RTA 12 (A) schematic?

w1jim
w1jim Posts: 8
edited August 2008 in Troubleshooting
How / where can I get a schematic for the crossover on my RTA12s. These are the original version and I want to upgrade / replace the caps. These are awesome speakers (much to the chagrin of my other speakers).
Tnx,
JimB
I can fix it but good!
G-22000 / SX-1250 / SX-1010 / SX-D7000 / SX5580 / CR2020 / KR9600 / MAC-1900 / Marantz 2325 - RTA-12a / Monitor 10a / Monitor 7b / Walsh2 / Forte'...
Post edited by w1jim on
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  • ben62670
    ben62670 Posts: 15,969
    edited August 2008
    First welcome to Club Polk. Also I would suggest changing the resistors too. Those couple mods will bring them back to better than new specks.
    Enjoy
    Ben
    schematic
    http://www.polkaudio.com/forums/showthread.php?t=38755
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
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  • w1jim
    w1jim Posts: 8
    edited August 2008
    Ben,
    Thanks big time. I have some high quality instrumentation resistors on hand here. Values from 0.1 ohms to 1,000,000,000,000 ohms (that's a freaky glass thing). Any type of construction I should steer towards or away from?
    JimB
    I can fix it but good!
    G-22000 / SX-1250 / SX-1010 / SX-D7000 / SX5580 / CR2020 / KR9600 / MAC-1900 / Marantz 2325 - RTA-12a / Monitor 10a / Monitor 7b / Walsh2 / Forte'...
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  • ben62670
    ben62670 Posts: 15,969
    edited August 2008
    The values of the resistors are typically 2.7r to 15r, and you should use 10w or better noninductive resistors. What caps are you looking to use?
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
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  • w1jim
    w1jim Posts: 8
    edited August 2008
    For the tweeter circuitry I'll use the Dayton Metallized Polypropylene caps from parts express (250 volts - 10%). For the low frequency circuits I'll be using their bi-polar electrolytics (at least for now); they're 5% and rated for 100 Volts. I may upgrade these later but for now the bi-polars will have to do.
    BTW, some have suggested not using the bypass caps as these modern caps don't need that. I notice that the schematic doesn't show them so I'll plan on leaving them out.
    I'll be powering these with a Harman Kardon HK690i which is rated at 60 watts per channel. I also have a Sony STR-GX90ES receiver which I think is rated at 90w per in the other system. I have no plans to go for "big power" anytime soon.
    I see on the schematic that R is 1.69 ohms but I can't make out the value of R3; can you help me on that (else I can just measure the ones on the PCB.
    Thanks again,
    JimB
    I can fix it but good!
    G-22000 / SX-1250 / SX-1010 / SX-D7000 / SX5580 / CR2020 / KR9600 / MAC-1900 / Marantz 2325 - RTA-12a / Monitor 10a / Monitor 7b / Walsh2 / Forte'...
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  • ben62670
    ben62670 Posts: 15,969
    edited August 2008
    I would go poly on all caps. The cheap caps I have tried, and there was no improvement over the 20 YO caps that were originals. Its best to double check your XO boards with a meter anyways. Polk liked to mix things up a bit.
    Ben
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
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  • w1jim
    w1jim Posts: 8
    edited August 2008
    I just installed the poly caps in one of my crossovers and am comparing it with the other (stock) one. I think there is a significant improvement. I'll have to listen for a while like this and then swap their positions (one of my ears is certainly going to have a different response curve then the other from years of driving with my driverside window open. I guess the Brits and Japanese would have the situation with their right ears versus the left in most of the world. Hmmm, I wonder if anyone ever did a study of that and adjust with different specs for left versus right speakers?
    The Dayton Caps are larger. I siliconed them on the underside for support. There's also one 2uf cap on the underside of the PCB (making the 25 a 27)..
    So, I'm about $85 poorer but even happier with the performance of my beautiful RTA 12A speakers. Wow, now I've got a total of $135 invested in them. Works for me! (See attached pix.)
    JimB
    I can fix it but good!
    G-22000 / SX-1250 / SX-1010 / SX-D7000 / SX5580 / CR2020 / KR9600 / MAC-1900 / Marantz 2325 - RTA-12a / Monitor 10a / Monitor 7b / Walsh2 / Forte'...
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  • Face
    Face Posts: 14,340
    edited August 2008
    Nice job!
    "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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  • jimmyward
    jimmyward Posts: 1
    I also have the RTA 12s and the sound has degraded. I can not find a schematic or parts layout of the crossover. Could someone provide me with a copy so I can replace the caps as mine are not all labeled. thanks
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  • Gardenstater
    Gardenstater Posts: 4,459
    https://us.v-cdn.net/5021930/uploads/attachments/4/6/7/2/8/18709.pdf

    https://us.v-cdn.net/5021930/uploads/attachments/4/6/7/2/8/18710.pdf

    https://us.v-cdn.net/5021930/uploads/attachments/4/6/7/2/8/18711.pdf
    George / NJ

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