RTA12 differences
falconcry72
Posts: 3,580
I've been digging around here and this is the best compilation of info I've got, though I would imagine it's not entirely accurate nor complete, and I would greatly appreciate some editing 
RTA12: Cabinets flat on ground, peerless tweets
RTA12A: Cabinets flat on ground, sl1000's
RTA12B: Cabinets on raised base, sl1000's or sl2000's
RTA12C: Cabinets on raised base, sl2000's
OK now please tell me what's wrong and what's missing. THANKS!
RTA12: Cabinets flat on ground, peerless tweets
RTA12A: Cabinets flat on ground, sl1000's
RTA12B: Cabinets on raised base, sl1000's or sl2000's
RTA12C: Cabinets on raised base, sl2000's
OK now please tell me what's wrong and what's missing. THANKS!
2-Channel: PC > Schiit Eitr > Audio Research DAC-8 > Audio Research LS-26 > Pass Labs X-250.5 > Magnepan 3.7's
Living Room: PC > Marantz AV-7703 > Emotiva XPA-5 > Sonus Faber Liuto Towers, Sonus Faber Liuto Center, Sonus Faber Liuto Bookshelves > Dual SVS PC12-Pluses
Office: Phone/Tablet > AudioEngine B1 > McIntosh D100 > Bryston 4B-ST > Polk Audio LSiM-703's
Living Room: PC > Marantz AV-7703 > Emotiva XPA-5 > Sonus Faber Liuto Towers, Sonus Faber Liuto Center, Sonus Faber Liuto Bookshelves > Dual SVS PC12-Pluses
Office: Phone/Tablet > AudioEngine B1 > McIntosh D100 > Bryston 4B-ST > Polk Audio LSiM-703's
Post edited by falconcry72 on
Comments
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To my limited knowledge, you have it ABOUT right. I've read that Polk fairly regularly and indiscriminately swapped pieces on the RTA12's. It was kind of a "Well, what have we got lying around here today" method of building these excellent speakers. I had the the RTA12C's & they were great.
Hope others who know waaaay more than I chip in."Wish I didn't know now what I didn't know then." Bob Seger -
BottomFeeder wrote: »To my limited knowledge, you have it ABOUT right. I've read that Polk fairly regularly and indiscriminately swapped pieces on the RTA12's. It was kind of a "Well, what have we got lying around here today" method of building these excellent speakers. I had the the RTA12C's & they were great.
Hope others who know waaaay more than I chip in.
one thing I've noticed that they changed was the filter system board, that circuit board-looking thing that holds the crossovers. The one on my 12c's is greenish blue, and they have sl2000's; i recently saw a pair of 12b's that had a tan colored board and sl1000's.
is there a difference in the board other than the color?2-Channel: PC > Schiit Eitr > Audio Research DAC-8 > Audio Research LS-26 > Pass Labs X-250.5 > Magnepan 3.7's
Living Room: PC > Marantz AV-7703 > Emotiva XPA-5 > Sonus Faber Liuto Towers, Sonus Faber Liuto Center, Sonus Faber Liuto Bookshelves > Dual SVS PC12-Pluses
Office: Phone/Tablet > AudioEngine B1 > McIntosh D100 > Bryston 4B-ST > Polk Audio LSiM-703's -
My 12A came new with bases many many years ago...
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I have spent a huge amount of time researching this and taking 12s apart. i have three pair right now.There was some throwing whatever was around into the cabinet. I have 12Cs that were made at the same time as my Bs and they have all the same stuff. Go figure. Here it is.
RTA 12
1979-late 1980. Came with stands and had shorter cabinet with tweeter hanging vertical. OUTSIDE DRIVERS ARE NOT ROLLED OFF LIKE LATER ONES.
Tweeeter is HF 1000 marked 7514__ Peerless made in Denmark or 5514 __Peerless made in USA
Drivers are 6500s usually with gray paper trim
RTA12A
I think this when they went to the 6600X driver but I have never seen one
RTA12B
1981-1984 This one is screwy. Full size cabinet, two different crossovers but the only difference seems to be the type of caps used. Same values just different types
Tweeters ,early 1981-83 US made Peerless marked 5514__ Couple of different ones used and THEY DO NOT SOUND THE SAME.. Polk also called them SL1000s. Later (early 84) use the Silver faced real SL1000 Also switched from the pins for tophat location to trees for that. Late 83???
Drivers are 6600X
RTA12C
1984-87
Early 1984-85 Used same crossover and caps as late 12Bs. There are Cs made in early 84 and Bs made after them. All components are the same. Point is a late B is the same as an early C
Tweeters Silver faced SL1000
Drivers usually 6600X but some 6501s late
Late 1986-87 Slightly different caps. Same values but different manufacture. Also now has a Polyswitch in place of the fuse on the top crossover.
Tweeters SL2000
Drivers 6501s
Your mileage may vary. keith -
I have spent a huge amount of time researching this and taking 12s apart. i have three pair right now.There was some throwing whatever was around into the cabinet. I have 12Cs that were made at the same time as my Bs and they have all the same stuff. Go figure. Here it is.
RTA 12
1979-late 1980. Came with stands and had shorter cabinet with tweeter hanging vertical. OUTSIDE DRIVERS ARE NOT ROLLED OFF LIKE LATER ONES.
Tweeeter is HF 1000 marked 7514__ Peerless made in Denmark or 5514 __Peerless made in USA
Drivers are 6500s usually with gray paper trim
RTA12A
I think this when they went to the 6600X driver but I have never seen one
RTA12B
1981-1984 This one is screwy. Full size cabinet, two different crossovers but the only difference seems to be the type of caps used. Same values just different types
Tweeters ,early 1981-83 US made Peerless marked 5514__ Couple of different ones used and THEY DO NOT SOUND THE SAME.. Polk also called them SL1000s. Later (early 84) use the Silver faced real SL1000 Also switched from the pins for tophat location to trees for that. Late 83???
Drivers are 6600X
RTA12C
1984-87
Early 1984-85 Used same crossover and caps as late 12Bs. There are Cs made in early 84 and Bs made after them. All components are the same. Point is a late B is the same as an early C
Tweeters Silver faced SL1000
Drivers usually 6600X but some 6501s late
Late 1986-87 Slightly different caps. Same values but different manufacture. Also now has a Polyswitch in place of the fuse on the top crossover.
Tweeters SL2000
Drivers 6501s
Your mileage may vary. keith
awesome info; thanks keith!
my 12c's are from 86 and have polyswitches, sl2000's, and 6501's.2-Channel: PC > Schiit Eitr > Audio Research DAC-8 > Audio Research LS-26 > Pass Labs X-250.5 > Magnepan 3.7's
Living Room: PC > Marantz AV-7703 > Emotiva XPA-5 > Sonus Faber Liuto Towers, Sonus Faber Liuto Center, Sonus Faber Liuto Bookshelves > Dual SVS PC12-Pluses
Office: Phone/Tablet > AudioEngine B1 > McIntosh D100 > Bryston 4B-ST > Polk Audio LSiM-703's -
Bingo
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Ah! I was hoping that Keith (geppy1) would contribute. I think he's the bomb.com when it comes to RTA12's. They were definitely some odd, but excellent speakers. I remember finding some sweet real wood RTA12B's & contacting Polk & they said that they never even made real wood cabinets! Yet there I was, staring at a nice pair.
Cool speakers."Wish I didn't know now what I didn't know then." Bob Seger -
The 12Bs came in Rosewwod vinyl , Walnut vinyl and Real Walnut
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The RTA 12 1979 was a CES Design and Engineering Award winner as was the 1981 RTA 12B. I believe the RTA12C (early with 6600 and silver SL1000) was 1984 or 85 Audio Video Grand Prix award speaker of the year.
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The RTA 12 1979 was a CES Design and Engineering Award winner as was the 1981 RTA 12B. I believe the RTA12C (early with 6600 and silver SL1000) was 1984 or 85 Audio Video Grand Prix award speaker of the year.
alright Keith, so here's the million dollar question: what's the ultimate (non-modded) RTA12? What about modded? And more imprtantly, what's YOUR favorite RTA12?2-Channel: PC > Schiit Eitr > Audio Research DAC-8 > Audio Research LS-26 > Pass Labs X-250.5 > Magnepan 3.7's
Living Room: PC > Marantz AV-7703 > Emotiva XPA-5 > Sonus Faber Liuto Towers, Sonus Faber Liuto Center, Sonus Faber Liuto Bookshelves > Dual SVS PC12-Pluses
Office: Phone/Tablet > AudioEngine B1 > McIntosh D100 > Bryston 4B-ST > Polk Audio LSiM-703's -
I'm bettin' he says it's the C.
Gotta be.
Right?"Wish I didn't know now what I didn't know then." Bob Seger -
My 12b's are real wood vyneer also (1983)Main Rig:
Krell KAV 250a biamped to mid/highs
Parasound HCA1500A biamped to lows
Nakamichi EC100 Active xover
MIT exp 1 ic's
Perreaux SA33 class A preamp
AQ kingcobra ic's
OPPO 83 CDP
Lehmann audio black cube SE phono pre, Audioquest phono wire (ITA1/1)
Denon DP-1200 TT. AToc9ML MC cart.
Monster HTS 3600 power conditioner
ADS L1590/2 Biamped
MIT exps2 speaker cable -
I have a pair of early RTA12C's from mid 1983 (June) when I bought them new and they did indeed have the SL1000 tweets and fake veneer, 12B crossover board and fused. The tweets are about to be upgraded as they are strident and irritating with some material. Even DTV reveals sibilance in dialog often.
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Davesworld wrote: »I have a pair of early RTA12C's from mid 1983 (June) when I bought them new and they did indeed have the SL1000 tweets and fake veneer, 12B crossover board and fused. The tweets are about to be upgraded as they are strident and irritating with some material. Even DTV reveals sibilance in dialog often.
I have 12C's I bought new in 1984: fused, sl1000's, mw6600's. Also with genuine rosewood vinyl veneer - :rolleyes:
I upgraded both the upper and lower crossovers with sonicaps and mills, and there's not a hint of harshness in the 'ol sl1000. I've listened for it repeatedly due to the comments made here on the forum and it's just not there (to my ears). I'm usually sensitive to that type of harshness.
The new x-overs have taken these speakers to a level way above what they sounded like when they were new! Bass is tighter and more musical (it was no slouch in that dept. before), the highs are silky smooth, open and airy, and the imaging is wide and deep."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 -
The RTA 12 1979 was a CES Design and Engineering Award winner as was the 1981 RTA 12B. I believe the RTA12C (early with 6600 and silver SL1000) was 1984 or 85 Audio Video Grand Prix award speaker of the year.
1984 Audio Video Grand Prix award winner:cool:"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 -
drumminman wrote: »I have 12C's I bought new in 1984: fused, sl1000's, mw6600's. Also with genuine rosewood vinyl veneer - :rolleyes:
I upgraded both the upper and lower crossovers with sonicaps and mills, and there's not a hint of harshness in the 'ol sl1000. I've listened for it repeatedly due to the comments made here on the forum and it's just not there (to my ears). I'm usually sensitive to that type of harshness.
The new x-overs have taken these speakers to a level way above what they sounded like when they were new! Bass is tighter and more musical (it was no slouch in that dept. before), the highs are silky smooth, open and airy, and the imaging is wide and deep.
Did you change just the main large caps including the electrolytics or did you do away with the tiny silver/mica bypass caps as well?
I'm beginning to wonder if some of the ringing sound at certain frequencies is due to poorer crossover components?
Even though the electrolytics were used in shunts mainly, I'm certain that they do not age well.
OT: As an aside, there are many good reasons to use solid caps in even non audio applications for longevity. Some higher end computer motherboards are using solids and since one of my hobbies is dealing with old Sun Cobalt servers and adapting a firewall os to run on them, the Raq3/4 are notorious for bursting the aged electrolytics sometimes. -
Davesworld wrote: »Did you change just the main large caps including the electrolytics or did you do away with the tiny silver/mica bypass caps as well?
I'm beginning to wonder if some of the ringing sound at certain frequencies is due to poorer crossover components?
Even though the electrolytics were used in shunts mainly, I'm certain that they do not age well.
OT: As an aside, there are many good reasons to use solid caps in even non audio applications for longevity. Some higher end computer motherboards are using solids and since one of my hobbies is dealing with old Sun Cobalt servers and adapting a firewall os to run on them, the Raq3/4 are notorious for bursting the aged electrolytics sometimes.
the inductors. Really, it's no exaggeration to say that it takes them to another level. I used all soncaps and mills resistors. From what I read here on the forum the silver mica bypass caps are unnecessary when using high grade film caps, so I got rid of them. I also rewired the speakers with teflon insulated OCC copper wire. A bit of an extravagance, but, hey, it's a hobby :biggrin:
I did a couple of other tweaks too: I installed Hurricane nuts and socket head screws so I could apply some torque and couple the drivers to the front baffle more solidly; and I dynamatted the MW's and PR.
The caps used by Polk were probably among the best for the time, but they age poorly (lose their values or leak or both!) and even when new don't compare to good film caps made today.
Hope this helps."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 -
I just picked up a pair of RTA 12's - at least that is what I am assuming because none of the literature mentions A, B, or C, and the tweeter is mounted sideways (longways). They sound great for their age!
$200 on Craigslist, complete with the hats and stands. And they are in Walnut cabs with not a mark on them.
Can I upgrade the tweeters to the SL1000's ?Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd). -
If the tweeter is mounted as you say and it has stands they are RTA12s not b or c. A picture would help. keith
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Michael8it wrote: »...the tweeter is mounted sideways (longways). ...Can I upgrade the tweeters to the SL1000's ?
I saw my name on this thread, but I didn't remember starting it... because it was a year and a half ago! I've learned so much since then...:biggrin:
I believe that if the tweeter is mounted with the longer side going vertically then they use the peerless tweeters. (they're black). If this is the case, then the sl-1000 would not be an upgrade.
2-Channel: PC > Schiit Eitr > Audio Research DAC-8 > Audio Research LS-26 > Pass Labs X-250.5 > Magnepan 3.7's
Living Room: PC > Marantz AV-7703 > Emotiva XPA-5 > Sonus Faber Liuto Towers, Sonus Faber Liuto Center, Sonus Faber Liuto Bookshelves > Dual SVS PC12-Pluses
Office: Phone/Tablet > AudioEngine B1 > McIntosh D100 > Bryston 4B-ST > Polk Audio LSiM-703's -
They are definitely the original 12's and after closer inspection they are not real Walnut. No biggie there.
I am not unhappy with the sound but may replace the caps in the crossovers just becaue of thier age.Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd). -
Lets see if this upload worksCarver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd). -
I looked up how to post pictures in the FAQ and it references a link to "Pictures and Albums" in my portfolio which I do not have. Thoughts?Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd).
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RTA 12
1979-late 1980. Came with stands and had shorter cabinet with tweeter hanging vertical. OUTSIDE DRIVERS ARE NOT ROLLED OFF LIKE LATER ONES.
Tweeeter is HF 1000 marked 7514__ Peerless made in Denmark or 5514 __Peerless made in USA
Drivers are 6500s usually with gray paper trim
keith
Keith, can you roll off one of the Mid-Bass drivers on a 12 like they are on the 12B. If I am reading the schematics right, the only difference is 2 27uF caps and a 7.5ohm resistor. Since I am rebuilding the XO's anyway 2 more caps and a resistor are reasonable if they improve things.Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd). -
You would also need different drivers as well to perform the rolloff mod unless your RTA12's have the 6600 MW's.
