[FIXED] Cornwall 1 bad crossover help

[gsgleason]

Hi.

 

I got a busted up pair of Cornwall 1s (1979) recently.  The tweeters were both dead, so I just replaced the diaphragms with new ones from Simply Speakers.

 

When I connected it all up to test, one of the speakers sounded good for about 2 seconds and then there was a sudden drop in the treble.  The tweeter and squawker are putting out sound, just very little compared to the other channel.

 

After lots of troubleshooting, I found that the problem follows the crossover.  It's a type B.

 

I found it really weird that the treble dropped out so suddenly. 

 

What could be the issue?  I measured the capacitors with my DMM and they seem to be measuring properly.

Edited January 17, 2022 by gsgleason

[DeanG Crossovers]

Did you loosen and retighten all of the screws on the barrier strip?

[OO1]

1 hour ago, gsgleason said:

Hi.

 

I got a busted up pair of Cornwall 1s (1979) recently.  The tweeters were both dead, so I just replaced the diaphragms with new ones from Simply Speakers.

 

When I connected it all up to test, one of the speakers sounded good for about 2 seconds and then there was a sudden drop in the treble.  The tweeter and squawker are putting out sound, just very little compared to the other channel.

 

After lots of troubleshooting, I found that the problem follows the crossover.  It's a type B.

 

I found it really weird that the treble dropped out so suddenly. 

 

What could be the issue?  I measured the capacitors with my DMM and they seem to be measuring properly.

swap the crossover  with the crossover from the good speaker ,  ---------any changes ?

[gsgleason]

7 hours ago, Crankysoldermeister said:

Did you loosen and retighten all of the screws on the barrier strip?

 

All the ones on the speaker side, yes, when I swapped the crossovers.

[gsgleason]

6 hours ago, RandyH said:

swap the crossover  with the crossover from the good speaker ,  ---------any changes ?

 

That is what I already did.  I swapped the crossover the the problem followed it.

[DeanG Crossovers]

A capacitor can be shorted and still present a capacitance reading on a multimeter. 
 

Just replace the capacitors. I mean, they are 40 years old. 

[gsgleason]

48 minutes ago, Crankysoldermeister said:

A capacitor can be shorted and still present a capacitance reading on a multimeter. 
 

Just replace the capacitors. I mean, they are 40 years old. 

 

I'm just trying to avoid the $175 investment if I can avoid it. 

 

Do you find it odd that the treble just suddenly crapped out like a switch?

[OO1]

3 hours ago, gsgleason said:

 

That is what I already did.  I swapped the crossover the the problem followed it.

,   what you are saying is that the problem is identical with both crossovers , this makes no sense since 1 side or at least 1 crossover  is working correctly ,  you must verify the wiring -

 

1).......did you check the wiring   from the amplifier to the speaker ,  by that I mean did you swap the speaker wiring from the good speaker into the bad speaker

 

2)..... what is the DCR of both tweeters and  midrange drivers ?   is the DCR the same in the left and the right speaker   ,  the tweeters are 6.2 Ohms , the Mids are closer to 10.5 Ohms .

[DeanG Crossovers]

Well, it seems like a connection issue, but you apparently ruled that out. So, that leaves the autoformer or the 2uF tweeter capacitor. Where did you get $175?

[gsgleason]

Just now, RandyH said:

,   what you are saying is that the problem is identical with both crossovers , this makes no sense since 1 side or at least 1 crossover  is working correctly ,  you must verify the wiring -

 

1).......did you check the wiring   from the amplifier to the speaker ,  by that I mean did you swap the speaker wiring from the good speaker into the bad speaker

 

2)..... what is the DCR of both tweeters and  midrange drivers ?   is the DCR the same in the left and the right speaker   ,  the tweeters are 6.2 Ohms , the Mids are closer to 10.5 Ohms .

 

No.  I didn't say that.  I said the problem followed the crossover, which is how I know the problem is related to the crossover.

 

I tested all the drivers independently first and they all seemed fine, so I swapped the crossovers between the speakers, and the problem followed the crossover, meaning the speaker that was sounding bad now sounds good after the swap, and the speaker that sounded good now sounds bad.

[billybob]

10 hours ago, gsgleason said:

Hi.

 

I got a busted up pair of Cornwall 1s (1979) recently.  The tweeters were both dead, so I just replaced the diaphragms with new ones from Simply Speakers.

 

When I connected it all up to test, one of the speakers sounded good for about 2 seconds and then there was a sudden drop in the treble.  The tweeter and squawker are putting out sound, just very little compared to the other channel.

 

After lots of troubleshooting, I found that the problem follows the crossover.  It's a type B.

 

I found it really weird that the treble dropped out so suddenly. 

 

What could be the issue?  I measured the capacitors with my DMM and they seem to be measuring properly.

Do you feel the Diaphragm exchange went smoothly?

What about the retighrening connections, snug fit of wires on that tweeter?

Thanks!

[jimjimbo]

5 minutes ago, gsgleason said:

 

I'm just trying to avoid the $175 investment if I can avoid it. 

 

Do you find it odd that the treble just suddenly crapped out like a switch?

Just go to Parts Express and take your pick of capacitors dependent on your budget.  They ship fast and you should have your answer by the end of the week.

[OO1]

2 minutes ago, gsgleason said:

 

No.  I didn't say that.  I said the problem followed the crossover, which is how I know the problem is related to the crossover.

 

I tested all the drivers independently first and they all seemed fine, so I swapped the crossovers between the speakers, and the problem followed the crossover, meaning the speaker that was sounding bad now sounds good after the swap, and the speaker that sounded good now sounds bad.

well then,  you have  a bad crossover, and the crossover will require a  repair

[gsgleason]

Just now, RandyH said:

well then you a bad crossover

 

Yes. 

 

My concern is that the treble just suddenly cut out, and it's my understanding that capacitors don't just *poof* stop working.

 

 

[billybob]

Sometimes when replacing tweeters, the 2 wires on same become crossed resulting in tweet out of phase.

[OO1]

1 minute ago, billybob said:

Sometimes when replacing tweeters, the 2 wires on same become crossed resulting in tweet out of phase.

the op says that by swapping the crossover , the bad speaker was fine , so nothing to do with the drivers or the wiring

[KT88]

if you want a quick answer, just swap (solder) the capacitors from one xover to the other. Then you will know if the caps (one of them?) are bad or another component. I have attached a schematic that Bob Crites posted in 2006 of the 1978 Cornwall 1. Is this your xover?

You write that both! Squaker and tweeter of this channel stop playing after two seconds. That's why I suspect that the first cap 4 mF (before the autoformer) is bad because both, the squaker and tweeter signal runs through it. If only the second cap (2 mF) was bad then you would probably still hear the squaker.

 

Even if your xover circuit should be different, in principle you have one cap in front of the autoformer and perhaps two after the autoformer in front of the tweeter, so again I would change the first cap in the downstream first.

[OO1]

23 minutes ago, gsgleason said:

 

Yes. 

 

My concern is that the treble just suddenly cut out, and it's my understanding that capacitors don't just *poof* stop working.

 

 

you can reach out to @JEM Performance  they are the USA  klipsch crossover repair center , they can give you the better advice ,

and they can also sell you some klipsch original capacitors to repair your crossover -

 

 theaudioroom@verizon.net ......JEM Performance Audio   (412) 401-6915

[captainbeefheart]

40 minutes ago, gsgleason said:

I'm just trying to avoid the $175 investment if I can avoid it. 

 

Capacitors are not expensive, you can re-cap them for less than $50 if you know how to solder.

[gsgleason]

2 minutes ago, captainbeefheart said:

 

Capacitors are not expensive, you can re-cap them for less than $50 if you know how to solder.

 

Yes indeed.  I'm now researching capacitors that won't break the bank.

 

Jantzen, for example, doesn't make a 2 uf. They have 1.8 and 2.2.  Which should be considered?