Just got these RTA 12B’s.

They are going to need some work. They sound awful. The right one’s base sounds ok, but the tweeter is almost in audible. The left one sounds weak but the tweeter works well.
I'm guessing the crossovers will need rebuilt. What are the ohm specs for all the drivers?

John
«134

Comments

  • F1nutF1nut Posts: 45,047
    edited October 11
    Test the fuse. If it tests ok then clean the fuse ends and the fuse holder clips. Check the mid-drivers for shifted magnets by gently and evenly pushing them in. If they don't move or you hear scratching the magnet has shifted.

    BTW, it's bass not base.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • GardenstaterGardenstater Posts: 1,364
    They should be DC resistance of 7.75Ohms if they are MW6501s. What tweeters do you have? Peerless tweeters are around 7.0 Ohm to 8.5 Ohms DCR depending upon the mfg date.
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • Harv2002Harv2002 Posts: 43
    Bass! Ha! How could I?
    I’ll start checking tomorrow. Thanks for the reply.

    John
  • NightfallNightfall Posts: 9,288
    Those are well worth getting squared away.
    afterburnt wrote: »
    They didn't speak a word of English, they were from South Carolina.

    Village Idiot of Club Polk
  • Tony MTony M Posts: 9,369
    How did you get them? :p
    Most people just listen to music and watch movies. I EXPERIENCE them.
  • Harv2002Harv2002 Posts: 43
    Tony M wrote: »
    How did you get them? :p

    They were on my local FB marketplace I talked them down a little (got em for 200, I should have gone lower) the only thing they had to “demo” them was a crappy old boom box.

    John
  • Harv2002Harv2002 Posts: 43
    jyv5arf37ryk.jpeg

    Ok. One non functioning Peerless tweeter. The drivers feel smooth look and now sound to be working. They sure are power hungry. I’m currently driving them out in my garage (not permanently) with my old Onkyo Integra integrated amp. I’ll be running them in the house with a GFA 5503.

    Are the Sonicaps really 55 bucks each? 7 per speaker right?

    Yeesh!

    John
  • GardenstaterGardenstater Posts: 1,364
    edited October 12
    It's only $282 total per speaker not including shipping and sales tax :# That's if you use a 22 and a 33 Clarity Cap CSA (for the 55) and the rest Sonicaps.
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • Harv2002Harv2002 Posts: 43
    xgy7cwtvpne2.jpeg

    Strange. This is on the working tweeter. I don’t even know what it could have touched?

    John
  • xschopxschop Posts: 1,732
    Someone touched a soldering iron to it perhaps?
  • GardenstaterGardenstater Posts: 1,364
    What are the #'s on each tweeter? Usually it is either 5514 or 7514 followed by a 4 digit date (Week and Year).
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • Harv2002Harv2002 Posts: 43
    y5fs9fnxw6th.jpeg
    That’s the working one.

    Here’s the non working one.
    psdf342dvtbe.jpeg

    John
  • GardenstaterGardenstater Posts: 1,364
    edited October 12
    Pretty bad ink stamping job but I guess they are 41st week of 1981. What are the DC Resistances of the tweeters and the midbass drivers? Are the midbass MW6501's? You can read it off of the label on the back of the speaker (pole piece). Also, there should be a date somewhere on the crossovers, maybe on the one's inside the cabinet.

    There are lots of members that have these speakers and can advise you on crossover upgrading. @CH46E I know has these and has done them up fully.
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • Harv2002Harv2002 Posts: 43
    8rdx8ndq6evb.jpeg

    Inner. I had to push the insulation back up.

    John
  • GardenstaterGardenstater Posts: 1,364
    edited October 12
    Those drivers are dated 9/22/81 and the tweeters are 41st week in 81, so those pretty much jive with each other within several weeks anyways. I'm not sure when they came out with the RTA 12B. I think but have to verify that MW6600x and MW6501 may be close to each other in parameters.
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • GardenstaterGardenstater Posts: 1,364
    edited October 12
    No date on the inner XO then. Anyway, I think they put the MW660X's in before they made a switch to MW6501 at some point in time......maybe late 84. The MW6600X seems to be a mystery to everyone as far as what Small Thiele Parameters it is supposed to have.

    You need to check and verify that your XO's match the schematic in the archives for the RTA 12B. Probably they do.

    You should also still check all the DC resistances of every driver and make sure they are close to each other. That bad tweeter will probably be 0 Ohms if it is a fried voice coil.

    This thread is about one that had a XO serial number close but a little earlier than yours:

    https://forum.polkaudio.com/discussion/191073/help-identifying-rta-12-12b-12c/p1
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • CH46ECH46E Posts: 2,537
    Pretty bad ink stamping job but I guess they are 41st week of 1981. What are the DC Resistances of the tweeters and the midbass drivers? Are the midbass MW6501's? You can read it off of the label on the back of the speaker (pole piece). Also, there should be a date somewhere on the crossovers, maybe on the one's inside the cabinet.

    There are lots of members that have these speakers and can advise you on crossover upgrading. @CH46E I know has these and has done them up fully.

    Thanks for the vote of confidence George. Since my cabinets are not in the best shape and I now have 2 other projects going on, i might be parting mine out. Can't believe I just said that.

    Of course members here would have 1st crack at discounted prices for anything a let go.
  • Harv2002Harv2002 Posts: 43
    edited October 12
    I think but have to verify that MW6600x and MW6501 may be close to each other in parameters.

    I’ll check the other drivers tonight. However I haven’t disconnected any drivers yet as you guys know they are soldered.

    John
  • CH46ECH46E Posts: 2,537
    None of mine were soldered. Thats odd. They must have ran out of spades?
  • NightfallNightfall Posts: 9,288
    Do I need to start saving up for your speakers minus the cabinets @CH46E ? Are they Bs with Peerless and 6600Xs?
    afterburnt wrote: »
    They didn't speak a word of English, they were from South Carolina.

    Village Idiot of Club Polk
  • GardenstaterGardenstater Posts: 1,364
    edited October 12
    "That bad tweeter will probably be 0 Ohms if it is a fried voice coil.

    Doh! I meant to say open circuit or infinite Ohms.

    My 79 vintage 7B's were all soldered.
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • Harv2002Harv2002 Posts: 43
    edited October 12
    All my drivers are MW6600X

    The schematic I downloaded shows MW6501 drivers. Am I to understand the crossovers are not different?

    John
  • CH46ECH46E Posts: 2,537
    edited October 12
    Pretty sure the crossovers are identical. I believe mine has one 6600x and one 6501 in each cabinet. I think the 6600x was used as a drop in for the 6501.


    You should be good with 4 6600x.

    Just know the speakers are marked for left channel and right channel. L AND. R should precede the serial number. Also make sure the plugs behind the tweeters and croosover are in thier correct position. Mine came jammed into the wrong orientation and that will fry a tweeter in a heart beat.
  • pitdogg2pitdogg2 Posts: 17,285
    MW6600 came first. The drivers I've always thought were the same or so close it didn't matter. My SDA 1 signature speakers came with all mw6600 with mw6501 in the dimensional spots. From what I've see the speakers that used both except for tweeter differences the XO is the same for the drivers between mw6600 and mw6501.
  • Harv2002Harv2002 Posts: 43
    Anyone have a nice used Peerless tweeter?
    I’d like to avoid buying two new repo’s.

    Or do I go RD0194’s like I did with my Monitor 10’s?

    John
  • CH46ECH46E Posts: 2,537
    Rdo194s are not a sutible replacement forbthe peerless. Let me put some of mine on a meter tomorrow. I think inhave 3 good ones. But let me double check. If I do have a 3rd you can have it for the cost of shipping.
  • Harv2002Harv2002 Posts: 43
    CH46E wrote: »
    If I do have a 3rd you can have it for the cost of shipping.

    Thanks so much for the offer. Let me know.

    Was I thinking RD098? I still don’t have all these tweeters straight in my head.

    John
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