1. Time for some upgrades in server hardware and software to enhance security and take AK to the next level. Please contribute what you can to sales@audiokarma.org at PayPal.com - Thanks from the AK Team
    Dismiss Notice

Pioneer CS-77a Refurbishing

Discussion in 'Speakers' started by turnitup, Dec 9, 2017.

  1. turnitup

    turnitup Well-Known Member

    Messages:
    666
    Location:
    California Bay Area
    Finally got around to finishing the refurbishment of my vintage Pioneer CS-77a's today. Think this has been about a 4 year project (got put on the back burner for a long time). When I bought them they were thrashed. Refinished the cabinets, replaced a few drivers with donors off of the auction web site, and refoamed the tweeter surrounds. Finally recapped the crossovers today. Replaced a 50, 30, 5, 3, and 0.5uf capacitor in each crossover, and thoroughly cleaned the pots. They're still mid-range Pioneer speakers, but they look awesome, and are now all restored.

    It was a fun project, even though I probably put more $$ into them than they're worth. 45 years old, and probably now ready for another 45.

    Both super tweeter horns test OK on the meter, but really don't put out much sound to add to the experience. Wondering if they were more aesthetic than functional on the original design. Wish they were more functional, the speakers seem to be lacking somewhat on the top end...at least for my preference.

    Surprising level of complexity for a mid-range vintage speaker (crossover especially). Wish they performed as well as they look! Built like a tank, with seemingly well made (but underperforming) components. Think I'll try another amp to see how that pans out.

    I read somewhere that the CSXX-A speaker series were designed by "S.A", anyone know what the SA stands for???
     

    Attached Files:

    Last edited: Dec 10, 2017

     

    Please register to disable this ad.

  2. turnitup

    turnitup Well-Known Member

    Messages:
    666
    Location:
    California Bay Area
    Posted this thread about a month ago, and have run the speakers with a number of different ~50 watt vintage receivers. The top end is just not there for me. I’m all about keeping speakers to their original design specs, but am considering swapping out the current (original) paper tweeters with “something else” - just haven’t figured out what alternatives might be best. The 77a’s have extremely well built cabinets, and their size is very close to the L100. Wish I had a set of L100 drivers at my disposal, I’d swap them out.

    I waited a long time to find some very good original tweeters for my 77a’s, but they just don’t perform well. If anyone has had success with replacing the tweeters in this model, I love to hear suggestions. I want to use these speakers, but am losing interest in them quickly...
     
  3. krimney

    krimney AK Subscriber Subscriber

    Messages:
    2,889
    Location:
    Calgary, Alberta
    I recently had a pair of 77a tweeters refoamed. Hooked up to an old sansui AU6500 I didn't notice them to be lacking in the highs. my crossovers are stock. don't give up on them yet, they are a very nice looking speaker.
     
  4. kryten79

    kryten79 Active Member

    Messages:
    208
    Location:
    VA Outside D.C.
    I have a pair I'm recapping and cleaning up. Hope to have them playing within the week. Refoamed a set of tweets. Will let you know.
     
  5. superdog

    superdog AK Member

    Messages:
    9,578
    Location:
    Southern Colo.
    Not to minimize anything you did for these but I had a original pair and while a very nice looking speaker it had to be one of the most unremarkable speaker I ever owned.
     
  6. spark1

    spark1 Super Member

    Messages:
    1,281
    Location:
    The Great Midwest
    I owned a pair of these several years back, and did a similar restoration on them. Pleasant enough speaker, but low-end definition was not good. Overall, just not a lot of detail, and certainly very "relaxed" sounding. You've probably already checked, but are you sure that you have the switch on the rear panel set to "full range?

    Are you sure the tweeters are working? They are not super-tweeters (which, depending upon your age, you might not be able to hear). These cross over somewhere around 5-6kHz. I know that the high-frequency output on mine was spotty until I cleaned the potentiometers.
     

     

    Please register to disable this ad.

  7. drbiggles

    drbiggles I like bacon Subscriber

    Messages:
    6,625
    Location:
    Richmond, CA
    Hey man,

    Even those older tweeters should be putting out plenty of highs. Maybe not much above 14 to 16k (a guess on my part, not familiar with the 77a), but they should be there. Especially with that new poly cap, that should have made them brighter when compared to the original electrolytic (even when they were within spec). What you need is a second set of ears to have a listen. Do you have anyone that can come by and have a listen? Someone who might know how they should sound? I'm in the East Bay Area, if you're close enough I can stop by and have a listen.

    Biggles
     
  8. spark1

    spark1 Super Member

    Messages:
    1,281
    Location:
    The Great Midwest
    A good way to be sure you are getting output from the tweeters is to use a cardboard tube (for example, from a spent roll of paper towels)...one end at your ear, and one end at the driver. And turn down the midrange as far as it will go. Or, if I remember correctly, you can drive only the tweeter (being very careful with power).
     
  9. turnitup

    turnitup Well-Known Member

    Messages:
    666
    Location:
    California Bay Area
    I’ve isolated both speakers independently to check for consistent output, and they both seem to be performing equally. I’m leaning toward “Superdog’s” conclusion that the speakers are simply in that unenviable “unremarkable category”. When you look at the quality build of the speaker cabinets, driver cages, cone material quality, crossover complexity/build, and even the speaker grills - it really is perplexing that perhaps the sole purpose for their existence (to generate quality sonic output) is really their weakest link.

    Still wish I had some spare JBL L100 drivers/crossovers laying around to throw into those beautiful walnut cabinets. Think I’ve got a low IQ supermodel speaker on my hands - looks great until they open their mouth...
     
    Last edited: Jan 13, 2018
  10. drbiggles

    drbiggles I like bacon Subscriber

    Messages:
    6,625
    Location:
    Richmond, CA
    It could very well be that the weak highs could be part of their design, unremarkable. I borrowed a pair of the CS-77's last year from a friend. He was having issues with them as well. Unremarkable with weak lows and searing highs. He did recap with a poly vs electrolytic, so that was part of the issue. He wasn't happy with them. Once I got a look at them, the first thing that came to mind was The Rolling Stones at blistering levels. I jacked them in with Some Girls and pushed between 30 and 40+ watts into 'em. I know this might sound crazy, but getting the Stones and Led Zeppelin to sound right, takes a "special" kind of speaker. In any case, the 77's did it in spades. I let them run for a few hours like that. It was GREAT fun! Critical listening? No, of course not. But the damned things were FUN. I returned them and they're languishing in his storage area. I can say with certainty, I'll end up with them back here. Yes, and they will only be for listening to the Stones or similar. I like fun.

    Biggles
     
  11. spark1

    spark1 Super Member

    Messages:
    1,281
    Location:
    The Great Midwest
    Wow...30-40 watts of continuous power? I'm surprised your ears weren't bleeding...those speakers have a very high sensitivity rating.

    Wondering about your comment regarding new capacitors - if same capacitance, how do they extend the frequency response? I would guess that there might be some small change in output levels due to the possibility of increased resistance in an old cap, but don't understand how a new cap changes the crossover point (unless, of course, the capacitance of the old one was not at spec).

    Thanks...always trying to learn.
     
    Last edited: Jan 13, 2018

     

    Please register to disable this ad.

  12. drbiggles

    drbiggles I like bacon Subscriber

    Messages:
    6,625
    Location:
    Richmond, CA
    You nailed it, ESR (Equivalent Series Resistance). New or old non-polar electrolytic caps have higher ESR. Modern poly caps have lower ESR. This translates to a little hotter tweeter. Some tweeters can handle it and perform just fine. Some however, do not. You can either buy a new NP Electrolytic to replace the original, or put a 1ohm resistor in series (on the positive side) with the tweeter to simulate the higher ESR with the new poly cap. New NP Electrolytics are notoriously off spec, sometimes enough to hear an audible difference. So, a resistor paired with a poly cap is preferred.

    I'll generally pop a poly cap in and take the speakers for a test run over a week and see what my ear thinks. If it's a no go, then I go back in and add the resistor.

    Biggles
     
  13. drbiggles

    drbiggles I like bacon Subscriber

    Messages:
    6,625
    Location:
    Richmond, CA
    Oh, and yes. The entire house lit up with a thunderous noise. I was able to do chores both inside and outdoors and still get a thrill.

    Biggles
     
  14. spark1

    spark1 Super Member

    Messages:
    1,281
    Location:
    The Great Midwest
    Ah...frequency response not greater, just a bit louder.
     
  15. sound man

    sound man Member

    Messages:
    66
    Location:
    Michigan
    Is there any reason not to re-cap with electrolytics? I have a pair of cs-88s that have the same "lacking good highs" type performance and I'm a little hesitant about throwing a lot of money into a re-cap if it's not going to do a lot of good. Thanks.

    Walt
     
  16. superdog

    superdog AK Member

    Messages:
    9,578
    Location:
    Southern Colo.
    I can see what your saying about put some power to them to open them up.I did that with some Nova 8 speakers.I wasn't hearing anything special with them until I put 150 watts behind them.It really opened them up.They came alive and earned the right to hang around for the time being as far as speakers go.I think when I had my cs77a I had just obtained some L100s and in comparison the Pioneer were just flat.Not saying the L100s are all that but at the time they were preferred by a large margin over these.This was about ten years ago.
     
    Last edited: Jan 13, 2018
    drbiggles likes this.

     

    Please register to disable this ad.

  17. spark1

    spark1 Super Member

    Messages:
    1,281
    Location:
    The Great Midwest
    The primary reason to use poly/film caps is that they don't degrade with time. However, I don't believe that one vs the other will provide dramatic differences...and in some cases, the crossover was designed with the ESR of any electrolytics being used in mind (for example, Snell speakers).

    Dayton polypropylene caps are quite reasonably priced. And, you can save money by using them only for the mid and tweeter circuits. If you have higher value caps (greater than 20-25uf or so) in your crossover, use electrolytics there.
     
    Last edited: Jan 13, 2018

Share This Page