Hey guys, the sub in my Carver Knight Shadow is making a rattling sound on some frequencies at louder volumes. It even rattles when the sub is being played out of the box. I find no breaks in the cone, spider or cap seal, to my eye. When i push down on the sub, the DC resistance goes to 0. Pushing up it gets a variable reading as I would expect. Is this a sign of a defective driver? The rattle sounds like something is being hit against the cone, getting louder as the volume increases. I would like to inspect inside the dust cap but have no idea how to get the cap off. I encourage your thoughts for remedy.
The driver generates voltage when pushed, which can make the meter read "0", though if held in any position, it should return to it's DCR.
It's possible a bit of glue or debris is making the noise, if that's the problem you should be able to hear it if you shake the driver cone down, up and down.
The dustcap can be removed using a sharp, thin knife blade:
The tinsel leads could also be intermittent at high excursion. You could try wiggling them while reading resistance of the voice coil, though if they're woven into the spider that might not show you everything that's going on.
I did shake the driver and heard nothing. The tinsel leads are still securely glued to the cone/spider junction. I will open up the dust cap and post back. Thanks for the troubleshooting tips.
The tinsel leads are glued down pretty well and run across the spider pretty neatly.
The cone rattles with the cap off! The glue holding it to coil is heavy duty and isn’t compromised. Anything unusual?
Aside from that dent at the top of the coil in the last pict.
No resistance or friction pushing cone in and out. Other than this rattle it operates fine.
Maybe Ill try putting a lead weight and stick it with bubblegun all around on the cone 😂
No resistance or friction pushing cone in and out. Other than this rattle it operates fine.
Maybe Ill try putting a lead weight and stick it with bubblegun all around on the cone 😂
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So are you hearing a rattle when you shake the speaker now or are you describing something else?
The VC former is heavily damaged (did that happen when you cut off the dust cap?) and it's definitely off-center. The distance of the VC former to the pole core is very close on the 12-2 o'clock range and very far away (last pic), same can be seen in all other pics too. The rattling is likely because the membrane makes a tumbling movement and the VC former hits the pole core or front pole plate. Did you drop the subwoofer? The pole core might have moved or the whole motor moved. Or the basket is bent. That would more likely some kind of a scratching noise unless the VC is hitting something. Does the driver have any vents below the spider? If it does, there's maybe some debris in the air volume in the magnet structure and is moved around with high excursions.
Is the protection screen/grid in the pole core bore loose? Anything in the pole core bore?
Three's no recone-kit for the subwoofer. You could theoretically remove the spider, surround, fix the VC former, replace the foam surround (can't be removed without damaging it, what dissolves the glue also destroys the foam) and re-assemble it again, carefully re-center it. Well, if the magnet hasn't moved or the pole core. Low chance of success though if you haven't done it yet.
Is the protection screen/grid in the pole core bore loose? Anything in the pole core bore?
Three's no recone-kit for the subwoofer. You could theoretically remove the spider, surround, fix the VC former, replace the foam surround (can't be removed without damaging it, what dissolves the glue also destroys the foam) and re-assemble it again, carefully re-center it. Well, if the magnet hasn't moved or the pole core. Low chance of success though if you haven't done it yet.
Blu-Tack actually is sometimes used to add mass temporarily to speaker cones. If you have something going on with the former or its interface to the cone it's not a crazy idea to do something along these lines to try to narrow down what's going on.
That doesnt sound promising. I'm not the guy for that job although a heat gun and removal of cap easy. The very top of the former is bent up, but when i run my finger just below on the inside, its smooth & uniform as can be. The rattle must be coming from behind the spider.
Any possibilities of using an alternative sub driver? I might have an 8 ohm Pyle laying around, or maybe i will write to Bob Carver.
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You can replace the driver, please measure the internal volume (or external dimensions and the wall thickness), the length of the port might not fit but that can be changed.
Which Pyle sub driver do you have?
Which Pyle sub driver do you have?
Maybe the basket has come loose from the top plate? (it is usually screwed and/or glued to the top plate) to test for that, place the speaker magnet down on firm base and while playing test tones, push down around the top of the basket to see if it stops the rattle.
In rare cases, the demodulation ring (if it has one) on the pole piece can come loose, in which case its an expensive job to rectify.
In rare cases, the demodulation ring (if it has one) on the pole piece can come loose, in which case its an expensive job to rectify.
That doesn't explain the damage to the VC. And you can't access the screws unless you remove the cone and the spider, which also includes removing the surround, Since it's a foam surround, you cannot dissolve the glue since that also destroys the foam surround. So no, that's not an option.
It doesn't have one. It even has a plastic ring over the pole core, which does nothing except lowering the BL (=motor). Despite having the Carver name on it, that's the cheapest way to build a subwoofer driver. I'm sorry but that's the cheapest crap on the market.
I wasn't trying to explain the damage to the voice coil. I was offering a possible cause to what might be causing the "rattle"
And sometimes it is possible to unglue the surround and tighten up basket screws without having to remove the cone, vc and surround.
Even if its a "Crap" driver, the op posted here to ask for any possible causes as to what might be causing the problem.
Cheers,
Arthur
Ofc, that's a good suggestion but unfortunately you can't remove the foam surround without damaging it.
I'm not judging about the driver quality but some construction details just scream 'I'm cheap'. Nonetheless, I try to help but it seems to replace the driver is the only option.
I'm not judging about the driver quality but some construction details just scream 'I'm cheap'. Nonetheless, I try to help but it seems to replace the driver is the only option.