My friend discovered that strange noise is coming from the woofer in the bass bin. It turned out that the dust cap is damaged, collapsed. What can be the cause of the collapse of the dust cap in the woofer? Assuming that no one physically pressed it by accident. Is it possible that the pressure in the chamber caused this damage? From what I know, 3 years ago he upgrade woofers to Bob Crites. Maybe then he damaged them and he does not want to admit 🙂 This applies to the four-year Klipsch LaScala with 15" Bob Crites woofer and probably 3" dust cap. I am curious if such damage can be causing something else than physical damage such as pressure?
Are you sure that the cause of the bad noise is actually the dented dust cap? If the voicecoil gets too hot, the glue holding it to the cone can fail and the coil can launch forward into the dust cap, denting it. Once cooled, the voicecoil is usually then misaligned and causes rubbing.
Paper and fabric dust caps can also develop warps/dents if exposed to moisture - usually this does not cause an audible problem.
Paper and fabric dust caps can also develop warps/dents if exposed to moisture - usually this does not cause an audible problem.
Thank you TMM for your answer. The cause of the noise was probably a partially detached cap (I forgot to tell). I think that if a coil hit in a cap, the damage would not be from the outside. Also the deflection of the diaphragm (X-max) of this woofer is too small due to the rigid suspension. In this case it looks like the cap has been sucked in. The amplifiers that he is using with such an effective speaker are not reaching more than 1 Watt, and I think the coil could not get hot enough to melt the glue. Any other ideas?
There are some drivers which are known for losing their dustcap, i.e. the ciare 12.00sw, especally in enclosures with high pressure/air load as bandpass or horn subs. That's often caused by asymmetrical load/air force. Since you've said he didn't use high power, it's still possible the pressure had effect on the dustcap, some drivers aren't suited for some enclosure types, despite having the ideal parameters for it. A lot of horns killed drivers, the cone folds or the dustcap caves in etc., same can happen at different bandpass constructions.
Aside from that, the dustcap might have been damaged without a visible sign. There are drivers which have different dustcap materials. All in all the dustcap does not change much in a subwoofer usage. I'd remove the old dustcap and simply glue on a different one or, if the driver isn't ventilated, just leave it off.
Ported enclosures can reach very wide excursions even with low power if they are forced to frequencies below the tuning. If the coil hits the back pole plate or goes into suspension progression, the dustcaps own weight might be enough to let it cave in, especally on larger or not so sturdy dustcaps.
Aside from that, the dustcap might have been damaged without a visible sign. There are drivers which have different dustcap materials. All in all the dustcap does not change much in a subwoofer usage. I'd remove the old dustcap and simply glue on a different one or, if the driver isn't ventilated, just leave it off.
Ported enclosures can reach very wide excursions even with low power if they are forced to frequencies below the tuning. If the coil hits the back pole plate or goes into suspension progression, the dustcaps own weight might be enough to let it cave in, especally on larger or not so sturdy dustcaps.
- Status
- Not open for further replies.