Intermittent tweeter

Ben Lawrence

Ben Lawrence

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Mar 2, 2011
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I have a JBL speak that is having some issues with the tweeter. I have had some blown subs in the past and they were all very obvious when blown. This one seems to be on and off. It works sometimes and other times nothing. I took a quick look and electronics and connections look pretty solid. High end did sound a little distorted at one point when it was working. Is this a common symptom of a blown tweeter? Is there a way to hook a voltmeter up and do a quick test?
Update watched a quick you tube video connected multi meter on ohms read back around 5.6 tested continuity and that beeped. Guess I might have to crack into amp and see if anything is fried?
 
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5.6 ohms sounds about right for an 8 ohm driver. HF drivers are almost never intermittent, likely a cold solder joint in the crossover (if passive) or at the amp connection.
 
hello

I can imagine two reasons with JBL hf-drivers.

The more expensive ones have springloaded terminals, so connection there is solid, but inside are some screw connections, that might get bit loose or corroded.

Lower cost line often have diapragm with blade terminals and the cable female ends tend to loosen their grip.
 
Timo Ulkuniemi said:
hello

I can imagine two reasons with JBL hf-drivers.

The more expensive ones have springloaded terminals, so connection there is solid, but inside are some screw connections, that might get bit loose or corroded.

Lower cost line often have diapragm with blade terminals and the cable female ends tend to loosen their grip.
Click to expand...

And just to expand on the same idea.

It sounds as if "something" is loose. It could be in any number of several different places in the driver itself, or the wiring going to it or the amplifier (if powered) or a passive crossover.

 
I'm not sure what the construction is like inside the driver on this unit, but I know some old Altec drivers basically had a wire lead that connected the terminals to each end of the voice coil. It was built in such a way that this piece of solid wire was bent at a 90 degree angle to absorb the diaphragm motion (like tinsel leads on a woofer). Over time the connection would get weak at that 90 degree bend and the wire would break. More than once I have seen guys solder those wires back together to get the show on the road without having to buy replacement diaphragms.

I'm just thinking it might be worthwhile to at least look at the diaphragm and see if there is a spot where the wire could be broken but still touching enough to sort of work.
 
Is this tweeter being power by its own amp channel or is it in a passive crossed over box? I had what I thought was an intermittent horn that all testing pointed to that as the problem and it didn’t make any sense because it would always work but just get quieter. It turned out to be an intermittent amp channel that tested fine when not under load. There were a few more amp channels available and after swapping it to another one the problem has disappeared.
 
The diaphragm all looks solid. It is a powered speaker but I believe there is a separate amp channels internally for the high and low. I am suspecting it is a cabling issue. Will let you guys know when I get a second look.
Thing is it seems to have popped up on two separate speakers at one time. Which led me to believe they were driven too hard at a job,
 
Ben Lawrence said:
The diaphragm all looks solid. It is a powered speaker but I believe there is a separate amp channels internally for the high and low. I am suspecting it is a cabling issue. Will let you guys know when I get a second look.
Thing is it seems to have popped up on two separate speakers at one time. Which led me to believe they were driven too hard at a job,
Click to expand...

If it is intermittant-then all will "look" OK. It is often next to impossible to spot with the naked eye.

It is very rare that an overdriven driver will become intermittant.
 
Josh Millward said:
I'm not sure what the construction is like inside the driver on this unit, but I know some old Altec drivers basically had a wire lead that connected the terminals to each end of the voice coil. It was built in such a way that this piece of solid wire was bent at a 90 degree angle to absorb the diaphragm motion (like tinsel leads on a woofer). Over time the connection would get weak at that 90 degree bend and the wire would break. More than once I have seen guys solder those wires back together to get the show on the road without having to buy replacement diaphragms.

I'm just thinking it might be worthwhile to at least look at the diaphragm and see if there is a spot where the wire could be broken but still touching enough to sort of work.
Click to expand...

I have fixed them just as you describe a good number of times.
 
I had a speaker once that had intermittent HF and it turned out to be a cold solder joint in the crossover.
It was mechanically fine, looked ok. only found it by checking every connection with a meter after bringing it back to the shop.

Jason
 
With the driver hooked up when i shook the entire speaker it would cut out. It seemed to be a simple connection problem in the spade connections. Tightened it up and ran it without issue for a bit. Im not 100% confident on it though so will be carrying a backup. Like I mentioned its strange that the problem arose in 2 cabinets at around the same time.
 
Hello

Glad you found it . That it is in two cabinets is indication of poor production quality. I would at least solder the wires on spade lugs to make sure there is good contact - better would be then solder the lug with LITTLE solder onto the driver lug - makes field replacement more difficult, but with self-powered cabinets that should be no problem, unless you are in the habit of cranking the shit out of them - pardon my language - after all, I´m a finn and not so initiated with all delightfull finesses of your tongue...
 
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