VonHess Posted October 13, 2022 Share Posted October 13, 2022 Just sort of re-inherited a pair of kg4.2s that I had given to my brother in the 90s. One of the speakers has what I would describe as a ‘knocking’ sound. It doesnt do it at lower volumes and it seems to only do it on certain bass frequencies. It gets worse as I raise the volume. I describe it as a ‘knocking to the beat of the music’. I switched the active woofers between speakers and the sound stays in the left speaker so I’m thinking it has to be in the crossover. Capacitor, possibly? 1 Quote Link to comment Share on other sites More sharing options...
billybob Posted October 13, 2022 Share Posted October 13, 2022 Yes since you didn't see anything loose while inside. Would make sure all is tight of course, not floppy to the music. Welcome @VonHess Quote Link to comment Share on other sites More sharing options...
MicroMara Posted October 13, 2022 Share Posted October 13, 2022 3 hours ago, VonHess said: Just sort of re-inherited a pair of kg4.2s that I had given to my brother in the 90s. One of the speakers has what I would describe as a ‘knocking’ sound. It doesnt do it at lower volumes and it seems to only do it on certain bass frequencies. It gets worse as I raise the volume. I describe it as a ‘knocking to the beat of the music’. I switched the active woofers between speakers and the sound stays in the left speaker so I’m thinking it has to be in the crossover. Capacitor, possibly? When bass drivers are driven at higher levels, the excursion of the diaphragm logically increases. A distinction is made between linear and maximum possible excursion. The linear excursion describes the condition with acceptable distortions. If the diaphragm is deflected further, we are in the non-linear range, i.e. the voice coil then leaves the linear range of the magnetic field. On the one hand the distortion increases, on the other hand the dynamic impedance of the driver collapses due to the missing "core effect" of the middle pole piece and the current in the coil increases significantly. The consequence of this is that the diaphragm is further and above all uncontrolled deflected and then at some point comes into the range "stop". Nowadays, however, good drivers are designed in such a way that the voice coil former can no longer strike the rear pole plate. Rather, the centering spider and the surround go to the stop, i.e. full extension. A similar noise is audible, which occurs when a sheet of paper is jerked. Not unlike a banging noise. You may need a spare woofer for the KG 4.2 https://www.ebay.com/itm/255723385831?hash=item3b8a4d33e7:g:X-8AAOSwpXtjH3s6&amdata=enc%3AAQAHAAAAoCcQspNKea2gbKun0dFaawiPwbT3Dt73qrq6ddGAY5yjLUSe1fLEWqYwMZpZofiyx5lFnnk2UuG1J4vO0%2FiCDGbcEyNKgJPQ8zofJg3Q5PjM%2BJ%2FJPnHN77kn37dUm2feaQUkejRq0irbrJRufKpYoXD4CzQAhbfzflB%2FNU9DxKIy45XXpKNbD5YeXM8mM%2Bzn8LW%2Bi6kIkBkCH8vJhBEQgsY%3D|tkp%3ABk9SR_SCzaf6YA Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted October 13, 2022 Share Posted October 13, 2022 5 hours ago, VonHess said: Just sort of re-inherited a pair of kg4.2s that I had given to my brother in the 90s. One of the speakers has what I would describe as a ‘knocking’ sound. It doesnt do it at lower volumes and it seems to only do it on certain bass frequencies. Sounds like you spun a bearing. Quote Link to comment Share on other sites More sharing options...
Peter P. Posted October 13, 2022 Share Posted October 13, 2022 You didn't switch the passive radiator, though. Swap those or remove it just for test purposes and see if it remains with the suspect speaker. I'm wondering whether it's the passive radiator although I couldn't explain what the passive radiator would be doing to cause the knocking. Pre-ignition due to bad fuel? 😁 I find it hard to believe it's the crossover. Quote Link to comment Share on other sites More sharing options...
VonHess Posted October 14, 2022 Author Share Posted October 14, 2022 15 hours ago, Peter P. said: You didn't switch the passive radiator, though. Swap those or remove it just for test purposes and see if it remains with the suspect speaker. I'm wondering whether it's the passive radiator although I couldn't explain what the passive radiator would be doing to cause the knocking. Pre-ignition due to bad fuel? 😁 I find it hard to believe it's the crossover. I did remove the passive radiator and switched the active woofers. Again the sound stayed in the same speaker and is coming from the woofer. Quote Link to comment Share on other sites More sharing options...
billybob Posted October 14, 2022 Share Posted October 14, 2022 4 hours ago, VonHess said: I did remove the passive radiator and switched the active woofers. Again the sound stayed in the same speaker and is coming from the woofer. Please to examine at your leisure the Passive Radiator and the woofer. Your tests may have eliminated those so, would consider swapping the crossover networks as a method of deduction, as you suspect same. Quote Link to comment Share on other sites More sharing options...
Peter P. Posted October 14, 2022 Share Posted October 14, 2022 6 hours ago, VonHess said: I did remove the passive radiator and switched the active woofers. Again the sound stayed in the same speaker and is coming from the woofer. Well then, it's either the crossover or the cabinet. Quote Link to comment Share on other sites More sharing options...
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