tunes the cabinet and the trapped air to produce much lower frequencies (a simple explanation).

    Good luck to ya!
     
  15. SweetDoug

    SweetDoug Member

    Messages:
    82
    Foam Replacements

    since you have a passive radiator, the cavity must be airtight. So, any air leak will affect the low frequency detail and steal sound quality.

    Beyond that any material with comparable rubber/elastic properties of the original foam surround should work.

    , it tunes the cabinet and the trapped air to produce much lower frequencies (a simple explanation).




    Well I finished the first speaker. Had some interesting times figure out the topology of the speaker using a square rig. I'll post my method later. It's obvious that it's not a great design, as the corners are the weak spots when the speaker moves and this flexes.
    I used some thin 1 ml styrofoam sheeting. Not too bad for sound. Way better than without any surround on them. They have a very bright sound and the PR actually passively radiates! Airtight! But, I'm thinking that the foam does not mimick the orginal paperthin rubbery-foam stuff that well.

    I'm going to search out some thin rubber sheeting, like a medical dam or latex rubber glove sheeting and try it on the other.

    I'll put some pictures up later. I'm not sure the chamois fix would work well on the passive radiator. Too firm. The original surround on the PR is about .3 mil. Actually, it's so thin, it's only got one side.

    Sorry...

    More later.

    SD
     
  16. goanlisten

    goanlisten Active Member

    Messages:
    412
    Location:
    Fremont, CA. 94536
    I remember reading a suggestion in this very forum, from one of the member's, about using Elmer's glue diluted with a few drops of water to coat foam. It would be worth the effort to try that on a piece of foam and see if that provides the film you're after.
     
  17. Mark Davies

    Mark Davies New Member

    Messages:
    16
    Sony APM 700s,

    Hi I've just been given a crackin pair of Sony APM 700s in fantastic condition apart from a little foam rot gonna get hold of a foam repair kit from flea/bay & bring em back to they're former beauty!to be brutally honest they sound mighty fine in this condition suffice to say they are gonna sound heavenly once repaired! I wait in eager antisipation..;)
    Regards Mark.
     

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