How to get the best sound possible out of these vintage Circle of Sound babies

Discussion in 'Speakers' started by DangerBoy, Oct 20, 2017.

  1. dshoaf

    dshoaf That high voltage buzz

    Messages:
    10,074
    Location:
    Santa Cruz, CA
    I remember those systems - mid-century modern if there ever was an example.

    IIRC, the cabinets are plastic, correct, as is the grill work on the top? If so, then the challenge for a more high-excursion driver will be the back pressure on the cabinet. I'd suggest you line the round cabinet with some of that sound-deadening material used by auto sound installers to keep doors and trunks from vibrating. Then put the insulation back into the cabinets after the replacement drivers are installed.

    Both will lower the efficiency of the speaker but will linearize the bass response. Don't expect room filling bass but do expect to be presented with a nice sound stage assuming the speakers are placed well enough. Also, I'd suggest other electronics than the old console. A nice Pioneer, Sony or Sansui receiver of the the 70s vintage would be far better.

    Cheers,

    David
     
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  2. jwrauch

    jwrauch AK Subscriber Subscriber

    Messages:
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    I'm looking forward to hearing your thoughts on your completed project. The idea of damping the inside is good. Spray on bed liner would also work>> I would go with which ever is cheaper. I love a good DIY thread !!!.
     
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  3. Ohighway

    Ohighway Wannabe Minimalist Subscriber

    Best of luck on this project. :thumbsup:

    A buddy of mine got either this system or one nearly identical for his birthday. I'm guessing around 1968 but could be off by a year or two. I remember it sounding decent for what it was, and in fact filled his room with sound quite nicely.

    I tend to believe most things can be improved with a little effort and there's no reason not to do it with this system. I'll be curious as to what improvements can be gained with a bit of brainstorming combined with building / modifying.
     
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  4. DangerBoy

    DangerBoy Active Member

    Messages:
    118
    Does anybody know what the impedance of the original full range (Zenith 49-1116) drivers in these speakers is supposed to be? I measure 6 ohm with my multi-meter.
     
  5. Porkloin

    Porkloin Oscar Heil Groupie Subscriber

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    Location:
    Kent, WA
    6 Ohms DC resistance is usually the reading on an 8 ohm impedence speaker.
     
  6. wallacefl

    wallacefl Active Member

    Messages:
    313
    Looks like big fun to me......if you can get a 3rd speaker you could make an isobaric subwoofer out of it by placing to Tang Band drivers face to face after removing the omni cone. An Anarchy woofer/s might fit and might also be used in the omni canisters but the tweeter mounting remains a problem. You could also use Alpair 10.3 full range drivers which will work in 0.25 ft3. The icing on the cake would be finding/using a pair of Infinity Walsh tweeters mounted on top.
     

     

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  7. SiliconTi

    SiliconTi AK Subscriber Subscriber

    Messages:
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    Caution: zombie thread!

    I am wondering how the OP made out.

    I just acquired a pair of these for free from the side of the road and want them to sound better.

    My first step is to reseal the cabinets, as the bottoms have holes in them. After that, I am thinking car stereo coaxial.

    BTW, the bodies are cardboard (think Sonotube) with steel rings top and bottom for strength. Legs are held on with screws through the cardboard. Bottom is pressboard. Top is a plastic screen material. "Top hat" is pressboard. Diffuser cone is hard plastic. All covered in woodgrain vinyl.

    Pretty cool to look at, let's see how they can sound...
     
  8. nfafan

    nfafan Well-Known Member

    Messages:
    633
    Location:
    East Coast
    It would have been kewl to find out what happened. As I understand it, several mfgs came up with these round omni-directional speakers and it would be interesting to hear of assessments.
     
  9. tdwpgtp

    tdwpgtp Active Member

    Messages:
    106
    I, too, wonder what the OP ended up with in the end. I've been keeping an eye out for a pair of these for cheap for this same reason for a few years now. Some additional sealing, damping, and better drivers would certainly improve things. I'm on the train of thought that some acceptable sound can bet gotten out of them with a little work, and they could be used for garage or background music. My plan, originally, was to get a pair and try mounting them on my garage ceiling, after the improvements, to see if I could get some uniform-ish sound throughout the garage.

    They are an interesting novelty with no sonic value as-is. Tinkering with them is fun, potentially rewarding, and in the end they can still be resold to be used as the bad sounding decorations they came as, only with improved sound.
     
  10. gdmoore28

    gdmoore28 Super Member

    Messages:
    2,561
    Location:
    Central Arkansas
    Fun project. Make your own. Grab a concrete form tube and go to town. Let us know how you do.

    GeeDeeEmm

    [​IMG]
     
  11. SiliconTi

    SiliconTi AK Subscriber Subscriber

    Messages:
    2,069
    Location:
    New Hampshire
    OK, step one: get them back to factory condition.

    That was easy, I just cleaned them out and made new bottoms for them to reseal the cabinets.

    Result: medíocre. Not great, but better than I expected. Very highs and lows are not there, but the mid is OK. My Mac 4100 has a built in EQ and variable loudness. If I crank the 10K EQ and crank the Loudness to boost the bass, they are not bad at all.They pull quite a bit of power, 3 W at mid volume which surprised me; not efficient at all. (This is what my AR-3s draw at a much louder volume.)

    Next step: better drivers. Not looking to sink $$ into these, so I'll look for used car audio coaxials.

    Stay tuned.
     
    Last edited: Jul 15, 2018

     

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  12. transmaster

    transmaster AK Subscriber Subscriber

    Messages:
    7,817
    Location:
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    I once had the very system you show in your photo. The big deal was the 2 gram turntable tracking weight. I recall the Circle of Sound Speakers sounded pretty good. My advice is to get one of the Lepai LP-2020TI audio amps from Parts Express; $28.88. I have 3 of these amp and I can say with confidence the 2020 is a vast improvement over the amp in the Zenith. The 2020 is 20 Watts x 2 into 4 Ohms which would less the 20 Watts into 8 Ohm which would be prefect for these speakers. You can use a 3.5mm cable to input a signal from a smart phone, or better yet an Echo Dot into this amp.

    579D7F2D-F066-4178-BEFE-611979EB749C.jpeg
     
    Last edited: Jul 17, 2018 at 11:05 PM

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