View Full Version : Are equipment racks tuned to certain Hz? - PLEASE DISCUSS
Wakefield Turntables
02-09-2012, 09:39
This question may sound silly but it may help me in understand a simple principle. I have been looking at spring to isolate my new plinth. My understanding is that a piece of machinery will oscillate (vibrate if you like) at a certain frequency. To eliminate this and turn vibration into harmless heat a spring can be used which oscillates at a similar frequency :scratch: If my statement is true then why dont we use said devices to mount our euipment and hopefully "decouple" it from the nasty vibrations??
I have included a few references to give you sall some ideas
http://www.cvimellesgriot.com/products/Documents/TechnicalGuide/Theory_of_Vibration_Isolation.pdf
http://en.wikipedia.org/wiki/Vibration_isolation
There is lots of stuff on the net. It makes for interesting reading and possibly better sonics.
Come again??
Could we have that in English, please? :)
Marco.
WOStantonCS100
02-09-2012, 23:16
...why dont we use said devices to mount our euipment and hopefully "decouple" it from the nasty vibrations??
Some folks do... costly; but, probably worth it. I'd love to have the SM-1. Be warned it has a WAF of -2,000,000.
Minusk Vibration Isolation Isolators (http://www.minusk.com/content/products-vibration-isolation-isolators-tables-systems.html)
http://www.minusk.com/img/products/sm1_low_frequency_vibration_isolator_minus_k.jpg
6Moons review of a smaller system (http://www.minusk.com/content/in-the-news/6Moo_1006.html)
sq225917
03-09-2012, 00:40
Andrew the vibration of any sprung system is constrained by its physical attributes. The weight of the gear being supported on it is one of those. So only manufacturers of true 'active' vibration sensing equipment tables (ie lab style vibraplanes etc) can make that claim as they can adjust the spring/load tension to counter the weight of the supported item and in doing so define the absorption frequency.
Makers of 'static' (none active) supports cannot rightly make that claim, unless it is bounded by weight constraints for the items to be supported. ie Townshend could say 'stand X will isolate 8-10kg at 6hz', they would be wrong to say 'will isolate any hifi' at a given frequency.
If I had real money to 'waste' my next purchase would be a couple of grands worth of isolation for my deck.
What sq has written is precisely correct.
Does anyone understand what Alan S was on about in post #2? :scratch:
Marco.
Stratmangler
03-09-2012, 08:50
Does anyone understand what Alan S was on about in post #2? :scratch:
Marco.
He doesn't think it will work very well.
The ride will be too bumpy (unpredictable).
Stratmangler
03-09-2012, 08:54
I'm a bit bemused with the idea of springs myself - it looks like a lot of trouble to perform a simple task.
I'd suggest experimenting with inflated bicycle inner tubes.
That way you'll achieve the sprung isolation being sought, with little in the way of resonant frequency.
He doesn't think it will work very well.
The ride will be too bumpy (unpredictable).
Lol... That still doesn't make any sense to me! He doesn't think that WHAT will work very well, and what "ride" are we talking about?? :confused:
I always have a real problem trying to understand what people are on about when they write in riddles and seemingly can't be arsed stringing a few sentences together to explain properly what they mean!! :rolleyes:
Marco
I haven't the slightest idea what he was on about either.
Inflated inner tubes, mass loaded, do work well (although are not very stable). However, they don't do away with 'resonant frequency' in the manner Chris suggests - the inflated inner tube is still a spring, just not a metal one. Also, sprung isolation doesn't really work in the way Andrew implies in his first post. The resonant frequency of the supported structure is defined by a combination of the compliance of the spring and its level of compression - at that frequency the suspension is ineffective. However, it isn't like a switch, one second it is isolating the next it isn't, there is a curve, as the resonant frequency is approached isolation becomes increasingly less effective. Active systems seek to suppress this resonant frequency.
The manufacturer Finite Elemente use an interesting approach, that is one of vibration dissipation by parasitic flexure - essentially, four tuning forks are attached to each shelf and the idea is that these resonate rather than the shelf. The problem is with all isolation systems is that there effectiveness depends on the weight supported. For this reason Finite Elemente supply a range of different 'tuning fork' elements depending on the weight of the item going on the shelf.
Another thing worth considering is that vibration will take the course of least resistance - there is no point in having a 3Hz vertical frequency if the system is rigid in the horizontal axis.
I haven't the slightest idea what he was on about either.
Lol... Which kind of proves my point. Alan, mate, you need to spit out what it was you were trying to say!
Anyway, back to the influence of inflated inner tubes, or whatever... I'll stick with my Mana supports :)
Marco.
Lol... Which kind of proves my point. Alan, mate, you need to spit out what it was you were trying to say!
Marco.
He usually only posts on Alex Magic Carpet Ride's threads, and since Alex MCR has not been around recently perhaps he is struggling a little? ;)
Lol... Perhaps we need new reference material, recorded in The Library: a translation from 'Alanese' to English'? ;)
Marco.
He usually only posts on Alex Magic Carpet Ride's threads, and since Alex MCR has not been around recently perhaps he is struggling a little? ;)
Also the Power Conditioner Thread of late. Nearly bought one.
QU: Are equipment racks tuned to certain Hz?
Ans No (they are not usually)
Bumpy - bounce the thread as little interest that day. Also bumpy (spring)
Too terse I guess
Cheers
Indeed. The buttons on your keyboard are your friends, not your enemies! ;)
Marco.
Ah - different ball game... That's *precisely* why I'd never access the Internet, using a mobile phone. Laptop only (with proper-sized keys), for me! :)
Marco.
I quite often post from my phone.
The Mana 'stack' is frequency tuned in a way - each time you add a new level the resulting increase in compliance lowers the resonant frequency.
Wakefield Turntables
03-09-2012, 17:00
Thats why Marco's setup looks like the shard in London :ner:
The Grand Wazoo
03-09-2012, 17:21
Are you planning on putting your 'doorstep turntable' on this structure we're discussing, Andrew?
If so, I'd think anything homemade & inflatable would be out as you need to get a TT level. Inflatable stuff has trouble coping with an asymmetrical centre of gravity.
Wakefield Turntables
03-09-2012, 18:09
the plinth is going to a stone mason that can level the stone and additionally cut the stone to fit the 301 (when it comes back from Dom's). I will have another piece of stone left over so I'm wondering whether to use this as a base and then have the actual plinth (which is 75mm thick) sitting on 4 massive pieces of EVA which will then sit on the base. So, it should be a two-tier plinth, total weight is over 80kg. I'm just wondering what to use as "feet", hence my idea for springs. The only idea's I have are four large bearings fitted into the plinth or to have four spikes machines for insertion into the plinth. I'm still no further forward :scratch: Any ideas would really really be helpful.
StanleyB
03-09-2012, 18:41
Aren't you killing the harmonics that go towards making the 301's distinctive musical projection? It's like taking a Stradivarius apart and replacing the woodwork. It might have some recognizable features at the end of the day, but it will never sound the same as the genuine article.
Wakefield Turntables
03-09-2012, 19:18
I'm not sure! Can you expand a little as to how the plinth will "kill" the 301, lots of people have them mounted in granite and they love the results. Additionally, which characteristics do you think i'll end up loosing?
StanleyB
03-09-2012, 20:22
The housing in which a turntable mechanism sits contributes towards the sound that you hear. I reckon it's the harmonics of the vibration exerted on the plinth. My views on this were shaped after hearing first an LP12 mechanism that was inserted into a new plinth made from a different wood to the original. Later on a heard the SP10 in an original Technics plinth and also in some plinths made by individuals.
On a sprung deck like the 301 the isolating springs interact with the cavity and housing in some ways. If you change the housing you also change the interaction. And with that you'll change the dynamics of the minute vibrations that the platter and arm assembly undergoes and that is ultimately transferred to the stylus. Don't forget that a turntable is a device that converts mechanical movement into an electrical signal. If you modify the mechanical movement in any way you'll also be modifying the electrical signal.
awkwardbydesign
03-09-2012, 20:38
Are you planning on putting your 'doorstep turntable' on this structure we're discussing, Andrew?
If so, I'd think anything homemade & inflatable would be out as you need to get a TT level. Inflatable stuff has trouble coping with an asymmetrical centre of gravity.
You could use 2 tubes, and inflate each to suit. However I found they are more useful under my speakers.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/SeismicSinks001.jpg
http://i1134.photobucket.com/albums/m604/awkwardbydesign/SeismicSinks005.jpg
My resprung Solid Tech Radius Duo, with all the equipment on it (about 100kg), oscillates at around 3Hz. I find the isolation from footfalls is very impressive and the sound quality very much better than without the springs.
Stratmangler
03-09-2012, 22:15
On a sprung deck like the 301
It isn't a sprung deck :scratch:
Garrard used to bung 'em into a concrete plinth to check 'em out.
The housing in which a turntable mechanism sits contributes towards the sound that you hear. I reckon it's the harmonics of the vibration exerted on the plinth. My views on this were shaped after hearing first an LP12 mechanism that was inserted into a new plinth made from a different wood to the original. Later on a heard the SP10 in an original Technics plinth and also in some plinths made by individuals.
On a sprung deck like the 301 the isolating springs interact with the cavity and housing in some ways. If you change the housing you also change the interaction. And with that you'll change the dynamics of the minute vibrations that the platter and arm assembly undergoes and that is ultimately transferred to the stylus. Don't forget that a turntable is a device that converts mechanical movement into an electrical signal. If you modify the mechanical movement in any way you'll also be modifying the electrical signal.
The LP12 and other suspended subchassis decks are far more susceptible to having the dynamics "sucked out" by heavy supports and plinths, as the drive components contribute (or "colour" if you will) the presentation. It's where "PRaT" comes fron (though some would say it comes from Ivor...)
Idler decks are a different breed, and while you are correct that changing the plinth changes the interactions of motor, platter/bearing and arm, it is a challenge to figure out what is right, as the decks were never originally "voiced" to any particular plinth type. In fact, factory plinths for the 301 and 401 were usually simple resonant boxes, with no consideration for those issues.
The goal of massive plinths for idlers is to remove the interaction of the drive system as much as possible from interaction with the stylus.
StanleyB
04-09-2012, 04:26
It isn't a sprung deck :scratch:
Garrard used to bung 'em into a concrete plinth to check 'em out.
I stand corrected :). The one I had to repair (quite a while back)was on a sprung chassis. I must assume therefore that it was a modification carried out by the owner or somebody he knew.
I stand corrected :). The one I had to repair (quite a while back)was on a sprung chassis. I must assume therefore that it was a modification carried out by the owner or somebody he knew.
In the late 60s the SME 2000 plinth was introduced, which had a sprung board to which the motor unit and arm were mounted. Also, Lencos were mounted on sprung chassis around the same time, among others, and certainly there would have been DIY efforts. There was the usual "hi-fi fashion" thing going around, I think, as even a Gramophone review of the SME plinth c. 1969 questioned the wisdom of spring mounting the 401 when such a mount raised the noise floor considerably over a firm mount. Put an idler in such conditions and it's no wonder they were quickly dismissed as noisy rumble generators. It's a stigma they retain, unfairly. My 401 doesn't produce rumble, or any other noticably audible artifact. I think its vibration may be muddying the output a little though, as it's in a relatively light "skeletal" type plinth. I hope to sink it in slate someday soon, and see where that leads.
Wakefield Turntables
04-09-2012, 12:27
The housing in which a turntable mechanism sits contributes towards the sound that you hear. I reckon it's the harmonics of the vibration exerted on the plinth. My views on this were shaped after hearing first an LP12 mechanism that was inserted into a new plinth made from a different wood to the original. Later on a heard the SP10 in an original Technics plinth and also in some plinths made by individuals.
On a sprung deck like the 301 the isolating springs interact with the cavity and housing in some ways. If you change the housing you also change the interaction. And with that you'll change the dynamics of the minute vibrations that the platter and arm assembly undergoes and that is ultimately transferred to the stylus. Don't forget that a turntable is a device that converts mechanical movement into an electrical signal. If you modify the mechanical movement in any way you'll also be modifying the electrical signal.
Stanley,
Thanks for the explanation. You do make an awful lot of assumptions with no actual proof. I fully respect your observations and please don't take the meaning of this message as confrontational, it's not :) I don't doubt what you say but for me I would need more proof or at least some science to try and explain your observations.
A
StanleyB
04-09-2012, 21:06
I don't doubt what you say but for me I would need more proof or at least some science to try and explain your observations.
Science? I think we have covered that aspect of audio engineering in numerous topics. Audio equipment design is 10% science and 90% pure experimentation. Stradivarius took his secrets to the grave and even the top brains in the world have yet to scientifically explain how he achieved what he achieved.
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