BIC Venturi Formula 4 recap and restoration

Discussion in 'Speakers' started by Jeremy Pare, May 22, 2018.

  1. JayPare

    JayPare AK Subscriber Subscriber

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    Can I paint over the brown rings? If so that should be fine! Or maybe there is some kind of black ring sticker I can put over it?
     

     

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  2. JayPare

    JayPare AK Subscriber Subscriber

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    I'm also looking the the thermistor value in the crossover. It's not on the electrical scheme and I can't find it anywhere online.
     
    Last edited: May 24, 2018
  3. homebrew

    homebrew Active Member

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  4. toxcrusadr

    toxcrusadr Omelette au Fromage Subscriber

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    I don't know that you have to replace the thermistor if it's working OK. I assume it has low impedance at low temps but higher as the temp rises under heavy loads. You might just check the cold resistance and see if the two match.
     
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  5. darkblue94

    darkblue94 It wasn't me. Subscriber

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  6. JayPare

    JayPare AK Subscriber Subscriber

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    The thermistor is a NTC, that means its resistance goes higher at low temperature and lower at high temperature (I tested with putting it in the freezer and applying my fingers on it after). At 25°C it has a resistance of about 16 ohms! However, I'm still missing the current rate! If someone could suggest me a value with explication I would appreciate. In the meantime, I decided to email BIC about it! I know it's a long shot but if I never try they will never give me any answers! :)
     

     

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  7. toxcrusadr

    toxcrusadr Omelette au Fromage Subscriber

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    After looking at the schematic, I am not sure what that thermistor is doing there, or what the Auto-Manual switch does. I have not seen either one of these on a crossover before. If anyone can explain this circuit, I'm curious.
     
  8. JayPare

    JayPare AK Subscriber Subscriber

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    From what I found on other threads, the thermistor is acting as a variable resistance to dynamically change the crossover value with the temperature (for example if there is more current passing through it, the temperature will go up so the resistance will go down). This is for auto. For manual (off) the thermistor is by-passed and the resistance is controlled with the potentiometer (knob). Someone correct me if I'm wrong.
     
  9. toxcrusadr

    toxcrusadr Omelette au Fromage Subscriber

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    Would have to trace out an actual schematic of the circuit to understand what effect that would have. Is it cutting power to the tweeter or what? That seems like the most likely application.
     
  10. JayPare

    JayPare AK Subscriber Subscriber

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    Anyone?
     
  11. fredgarvin

    fredgarvin AK Subscriber Subscriber

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    All I remember was putting it on 'auto' had no discernible effect on the sound. In fact, turning the knob all the way up on manual still wasn't enough top end.
     

     

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  12. JayPare

    JayPare AK Subscriber Subscriber

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    Was getting the same behavior as you before the recap but now I can see the difference. Maybe a little bit of this is in my head but there is a difference for sure.
     
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  13. JayPare

    JayPare AK Subscriber Subscriber

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    After comparing those speakers with the other pairs I've got, I will definately keep them. So I'll replace the capacitors I previously bought with better one.

    I might do an order from Mouser and they seems to carry Vishay / Sprague and Cornell Dubilier - CDE. Are these any good or I'm better with what you recommended?
     
  14. StimpyWan

    StimpyWan AK Subscriber Subscriber

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    I've never used any of the Mouser capacitors. But the Cornell Dubilier film capacitors get good reviews. Still, personally, I'd recommend the Mundorf E-Caps. Regardless of where you buy, make sure to get non-polarized electrolytic capacitors. I wouldn't use any capacitor with a high tolerance either. Definitely not higher than +/- 10%. I like 5% or less tolerances.

    Good luck.
     
  15. JayPare

    JayPare AK Subscriber Subscriber

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    Can't find some Mundorf 16µf. IYHO, should I go with the closer value (i.e. 15µf) or go with a different brand?
     
  16. StimpyWan

    StimpyWan AK Subscriber Subscriber

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    Capacitance adds together when you wire 2 or more capacitors in parallel. So, you could get 2 8uf caps, or add a 1uf to the 15uf. If you want to keep it simple, it's fine to buy a single 16uf cap, but Mundorf E-Caps are very good.
     
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  17. JayPare

    JayPare AK Subscriber Subscriber

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    I thought I already said it but apparently not. The old man I bought the speakers from had "modified". His wife didn't like the look of them so he relocated the connector in front and he glued some kind of rock countertop laminate all over the speakers (except the front ofc). He was then using them facing up the wall so the speakers looks like two living room small tables. I managed to remove all the laminate but there was a lot of glue residue (contact glue) on them. Here is a video of how I removed all the glue. I used a product called "The Goo Buster".

     
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  18. toxcrusadr

    toxcrusadr Omelette au Fromage Subscriber

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    Cool, thanks for sharing your methods!
     
  19. JayPare

    JayPare AK Subscriber Subscriber

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    Location:
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    Some more progress in the restoration:

    Removing the glue residue:
    1.jpg

    Sanding the front since the previous owner had tacked some mosquito net in front of the speaker to replace the front grills:
    2.jpg 3.jpg

    Adding some putty:
    4.jpg

    Sanding down the putty:

    5.jpg 6.jpg 7.jpg

    Spraying:
    8.jpg

    Next steps are to clean the woofer, built new crossovers with brand new parts, restore the back and finally put everything back together.
     
  20. kkd

    kkd Member

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    Silicon Valley
    Get a hold of sonofagun Bob Shafer in Evart MI
    spellings might be off a bit, but he's the one who made these:

    [​IMG]

    [​IMG]
     
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