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Old 3rd August 2008, 08:18 AM   #1
Whiting is offline Whiting  Australia
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Default Midrange speaker fault

G’day Guys

Recently purchased a pair of old BIC Model 44 speakers, which required new surround foam rubbers on the bass speakers.

Done that successfully, however the mid range speakers on both units do not have any sound from them. I don’t know if this has occurred before or since the repair of the bass speaker, as I did not try the speakers when purchased.

Anyone help with any ideas on where & how to start the faultfinding process. I've searched however can't find anything on this subject here. ( might be using the wrong terminology )

Cheers
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Old 3rd August 2008, 10:15 AM   #2
Dr_EM is offline Dr_EM  United Kingdom
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I'd firstly check the voice coil isn't shorted/burnt out with a multimeter. Should read about 3-7ohms in DC resistance test. If they pass that I'd try running them on thier own (perhaps use a 220uF capacitor just to prevent excessive low frequencies) to see if they output anything. If they do then it'll be a crossover or internal wiring problem and you'll have to go through testing all the parts in the crossovers midrange section! Good luck
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Old 3rd August 2008, 12:24 PM   #3
Whiting is offline Whiting  Australia
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Quote:
Originally posted by Dr.EM
I'd firstly check the voice coil isn't shorted/burnt out with a multimeter. Should read about 3-7ohms in DC resistance test. If they pass that I'd try running them on thier own (perhaps use a 220uF capacitor just to prevent excessive low frequencies) to see if they output anything. If they do then it'll be a crossover or internal wiring problem and you'll have to go through testing all the parts in the crossovers midrange section! Good luck

Thanks for your reply Dr EM. I've done as suggested and found that the speaker measures 6.1 ohm. I also connected it direct to the speaker cable with the capacitor and there is sound comming from it. So guess i'll have to check the crossover unit as suggested.

What equipment do I need to check the crossover unit as i only have a multimeter at present. Is there a one of type component within the crossover which normally fails and to check first ?

Cheers
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Old 3rd August 2008, 02:48 PM   #4
Dr_EM is offline Dr_EM  United Kingdom
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Electrolytic capacitors may dry up over time and solder joints may go dry too. Check the electrolytics first if there are any. Resistors should measure the value written on the body, inductors should measure close to 0 ohms at DC and capacitors should appear as open circuit usually. It can be more difficult to fully test the capacitors but if there are electrolytics in there they will likely be worth replacing anyhow (very cheap and modern ones should be superior)
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Old 4th August 2008, 02:52 PM   #5
Whiting is offline Whiting  Australia
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Thanks for your advice Dr.EM. I'll get onto it as soon as I have a chance and see if I can get these puppies up and singing again.

I'll let you know how they turn out.

Cheers
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