View Full Version : I need a little help with springs
Wakefield Turntables
23-01-2014, 21:23
I'm looking at solutions to limit vibration into my Garrard 301 plinth. I've been offered 4 pretty large springs. The idea being to simply sit the Garrard 301 plinth on the springs. Is this is good, bad, or pointless idea? I understand several decks in the past have incorperated spring suspension for the same idea but I'm not so sure about externally mounting a plinth on the springs themselves.
why not just use 3-4 slabs of your favourite material dude, sorbothane?
As in a mass/spring damper?
I think that tt needs to be tuned to the frequencies you want to eliminate, so it's not straight forward.
Wakefield Turntables
23-01-2014, 21:37
why not just use 3-4 slabs of your favourite material dude, sorbothane?
Dave, already thought about it. It would probably dampen the deck too much. I tried this with the 1210 and HATED the results, but thanks anyway.
As in a mass/spring damper?
I think that tt needs to be tuned to the frequencies you want to eliminate, so it's not straight forward.
Yep, thought about this as well, your correct, it's not as straight forward as I thought. :(
Dave, already thought about it. It would probably dampen the deck too much. I tried this with the 1210 and HATED the results, but thanks anyway.
Not sure what sort of plinth you have, but how about a two stage setup. use a massive slab of slate or some other high mass item, isolate that from the support with sorbothane, then point couple the 301 to that layer.
As you say, it depends on the frequencies you are trying to deal with, below some frequency, it might be better to just let the entire system move together. I would guess the trick is to make sure the support resonances are not related to the arm cartridge ones.
Further thoughts, I am not sure you can expect a 301 to behave in any way like a 1210 with respect to how it responds to supports.
Wakefield Turntables
23-01-2014, 22:23
Not sure what sort of plinth you have, but how about a two stage setup. use a massive slab of slate or some other high mass item, isolate that from the support with sorbothane, then point couple the 301 to that layer.
As you say, it depends on the frequencies you are trying to deal with, below some frequency, it might be better to just let the entire system move together. I would guess the trick is to make sure the support resonances are not related to the arm cartridge ones.
Further thoughts, I am not sure you can expect a 301 to behave in any way like a 1210 with respect to how it responds to supports.
Nick,
Hi! I dont expect the 1210 to work like a 301, I just dont want the 301 to be dampened and sounding crap :( Funnily enough I have some old granite chopping boards (but I've heard these resonate) and shit loads of sorbothane so I could try this I suppose. The plinth incidently is 90mm birch ply.
sq225917
24-01-2014, 09:33
Weigh the deck, and weigh the plinth, then its time to do some maths to work out how much deflection you want and at what frequency.
Have a look at sonicdesigns.co.uk and also possibly speak to Bob at rjcaudio.co.uk
I have two of his Hush platforms, one under my Techie, and they work a treat. He uses some form of tuned suspension and is also a Garrard fan having built plinths for them utilising his suspension system.
There is a review of a Hush platform with the Techie on HiFi Pig.
Hope this helps.
Wakefield Turntables
24-01-2014, 15:45
Weigh the deck, and weigh the plinth, then its time to do some maths to work out how much deflection you want and at what frequency.
Oi! What you doin answerin posts on threads, get back to building that phonostage :whippin: !!!! Hi, Si, how you doin. Thanks for the info, can you enlighten me a little by sending me a PM or reply back to the thread with regards how this works?
[QUOTE=freem;520187]Have a look at sonicdesigns.co.uk and also possibly speak to Bob at rjcaudio.co.uk
I have two of his Hush platforms, one under my Techie, and they work a treat. He uses some form of tuned suspension and is also a Garrard fan having built plinths for them utilising his suspension system.
There is a review of a Hush platform with the Techie on HiFi Pig.
Hope this helps.[/QUOTE
Thanks for the heads up, will do a little reading tonight when I get chance.
Oldpinkman
24-01-2014, 15:50
As you say, it depends on the frequencies you are trying to deal with, below some frequency, it might be better to just let the entire system move together. I would guess the trick is to make sure the support resonances are not related to the arm cartridge ones.
I believe that is the principal used in suspended sub-chassis design. It also wants to be out of the audio frequency. Since you are unlikely to build a system with a resonant frequency above 20Khz you are left targetting 4-5 Hz as the ideal. Or so I am told.
pure sound
25-01-2014, 07:04
One of my decks is an SP10 mounted in a 60mm thick piece of slate. That stands on another similarly thick piece of slate. All of that weighs around 65 Kg. It stands on 4 springs which compress from about 5 inches to about 2.5" The natural bounce frequecy of this arrangement is around 2 Hz. It all stands on a Sound Org type table on a wooden floor. You can jump up and down next to it with no effect on the stylus in the groove. I'd say it was earthquake proof. The only issue was that I had to coat the springs themselves to suppress higher frequecy resonance. It works very well. I think the biggest deal in a Garrard is to deal with the vibration from the motor first and prevent it from reaching where the arm mounts. Then concern yourself with external vibration.
If you know the weight to be supported and the compression desired when loaded most spring suppliers give the information needed to choose the appropriate items. Compression by half seems a decent rule of thumb.
Are those valve springs you are using Guy?
walpurgis
25-01-2014, 10:49
Anybody planning to use four springs to support a TT has some experimentation to do.
Assuming a spring is to be used at each corner, unless you add mass here and there to balance the complete TT base & motor assembly, it just won't sit level. The other way to keep things level is to move the spring positions around, ensuring the heaviest area has the most support.
Springs need damping otherwise they just keep bouncing and wobbling, an easy way to achieve this is to use neoprene 'O' rings in tension alongside the springs, the bottom end attached to a hook at the bottom board and the top end similarly attached by hook to the underside of the plinth board, Neoprene has high internal damping and will help keep the springs under control.
I sit my Garrards on (double) yellow dot squash balls. Springs resonate, whereas yellow dot squash balls are critically damped. In fact, I doubt the ability of hefty metal springs to isolate from higher audible frequencies. Sound travels well in a metal bar, even round bends.
At the mongers you can buy, for pennies, black rubber plumbing seals about the diameter of a squash ball. I sit the squash balls in these so that they don't roll. Tuning a squash ball suspension is simply a question of deciding on the right number of balls. It is an extremely effective method of isolation and I can knock the support surface quite hard when the stylus is sitting on a stationary record without hearing anything come through the speakers, even at high volumes. Even elastic bands would be better than springs IMO.
The deck can be levelled by moving the squash balls around under it. Periodically I turn the balls so that their longest dimension is vertical and long term deformation is reduced.
http://cyberphotographer.com/garrards/deck2complete/plinth2deck1/4.jpg
But squash balls aren't critically damped , they are over damped. The resonant frequency will not be a few hertz it will be higher hundreds.
pure sound
25-01-2014, 17:36
No, bigger diameter than any valve springs I've seen.
Im not really that enamoured of rubber, squash balls or sorbothane. I prefer a more effective higher Q isolation. 65 Kg decoupled at an Fs of 2 Hz takes alot of exciting. More than this ever encounters in typical use.
Wakefield Turntables
25-01-2014, 19:42
Certainly lots to think about, I'm just chasing a few ideas at the moment. My valve system is undergoing some upgrades and I thought I'd address the TT whilst the amps and speakers are having some work done.
But squash balls aren't critically damped , they are over damped. The resonant frequency will not be a few hertz it will be higher hundreds.
If I displace the deck I would estimate that it wobbles at around 3 - 5 Hz, and the movement is only visible for about one cycle. That is the primary resonant frequency of the suspension system. As regards the higher frequencies, it would certainly be interesting to record cartridge output while the DAC plays a frequency sweep. My guess is that chunky metal springs might do a surprisingly good job of transmitting higher frequency sound into the plinth. Real springs are far from ideal. Only experimentation will give real answers, but my squash ball set up kicks the feedback problem into the long grass in practical terms, because as I said, I get SFA signal when exciting the support.
Does it move in a pistonic motion at 5 cycles per second? Wobbling is not the same thing at all (it may provide lateral isolation at 5Hz but not vertically. You may guess regarding springs but I don't have to and your guess is incorrect.
You can achieve low frequency isolation by mass loading racket balls but these have a significantly greater ratio of trapped air to rubber and are much more compliant.
The Barbarian
25-01-2014, 21:45
I'm looking at solutions to limit vibration into my Garrard 301 plinth. I've been offered 4 pretty large springs. The idea being to simply sit the Garrard 301 plinth on the springs. Is this is good, bad, or pointless idea? I understand several decks in the past have incorperated spring suspension for the same idea but I'm not so sure about externally mounting a plinth on the springs themselves.
Get yersen a SME 'System 2000'
:sofa:
Wakefield Turntables
26-01-2014, 11:07
Get yersen a SME 'System 2000'
:sofa:
NO!
Does it move in a pistonic motion at 5 cycles per second? Wobbling is not the same thing at all (it may provide lateral isolation at 5Hz but not vertically.
I'll check but it's not fast.
You may guess regarding springs but I don't have to and your guess is incorrect.
I guess that you won't be showing us any useful measurements.
You can achieve low frequency isolation by mass loading racket balls but these have a significantly greater ratio of trapped air to rubber and are much more compliant.
I'm looking to isolate in the audible range. Mass loaded pneumatic rubber balls are quite bad transducers of sound energy. So are springs, but this discussion needs measurements or it's pointless.
The Barbarian
26-01-2014, 21:02
NO!
Because of how it looks? :rolleyes:
Wakefield Turntables
26-01-2014, 21:30
Because of how it looks? :rolleyes:
No I have a funny feeling the Moldovan plinth wont fit inside it! Otherwise it looks pretty cool and would fit nicely in my valve setup.
OK OK OK - If I get time tomorrow I will measure the mass of the plinth and the TT.
No I have a funny feeling the Moldovan plinth wont fit inside it! Otherwise it looks pretty cool and would fit nicely in my valve setup.
OK OK OK - If I get time tomorrow I will measure the mass of the plinth and the TT.
Buy 8 squash balls. Sit your plinth on them. Put your stylus on a stationary record and turn the volume right up. Then get a hammer and start whacking your support/shelf. Perhaps begin gently just in case. This process reassured me greatly that feedback was vanishingly small, and there were better things to worry about. Those Moldovan plinths look very nice btw.
That's fine if you are looking to isolate your turntable from dangerously close carpentry - but otherwise is of limited value.
I actually have done measurements (no you can't have them) and I don't mean I bashed around with a hammer. Frankly, it's a bit rich you saying the thread needs measurement when everything you have so far said is pure conjecture, estimation and a dash of random hammer bashing - certainly no evidence of any measurement (what frequency do you think your hammer blows are?).
A rubber ball filled with air is still a spring - the smaller the air volume the stiffer the spring.
I've done extensive measurements too, but like you, I'm not at liberty to discuss them. ;-)
The Barbarian
27-01-2014, 11:31
Top secret as usual :lol: however im sure i wont loose sleep
Wakefield Turntables
27-01-2014, 11:56
+1 to that one andr'e what's the point in saying that you've measured something and not sharing the results. Let's not turn thread into an argument or a childish slagfest. I'm only looking into the possibility of using springs at improve the performance of my tt, it's not the end of the world if it dosent work.
With respect Sondek, if your measurements show that you are achieving sub 5Hz isolation from mass loading eight squash balls I suggest you repeat them because there has been an error. As I wrote earlier, you can achieve close to this but you need a more compliant arrangement, a larger ball with a larger air to rubber shell ratio - a racket ball for example (which is basically a large squash ball). They will give you a low Hertz vertical isolation but lateral isolation will still be at a significantly higher frequency depending on how they are mounted/used.
Sorry if not sharing my experience sufficiently boys - I didn't realise it was an obligation! Anyway, you do/believe whatever you like, arguing the toss over this is of no interest and my participation has concluded. This isn't a 'black art' anfd there is plenty of research that has been done in to isolation at low frequencies (if one wants to learn about it).
The Barbarian
27-01-2014, 12:57
What exactly is the point in even mentioning you have done this that & the other when you choose to keep things top secret! not that im inetrested, but other maybe. Incase you forgot Rexon was looking at solutions to limit vibration into my Garrard 301 plinth.
I think YNWaN might be contemplating producing a commercial product one day, and may wish his experiments to remain a trade secret, so it's fair enough. For my part, I was just kidding, and put forward my suggestions because they are easy and cheap to implement, and seem to work very well indeed, and are in use here on a daily basis. Whether they are technically inferior, and whether that matters, seem to me to be open questions.
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