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. DangerBoy

    DangerBoy Active Member

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    I have just acquired a 1960s Zenith Moderne Z565 Record Player system with Circle of Sound speakers. A picture of the actual system is below.

    My intention is to transform this system into something very cool and decent sounding so I want to do whatever I can within a reasonable budget to make these speakers sound as good as possible. As part of the overall project it is likely that I'll be adding a Raspberry Pi music streamer to the record player unit so it will also be able to stream and play digital music from several sources (mobile devices, network shares and the Internet) by various means as well as play records. That part of the project will be documented in a different forum, likely the DIY forum. I will post a link to that thread in this one as soon as I have it started.

    In this thread I'd like to explore various options for upgrading these speakers and then document the work done to do those upgrades.

    I know there has been a lot of discussion on these speakers prior to this and I've researched and gone through a lot of it. Most of the threads I found had people making lots of suggestions as to what could be done to upgrade these speakers but almost none of them actually documented/discussed what ended up being done and what the results were. I intend to take this thread through the whole process by keeping a record of what I did, how I did it and how it turned out.

    So at this point, what I would like to discuss is what I could do with these speakers and also have people chime in with what they have done with theirs and what the results were. I have created a media Gallery for the overall project which is open to AK members to contribute photos to.

     
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  2. swechsler

    swechsler Frog Whisperer

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    The first thing I'd do is determine the internal volume of the cabinets, then use some loudspeaker design software to see what could be done with them. Something like a Kef Uni-Q driver (or a coaxial driver, if the former isn't easily modeled) would allow you to center both the woofer and tweeter so they can both point upwards towards the sound disperser. An alternative would be to mount the tweeter on top and the woofer on the bottom, but due to a fairly high crossover frequency that would be required for a 2-way system, that might give you less than idea lower midrange.

    Also keep vibration in mind. How solid are the cabinet walls?
     
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  3. JoeESP9

    JoeESP9 ESL's & tubes since 83

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    You can't make a silk purse out of a Sows ear!:dunno:
     
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  4. DangerBoy

    DangerBoy Active Member

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    Here's what I'm thinking are possible options for upgrading these speakers:

    1. Replace the driver with a good quality upward facing full range (maybe Fostex) driver with whizzer cone. Would want to choose a full-range that has some decent treble response.

    2. Replace the driver with a decent quality 2 or 3 way coaxial speaker.

    3. Cut out the bottom of the speaker and have a downward facing woofer out the bottom and a coaxial midrange/tweeter driver out the top. This would of course require a crossover.

    Adding cross bracing and sound deadening material around the cylinder walls would be a good idea in any of these options.

    Here are some dimensions:

    Maximum available cylinder height: ~7.5"

    Cylinder ID: approx. 8-3/8"

    Cylinder wall thickness: Approx 1/8"

    I haven't opened them up yet to see what's inside but from other threads I believe it's a 6.5" full range with a small magnet. Possibly with a whizzer cone.
     
  5. DangerBoy

    DangerBoy Active Member

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    That may be true but it's not helpful to this discussion. The point of this discussion is to figure out what can be done to get the best sound possible out of these speakers. If you have some ideas on what we could do, I would like to hear them.
     
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  6. DangerBoy

    DangerBoy Active Member

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    Here's a pic of one of the speakers just to give you a better idea of it's dimensions
    Circle of Sound 1.jpg
     

     

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  7. JoeESP9

    JoeESP9 ESL's & tubes since 83

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    Sorry, I don't understand why anyone would spend time, money and effort on a pair of "sows ears" when you could buy much better starting performance for the same or less money than you're talking about investing.

    If trying to make a "silk purse" from a Sows ear is your thing go ahead. Beware, the results most likely will not be worth the time and effort expended.

    BTW: I'm quite familiar with those Zenith Circle of Sound speakers. OTOH: The electronics and TT aren't that good either.
     
  8. swechsler

    swechsler Frog Whisperer

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    I had no idea these were so small. My calculations give you about 1/4 cu foot, which is not going to get you much bass no matter what sort of driver(s) you install. Also, it looks like the material is plastic, which is a less than ideal material for speaker boxes (at least when it's this thin).
     
  9. DangerBoy

    DangerBoy Active Member

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    Yes I know the size and construction is quite limiting. Despite that, I've seen it reported that some people have managed to get them to sound half decent. I will get one of these units apart and report back with pictures to see what we have to work with.
     
  10. tarior

    tarior Dirty pool, old man? Subscriber

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    No amount of wishful thinking is going to make that into a decent sound system. It's a cool looking retro setup, but it is what it is---mediocre at best for music reproduction.
    The best advice I can give is to just enjoy it for what it is. If you want a nice sounding stereo, get something else.
     
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  11. DangerBoy

    DangerBoy Active Member

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    I fully realize that these systems were never great Hifi and that it would be so much easier and maybe even more cost effective to start with a better system. That being said, this system has a very undeniable retro coolness and charm to it that really encapsulates or personifies the vibe of a certain bygone era. And that's why it's worthwhile to me, and to others I think, to preserve this system and find ways to make this system as good as it can be using today's technology. It's highly possible that in the end it won't sound fantastic but if we try we might be able to make it sound decent enough to listen to and it will still be very, very retro cool and sound better and do more than it did originally which I know will have a lot of appeal to a lot of younger people who are into MCM retro cool stuff, especially hipsters. I'll think it's cool and like it too.

    And so I ask again that if you have ideas on how we can make this system the best that it can be and to do things well beyond what it was designed to do (e.g. stream music) then please feel free to contribute. But posting comments detracting or downplaying the sensibility or worthiness of doing this project is not helpful towards achieving the stated goals. It sounds like you have knowledge of these systems so I really would appreciate it if you could share what you know and help us along the way toward making this system as good as it can be. Thanks.
     
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  12. DangerBoy

    DangerBoy Active Member

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    See the above comment.
     
  13. kirk57

    kirk57 Some guy on the Internet Subscriber

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    One approach would be to build a separate subwoofer in a tube (there are designs out there using various kinds of pipes) and then would only need to get down to 90Hz or so with the main speakers. I'd dampen the hell out of those plastic enclosures with something like Mortite or Dynamat; doing so should get a reasonably resonance-free enclosure.

    Maybe the OP wants to do this project because these sorts of systems are finding a whole new group of people who appreciate them for the style which is not available in anything new. We older guys remember these as just bad-sounding; a different generation might think of them as cool.

    I'd agree that even if you have a good front end and much improved speakers, the electronics are going to be a limiting factor. A $25 Lepai class D amp would sound much better...
     
    Last edited: Oct 20, 2017
  14. tarior

    tarior Dirty pool, old man? Subscriber

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    OK, after thinking about it for a minute, here is what I would do (other than selling that stuff to a sucker). Assuming you have no electronics skills.

    1) Go to a car audio shop and buy the best sounding pair of two way car speakers that will fit in the cabinet and that you can afford.
    2) Add a small powered subwoofer that will operate off the speaker level outputs on the "receiver".
    That's about as simple and practical as I can imagine.
     
  15. WaynerN

    WaynerN AK Subscriber Subscriber

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    I have the JBL S109 Aquarius IV speakers that "in principal" are like your speakers.

    JBL Sell Sheet page1.jpg

    They use a full range driver called the LE8T-2, which is an 8" speaker. That speaker is mounted just under the grill-cloth band near the top. Inside of the unit, there is a parabolic type of diffractor pointing downwards at the driver, designed and positioned in such a way that the music is aimed at the grill cloth bands. There is also an external tweeter (LE20-1) pointing at another parabolic horn located in the rear of the speaker.

    JBL Sell Sheet page2.jpg

    I don't think that Zenith horn loaded their speaker(s) properly, so that is an area that could be improved.
     
    Last edited: Oct 20, 2017
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  16. alteclipsch

    alteclipsch Super Member

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    I think this is a noble goal, and with decent drivers, you can go a long way towards decent sound. Maybe a sub will be needed, but some stiffening, insulation, and a good coax speaker should help. What's the diameter of the drivers now?
    My brother had them back in the 70's, I always thought they were kinda cool. Good luck!
     

     

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  17. DangerBoy

    DangerBoy Active Member

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    Thanks to all who have contributed thus far.

    Okay the fist challenge has been encountered. On the bottom there is a melamine type plate. I've taken the four main screws off and cannot get the plate to budge. I tried taking out the screws holding the wire racks on but the plate didn't fall out and I no longer had a way of pulling on it so I advanced the four screws affixing the wire racks onto the bottom plate just a little ways in and tried pulling on the racks but still the plate would not move. Those bottom plates are stuck in there pretty good it would seem.

    If anyone has had a pair of these apart before, now would be a good time to chime in and tell me what I need to do to get these things apart.

    > What's the diameter of the drivers now?

    I'm trying to verify that now but from looking at other threads I believe they're 6.5" full range drivers with small magnets, possibly with whizzer cones.

    Speaker Bottom.jpg
     
    Last edited: Oct 20, 2017
  18. DangerBoy

    DangerBoy Active Member

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    On the subwoofer idea, if I could find a pair of the square versions of these speakers that came out after these ones did, I could either just concentrate my efforts into modifying those or convert one of them into a subwoofer/base unit and convert these cylindrical units into satellites with only a midrange and tweeter in them. My current speaker system is set up that way and it sounds really good. Or I could still make these units full range and supplement the bass with a subwoofer.
     
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  19. tcdriver

    tcdriver AK Subscriber Subscriber

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    Looks like a fun project. I look forward to seeing what you come up with.
     
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  20. DangerBoy

    DangerBoy Active Member

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    Just spitballin' here. Would a downward facing woofer out the bottom and a dome or other type tweeter out the top possibly work?
     

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