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  1. #1

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    Default SDA2RTA12cTL Hybrid?

    I just got a pair of RTA12c's, and I was taken aback by how similar they are to the SDA 2's. Same exact sized cabinets (measuring to the top of the RTA's exposed tweeter), same tweeter type, same kind, number and placement of woofers, and same placement and type of passive radiator. So here's the question: could you wire the rta12c to act as a SDA? I don't know what this would entail, but I'd imagine there would some guts from the SDA you'd have hook up into the RTA to make one of the woofers send out the stereo signal and one send out the dimensioanl signal. Then there's the matter of the interconnect cable. Is this possible? It seems to me that if this could be reasonably done you'd end up with a really cool speaker set. It would have the stereo dimensional array of the SDA while maintaing the real time array of the RTA with the recessed tweeter. Best of both worlds? Heck, you could even TL'em while your at it and make a SDA2RTA12cTL.

    Is any of this possible? Sane? Thanks experts! :o

  2. #2

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    Yes, anything is possible.

    You would need to rework the crossover. The drivers need a divider also. I was told once it is at a 7 degree angle. You would need to check the divider and what drivers it has. A SDA-2B crossover would be a good starting point. Rebuild it with the proper caps and resistors. I would TL it at the same time. They may take some tweaking to the crossovers to get that sound we know and love.

    Most people might not agree but done properly you should have a great set of speakers.
    TNTsTunes

    Man Cave/Shop System
    Yamaha RX-V870 reciever
    Polk Audio SDA-2B's - Yamaha M-70 amp
    Polk Audio SDA-2's - Yamaha MX830 amp
    BSR-3000 Graphic EQ/Spectrum Analyzer
    ADC SS-315X Graphic EQ/Spectrum Analyzer
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    JVC XL-Z411 CD player
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  3. #3

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    The drivers and the tweeters are NOT in the same placement. It's also not possible to retain the "RTA" characteristics and SDA characteristics simultaneously. The amount of re-engineering to make them into SDA's is not worth it. If you want SDA's........buy SDA's.

    H9
    "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 Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  4. #4

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    Just find some 2B's and do the TL mod and you will much happier. IMHO.
    I like speakers that are bigger than a small refrigerator but smaller than a big refrigerator:D

  5. #5

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    Quote Originally Posted by MillerLiteScott View Post
    Just find some 2B's and do the TL mod and you will much happier. IMHO.
    Yep.
    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

  6. #6

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    Quote Originally Posted by heiney9 View Post
    The drivers and the tweeters are NOT in the same placement. It's also not possible to retain the "RTA" characteristics and SDA characteristics simultaneously. The amount of re-engineering to make them into SDA's is not worth it. If you want SDA's........buy SDA's.

    H9
    It looks to me like the drivers and passive radiators are in the same placement, with the SDA2a's and b's anyway, I guess I should have clarified that to exclude the first SDA 2's. I didn't say that the tweeters were in the same placement, just that they were the same model and quantity. And please correct me if I'm wrong, but I thought the RTA effect happening on the 12c's was due to the placement of the tweeter: recessed so its voicecoil is aligned with the drivers' voice coils. If that is true, then you could have the SDA and RTA effect happen simultaneously. Now please tell me where I'm wrong. Thanks again, your noob friend, falcon.

  7. #7

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    They aren't. The baffle on SDA's has anywhere between a 7* and 12* slant inwards on the dimensional array, probably not visible to the naked eye. I have never measured the distance between the drivers on RTA12's or M10's but if they are even off by 1/4" compared to the distance between the regular and dimensional drivers on the SDA's then the SDA properties are diminished.

    If you can find the original "white paper" published in Audio Magazine in the 80's it gives a superb overview of all that's involved including theories on SDA's and you would then see just slapping a X-over in M10's or RTA 12's won;t get it done.
    "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 Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  8. #8

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    Quote Originally Posted by falconcry72 View Post
    It looks to me like the drivers and passive radiators are in the same placement, with the SDA2a's and b's anyway, I guess I should have clarified that to exclude the first SDA 2's. I didn't say that the tweeters were in the same placement, just that they were the same model and quantity. And please correct me if I'm wrong, but I thought the RTA effect happening on the 12c's was due to the placement of the tweeter: recessed so its voicecoil is aligned with the drivers' voice coils. If that is true, then you could have the SDA and RTA effect happen simultaneously. Now please tell me where I'm wrong. Thanks again, your noob friend, falcon.
    The SDA properties don't use "real time alignment" as part of the design. In multiple tweeter SDA's the tweeters are arranged in a progressive point source array. Something completely different than RTA. Not saying RTA isn't a great thing.............I don't see how you can have both in the same cabinet. Again reading the "white paper" would illuminate a lot of these things.

    H9
    "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 Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  9. #9

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    H9,

    Thanks for all the insight. I think I'll just wait for some SDA's and not screw up my RTA's. :o

    So my new question, which I'm sure has been answered here but I couldn't find it, is: what's the difference between SDA 2b's and 2a's?? Thanks again,

    falcon

  10. #10

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    Falcon, that's really the best. The RTA 12's are very nice and there just isn't an easy, cut and dried way of converting them into SDA's.

    Start looking for a pair of SDA's locally or within driving distance.

    H9
    "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 Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  11. #11

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    Quote Originally Posted by falconcry72 View Post
    H9,

    Thanks for all the insight. I think I'll just wait for some SDA's and not screw up my RTA's. :o

    So my new question, which I'm sure has been answered here but I couldn't find it, is: what's the difference between SDA 2b's and 2a's?? Thanks again,

    falcon
    The midbass drivers and crossovers are different.

    Check out the SDA wiring diagrams in the stickys on the top of the vintage speaker forum.
    TNTsTunes

    Man Cave/Shop System
    Yamaha RX-V870 reciever
    Polk Audio SDA-2B's - Yamaha M-70 amp
    Polk Audio SDA-2's - Yamaha MX830 amp
    BSR-3000 Graphic EQ/Spectrum Analyzer
    ADC SS-315X Graphic EQ/Spectrum Analyzer
    Magnavox (Philips) CDB-586 6 disc CD Changer
    JVC XL-Z411 CD player
    Panamax MAX-5100 power conditioner

  12. #12

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    2B's are the better choice. Better cabinets, x-overs and drivers. 2A's are nice too, but always hold out for the "newest" SDA's or later generation SDA's as they were on a constant improvement path with the last 2 generations being the best (which includes the 2B's)

    H9
    "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 Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  13. #13

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    Quote Originally Posted by heiney9 View Post
    2B's are the better choice. Better cabinets, x-overs and drivers. 2A's are nice too, but always hold out for the "newest" SDA's or later generation SDA's as they were on a constant improvement path with the last 2 generations being the best (which includes the 2B's)

    H9
    what other SDA's as are a part of the "last 2 generations"? I'm guessing all of the SRS's, maybe 1C's?

  14. #14

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    Last generation would have been the last SDA's

    SRS 1.2TL
    SRS 2.3TL
    SRS 3.1TL

    The gen before that was

    CRS +
    2B's
    1C's
    SRS 2.3
    SRS 1.2

    To me those are the more desirable SDA's. Special mention to the SRS 2's.

    H9
    "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 Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

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