Modding advice for a newb, please

John30_30
John30_30 Posts: 1,024
edited September 2008 in Vintage Speakers
I've got a set of RTA 11T's, everything works except the bottom radiator on one has the foam all shot. They've been in storage a while, and appreciate being aired out and used again. :) These have 2 sets of slightly different 8" radiators each.

The radiators are 8". So, without knowing squat about the design intent, rather than re-foaming the bad one, I was thinking of just enlarging the holes on just the bottom radiators to 10" and putting some 10" passives in. :confused:

Do I need an intervention before I commit sacrilege here?:eek:
Post edited by John30_30 on
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  • Early B.
    Early B. Posts: 7,900
    edited September 2008
    Why would you do that? Just call Polk Customer Service and order another radiator or spend a few bucks to get yours refoamed. Problem solved.
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  • John30_30
    John30_30 Posts: 1,024
    edited September 2008
    Early B. wrote: »
    Why would you do that? Just call Polk Customer Service and order another radiator or spend a few bucks to get yours refoamed. Problem solved.

    Call it that wild-hair notion thinking it can improve on a design that actually ends up FUBARing it up. Keep talking me down, please, I'm feeling almost rational again. Must be all the Higgs-Bosons in the air.:p
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  • fbm211
    fbm211 Posts: 1,488
    edited September 2008
    Okay.Its usually best not to mess with the original design.They did a-lot of testing in driver size,cabinet size,etc.Early B is a guru.Take his advice.
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  • Face
    Face Posts: 14,340
    edited September 2008
    I don't believe the radiators are available anymore, I would call Polk to confirm.
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • John30_30
    John30_30 Posts: 1,024
    edited September 2008
    Okay, thanks guys. Reason I even got the notion is I saw several sets of the 10" on ebay, but I'll lay off those and do it right.
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  • BAD ASP
    BAD ASP Posts: 361
    edited September 2008
    +1 FBM

    Cabinet volumes are critical when manufacturers assess speaker movement. I don't know the particulars but obviously the 10" passive presents a different movement parameter than does an 8" driver. If that movement parameter is within the design spec. it might be doable. I personally wouldn't make arbitrary changes without a little research. You're in the right place for information though! just my 2c.
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  • John30_30
    John30_30 Posts: 1,024
    edited September 2008
    Well, now that I'm looking at it, there's not even enough room between the bulkheads to cut out a 10" hole. Bonehead move that, H.I.
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  • heiney9
    heiney9 Posts: 25,204
    edited September 2008
    The radiators are not avail anymore. All Polk drivers in the RTA 11 line use butyl-rubber surrounds. The rarely fail/disintegrate without either an extreme chemical reaction or other abuse.

    If you mean by re-foam having the exact same butyl-rubber re-done then I guess that's your only option other than finding a used one on e-bay (rare). Using foam in place of the rubber surround will dramatically change the response characteristic of the woofer and it will affect the sound.

    Another option which would be better than using foam on the surround is to visit Parts Express or Madisound and see if you can buy (2) new passive radiators with about the same specs as the Polk and replace each one in each speaker so they are the same. Not as good as an original but perhaps a satisfactory alternative.

    Call Ken Swauger at Polk CS and see if maybe he'll help you match the specs with an aftermarket passive radiator.

    GL

    H9

    P.s. If any of the drivers have actual foam surrounds then they aren't original Polk drivers.
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
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  • John30_30
    John30_30 Posts: 1,024
    edited September 2008
    heiney9 wrote: »
    The radiators are not avail anymore. All Polk drivers in the RTA 11 line use butyl-rubber surrounds. The rarely fail/disintegrate without either an extreme chemical reaction or other abuse.

    If you mean by re-foam having the exact same butyl-rubber re-done then I guess that's your only option other than finding a used one on e-bay (rare). Using foam in place of the rubber surround will dramatically change the response characteristic of the woofer and it will affect the sound.

    Another option which would be better than using foam on the surround is to visit Parts Express or Madisound and see if you can buy (2) new passive radiators with about the same specs as the Polk and replace each one in each speaker so they are the same. Not as good as an original but perhaps a satisfactory alternative.

    Call Ken Swauger at Polk CS and see if maybe he'll help you match the specs with an aftermarket passive radiator.

    GL

    H9

    P.s. If any of the drivers have actual foam surrounds then they aren't original Polk drivers.

    Thanks. It looks like all the other drivers were flexible rubber like butyl, but this one's in brittle chips, and that ring is gone. I thought it would be odd that they'd use rubber on all but the bottom radiator. The one on the other speaker seems rigid also, not flexing like you'd expect. But it's intact, although I'm thinking it's not really doing its job either, since it's not so supple.
    I'd wonder if the guy had them stored next to some chemical, although nothing else seems damaged.
    Polk told me the same thing, to check out Madisound.
    Thanks for the info.
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