brightpav
Member
I wonder if the factory Music Hall Tracker cartridge would be any better? I still have that it just needs a new stylus.
crazy speaker pulsating with turntable
I wonder if the factory Music Hall Tracker cartridge would be any better? I still have that it just needs a new stylus.
brightpav
Member
Thanks for this. I did try that. In fact the video was taken with no dust cover. Unfortunately that doesn’t seem to be the culprit.
brightpav
Member
I meant there was no record playing i.e. no music playing. In the video the needle is on a record but not spinning. But yes, it is also a silent room.
brightpav
Member
Not sure haven’t tried that since it’s such a pain in the ass to disconnect the leads from the cartridge. The tone arm/needle does need to be on the record surface tho. This doesn’t happen when the tone arm is in the rest.
brightpav
Member
Was looking at these for under the speakers. Thoughts?
https://herbiesaudiolab.com/collect...oducts/herbies-fat-dot?variant=12645162352695
https://herbiesaudiolab.com/collect...oducts/herbies-fat-dot?variant=12645162352695
The RIAA equalisation that is required to play back vinyl is a big factor is this. Basically, the eq cuts treble and boosts bass - and it boosts bass a lot, by about 20dB compared to the midrange. The compliance of the stylus (how springy it is) and the effective mass of the tonearm form a resonant system with the resonant frequency somewhere between about 4Hz and 18Hz, ie at a subsonic frequency. The cartridge gets a lot of gain from the phonostage and it gets most gain at low frequencies, just where the arm/cartridge resonance lies, unless a subsonic filter is fitted. It used to be very common, even on cheap'n'cheerful turntables, that the platter was on some kind of suspension to isolate the platter from external and motor vibrations but unfortunately suspension systems are less common now (probably because they cost more to manufacture). The turntable you have is typical of many modern turntables in that it has no suspension other than a bit of squidginess in the feet. The upshot is that the platter is sensitive to vibration and feedback can occur.
Good isolation requires some kind of compliant/springy suspension such as this:
https://audiokarma.org/forums/index.php?threads/anti-vibration-stand.867155/
I doubt very much that they would be very effective but you could try them if you want to risk the relatively modest cost.
With non-suspended turntables such as the one the OP has it is almost inevitable that external vibrations will reach the platter - what's to stop them? Ok, the feet provide some isolation, but not very much.
Good isolation requires some kind of compliant/springy suspension such as this:
https://audiokarma.org/forums/index.php?threads/anti-vibration-stand.867155/
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PastorTube
Well-Known Member
Here Is a thought. Could there be an issue with the arm? Could any set screws or gimbles or even the lever to lower the arm be loose or shudder in such a way so that when you place the arm down on a non rotating lp there is some movement in the arm that is transfered to the cart and then to the speakers and thus creating the feedback loop? Move the arm around and watch your speakers but don’t hole the arm in such a way as to dampen and noise. Is the cart secure to the head shell? Is the headshell secure to the arm? And is your VTF set correctly?
timmy.timmy
Well-Known Member
My lead also indicates some platter (alloy) vibration/resonance transmission to the cartridge. This requires some isolation/dampening under the turntable feet and/or plinth. This turntable effective mass is not the highest I believe (higher = better) and so a "spring" solution is not so good IMHO.
The turntable requires a maximum of inertia for the cartridge to perform as it should. So I'd rather have a heavy and sturdy support even if one uses some sorbothane discs under the turntable's feet to couple and dampen the support and the turntable . Caution with the calculation in calibration there.
And why not dampen the platter from the cartridge pick-up with extra and/or thicker mats ? As for under the speakers, it's true that a little damping is always welcome. Especially if the support is not of the sturdiest kind. Here I have taken some spare dense thick "industrial" carpet I had and cut it to size.
There's always movement in the arm to allow the stylus to track the groove, and there's always compliance in the stylus so there's always a resonant system in operation. There doesn't need to be anything loose to cause the problem the OP has.
A spring solution is always a good idea, which is why it is employed on the most expensive turntables. The key to success is getting the resonant frequency low and avoiding any tendency to wobble from side to side, which is why hanging from springs rather than sitting on springs is the best solution.
ETI_5000
Super Member
Try using some thick foam (mattress or upholstery foam is good) on your shelving, underneath a bit of turntable-sized wood or stone (large paving stones are good), with the turntable sitting on top. A piece of cloth can be used to hide unsightly bits of stone or unveneered wood and unfinished foam! That should reduce the vibration enough that you don’t have the problem, and be relatively low cost. Many stores which sell foam (mattress manufacturer and supplies seller, upholstery supplies, and rubber and pool supplies are three in my own city – there may be more) will cut it to size for you, if you tell them how large you want the piece.
I’ve used the same solution for decades with many different designs of turntable, and never had a problem with acoustic feedback, even with subwoofers or large floor-standing tower speakers right next to the audio rack the turntable was on.
I’ve used the same solution for decades with many different designs of turntable, and never had a problem with acoustic feedback, even with subwoofers or large floor-standing tower speakers right next to the audio rack the turntable was on.
I'm confused. If there is no sound in the room to cause externally-sourced vibration, how will isolating the turntable help?
Maybe I've missed something in the thread, but isn't it likely that the vibration coming from the turntable itself?
Is it powered on in the situation in which the stylus is sitting on the idle platter?
I'm not suggesting that isolation is not a good thing - it definitely is. I just don't see what the table is being isolated from in the case of no sound from the speakers (and assuming no other source of vibration in the room, such as an aquarium pump, fan, etc)
Maybe I've missed something in the thread, but isn't it likely that the vibration coming from the turntable itself?
Is it powered on in the situation in which the stylus is sitting on the idle platter?
I'm not suggesting that isolation is not a good thing - it definitely is. I just don't see what the table is being isolated from in the case of no sound from the speakers (and assuming no other source of vibration in the room, such as an aquarium pump, fan, etc)
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The issue is subsonic resonance. Any movement in the structure of the building due to traffic outside, or a door slamming, or footsteps in the room, would cause enough subsonic vibration to set the system off. There doesn't need to be any audible sound to cause the problem.
And once it starts it's not going to stop easily. After the door slams, for example, you might think the feedback would also stop on its own but it might not.
Uhhhh, yeah...I understand the notion of subsonic vibration. And I understand the notion of a self-perpetuating feedback loop. The OP made no mention of other vibration sources....audible or not.
I would still like to know if the table is powered on when this happens.
If not, then I agree there is some external source initiating the feedback cycle.
I see that there are smartphone apps for identifying infrasound sources, but I have no idea of their effectiveness.
I would still like to know if the table is powered on when this happens.
If not, then I agree there is some external source initiating the feedback cycle.
I see that there are smartphone apps for identifying infrasound sources, but I have no idea of their effectiveness.
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ETI_5000
Super Member
What starts the vibration off is anyone’s guess – possibly the arm/cartridge resonant frequency being stimulated by some external vibration (footsteps, traffic, trains, washing machines etc), or maybe even the click when the stylus is dropped onto the record. But isolating the turntable should cure it. I've never seen stationary (non-rotating) turntables vibrating though, so I wouldn't think that's the source.
It doesn’t have to be powered on for a feedback loop to exist (since the stylus is sitting on the record), although normally it’s the recorded sound from a record which would start it off. We can only guess that it would be much worse when a record’s playing, which might cause howling. It’s almost certainly feedback, and that’s why it starts off low and gets worse.
I did not intend to suggest that the table must be powered on for the feedback to propagate.
I did not notice the noise getting louder/worse....but my hearing is not what it once was.
I have seen/heard a turntable with a vibrating, non-turning motor. An AR XA to be precise.
I did not notice the noise getting louder/worse....but my hearing is not what it once was.
I have seen/heard a turntable with a vibrating, non-turning motor. An AR XA to be precise.
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timmy.timmy
Well-Known Member
You mean like the Thorens suspended sub-chassis ? OK, but this is in the turntable plinth. Here we are talking for the turntable feet.
PastorTube
Well-Known Member
To clarify: of course there will be movement in the arm. But the movement (in a normal operating arm) should be smooth, but if the arm is not set properly there could be slight movements that create low Freq vibrations. Think of a cars shocks and springs. If they are bad the wheels won’t “track” the road and you can see them bouncing. That’s what I was thinking about.
Yes, like a Thorens suspended sub-chassis. In that type of design the suspension will isolate the platter from both external vibrations and from motor noise. A similar thing can be done to suspend an entire turntable like the one the OP has, but it would only isolate the platter from external vibrations, not motor noise.