Hi there, I own old JBL LSR25P in great condition. Its amplifiers are made using LM3886 and the enclosures are from solid metal, so the sound is rather amazing.
One thing that really bugs me is that there must be something wrong with the electronic - I recorded the sound in attachment playing solid 50Hz from the speaker recording with my measurement mic and then high pass above 50Hz so only the parasite sound stays in the recording without the 50Hz...
I am absolutely positive it comes from the electronics, because one speaker does it on 50-60Hz and one 60-70Hz and when i switch the drivers between them, it stays the same - th one that did it on 50-60Hz still does it on 50-60Hz even with different driver...
My question is - is there something I can try to change in electronics to make it go away, can this noise be comming from something specific or is it hard to tell? I am no electronic engineer, I know my basics and I can build amps frmo kits but when ti comes to debugging the amp problems I am lost.
Its really very sad - those speakers are so great, yet this makes them hard to listen to electronic music or any bass intesive music, because the noise can make itself pretty pronounce there... apart frmo that they sound great on any other frequencies, its only the very low bass producing this...
here is the service manual with complete schematic if that can help to anyone trying to help http://www.jblproservice.com/pdf/LSR Series/LSR25P.pdf
One thing that really bugs me is that there must be something wrong with the electronic - I recorded the sound in attachment playing solid 50Hz from the speaker recording with my measurement mic and then high pass above 50Hz so only the parasite sound stays in the recording without the 50Hz...
I am absolutely positive it comes from the electronics, because one speaker does it on 50-60Hz and one 60-70Hz and when i switch the drivers between them, it stays the same - th one that did it on 50-60Hz still does it on 50-60Hz even with different driver...
My question is - is there something I can try to change in electronics to make it go away, can this noise be comming from something specific or is it hard to tell? I am no electronic engineer, I know my basics and I can build amps frmo kits but when ti comes to debugging the amp problems I am lost.
Its really very sad - those speakers are so great, yet this makes them hard to listen to electronic music or any bass intesive music, because the noise can make itself pretty pronounce there... apart frmo that they sound great on any other frequencies, its only the very low bass producing this...
here is the service manual with complete schematic if that can help to anyone trying to help http://www.jblproservice.com/pdf/LSR Series/LSR25P.pdf
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Very much doubt it´s an Electronic problem and much suspect it´s an enclosure, "mechanical" one.
A useful tool to find squeals , whistles, etc. is a cheap medical type stethoscope with the membrane head removed, you then use the free rubber pipe end to find the culprit.
A useful tool to find squeals , whistles, etc. is a cheap medical type stethoscope with the membrane head removed, you then use the free rubber pipe end to find the culprit.
Hi thanks for answering, it is not mechanical, I really took the driver out the enclosure, took out the electronic and recorded the sound - it's not even in the enclosure on the recording 🙂 the sounds comes from driver, yes, but the driver is completely ok, it does not do this on another amp... it comes from the amp... so...
I have that very cheap osciloscope on my hand, maybe i should try that right? should be able to se what signal is coming to the driver
I have that very cheap osciloscope on my hand, maybe i should try that right? should be able to se what signal is coming to the driver