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  1. #1

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    Default RTA12C...A Love Reunited !

    Hello Vintage Polk Lovers..:-)

    Just got my hands on an excellent condition pair of RTA12C's...I used to own a pair back in the late 80's and thought they were very nice by the standard back then. I had listened to the bigger SDA's but my heart throbbed for the RTA12's nonetheless. Fast forward to just a few days ago and snatched a pair from my friend who used to be the Polk distributor back then. We're both in our early 50's and have owned and heard quite a handful of loudspeakers. The RTA12c always held a very special place in my heart.

    I'm going to do some upgrades and replace the Xover caps and resistors. I've settled on an all Solen cap replacement and Mundorf Supreme resistors. Have some nice Furutech OCC wires for the internals as well. I'll however do the electronics first and have an extended listen before changing the internal wires.

    The biggest surprise in all this is how musical they sound with my Audio Note Kits amplifiers !! I tried them with 8 watts 300B's, 17 watts El84's and 35 Watts EL34's...They sang beautifully with all of them but were best controlled bythe 35 watter. I had used them back then with ok SS integrateds of that era and they sounded nice. However, I never expected them to be THAT good today. Infact, I can say that in hindsight those speakers were much ahead oftheir time. They are as good today as they were back then and even more so today. They don't sound outdated at all and are even more transparent and more detailed with the better electronics and cables i'm using with them now. I won't go into the details of their superb performance , you all already know that..:-) Their SL2000 tweeters still remains the icing on the cake..:-)

    I'm very happy to have been reunited with a long lost love and am planning to keep them indefinitely.

    Any comments and advice on the upgrades are very welcome.

    Greetings from Egypt!

    Sherif

  2. #2

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    Hi RTA12C'er and welcome to the forum.

    I have a pair I bought new in Aug '84, used 'em for almost 20 years and then put 'em in storage. About 8-9 months ago I decided to use them for a new home theater set up as the front L-R speakers. Realizing their age, I thought a refresh was in order.

    When I searching this site I came across Geoff727's most excellent thread on the same, here: http://www.polkaudio.com/forums/show...light=geoff727

    If you do these mods you will be rewarded, no doubt. I also strongly advise using Sonicap generation 1 caps instead of Solens. The Solens, by most accounts, sound a bit etched; the Sonicaps, much smoother and more liquid. They're pricey for the complicated Xover in the 12C's, but worth it IMHO. The schematics for the Xovers are posted on this site too. The 12C is not listed but the 12B is the same. Do yours have fuses or polyswitches?

    It is recommended to change out the tweeter as Polk developed upgraded RD-0 tweeters to correct flaws in the SL1000 (which I have) and the SL2000's. Polk has them and you get special pricing and free shipping by mentioning you're a CP member.

    In addition to mods cited in the above post, I replaced all internal wiring with teflon OCC copper from Chris Ven Haus' site. I can't say exactly what difference, if any, the wire made as I did all the mods at once. But, man those speakers sound amazing, better than when new as the film caps, resistors, etc. are much higher quality than what they replaced.

    Good luck and have fun with it! And post any questions here - there are lots of folks who have knowledge and skills that are willing to help.
    Last edited by drumminman; 12-19-2011 at 09:31 AM.
    "Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills, polyswitches removed, Lg Solen inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR BP's, upgraded IC Cable, Black Hole Damping Sheet strips installed on back wall behind MW's & Tweeters, interior of cabinets sealed, AI-1 interface with 1000VA A-L transformer

  3. #3

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    Quote Originally Posted by drumminman View Post
    Hi RTA12C'er and welcome to the forum.

    I have a pair I bought new in Aug '84, used 'em for almost 20 years and then put 'em in storage. About 8-9 months ago I decided to use them for a new home theater set up as the front L-R speakers. Realizing their age, I thought a refresh was in order.

    When I searching this site I came across Geoff727's most excellent thread on the same, here: http://www.polkaudio.com/forums/show...light=geoff727

    If you do these mods you will be rewarded, no doubt. I also strongly advise using Sonicap generation 1 caps instead of Solens. The Solens, by most accounts, sound a bit etched; the Sonicaps, much smoother and more liquid. They're pricey for the complicated Xover in the 12C's, but worth it IMHO. The schematics for the Xovers are posted on this site too. The 12C is not listed but the 12B is the same. Do yours have fuses or polyswitches?

    It is recommended to change out the tweeter as Polk developed upgraded RD-0 tweeters to correct flaws in the SL1000 (which I have) and the SL2000's. Polk has them and you get special pricing and free shipping by mentioning you're a CP member.

    In addition to mods cited in the above post, I replaced all internal wiring with teflon OCC copper from Chris Ven Haus' site. I can't say exactly what difference, if any, the wire made as I did all the mods at once. But, man those speakers sound amazing, better than when new as the film caps, resistors, etc. are much higher quality than what they replaced.

    Good luck and have fun with it! And post any questions here - there are lots of folks who have knowledge and skills that are willing to help.
    Many thanks Drumminman! I'll stick with the Solens for cost constraints at the moment. They should surely be a very good step up from the originals. Will work my way up after the new caps. There's no fuse so I guess it's the polyswitch. I checked Geoff's detailed upgrades on his friend's RTA 12's. Looks awesome for sure! Thanks for the tweeter heads up. Best wishes and Happy Holidays!

  4. #4

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    Those speakers were definitely a worthwhile project. My only wish is that Roger would have let me re-veneer them!

    If you can swing it, try stepping up to something like Clarity Caps (like the SA series), for the 4.4uf positions in the tweeter circuit.

    Good luck.
    ~G
    Polk SDA SRS 2
    Polk RTA 15tl
    Polk Monitor 7C
    Polk Monitor 4.6
    Polk Lsi9

    Infinity RS-II (modded)
    Infinity RS-IIIa (modded)
    Infinity RS 2.5 x 2

    Magnepan 1.6QR (modded)

    System: http://forum.audiogon.com/cgi-bin/fr...vol&1290711373

  5. #5

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    Quote Originally Posted by geoff727 View Post
    Those speakers were definitely a worthwhile project. My only wish is that Roger would have let me re-veneer them!

    If you can swing it, try stepping up to something like Clarity Caps (like the SA series), for the 4.4uf positions in the tweeter circuit.

    Good luck.
    ~G
    Thanks Geoff..Your work on the 12's is amazing!!. I may not go as far with regards to the box but will definitely do the cap upgrades. I also got 5 NEW pairs of SL2000's and 2 midbass units with the speakers. Do you recommend upgrading the inductors as well..? Do you think having a mix of Clarities and Solens on the tweeter board won't negatively affect the basic sonic signature..? Many thanks.

  6. #6

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    Quote Originally Posted by RTA12C'er View Post
    I may not go as far with regards to the box but will definitely do the cap upgrades. Do you recommend upgrading the inductors as well..? Do you think having a mix of Clarities and Solens on the tweeter board won't negatively affect the basic sonic signature..? Many thanks.
    Sherif,

    I always advocate a "going all-out" approach, even if you need to take a year extra to afford it. In the end, I find the sonic benefit worthwhile, and, most of the time, each positive upgrade path allows you to better 'get your money's worth' out of every other upgrade that you've thrown at them. In other words, the cumulative effect of the upgrades is higher.

    Don't worry about the inductors, use the existing ones.

    A mix of capacitors will be just fine. The AXON caps I used on those are identical to the SOLEN's (although I forget which series), made by the same folks the same way with the same stuff. I got them on a special buy, so the choice was easy. If you want to go with the best capacitor for the shunt and 55uf positions, then yes, the SONICAP would be a bit better. Pretty pricey, though, for all those caps. But on the other hand, if you're planning to keep them forever because they have such a high value for you, then maybe.......

    And please post the work you do on them. We all love to see it! It must be particularly interesting to be witnessing all the changes in Egypt in this point in history.

    Good luck.
    Geoff
    Polk SDA SRS 2
    Polk RTA 15tl
    Polk Monitor 7C
    Polk Monitor 4.6
    Polk Lsi9

    Infinity RS-II (modded)
    Infinity RS-IIIa (modded)
    Infinity RS 2.5 x 2

    Magnepan 1.6QR (modded)

    System: http://forum.audiogon.com/cgi-bin/fr...vol&1290711373

  7. #7

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    I can hardly wait to get my 12b's in that kind of shape!
    Main system:
    Denon PRA-1500, Denon POA-2400, Denon TU-660, Denon DCD-2560, Denon DVD-2910, Denon DRS-640, Denon DP-30L II w/DL-301 mc cart, BSR EQ-3000, DCM Timeframe 600's

  8. #8

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    Quote Originally Posted by geoff727 View Post
    Sherif,

    I always advocate a "going all-out" approach, even if you need to take a year extra to afford it. In the end, I find the sonic benefit worthwhile, and, most of the time, each positive upgrade path allows you to better 'get your money's worth' out of every other upgrade that you've thrown at them. In other words, the cumulative effect of the upgrades is higher.

    Don't worry about the inductors, use the existing ones.

    A mix of capacitors will be just fine. The AXON caps I used on those are identical to the SOLEN's (although I forget which series), made by the same folks the same way with the same stuff. I got them on a special buy, so the choice was easy. If you want to go with the best capacitor for the shunt and 55uf positions, then yes, the SONICAP would be a bit better. Pretty pricey, though, for all those caps. But on the other hand, if you're planning to keep them forever because they have such a high value for you, then maybe.......

    And please post the work you do on them. We all love to see it! It must be particularly interesting to be witnessing all the changes in Egypt in this point in history.

    Good luck.
    Geoff
    Thanks Geoff for the advice. I'll keep you posted as I go along. Merry Christmas to all and Happy Holidays!

    Sherif

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