JayPare
Active Member
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?
BIC Venturi Formula 4 recap and restoration
- Thread starter JayPare
- Start date
homebrew
Super Member
Try these diffraction control tweeter rings.
https://www.madisoundspeakerstore.com/acoustic-damping/dampers-felt-defraction-ring-for-tweeters/
https://www.madisoundspeakerstore.com/acoustic-damping/dampers-felt-defraction-ring-for-tweeters/
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.
darkblue94
The Devil made me do it.
Tweeter diffraction rings are for dome tweeters, they'll have zero effect on cone tweeters. Painting the brown rings will not harm the tweeters at all just be sure to use a special formula "audiophile approved" (i.e. snake oil) paint when doing it.
JayPare
Active Member
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!
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.
JayPare
Active Member
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.
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.
JayPare
Active Member
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!
Anyone?
fredgarvin
Super Member
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.
JayPare
Active Member
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.
JayPare
Active Member
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?
StimpyWan
Addicted Member
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.
Good luck.
JayPare
Active Member
Can't find some Mundorf 16µf. IYHO, should I go with the closer value (i.e. 15µf) or go with a different brand?
StimpyWan
Addicted Member
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.
JayPare
Active Member
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".
Cool, thanks for sharing your methods!
JayPare
Active Member
Some more progress in the restoration:
Removing the glue residue:
Sanding the front since the previous owner had tacked some mosquito net in front of the speaker to replace the front grills:
Adding some putty:
Sanding down the putty:
Spraying:
Next steps are to clean the woofer, built new crossovers with brand new parts, restore the back and finally put everything back together.
Removing the glue residue:
Sanding the front since the previous owner had tacked some mosquito net in front of the speaker to replace the front grills:
Adding some putty:
Sanding down the putty:
Spraying:
Next steps are to clean the woofer, built new crossovers with brand new parts, restore the back and finally put everything back together.
kkd
Member
Unfortunately those speaker covers all have deteriorated with time and it's pretty much impossible to find some! I might end up doind custom covers but I kinda like the rest of the speaker look. So if I could hide that ugly brownish ring I would be happy!
Get a hold of sonofagun Bob Shafer in Evart MI
spellings might be off a bit, but he's the one who made these:
