Back to the use of the multimeter:
Notice the '0ΩADJ' wheel on the left hand side of the meter. You use this wheel to set the pointer to 0Ω on the scale while shorting the free ends of your test probes together.
Only then can you get an accurate reading of the woofer resistance. Since the reading must be multiplied by 10, a 5Ω resistance will read as only 0.5Ω on the scale.
Notice the '0ΩADJ' wheel on the left hand side of the meter. You use this wheel to set the pointer to 0Ω on the scale while shorting the free ends of your test probes together.
Only then can you get an accurate reading of the woofer resistance. Since the reading must be multiplied by 10, a 5Ω resistance will read as only 0.5Ω on the scale.
Thanks - this is a critical thing I did not know - I had done the wheel on the side thing with sticking the probes together and setting it to zero, but didn't know it was at 0.5 to be the reading I needed. I am going to double check it.
And now I am thinking I may just be crazy/incompetent, as I grabbed a new amp and hooked it up and now after switching the woofers in the cabinets it seems like everything is getting bass. Is it possible an amp would not send out just the low end to one channel? And again, thanks for all this help. I'm so bad at this stuff but like learning so patient advice is much appreciated.
In your first post you said you'd already tried switching amps, but to no avail. So exactly how many amps have you tried? It is unlikely that more than one amp would be faulty in the way you suggest. If you now connect the working speakers to the original amp you will be able to confirm if it was indeed faulty.
It's possible that you've made a bad connection good when switching the woofers round.
It's also possible that there is an intermittent fault in the dodgy woofer. Inspect the tinsel leads which go from the woofer terminals to its cone (and hence to the voice coil) and make sure the solder connections are secure.
Will check for any updates after my beauty sleep!
It's possible that you've made a bad connection good when switching the woofers round.
It's also possible that there is an intermittent fault in the dodgy woofer. Inspect the tinsel leads which go from the woofer terminals to its cone (and hence to the voice coil) and make sure the solder connections are secure.
Will check for any updates after my beauty sleep!
The new battery did the trick with the multimeter- I had tested the battery in there and it had said it was fine, but i guess it wasn't fine enough. I seemed to get a reading of around 0.5 for each woofer. I wouldn't recommend the multimeter to anyone - hard to use and get an accurate reading, but also only like $12 so I guess you get what you pay for.
I thought I had it figured out that everything worked, but now I am back to where I started - I am going to get some other ears in here this weekend and see what they think to make sure I'm not losing my mind.
I've used two amps in testing this, and with one it is definite it doesn't deliver bass to the right channel, but that amp may also be having issues. With the other amp it's harder to try to switch from each speaker to compare, but it seems like the bass in that same right channel is diminished. But again, I am going to get some critical ears in here Saturday to help figure it out.
The other weird thing is that on the driver that is giving me issues I noticed what appears to be a dried looking liquid stain sort of thing on the part that is magnetized. I took a picture but can't figure out how to post it here from my computer - all the options in posting seemed to require it to be hosted somewhere but I may just be missing something. I don't know if that is relevant or indicative of anything, but offer it up in case it is.
I thought I had it figured out that everything worked, but now I am back to where I started - I am going to get some other ears in here this weekend and see what they think to make sure I'm not losing my mind.
I've used two amps in testing this, and with one it is definite it doesn't deliver bass to the right channel, but that amp may also be having issues. With the other amp it's harder to try to switch from each speaker to compare, but it seems like the bass in that same right channel is diminished. But again, I am going to get some critical ears in here Saturday to help figure it out.
The other weird thing is that on the driver that is giving me issues I noticed what appears to be a dried looking liquid stain sort of thing on the part that is magnetized. I took a picture but can't figure out how to post it here from my computer - all the options in posting seemed to require it to be hosted somewhere but I may just be missing something. I don't know if that is relevant or indicative of anything, but offer it up in case it is.
O.K. At least we have established that the suspect woofer is not open circuit!
I'm not sure from your description what is going on with the amplifiers. You must have other speakers that will confirm that both your amplifiers are working correctly.
Once you are sure you are using a properly working amplifier, the next step would be to try the other trouble shooting measures that have been suggested.
Hopefully, recruiting a fresh pair of ears at the weekend will help make sense of all this.
Regarding posting pictures, it is simplest to post them as attachments and here's how:
I'm not sure from your description what is going on with the amplifiers. You must have other speakers that will confirm that both your amplifiers are working correctly.
Once you are sure you are using a properly working amplifier, the next step would be to try the other trouble shooting measures that have been suggested.
Hopefully, recruiting a fresh pair of ears at the weekend will help make sense of all this.
Regarding posting pictures, it is simplest to post them as attachments and here's how:
- Click on the 'Go Advanced' button under the 'Quick Reply' box.
- Click on the paperclip symbol in the menu at the top of the new 'Reply to Thread' box
- The 'Manage Attachments' box will open and from here you can browse your computer for the picture you wish to attach. When found, you can highlight the picture then upload it to your post. Your picture will be attached to your post as a thumbnail.
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May just be excess adhesive, but unlikely to indicate a fault in the woofer. I'd be more concerned with checking the tinsel leads as I have suggested.
Often, the crossover is mounted on the rear of the speaker input terminal plate seen in the attached photo.
Unscrew the plate and, if the crossover is revealed, take photos of it from all angles. Some photos showing the condition of the driver surrounds would also be welcome.
Often, the crossover is mounted on the rear of the speaker input terminal plate seen in the attached photo.
Unscrew the plate and, if the crossover is revealed, take photos of it from all angles. Some photos showing the condition of the driver surrounds would also be welcome.
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Well "good" news and I fear mostly bad news. My brother-in-law helped me figure out the problem. It is one bass driver. Everything tests fine on the multimeter, but the woofer on one is frozen in place. We used an online tone generator and then chromecasted it to the stereo to be able to really isolate it.
He figured out that one cone is just frozen in place. Is there anything I can do about this?
Sounds like the woofer has been overdriven, the voice coil has overheated and is now stuck in the magnetic gap. The stain on the magnet could be due to melted enamel/adhesive leaking out.
The woofer is in need of professional repair and you could get in touch with 'The Speaker Exchange' in Tampa.
The cost of repairing the woofer plus the cost of replacing the surrounds of the other drivers will have to be balanced against what the speakers are worth to you. A new pair of speakers may be more cost effective.
Good luck and keep us posted!
The woofer is in need of professional repair and you could get in touch with 'The Speaker Exchange' in Tampa.
The cost of repairing the woofer plus the cost of replacing the surrounds of the other drivers will have to be balanced against what the speakers are worth to you. A new pair of speakers may be more cost effective.
Good luck and keep us posted!
Another possibility is that the magnet could have gone off-center, which can happen when the the speaker gets so hot that the adhesive holding the magnet in place starts to soften. The voice coil may be stuck because it has expanded with the heat, or because the magnet has shifted, or both!
Since the voice coil still has continuity and the woofer is producing a small amount of sound, an off-center magnet is a strong possibility.
Professional repair or a replacement woofer are the options open to you as expertise is required in magnet realignment and cone/voice coil replacement.
Another thing to consider is the condition of the other woofer as it too may have been overloaded, if not quite as badly as this one. In addition, re-coning is usually best done in pairs to keep the the two speaker systems in balance.
Since the voice coil still has continuity and the woofer is producing a small amount of sound, an off-center magnet is a strong possibility.
Professional repair or a replacement woofer are the options open to you as expertise is required in magnet realignment and cone/voice coil replacement.
Another thing to consider is the condition of the other woofer as it too may have been overloaded, if not quite as badly as this one. In addition, re-coning is usually best done in pairs to keep the the two speaker systems in balance.
Thanks! I've emailed speaker exchange as well as a local repair place. I'll let you know how this turns out. At the very least I've learned quite a bit.
So it seems like it won't be worth it to ship to a specialized repair place as there's no guarantee it will work and the quote is as much as $220 plus shipping. Everyone in my area said they couldn't fix it.
Can I replace the woofers with some other woofers? If so, how do I figure out what would work with it?
Let's try some more troubleshooting!
Does the woofer cone move in and out when you press down gently and symmetrically on it with your thumbs?
Post a photo of the rear of the magnet assembly. I'm looking for screws. Sometimes its possible to re-centre the magnet by clouting it with a rubber mallet. You've nothing to lose!
Regarding possible replacement, measure the diameter of the woofer opening in the cabinet. Measure also the width of the mounting space so that we can choose a woofer whose outside diameter will fit into the space available. A photogaph of the opening would help.
Does the woofer cone move in and out when you press down gently and symmetrically on it with your thumbs?
Post a photo of the rear of the magnet assembly. I'm looking for screws. Sometimes its possible to re-centre the magnet by clouting it with a rubber mallet. You've nothing to lose!
Regarding possible replacement, measure the diameter of the woofer opening in the cabinet. Measure also the width of the mounting space so that we can choose a woofer whose outside diameter will fit into the space available. A photogaph of the opening would help.
I can't find specifications for the CM4 woofer, so finding a replacement having close electrical and mechanical parameters is a big problem.
All we have to go on are the specifications of the CM4 speaker system as a whole. From those I conclude that we are looking for 165mm diameter, 8Ω impedance, 90dB sensitivity, minimum 50W power handling and resonant frequency around 40Hz - all a bit of a hit or a miss really!
Provided its dimensions suit, here is a very low cost substitute which you could use simply to test the feasibility of replacement before committing yourself to more expensive woofers.
Silver Flute W17RC38-08 6-1/2" Wool Cone
Have you a speaker store of preference so that we can narrow down the possibilities?
IMHO I find that suggesting a replacement for a woofer without knowing T/S parameters and FR + impedance (not the nominal one, but the function impedance vs frequency) is bad advice.
Throwing in a woofer with only similar outside dimensions as the original, very often results in mismatched sensitivity, bad overlap in the crossover region and bad tuned bass.
OP's best deal would be to find an original woofer, either NOS or used.
That answer is crucial in understanding if something can be done. As I see it, if the DC resistance of this woofer is not zero, and is equal to the other within tolerances, the VC is not shorted. If the VC is stuck in the gap, but can move at least a bit, you can try to have it out. Since you need to change the surrounds anyway, you can remove the surrounds and see if afterward the VC moves freely.
Ralf
Hi Ralf, and welcome to the party!
I agree completely, and that is why my advice from the outset has been to have the woofer professionally repaired. Unfortunately, Narkopop has rejected this advice on grounds of cost.
So, we are back to troubleshooting and the possibility of DIY repair. If Narkopop reports whether the cone can move freely in and out, we can proceed from there.
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I was busy with work and kids but just pulled out the woofer. the cone does not move in and out freely when pressed.
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Either the voice coil has overheated and has swollen up, or the rear plate of the magnet assembly has slipped, moving the centre polepiece - either would mean that the voice coil would get stuck in the gap between centre polepiece and front plate.
Check the spider for any signs of burning due to an overheated voice coil. If visible you will almost certainly require re-voice coiling.
If there's no sign of burning, then attempting to move the rear plate with a sideways blow from a rubber mallet might just re-align the assembly.
Beyond that, you can start to pull the front surround and rear spider off the basket just to get a good look at the damage for educational purposes!
Check the spider for any signs of burning due to an overheated voice coil. If visible you will almost certainly require re-voice coiling.
If there's no sign of burning, then attempting to move the rear plate with a sideways blow from a rubber mallet might just re-align the assembly.
Beyond that, you can start to pull the front surround and rear spider off the basket just to get a good look at the damage for educational purposes!
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