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  1. #1

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    Post Polk Monitor 7a's vs 7c's comparison

    Starting a new thread for comparison between 7a's and 7c's.

    7a
    --
    Peerless tweeter.
    PR dustcap is smaller and cone is deeper than 7c.
    Mid/PR baskets protrude on top of baffle.

    Dull/recessed but smooth mid/highs.
    Bass is smoother/softer than 7c.
    Images better than 7c. It sounds right in the middle while 7c's are more directional to speaker location.

    7c
    --
    SL2000 tweeter.
    PR dustcap is bigger, cone is flatter than 7a.
    Mid/PR baskets are recessed on the baffle level.

    Bright, forward/sharp, more metallic mids/highs.
    More chhik chhik sizzling highs sound in 7c's that are very recessed in 7a.
    Bass is tighter, lower and punchier than 7a.
    Also, much louder overall than 7a.

    It's really interesting that in some songs I really like 7c's while in others, 7c's sounded very crowded and harsh.
    'Hungry Heart' by Bruce Springston: 7c's sounded harsh crowded but 7a's are smooth and clear but in some other songs, 7a's sounded very dull while 7c's sounded perfect.
    'Truly Madly Deeply' by Savage Garden: 7c's sounded very nice, strings/music all present while 7a's sounded very dull/veiled like sound coming from a hall with most of string instruments gone.

    Really interesting is after listening 7a's a while then switching back to 7c's, it sounds like suddenly singer is screaming little bit as it's brighter and louder/tighter/punchier.
    It's not only the tweeter that's different on these.
    Even mids/bass is different.
    7a's sound sad while 7c's sound romantic and happy.

    I checked schematics and both versions use same crossover part values except the inductor (1.22mH vs 1.23 mH).
    Even mids are same MW6502.
    Looks like the peerless tweeter is swappable with SL2000 at least from the schematics of orginal 7 and revised 7.

    7a's may really need re-cap to bring all the drivers to original specs.

    Conclusion:
    -----------
    Music:
    Undecided as of first debate/comparison :).
    Need more debate sessions to sway my vote one way or the other.

    But I'm liking 7a's little better due to it's much better imaging than 7c's.
    7a's disappear better than 7c's.
    Perfect would be the combination of 7c's mids/bass andd 7a's tweeter.

    Movies:
    Watched clips of action movies and 7c's are more dynamic, punchier, lower, thrilling and sometimes harsh at louder volume while 7a's are smoother not harsh but don't have that dynamic sizzling sounds. Also 7a's sound like hall sound.

    I agree that depending upon songs and movie scenes, 7c's silver tweeter do sound metallic/harsh at louder volumes.

    Name:  Polk 7a and 7c.jpg
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    Boston A400, DefTech BP10,BP-2, Klipsch KG2.5,KG4,KSP-400,KSF-C5,RF3,RC3.
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  2. #2

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    The consensus here is that the SL2000 tweeter is indeed very harsh. You should replace those with the official Polk replacement tweeter, the RD-0194. It's supposed to cure those ills, then you would have the best of both worlds.

    Also, if the Xovers haven't been touched they're due for freshening with new caps and resistors.
    "Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills, polyswitches removed, Lg Solen inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR binding posts, upgraded IC Cable, Black Hole Damping Sheets (3" strips) installed on back wall behind MW's & Tweeters, interior of cabinets sealed, AI-1 interface with 1000VA transformer

  3. #3

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    Ditto x100
    Main Rig:
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    Monster HTS 3600 power conditioner
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  4. #4

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    I know that caps will and do go bad and need to be replaced. But do resistors also degrade with age?

    Quote Originally Posted by drumminman View Post
    The consensus here is that the SL2000 tweeter is indeed very harsh. You should replace those with the official Polk replacement tweeter, the RD-0194. It's supposed to cure those ills, then you would have the best of both worlds.

    Also, if the Xovers haven't been touched they're due for freshening with new caps and resistors.
    HT System:
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  5. #5

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    I have similar observations comparing the Monitor 5A (Peerless) and 5B (SL2000) in both the highs and bass. I like the bass of the 5B but the highs of the 5A. The 5B with swapping the tweeters for RDO-194 may be the best of both worlds. The same may be true for your 7C.

  6. #6

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    Before I order RDO-194 or RDO-198, I'll re-cap the older 7a's to see if that improves their mid/bass.
    If that does, I can let go the silver ones.

    Boston A400, DefTech BP10,BP-2, Klipsch KG2.5,KG4,KSP-400,KSF-C5,RF3,RC3.
    JBL L20t,L80t3,L166, EPI 20+,T/E 280, Polk 4,4.5,7C,RTA-11T, KEF Coda III, Yamaha NS-690.
    SUB:PF15TL+, Energy e:XL-S8, Optimus SW-10P, Velodyne VA08BVX10. Pre: HK AP2500. Amps: BB175, Adcom GFA-555II, Rotel RB-990BX.

  7. #7

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    Nice review,I have heard the peerless described many ways but never dull.Im thinking maybe the crossovers need to be updated on the 7As.
    Dan

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    Quote Originally Posted by gmjungbluth View Post
    I know that caps will and do go bad and need to be replaced. But do resistors also degrade with age?
    Other than burning out I don't know that resistors go bad. But, the technology today, e.g. Mills non inductive resistors, is way better than what Polk used back in the 70's and 80's. New higher quality resistors would have a very positive impact on the high end of the spectrum.

    The thing is they're cheap, too. Something like $4 each. To me it's a no brainer.
    "Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills, polyswitches removed, Lg Solen inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR binding posts, upgraded IC Cable, Black Hole Damping Sheets (3" strips) installed on back wall behind MW's & Tweeters, interior of cabinets sealed, AI-1 interface with 1000VA transformer

  9. #9

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    Some resistors can change in value with heating (abuse). Also, the originals were rather loose tolerance (10% I believe) Vs 1% for Mills. Also, the Mills are non-inductive.

  10. #10

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    Both pairs are resting now until I cull the herd little bit.
    Have few other speakers in line for rotation.
    Speakers just don't leave me alone.

    Boston A400, DefTech BP10,BP-2, Klipsch KG2.5,KG4,KSP-400,KSF-C5,RF3,RC3.
    JBL L20t,L80t3,L166, EPI 20+,T/E 280, Polk 4,4.5,7C,RTA-11T, KEF Coda III, Yamaha NS-690.
    SUB:PF15TL+, Energy e:XL-S8, Optimus SW-10P, Velodyne VA08BVX10. Pre: HK AP2500. Amps: BB175, Adcom GFA-555II, Rotel RB-990BX.

  11. #11

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    I really like the peerles tweets myself.

  12. #12

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    are the new 194's better?

  13. #13

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    Thanks for the info- will keep in mind!

    Quote Originally Posted by skrol View Post
    Some resistors can change in value with heating (abuse). Also, the originals were rather loose tolerance (10% I believe) Vs 1% for Mills. Also, the Mills are non-inductive.

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    Mystery, did you ever upgrade the crossovers on the 7As?

  15. #15

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    Quote Originally Posted by Hofy View Post
    Mystery, did you ever upgrade the crossovers on the 7As?
    Yes I did and the dullness went away.
    In fact, they sounded brighter/punchier/forceful than SL2000 with new capacitors and resistors.
    I liked them but sold already as I was over crowded with speakers.

    Edit: pictures here: http://www.audiokarma.org/forums/sho...d.php?t=519055
    Last edited by Mystery; 03-12-2014 at 12:17 PM.

    Boston A400, DefTech BP10,BP-2, Klipsch KG2.5,KG4,KSP-400,KSF-C5,RF3,RC3.
    JBL L20t,L80t3,L166, EPI 20+,T/E 280, Polk 4,4.5,7C,RTA-11T, KEF Coda III, Yamaha NS-690.
    SUB:PF15TL+, Energy e:XL-S8, Optimus SW-10P, Velodyne VA08BVX10. Pre: HK AP2500. Amps: BB175, Adcom GFA-555II, Rotel RB-990BX.

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    Interesting, my 7s have the SL2000 and their imaging is nothing short of amazing? Makes me wonder. The imaging was one of the most impressive features of the 7s and they did that better than my 5As which have the peerless (I realize they're different models).

    As to the harshness of the SL2000s. I can only hear to 14 Khz in my good ear and not sure about the other (maybe a bit less). So I don't notice that bump much as it's at the very edge of my range and I might actually prefer it to be there as it makes it easier to hear the extreme highs? Don't worry, your hearing will also degrade to this level in a decade or two! lol

    cnh
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    Vintage Polks: Polk Monitor 5As, Monitor 7Bs [HK 730], Monitor 10As [Marantz 2265], SDA-2Bs [Jolida JD-303, Jolida MV-MK4]
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  17. #17

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    They are better in everything than 5's but between 7A's and 7C's, 7A's imaged better, at least the pair I had during testing.
    But I'm sure if I fool around with the positioning, both versions will image fine.

    Boston A400, DefTech BP10,BP-2, Klipsch KG2.5,KG4,KSP-400,KSF-C5,RF3,RC3.
    JBL L20t,L80t3,L166, EPI 20+,T/E 280, Polk 4,4.5,7C,RTA-11T, KEF Coda III, Yamaha NS-690.
    SUB:PF15TL+, Energy e:XL-S8, Optimus SW-10P, Velodyne VA08BVX10. Pre: HK AP2500. Amps: BB175, Adcom GFA-555II, Rotel RB-990BX.

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