What's Wrong with 4343 Woofer?

[pyonc]

Hi, all,

Please give me your diagnosis and solution. And this is what happened:

I was trying to test vintage Crown VFX-2 crossover for 4343 this afternoon.
I hooked all the input and interconnect cables, only turning on the loss pass Xover switch, with the high-pass swtich off. When I did so, I heard some sort of strange
audible noise coming from the woofer (2231A) of the right speaker initially, and it disappeared. I didn't hear that from the left woofer.
When I did it the second time, I heard the same. Now the problem was since that happened, I could not hear any bass from that right woofer. What's wrong here? Any way to fix it by myself? Please help me out!!! At this point I just regret toying with this old Crown X-over, not knowing fully about its function...:banghead:

[hjames]

What do you get when you remove the Crown crossover from your system and hook everything back up normally?


Hi, all,

Please give me your diagnosis and solution. And this is what happened:

I was trying to test vintage Crown VFX-2 crossover for 4343 this afternoon.
I hooked all the input and interconnect cables, only turning on the loss pass Xover switch, with the high-pass swtich off. When I did so, I heard some sort of strange
audible noise coming from the woofer (2231A) of the right speaker initially, and it disappeared. I didn't hear that from the left woofer.
When I did it the second time, I heard the same. Now the problem was since that happened, I could not hear any bass from that right woofer. What's wrong here? Any way to fix it by myself? Please help me out!!! At this point I just regret toying with this old Crown X-over, not knowing fully about its function...:banghead:

[pyonc]

What do you get when you remove the Crown crossover from your system and hook everything back up normally?

Well, I turned back to my existing biamp set-up with JBL M552 X-over, and I could hear no bass from the woofer in question. And I tried single amp mode this time from biamping, and the outcome was the same. Any possibility that the woofer's been damaged in one way or another, or any other problem?

[grumpy]

Biamp switch on 4343? tried moving that back and forth a bit (scrubbing the switch
contacts in doing so)?

[PaulB]

:(

My babies... my poor poor babies...

Do you know how to use an ohmmeter? I've got a bad feeling about this...

[pyonc]

:(

My babies... my poor poor babies...

Do you know how to use an ohmmeter? I've got a bad feeling about this...

Dear Paul,

Glad to hear from you. Ohmmeter? What's that?
I just keep my fingers crossed no damage has been done to the woofer.

[pyonc]

Biamp switch on 4343? tried moving that back and forth a bit (scrubbing the switch
contacts in doing so)?

Yea, it doesn't help either.
Do you see any possibility some sort of damage being done to the woofer with this vintage Crown X-over?

[grumpy]

sure. If it put out DC and it wasn't blocked or limited by the amp fast enough...
poof. Could still be something else, like a loose contact, but if they were mine
the woofer would be coming out for testing (such as testing with an ohm meter
to measure resistance... see if the coil has opened/burnt or shorted). Crossing fingers
for you...

[PaulB]

An ohmeter measures resistance (continuity of the voice coil in this case). I hate to say it but my guess is that it's fried.

If you want me to walk you through how to test this, shoot me an email. I hope I'm wrong but sure sounds like it to me. If you tested it in normal mode and that's consistently the only driver not working (just for fun, did you try switching amp channels?), then the most likely explanation is that the Xover was faulty and burned out the woofer voice coil.

:(

[opimax]

Chang,

I can be available Mon night and I have a meter :)

Mark

[hjames]

An ohmeter measures resistance (continuity of the voice coil in this case). I hate to say it but my guess is that it's fried.

If you want me to walk you through how to test this, shoot me an email. I hope I'm wrong but sure sounds like it to me. If you tested it in normal mode and that's consistently the only driver not working (just for fun, did you try switching amp channels?), then the most likely explanation is that the Xover was faulty and burned out the woofer voice coil.

:(

If his system is setup for Biamp, he should have just the Woofer leads coming out of the back of the system somewhere, right?

Unless the biamp switch has failed and completely removed the woofer out of the circuit somehow, can't he use a regular 1 1/2 volt battery (a single AAA, AA, C or D-cell) and, with a short piece of speaker wire, briefly connect the battery across the woofer leads and get a thump to verify the woofer is still useful??

I mean just the basic go - no go test?

[grumpy]

yep... in fact, it shouldn't really matter if it's in biamp mode or not.

I -did- say if they were mine ... :) Then again, I have no compunction about ripping
things (like speakers) completely apart for grins; and these were made to be serviceable.

[pyonc]

Chang,

I can be available Mon night and I have a meter :)

Mark

Hi, Mark,

Looks like the voice coil has been burnt, according to our forum members.

What time are you available Mon. night? Just let me know.

Thanks, my friend.

[pyonc]

sure. If it put out DC and it wasn't blocked or limited by the amp fast enough...
poof. Could still be something else, like a loose contact, but if they were mine
the woofer would be coming out for testing (such as testing with an ohm meter
to measure resistance... see if the coil has opened/burnt or shorted). Crossing fingers
for you...

I'm afraid the cause of the malfunctioning belongs to one of the three causes you've just mentioned. I played Test CD to check the bass of the woofer in question, but I heard no sound or noticed no treble, starting with 80Hz warble and up, compared with the other woofer that works perfectly okay. Now, how can I have it fixed? Send it to a JBL dealer? Just this one in trouble, or both? Thanks always.

[PaulB]

If his system is setup for Biamp, he should have just the Woofer leads coming out of the back of the system somewhere, right?

Unless the biamp switch has failed and completely removed the woofer out of the circuit somehow, can't he use a regular 1 1/2 volt battery (a single AAA, AA, C or D-cell) and, with a short piece of speaker wire, briefly connect the battery across the woofer leads and get a thump to verify the woofer is still useful??

I mean just the basic go - no go test?

He could use a battery Heather, I prefer an ohmmeter because it limits the current although a small battery isn't likely to do any harm. But a battery won't tell him if it's shorted or open (open being much more likely). I'd pull the woofer (4 screws IIRC) so that you can double check the remote possibility of a loosened connector. In any event methinks it's a toasted woofer :(

[pyonc]

If his system is setup for Biamp, he should have just the Woofer leads coming out of the back of the system somewhere, right?

Unless the biamp switch has failed and completely removed the woofer out of the circuit somehow, can't he use a regular 1 1/2 volt battery (a single AAA, AA, C or D-cell) and, with a short piece of speaker wire, briefly connect the battery across the woofer leads and get a thump to verify the woofer is still useful??

I mean just the basic go - no go test?

Thanks. I just tested a regular AA battery, with both black and red leads on their ends.
I don't see the cone moving out or in as it used to do so before...:banghead:

[pyonc]

He could use a battery Heather, I prefer an ohmmeter because it limits the current although a small battery isn't likely to do any harm. But a battery won't tell him if it's shorted or open (open being much more likely). I'd pull the woofer (4 screws IIRC) so that you can double check the remote possibility of a loosened connector. In any event methinks it's a toasted woofer :(

Yea, Paul. I'm just as sad as you're at the moment. :( All to blame myself. I'm going to pull out the woofer to check it by my own eyes, and report back.

[PaulB]

Yea, Paul. I'm just as sad as you're at the moment. :( All to blame myself. I'm going to pull out the woofer to check it by my own eyes, and report back.

There won't be anything visible... If the other fella is going to bring an ohmmeter to verify, that will give you your final answer. There may be someone out there that can rewind a voice coil, you guys would know better than I. I've successfully rewound solenoids, same principal but not fun ;)

[pyonc]

There won't be anything visible... If the other fella is going to bring an ohmmeter to verify, that will give you your final answer. There may be someone out there that can rewind a voice coil, you guys would know better than I. I've successfully rewound solenoids, same principal but not fun ;)

Thanks, Paul.
Please take a look at the pics of the troubled woofer.
To my eyes, I don't see anything wrong on the surface ...
The burnt voice coils are inside, right?

[PaulB]

Thanks, Paul.
Please take a look at the pics of the troubled woofer.
To my eyes, I don't see anything wrong on the surface ...
The burnt voice coils are inside, right?

Correct, the photos tell you nothing...

[JeffW]

So what amp did you have hooked to the woofer?

[pyonc]

So what amp did you have hooked to the woofer?

Thanks for asking, JeffW. It's Crown DC300A, which I've used for bass in the bi-amp mode.
And the Crown x-over is VFX-2 (attaced pic). When I hooked them up, I turned off the Hi Pass Hz off, only with the Low Pass Hz on, with x-over at x10, and 3.5 initially.
Do you have any clue if this amp might be the cause, along with the x-over?

[JeffW]

I guess it could be either. If, for some reason, the X-over is passing a DC voltage to the amp, the Crown Amp will amplify that DC signal. On the other hand, the amp could have a DC voltage on its own. Again, a volt-ohm meter is priceless when using these things.

When Mark comes over with the multimeter, turn the gain knobs on the front of the amp all the way down. Disconnect any speaker leads and the x-over. Power up the amp with no input signal. Put the volt meter on "DC Volts" and connect it to the speaker terminals, one side at a time. It should read a few millivolts, hopefully less than 10~15mv.

If it passes that, go to the next step. If it fails, the amp probably needs service. I wouldn't want to see more than 25mV, but you can download the DC300A Service Manual Here (http://www.jblpro.com/pub/obsolete/2240.pdf)

If it passed, then with the volt meter leads still attached, increase the gain knob and see what the amp does. It might go up a little, but should still be in the millivolt DC range.

Next hook the X-over up, turn it on, and see if that makes the DC at the speaker terminals increase. Start with low gain on the amp and go up.

What you want in all cases is for the DC voltage on the speaker terminals to remain very low. If you get more than maybe .1 volts with the gain all the way up, I'd say there is a problem in the x-over or amp.

Your speaker is likely fried. It looks like JBL kits are still available.

[pyonc]

I guess it could be either. If, for some reason, the X-over is passing a DC voltage to the amp, the Crown Amp will amplify that DC signal. On the other hand, the amp could have a DC voltage on its own. Again, a volt-ohm meter is priceless when using these things.

When Mark comes over with the multimeter, turn the gain knobs on the front of the amp all the way down. Disconnect any speaker leads and the x-over. Power up the amp with no input signal. Put the volt meter on "DC Volts" and connect it to the speaker terminals, one side at a time. It should read a few millivolts, hopefully less than 10~15mv.

If it passes that, go to the next step. If it fails, the amp probably needs service. I wouldn't want to see more than 25mV, but you can download the DC300A Service Manual Here (http://www.jblpro.com/pub/obsolete/2240.pdf)

If it passed, then with the volt meter leads still attached, increase the gain knob and see what the amp does. It might go up a little, but should still be in the millivolt DC range.

Next hook the X-over up, turn it on, and see if that makes the DC at the speaker terminals increase. Start with low gain on the amp and go up.

What you want in all cases is for the DC voltage on the speaker terminals to remain very low. If you get more than maybe .1 volts with the gain all the way up, I'd say there is a problem in the x-over or amp.

Your speaker is likely fried. It looks like JBL kits are still available.

Thanks much for your kind explanation. I think I've paid a big price for trying this vintage X-over that I'm not so familiar with. I've had no issue with this Crown amp when I used it with JBL M552 or Ashly XR1001.:(

[JeffW]

If you're comfortable with the amp, then just check the DC level on the output of the X-over first. I would expect it to be very low, but one of the features of some of the Crown Amps (and I think the DC300A was one of them) was the ability to amplify DC voltages. This is why they found service in industrial applications such as motor drives. If the x-over has introduced a DC voltage to the input of the amp, then the amp will faithfully amplify that voltage. And speaker voice coils absolutely hate any significant DC voltage.

[John]

Hi, all,

Please give me your diagnosis and solution. And this is what happened:

I was trying to test vintage Crown VFX-2 crossover for 4343 this afternoon.
I hooked all the input and interconnect cables, only turning on the loss pass Xover switch, with the high-pass swtich off. When I did so, I heard some sort of strange
audible noise coming from the woofer (2231A) of the right speaker initially, and it disappeared. I didn't hear that from the left woofer.
When I did it the second time, I heard the same. Now the problem was since that happened, I could not hear any bass from that right woofer. What's wrong here? Any way to fix it by myself? Please help me out!!! At this point I just regret toying with this old Crown X-over, not knowing fully about its function...:banghead:

When you say strange noise, was it more like a huge thump and then silence? Or did it sound like 60 cycle hum, kind of loud and then nothing? Does the cone have movement with no scraping?:(

[HCSGuy]

Have you tested the woofer now that it is out of the enclosure? Battery test may help now that the switch is out of the way. If you smell the woofer behind the cone, does it stink? I used to work at Circuit City and we would take unsellable open box speakers over to the car stereo room and hook to the demo board's 12V power supply to render them truly unsellable. It was always accompanied by that pungent "Burnt electronics" smell - you know the one?

[pyonc]

When you say strange noise, was it more like a huge thump and then silence? Or did it sound like 60 cycle hum, kind of loud and then nothing? Does the cone have movement with no scraping?:(

Thanks. It sounded more like the latter, but with that peculiar sound of something burning, then fizzling out, which was audible to me. When I heard it, I turned off the Loss Pass switch. When I turned it on, then I heard the same sound, and no more since then.

[pyonc]

Have you tested the woofer now that it is out of the enclosure? Battery test may help now that the switch is out of the way. If you smell the woofer behind the cone, does it stink? I used to work at Circuit City and we would take unsellable open box speakers over to the car stereo room and hook to the demo board's 12V power supply to render them truly unsellable. It was always accompanied by that pungent "Burnt electronics" smell - you know the one?

Yea, I took it out, and did the battery test. No movement of the cone either in or out, just like it used to. Actually I failed to smell the woofer even after all this happened yesterday afternoon, as I was not sure of the cause. A moment ago, I tried to smell the woofer behind the cond, and smelt some slight stink. The definitive conclusion among the forum members here is its voice coil was burnt out...:(

[Eaulive]

The definitive conclusion among the forum members here is its voice coil was burnt out...:(

I hate to say it but I agree :(

[opimax]

put the ohm meter across contacts, read 5.7 os something, kind of surprised. Pushed on woofer to see if I could hear a scraping noise, WOULD NOT MOVE!:blink: it does move in and out with much force and major scraping noises.

Is there a forum memeber that is a professional within the DC area that could be driven to? Oldmics is in Baltimore, any others? Philly or even NY, as far south as Carolina? I have such poor luck shipping anything these days I would avoid shipping more than choose my repair center by reputation.

Is it surprising that prices for recones vary from say 440 to over 700 for the same speakers? Both are supposed to be factory original componets?????

Mark

[JeffW]

Did you happen to check his amp and crossover for DC while you had the meter there? It'd be a shame to get the speaker reconed only to have the same thing happen again.

[opimax]

He sent the Xover back already and didn't test amp. The amp was checked out /sold by company w/repair staff and used since the "noise".

Xover strongly suspected!

Mark

[Eaulive]

put the ohm meter across contacts, read 5.7 os something, kind of surprised. Pushed on woofer to see if I could hear a scraping noise, WOULD NOT MOVE!:blink: it does move in and out with much force and major scraping noises.

Is there a forum memeber that is a professional within the DC area that could be driven to? Oldmics is in Baltimore, any others? Philly or even NY, as far south as Carolina? I have such poor luck shipping anything these days I would avoid shipping more than choose my repair center by reputation.

Is it surprising that prices for recones vary from say 440 to over 700 for the same speakers? Both are supposed to be factory original componets?????

Mark

Dayum! Voice coil heated up enough to burst the former but didn't open...
Either way you'll need a recone.

[hjames]

Dayum! Voice coil heated up enough to burst the former but didn't open...
Either way you'll need a recone.

I thought what happens in this kind of scenario is when the voice coil heats up
the varnish that holds it in place bubbles up and binds it into the gap ...

'course it still only fixable with a recone, like you said ...

[Eaulive]

I thought what happens in this kind of scenario is when the voice coil heats up
the varnish that holds it in place bubbles up and binds it into the gap ...

Yes, and also expands inwards and pushes the former which scrapes the pole piece. basically it's bad :crying:

[opimax]

seems like what Heather said and it was BAD!

Mark

[hjames]

seems like what Heather said and it was BAD!

Mark
I think a woofer in one of our L60T speakers was like that - but it was Frozen SOLID!

[pyonc]

Thanks so much for your invaluable insight and feedback,

especially to Mark who drove all the way to my house to find out the cause.:applaud:

My conclusion is to have the troubled woofer reconed, along with the other good one

for the best performance, and I'm going to do so.

I sent back the Crown X-over to the ebay seller who wrongly described its condition.

Though it's painful to know my ignorance and overzeal ruined one of the woofers,

I've learnt a good lesson from this incident on my journey to this tricky audio world:

Never try or experiment any equip, vintage stuff in particular, like the decades-old Crown X-over, unless you're fully confident.