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

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Mystery
Mystery Posts: 2,546
edited March 2014 in Vintage Speakers
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.

Polk 7a and 7c.jpg

Klipsch RB81, KG3.5, B&W DM602.5, Polk.
Subwoofers: Klipsch RW10, Triad ProSub Bronze.
Post edited by Mystery on

Comments

  • drumminman
    drumminman Posts: 3,396
    edited October 2012
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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/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
  • soundfreak1
    soundfreak1 Posts: 3,405
    edited October 2012
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    Ditto x100
    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
  • gmjungbluth
    gmjungbluth Posts: 232
    edited October 2012
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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?
    drumminman wrote: »
    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:
    Marantz NR-1403
    Front: Klipsch CF-4
    Rear: Paradigm Atom V3
    Center: Boston Acoustic VR12
    Sub: Bowers & Wilkins ASW600

    2Ch:
    Restored Fisher 500C
    Yamaha P-500 Turntable

    Living Room:
    Harman Kardon 3380
    Restored Polk Monitor 7B

    Bedroom:
    Harman Kardon VR-3750
    Cambridge Soundworks Ensemble
    Polk PSW10

    In and out of rotation:
    KLH Model 6,
    Polk LSI7
    NAD 7100
  • skrol
    skrol Posts: 3,345
    edited October 2012
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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.
    Stan

    Main 2ch:
    Polk LSi15 (DB840 upgrade), Parasound: P/LD-1100, HCA-1000A; Denon: DVD-2910, DRM-800A; Benchmark DAC1, Monster HTS3600-MKII, Grado SR-225i; Technics SL-J2, Parasound PPH-100.

    HT:
    Marantz SR7010, Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S4, CS250, PSW110 , Marantz UD5005, Pioneer PL-530, Panasonic TC-P42S60

    Other stuff:
    Denon: DRA-835R, AVR-888, DCD-660, DRM-700A, DRR-780; Polk: S8, Monitor 5A, 5B, TSi100, RM7, PSW10 (DXi104 upgrade); Pioneer: CT-6R; Onkyo CP-1046F; Ortofon OM5E, Marantz: PM5004, CD5004, CDR-615; Parasound C/PT-600, HCA-800ii, Sony CDP-650ESD, Technics SA 5070, B&W DM601
  • Mystery
    Mystery Posts: 2,546
    edited October 2012
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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.

    Klipsch RB81, KG3.5, B&W DM602.5, Polk.
    Subwoofers: Klipsch RW10, Triad ProSub Bronze.
  • Oldfatdogs
    Oldfatdogs Posts: 1,874
    edited October 2012
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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
  • drumminman
    drumminman Posts: 3,396
    edited October 2012
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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?

    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/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
  • skrol
    skrol Posts: 3,345
    edited October 2012
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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.
    Stan

    Main 2ch:
    Polk LSi15 (DB840 upgrade), Parasound: P/LD-1100, HCA-1000A; Denon: DVD-2910, DRM-800A; Benchmark DAC1, Monster HTS3600-MKII, Grado SR-225i; Technics SL-J2, Parasound PPH-100.

    HT:
    Marantz SR7010, Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S4, CS250, PSW110 , Marantz UD5005, Pioneer PL-530, Panasonic TC-P42S60

    Other stuff:
    Denon: DRA-835R, AVR-888, DCD-660, DRM-700A, DRR-780; Polk: S8, Monitor 5A, 5B, TSi100, RM7, PSW10 (DXi104 upgrade); Pioneer: CT-6R; Onkyo CP-1046F; Ortofon OM5E, Marantz: PM5004, CD5004, CDR-615; Parasound C/PT-600, HCA-800ii, Sony CDP-650ESD, Technics SA 5070, B&W DM601
  • Mystery
    Mystery Posts: 2,546
    edited October 2012
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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. :mrgreen:

    Klipsch RB81, KG3.5, B&W DM602.5, Polk.
    Subwoofers: Klipsch RW10, Triad ProSub Bronze.
  • gigbyt
    gigbyt Posts: 145
    edited October 2012
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    I really like the peerles tweets myself.
  • gigbyt
    gigbyt Posts: 145
    edited October 2012
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    are the new 194's better?
  • gmjungbluth
    gmjungbluth Posts: 232
    edited October 2012
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    Thanks for the info- will keep in mind!
    skrol wrote: »
    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.
    HT System:
    Marantz NR-1403
    Front: Klipsch CF-4
    Rear: Paradigm Atom V3
    Center: Boston Acoustic VR12
    Sub: Bowers & Wilkins ASW600

    2Ch:
    Restored Fisher 500C
    Yamaha P-500 Turntable

    Living Room:
    Harman Kardon 3380
    Restored Polk Monitor 7B

    Bedroom:
    Harman Kardon VR-3750
    Cambridge Soundworks Ensemble
    Polk PSW10

    In and out of rotation:
    KLH Model 6,
    Polk LSI7
    NAD 7100
  • Hofy
    Hofy Posts: 169
    edited February 2014
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    Mystery, did you ever upgrade the crossovers on the 7As?
  • Mystery
    Mystery Posts: 2,546
    edited March 2014
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    Hofy wrote: »
    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/showthread.php?t=519055

    Klipsch RB81, KG3.5, B&W DM602.5, Polk.
    Subwoofers: Klipsch RW10, Triad ProSub Bronze.
  • cnh
    cnh Posts: 13,284
    edited March 2014
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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
    Currently orbiting Bowie's Blackstar.!

    Polk Lsi-7s, Def Tech 8" sub, HK 3490, HK HD 990 (CDP/DAC), AKG Q701s
    [sig. changed on a monthly basis as I rotate in and out of my stash]
  • Mystery
    Mystery Posts: 2,546
    edited March 2014
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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.

    Klipsch RB81, KG3.5, B&W DM602.5, Polk.
    Subwoofers: Klipsch RW10, Triad ProSub Bronze.
  • DozerCSX
    DozerCSX Posts: 22
    edited January 15
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    I'm the original owner of an almost perfect pair of Monitor 7Cs from the 80s. They were born with the SL2000 tweeters. In the 1989 Loma Prieta earthquake, the left speaker fell over and the original SL2000 was damaged. I replaced it with the OEM Polk replacement RD-0194 - but only that one. So I have a hybrid pair with both the OEM replacement tweeter and the original. I actually have come to love it. The RD is indeed smoother, the original brighter, but together they create an interesting magic that I wouldn't change unless I had to. Plus it's a great story. They are currently the centerpieces of my main home theater system (mated with a CS400i center, RT10 sides and FX300i rears.)

    ez57076qb454.jpg
    Post edited by DozerCSX on
    HT1: Polk Monitor 7C's L/R, Polk CS400i center (bi-wire)
    Sides: Polk RT10+, modified with Vifa 1" polymer dome tweeters
    Rears: Polk VX300i surround speakers
    Subwoofer: Pioneer PSW-8mk2
    Receiver: Denon HD-750H 7.1

    HT2: Polk CS175i+ L/Rs with Vifa 1" polymer dome tweeter
    Center: Polk CS300
    Sub: modified Polk PSW10 (ratcage fix)
    Surrounds: CSW cubes sides, rears
    Panasonic SA-XR57
  • xschop
    xschop Posts: 4,837
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    So right channel is for The Green Mile, left is for Miles Davis.
    Don't take experimental gene therapies from known eugenicists.
  • mhardy6647
    mhardy6647 Posts: 33,355
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    My 7As survived Loma Prieta unscathed in Milpitas.
    Just thought I'd toss that in since this thread was inexplicably reanimated. :#

  • DozerCSX
    DozerCSX Posts: 22
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    xschop wrote: »
    So right channel is for The Green Mile, left is for Miles Davis.

    ...or Miley Cyrus!
    HT1: Polk Monitor 7C's L/R, Polk CS400i center (bi-wire)
    Sides: Polk RT10+, modified with Vifa 1" polymer dome tweeters
    Rears: Polk VX300i surround speakers
    Subwoofer: Pioneer PSW-8mk2
    Receiver: Denon HD-750H 7.1

    HT2: Polk CS175i+ L/Rs with Vifa 1" polymer dome tweeter
    Center: Polk CS300
    Sub: modified Polk PSW10 (ratcage fix)
    Surrounds: CSW cubes sides, rears
    Panasonic SA-XR57
  • DozerCSX
    DozerCSX Posts: 22
    edited January 15
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    mhardy6647 wrote: »
    My 7As survived Loma Prieta unscathed in Milpitas.
    Just thought I'd toss that in since this thread was inexplicably reanimated. :#

    Are they still alive? Do you still have them? Post a picture!
    HT1: Polk Monitor 7C's L/R, Polk CS400i center (bi-wire)
    Sides: Polk RT10+, modified with Vifa 1" polymer dome tweeters
    Rears: Polk VX300i surround speakers
    Subwoofer: Pioneer PSW-8mk2
    Receiver: Denon HD-750H 7.1

    HT2: Polk CS175i+ L/Rs with Vifa 1" polymer dome tweeter
    Center: Polk CS300
    Sub: modified Polk PSW10 (ratcage fix)
    Surrounds: CSW cubes sides, rears
    Panasonic SA-XR57
  • xschop
    xschop Posts: 4,837
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    Keep the 7Cs unless you plan on countersinking the MW's on the 7A's.
    Don't take experimental gene therapies from known eugenicists.
  • mhardy6647
    mhardy6647 Posts: 33,355
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    DozerCSX wrote: »
    mhardy6647 wrote: »
    My 7As survived Loma Prieta unscathed in Milpitas.
    Just thought I'd toss that in since this thread was inexplicably reanimated. :#

    Are they still alive? Do you still have them? Post a picture!

    Of course they're still alive! They are forever loudspeakers.
    Not currently in service, but always rarin' to go.

    They've gotten a bit camera shy in their dotage, though...

    9420465531_6f3b7ba93f_c.jpg