Help with RTA 12B Crossovers

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  • pitdogg2
    pitdogg2 Posts: 24,554
    edited June 2020
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    The mw6500 is the wrong driver. The RTA 12 either came with MW6600 or later MW6501. there was never a MW6500 in the equation

    I'ver always considered the MW6600 and MW6501 to be the virtually the same
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  • Gardenstater
    Gardenstater Posts: 4,181
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    geppy1 said:

    "RTA12s 1979-1980 6500 drivers with Peerless from Denmark
    Short cabinet on stands NO rolled off drivers and one crossover on top with fuse"

    Maybe he meant 6501 drivers.....dunno.

    Then he said all the 12Bs had the 6600X, but then why does our schematic say 6501?

    Anyway, since we don't have the other parameters for the 6600X besides DCR, I'd be inclined to make the rolloff drivers either 6600X or 6501, if you're not going to make them all one or the other. That way things should stay balanced sounding.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • pitdogg2
    pitdogg2 Posts: 24,554
    edited June 2020
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    Gardenstater wrote: »
    geppy1 said:

    "RTA12s 1979-1980 6500 drivers with Peerless from Denmark
    Short cabinet on stands NO rolled off drivers and one crossover on top with fuse"

    Maybe he meant 6501 drivers.....dunno.

    Then he said all the 12Bs had the 6600X, but then why does our schematic say 6501?

    Anyway, since we don't have the other parameters for the 6600X besides DCR, I'd be inclined to make the rolloff drivers either 6600X or 6501, if you're not going to make them all one or the other. That way things should stay balanced sounding.

    I'd trust @geppy1 he did a ton of research on this model. I on the other hand seen no schematic that had them listed. All models I ever heard had either MW6600/MW6501.

    I would also make them all the same drivers of one or the other MW6600/MW6501
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  • Gardenstater
    Gardenstater Posts: 4,181
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    geppy1 was saying that was the first 12 (not B or C), where it didn't solve the lobing and imaging problem because both MWs received the same frequencies and there were no left and right speakers. We don't even have a schematic for that one, so I'd certainly trust him too.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • tholl1go
    tholl1go Posts: 13
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    I found a good price on two MW6600Xs, so I will have four of those. Thanks again everyone!
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  • Gardenstater
    Gardenstater Posts: 4,181
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    Let us know your impressions after the install!
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • geppy1
    geppy1 Posts: 3,071
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    I just saw this Based on the cabinet number they should be 6600X and the tweeter would be either the Peerless with a gold back with a dimple in the middle 5514 and round magnet (verses the not round magnet) This one tends to sound warmer then the earlier Peerless units. The face plate of the tweeter has kind of a rougher texture to it.

    It could also come with the SL 1000 silver faced unit as they started using those very late 1983 Little more open and airy sounding but with its own issues.

    The numbers on the xover and cabinet never match

    The 6501 was not really used until they went to the SL 2000 and switched from a fuse to a Polyswitch A few seem to have been done with the SL1000 and the 6501 but sounds different

    I wore screw holes out and and also had two pairs of speakers comparing drivers and combinations. The 6501 and 6600x sounded different the 6600x seems to be more intense. The 6501 more diffuse.

    FYI the Peerless was also called the SL 1000 Strange but true. ew9460drfof1.jpg
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  • Gardenstater
    Gardenstater Posts: 4,181
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    @geppy1 - When they say: "The dome is vented (aperture tuned) in much the same way that woofer systems are tuned to further smooth out its response curve and improve transient response and power handling", are they referring to the small hole that was burned in the center of the silk domes of the Peerless?
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • geppy1
    geppy1 Posts: 3,071
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    Yes This was NOT done on the silver faced SL 1000
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  • tholl1go
    tholl1go Posts: 13
    edited June 2020
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    My finished (for now) RTA 12B/C's with the four MW6600Xs and the RD-0194 tweeters sound fantastic. Count me a new Polk lover.
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  • CH46E
    CH46E Posts: 3,546
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    Welcome to the Rabbit Hole! Sucker!!!!😁😁😀😄
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  • drumminman
    drumminman Posts: 3,396
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    FYI I have the RTA 12C's that I bought new from the dealer in 1984. They came with the silver face SL1000, circuit boards that say RTA 12B and fuses rather than poly switches. They also have 4 MW6600X mw's.
    Recapping is expensive, but IMHO worth it as these are truly excellent speakers with fantastic imaging. I once set them up beside my modded 2.3tl's and they were not a big step down, though the imaging wasn't quite on par.
    "Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills/jantzen inductors, Gimpod's boards, Lg Solen SDA 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, interior of cabinets sealed with Loctite Power Grab, AI-1 interface with 1000VA A-L transformer
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  • CH46E
    CH46E Posts: 3,546
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    I'd agree 100%. The RTA12B/C are amazing speakers. Especially when recapped. I had a mint pair of SDA SRS II in the same room as the 12b. (Disclosure notice here! The room, according the the SRS II manual was shy by 13 inches of clearance of the side walls. Everything else was within spec.) The 12B just walked all over my SRS II. (Was it the room? Maybe) I've let a lot of speakers go but these 12b are still here.

    I've been wondering if anyone will bring some 12B/C to this years Polk Fest????
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