LP12 Bounce

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Mikeg
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LP12 Bounce

Post by Mikeg »

Hi

Is there a simple way to see if the suspension bounce on an LP12 is correct for the right reason. By that I mean it should have a piston like movement free from any pull or drag or twist. However if all springs are exerting an equal pull surely you would also get a piston like movement when tapped but it would not be for the right reason!

Mike
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Post by Charlie1 »

Hi Mike. I'm no LP12 setup expert and I hope I haven't misunderstood you, but I'll have a go. I presume the pressure across the three springs is unequal, because the weight of the sub-chassis and arm is not distributed evenly across the centre of gravity (i.e. centre point of the 3 springs). Therefore, if the spring pressure WAS equal then the weight of the arm and armboard etc would cause the whole thing to tilt over towards the arm.

AFAIK, the centre of gravity is approx 2 inches away from the spindle in a direct line with the arm base. If correctly setup, a gentle tap here should cause the bounce you referred to.
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Post by ThomasOK »

Well Mike, I think I understand your question. If each spring pulls a bit to the outside they would be equally balanced and the suspension would move up and down properly. As opposed to each spring moving up and down with no pull at all. My first answer is that it really doesn't matter as long as it bounces properly. As Charlie mentioned, since each spring has a different amount of weight on it they aren't all going to behave exactly the same anyway. There are some simple things worth doing and one I strongly recommend is making sure the nuts that adjust the springs are cut properly. If the top surface of the nut is not perfectly perpendicular to the bolt you will change the angle of the washer as you adjust the height of the spring. This caused many headaches before it was understood as you could have the suspension bouncing nicely, adjust the height just a touch and all of a sudden the bounce would be off. Turning the nut made a washer that was pointing slightly right point slightly left and now the bounce was bad. Despite Linn having gone through about 5 different nuts you still have to check each one to make sure it is cut properly. You do this by adjusting the spring height and seeing if the washer goes up and down without any wobble. Luckily each LP12 has several nuts that can be swapped in to find three good ones. I have a drawer full here so that I can get them right.

Another important thing is to make sure that the three suspension bolts are all straight and pointing straight down. I don't know of an easy way to do this without the T-Bar tool Linn make for this purpose. It has a level on it and fits over the bolt so that it can be adjusted to be correct.

There is one way to see if everything is working the way it should be but I would hesitate to call it simple - install a Keel! I have found that the Keel is very unforgiving of suspension problems. I have had cases where inserting a Keel into a turntable that was bouncing nicely caused it to hardly bounce at all! The Keel requires the bolts to all be near perfectly straight and the springs and grommets must be right too. As an example I put a Keel on our demo turntable that had been bouncing pretty well. With the Keel it didn't bounce well at all. Straightening all the suspension bolts TWICE got it to bounce reasonably well. But I didn't get a really good bounce out of it until I replaced the spring in the front and the upper grommet on the left side. Once that was done it bounced like a champ. It my experience the usual twisting around of the spring itself has little effect on the suspension with a Keel - it just wants springs that work properly. I have a drawer full of springs for this purpose as well. I have had to replace a spring or grommet (or two) on more than half of the Keels I've installed and I've had to straighten the bolts on all of them. So there is your best test - plus you get a great performance boost. :)
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Post by Charlie1 »

Cheers Thomas. I thought I was pushing it a bit by commenting on LP12 setup! I think I'll leave it to the experts in future :)
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Re: LP12 Bounce

Post by Defender »

I installed my Radikal recently and later thought I should try to optimize bouncing.
O my! Couldnt make it bounce properly. It still has a sideways bounce and sometimes the bounce shifts from the armboard to the platter and back ... if that makes sense.
Changed all the springs and grommets but coulnt get it to work properly. Used the different stiffness/softness of the springs at the right places.

What is the procedure to adjust the springs - do you start at the one close to the arm?
What indicators do you use to decide which spring needs optimization?
How long should the bounce last - 7 seconds? 12 seconds?

Some kind of advice would be really appreciated :)
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Re: LP12 Bounce

Post by dasher »

My starting point, once that I have the springs re-tensioned roughly back to where they were before strip down, is to get the arm board flush and parallel to the top-plate /plinth. I'm assuming that you haven't removed the top plate- and that the bounce was OK before surgery. I find that just twisting the springs is of no real help - you have to make the adjustment by twisting the top (large) grommet and this isn't easy. I usually find that if the top plate is orientated correctly and the springs have no twist under tension, then the bounce almost falls into place. Conversely, I find it almost impossible to start by getting the bounce right first and then trying to adjust the arm board - and, maybe wrongly but it works for me, I consider that the orientation of the arm-board is of paramount importance. The critical to set-up components of both my LP12s are less than a decade old and I know that my spring studs are perpendicular. Like Thomas, I have plenty of springs nuts and washers. I recently installed my Karousel and 'treated' the LP12 to the new springs - big mistake - the arm board just wouldn't level out- fortunately I had labelled the old ones and had taken measurements for a starting point. The old ones went back in - but I did use the new washers.

One of my LP12s can be a pig. I have very little clearance between the arm plug (Grey T Cable - Ekos 2) and the hole in the Trampolin. If the bounce wasn't pistonic then I would really struggle to keep its from fouling.

Look carefully at your top plate - generally the spring closest to the motor will affect side to side orientation and the two remaining springs impact front to back orientation (more difficult).

Hope this helps - feel free to PM if you feel that I can help further.
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Re: LP12 Bounce

Post by Defender »

hi dasher,
thank you for your comments - I haven’t moved the springs without the grommets as that makes things worse as the sharp edges of the springs might cut into the grommets. yes its difficult to grab the large grommet on top and move it - thats why some use some kind of lubricant (talkum) to make it move easier but thats the lazy ones shortcut which is not a shortcut in the long run. And thats also the reason I have sore fingers today ;)
I agree that I want the armboard parallel and level to the plinth but in my case the best bounce was achieved when it was not parallel even though it was level to the plinth.
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Re: LP12 Bounce

Post by sktn77a »

Conventional wisdom is to get the bounce right and not worry about the armboard being perfectly square in the opening(?)
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Re: LP12 Bounce

Post by kota »

dasher wrote: 2021-01-02 12:48 I find that just twisting the springs is of no real help - you have to make the adjustment by twisting the top (large) grommet and this isn't easy.
Many moons ago I was told by a very respectful Linn rep that in order to rotate the large grommets/springs easily was to apply some saliva to the large ones where they make contact with the subchassis holes, lift the bottom ones with your fingers by the washers and then rotate them until you're satisfied. The saliva will dry in a couple of hours and that's it. Works for me all the time.
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John
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Re: LP12 Bounce

Post by John »

What is the cause of the knocking sound when the suspension is tested with a test bounce with more force? Is this something one should try to eliminate if the suspension is otherwise bouncing nicely after the initial knock? Hard to fix if you don’t know where it’s coming from.
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Re: LP12 Bounce

Post by Defender »

the knocking comes from springs that „grab“ the edge of the larger/top grommet see in the picture:
A7EC7BC4-E4EE-4D75-8C66-BAFC79BCC338.jpeg
you see the mark the spring wire left in the rubber and if you carefully look at the edge of the grommet on the right side you see where the wire hit the edge

@kota: I think you have a good point as that also makes sure there is no residual oil/fats between the two surfaces
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Re: LP12 Bounce

Post by sktn77a »

Hmmm.............. not following. Every LP12 I've owned had this knocking with anything more than a very gently bounce. Can you elaborate?
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Re: LP12 Bounce

Post by lejonklou »

Defender is right, the knocking comes from the spring rubbing and catching the top grommet.

If you cut off the "neck" (upper part in the picture above), the knocking disappears completely. The only problem is that it sounds worse that way. Why that is the case I have never completely understood, you can get a really nice bounce with cut off grommets, but the LP12 will sound much less musical. Perhaps there are more small horizontal movements that aren't really visible in the bounce test (the horizontal stability is compromised). That's the most likely explanation I can think of.

The low amplitude bounce is important. The high amplitude is in my opinion not. You don't have to adjust until there is zero high amplitude knocking, it's enough that the low to mid amplitude bounce is harmonic and without overtones or knocking.
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Re: LP12 Bounce

Post by Mikeg »

Another simple reason for the knocking or rubbing sound is not cleaning new springs before use
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Re: LP12 Bounce

Post by Defender »

mmh and I thought you should not clean them
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Re: LP12 Bounce

Post by John »

Thanks for the info. I checked the seating of the grommets into the subchassis at the time and all was fine. I also removed each spring and replaced them back on and got a nice bounce without having to fiddle with them once that was done. The only thing was a knocking that occurred during a high amplitude bounce. Mid to low amplitude, no knocking.

Reading the Cymbiosis write up had me thinking that there should be zero knocking but as long as it’s not happening at mid to low amplitudes I should be fine from what I gather from Frederick’s comments.
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Re: LP12 Bounce

Post by ThomasOK »

lejonklou wrote: 2021-01-04 01:04 Defender is right, the knocking comes from the spring rubbing and catching the top grommet.

If you cut off the "neck" (upper part in the picture above), the knocking disappears completely. The only problem is that it sounds worse that way. Why that is the case I have never completely understood, you can get a really nice bounce with cut off grommets, but the LP12 will sound much less musical. Perhaps there are more small horizontal movements that aren't really visible in the bounce test (the horizontal stability is compromised). That's the most likely explanation I can think of.

The low amplitude bounce is important. The high amplitude is in my opinion not. You don't have to adjust until there is zero high amplitude knocking, it's enough that the low to mid amplitude bounce is harmonic and without overtones or knocking.
I am in total agreement with this. I have had to replace a number of cut off grommets and found over time that even many of them knocked. It could also be that the contact with the spring damps vibrations in the spring that may harm the music.
I would guess it is either that or the possible horizontal movements Fredrik suggests.

Knocking at high amplitudes can be eliminated with enough time and enough springs but what is the point? How much does the suspension actually move when it is playing a record? If it knocks a bit at high amplitudes I don't worry about it, but if it does so at small to medium modulations, and small is all you might see when playing a record, then I fix it. Sometimes that just requires turning the spring/grommet and sometimes replacing one or both. I have a stethoscope in my kit so I can easily tell which spring is knocking and when it dies away. Sometimes it knocks a tiny amount all the way until it stops moving so I make sure to take care of those even though the knocking might be hard to hear normally.
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Re: LP12 Bounce

Post by Mikeg »

Defender

"mmh and I thought you should not clean them"

I thought the same. I had a lovely silent bounce then swapped the springs for the new ones that came with the karousel. I couldn't get rid of the knocking until I saw this comment bt ThomasOK

"you should always clean the protective oil off the springs before you use them"

That was what was rubbing and causing the noise
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Re: LP12 Bounce

Post by John »

Thanks to those that responded. I’m certain I did not clean the springs or grommets before installing them. I had no idea that was something that was needed to be done. Maybe next time I’m in the deck I’ll remove them one at a time and clean them. Is dish detergent OK to use?

If this is not a big deal, I’ll just continue enjoying the music as it only knocks at high amplitude.
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Re: LP12 Bounce

Post by Hermann »

Many thanks to Mike for the topic. It gives me food for thought. All the years I never had problems to set up the LP12 correctly in terms of musicality. Since the Keel has been installed, I can't get the arm board to align in parallel at the same time and get a correct bounce. This is affecting the sound. The last setup did not work. When the board was misaligned I was almost happy. But that almost alone was enough to set up the LP12 again. This time the board was parallel with good bounce. Unfortunately the musicality suffered a bit.

Thomas and Fredrik's comments shed considerable light on the background. Many thanks for that.

When I do the next setup, these things will come into play. However, replacement parts such as springs, washers and screws are missing.

I followed on a hint from my dealer that turning the rubbers has a not so great effect on the bounce effect. His recommendation is not to move the rubbers with small turns, but if necessary, turn in large steps. However, did not work.

What I understand now is the dependency of the rubbers and springs in the right place is much more important than the turning. As well as the correct washers and screws.
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John
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Re: LP12 Bounce

Post by John »

Mikeg wrote: 2021-01-05 20:53 Defender

"mmh and I thought you should not clean them"

I thought the same. I had a lovely silent bounce then swapped the springs for the new ones that came with the karousel. I couldn't get rid of the knocking until I saw this comment bt ThomasOK

"you should always clean the protective oil off the springs before you use them"

That was what was rubbing and causing the noise
Where did you see that quote? Do you have a link? It sounds like cleaning the springs is no guarantee the knocking will go away as Thomas has just stated he has decks that knock at higher amplitude. Not sure how you can attribute cleaning the spring causing the knocking to go away as it could be attributed to just removing them and reorienting them to a different position.
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Re: LP12 Bounce

Post by tokenbrit »

John wrote: 2021-01-06 14:15
Mikeg wrote: 2021-01-05 20:53 Defender

"mmh and I thought you should not clean them"

I thought the same. I had a lovely silent bounce then swapped the springs for the new ones that came with the karousel. I couldn't get rid of the knocking until I saw this comment bt ThomasOK

"you should always clean the protective oil off the springs before you use them"

That was what was rubbing and causing the noise
Where did you see that quote? Do you have a link? It sounds like cleaning the springs is no guarantee the knocking will go away as Thomas has just stated he has decks that knock at higher amplitude. Not sure how you can attribute cleaning the spring causing the knocking to go away as it could be attributed to just removing them and reorienting them to a different position.
I was curious too so did a search for the comment, including quotes, && 'ThomasOK', of course ;) The first result was this 'wam thread
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Re: LP12 Bounce

Post by John »

Well I went in and cleaned all the grommets and springs and reset the deck. I think it’s bouncing a bit better and making less knocking though it’s still knocks a bit at the beginning. Here’s a video that shows how long it sustains it’s bounce.

https://youtu.be/we1P1-4uzFU
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Re: LP12 Bounce

Post by Defender »

wow thats nice and to hope for more would be greedy
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Re: LP12 Bounce

Post by sktn77a »

That's definitely more bounce than would cause the spring knocking on my LP12. I guess that means there's hope - I'll be more persistent next time I adjust the springs.
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