Speakers uncontrolled when playing turntable

brian220709

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Nov 20, 2022
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I have a Rega P1, Marantz PM7000N and B&W 707 S2’s.
Noticed tonight when playing vinyl that the sound wasn’t right, then noticed the bass/mid drivers were bouncing uncontrollably out/in.
Turning volume down this would stop.
Tried the same song on Spotify and sound was fine, speakers fine even at high volume.
Tried a couple of different vinyl's and the same.
So issue seems to be with the turntable.
Any ideas what would cause this?
Cartridge needing replace, downforce not correct?
Any help much appreciated.
 

Freddy58

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That’s an odd one. I’m leaning towards an issue with the cartridge or the earth connection but I don’t know. It might help others to identify the cause if you could say if this issue has arisen suddenly when previously it was ok.
 
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Cone flap due to subsonic frequencies can be caused by a number of issues and are more noticeable in speakers that are on a suspended floor, ported, and too close to the turntable.
See this thread.
https://forums.whathifi.com/threads/speaker-cones-oscillating-violently-when-playing-vinyl.62917/

If really serious you may need a subsonic filter inline.
 

Gray

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Any ideas what would cause this?
What you're (almost certainly) suffering is acoustic feedback.
The cartridge is picking up the output from the speakers.
Have you by any chance got the turntable and the speakers on the same surface?

EDIT: Al beat me to the reply in post #3.
A warped record can cause cone flap (much more noticeable without a subsonic filter) - but I'm guessing it's the same with any of your vinyl.
 
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martois

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Cone flap due to subsonic frequencies can be caused by a number of issues and are more noticeable in speakers that are on a suspended floor, ported, and too close to the turntable.
See this thread.
https://forums.whathifi.com/threads/speaker-cones-oscillating-violently-when-playing-vinyl.62917/

If really serious you may need a subsonic filter inline.
I learn a lot on this forum--Thanks!
 
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daytona600

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Rega have no isolation & sounds like acoustic feedback

1/ isolation feet like Lehmann 3S Device Feet work well
2/ Rega wall shelf , or 3rd party isolation platform
3/ Move turntable into another room or buy a good hifi rack
4/ Try a deck with isolation as standard like Project/Technics
4ll 37601068_978052434324514_5610828041493256879_n.jpg
 
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brian220709

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Nov 20, 2022
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What you're (almost certainly) suffering is acoustic feedback.
The cartridge is picking up the output from the speakers.
Have you by any chance got the turntable and the speakers on the same surface
Yes they are on the same surface
I think you'll find that's the problem.
Move one or the other to solve.
Cant move them really, no idea what to do, would isolation cure this or just reduce it?
 
Yes they are on the same surface

Cant move them really, no idea what to do, would isolation cure this or just reduce it?
Worth experimenting with household items. A small difference can be important. For example, carefully pop the speakers on a big book or a stack of magazines, or a folded towel.

Unfortunately low frequencies generated by warps or arm/cartridge resonance often aren’t filtered well in amplifiers designed mainly for digital sources. In the heyday of LPs the LF was either rolled off anyway, or a ‘rumble filter’ or similar was fitted. And acoustic feedback has always been an issue with turntables, hence the proliferation of stands and racks. Today’s fad for mid-century sideboards with turntables and speakers together has a lot to answer for! Interior designers often aren’t Hifi enthusiasts!
 

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