Decoupling turntables from floor vibrations

[Lee in Montreal]

There are indeed many ways to decouple a turntable from the floor vibrations. Making it simple is more difficult than making it complex. ;-)
Designing a new system is a very good intellectual exercise. It definitely turns me on. The system I drafted works. Now I have to rethink it and make it even simpler.

Lee

[gasfan]

Three feet?

[SEAWOLF97]

I can tell you from running an 8 X 10 photo enlarger on a third floor of a commercial building in Chicago that vehicle traffic is much worse.

I was in the darkroom on an Aircraft Carrier in a prior life ....When the catapult hits the stopping block during a launch, the whole ship shudders. If it happened during a print exposure , we just tossed it , knowing what the result would be.

You want a base or plinth that's dead to resonance. Springy isn't as good. Granite also not a good since it rings like a bell.
Nick

Mine is on a 18x25 slab of marble. Pretty dead, no ringing.

[Val33]

If you guys are in to the Technics 1210, you might like to look at 'The Art of Sound' forum, its UK based, but heavily biased to the Technics. Some of the mods are very interesting. http://theartofsound.net/forum/forum...he-Techiepedia

The normal isolation used here are Isonoes http://www.isonoe.com/products/audio-isolation-system/

Val

[macaroonie]

Just a point of info here , the sprung suspension turntables like AR , Thorens , Ariston , Linn and so on are very effective at isolating the playing mechanism from footfall and mechanical noise in the structureof the building. Why , because the sprung suspension is a high Q mechanical filter. It is crucial in all of these decks that the suspension is set correctly. You can read all about this all over the web esp about the Linn.
In a nutshell the springs must all work in unison to provide a single uniform resonance of the mechanical structure. Generally referred to as the ' bounce ' the sub chassis will have a movement, if agitated in any way that will resolve itself to a single motion up and down . Any sideways components of this movement , wiggles, or rubbing of the mechanism will defeat the effectiveness of the ' filter' ie short circuit.
In practice a properly adjusted sprung suspension deck will tolerate a significant fist thump ( a big one ) on the surface it is sitting on.

Internally all of these types of decks have a minimal chassis the sole purpose of which is to connect all the playing components together and at the same time to control the spurious resonances that are in the structure.
These resonances can be very very small indeed , coming from the needle/ arm , motor noise via the belt, spindle noise from the platter , ambient noise from the environment. Hi Fi is all about incremental improvements , any step forward is a good step no matter how small. It's surprising for example how nuch mush / background noise is generated by a less than good main bearing , or even dry lube or worn bearing surfaces. Sometimes just a good clean up and re lube is all it takes , just like cleaning your glasses ( drink or vision )
Some do this better than others needless to say.

Hope this helps a little.

[gferrell]

I hung an old Pioneer from the ceiling of my 1 story house about 35 years ago and it worked very well.

[stephane RAME]

http://images.junostatic.com/full/IS...-01-01-BIG.jpg

Stéphane

[Lee in Montreal]

Yop. Seen that a while ago. Not as effective as rubber band suspension though.
Interestingly, years ago on a French DJ forum, I had discussed the principle of using rubber bands for suspending turntables and that it has been used for 4 decades in North America, and not a single DJ heard about the principle before. Back in the days, when a club would be built, it would use two layers of 3/4" plywood for the counter, and two square holes would be cut for the turntables. Hooks underneath to strap the rubber bands, and here you go. That was a common way to isolate the TTs from their environment.

[macaroonie]

The very expensive SME turntable uses elastic to suspend the playing chassis

[David Ketley]

Two weeks ago, I was at a friend's place and we mixed some music for his MixCloud channel. When I listened to it back at home, and with the heavy sub bass I have, I couldn't help notice all the thumping in the background. Yup. The needle was catching people walking around the room. Soft floor in an old appartment. So, I checked for some old drafts I did years ago. Added a few notes and sent the blueprint into production. Here's what I ended with. The basic idea is to decouple the Technics SL1200 from floor vibrations by using rubber bands. exactly what you could find in clubs and discos back in the 1970s and 1980s. I made a pair for my friend and another for myself as prototypes. I will spend some time experimenting with rubber bands, positionning and weight distribution. But at least, we can do some mixes at my buddy's place without having to care how heavy we walk.

I think it is best to try and remove the turntable from the room if possible as even the best suspension will not isolate it sonically from the bass. I even do this with my CD player. I am amazed at the number of systems where the turntable is stuck in the middle of the speakers, surely the worst place possible?

[Lee in Montreal]

The problem I am working on to solve, is not the turntable being exposed to bass frequencies coming from speakers. It is undulations on the floor from people walking around. Mostly a problem in old houses and buildings and people walking heavily.

[gasfan]

I get it. It's really tough to cancel that kind of movement without introducing a more complex one. I think the best way to deal with that is simply to remove the tt from the source by hanging a shelf on the wall first, and then let your decoupling system do it's thing. Now all you need do is match compliance to vibration.

[Lee in Montreal]

I have developped the idea further and shall have something to show next week. I added a light subframe on which the TT can simply be bolted, or installed using the stock feet. I have reduced the height of the 8 pods from 3.5" to 1.5" to lower the overall height. e new subframe also allows to simplify the installation. Oh, and I have drafted a third version that is not as sexy looking but will do the same job. with less parts, and thefore cheaper to produce. ;-)

Lee

[SEAWOLF97]

My "daily driver" TT is isolated via ..

Double float system: The PL-530 Has a standard wood press board plinth base . And a steel sub- chassis. The tone arm connects to the subchassis. The subchassis is suspended from the plinth, along with the tone arm. All vibrations are absorbed twice, before they have a chance to spoil the record's tonal quality.

the platter is also on this steel sub-chassis. And with shock absorbing feet too, it works very well.

BUT, Lee's device sure is sexy. Need something better than rubber bands, they have a limited life (well,the ordinary ones)

[Lee in Montreal]

Need something better than rubber bands, they have a limited life (well,the ordinary ones)

One bag of 100 rubberbands for $1.50... Can't beat that for testing. Nonetheless I agree that something sexier is needed. I checked some large size o-rings but they seemed too stiff. I will investigate further after I have assembled the next version of the prototype.

BTW On the technical side, I found on my first attempt that when rubberbands are too soft, then the direct drive motor's impulsions will make the turntable oscilate radially. This greatly affects the sound. You can see the spots in the stroboscopic shake back and forth. But as soon as the bands are stiffened, the oscilation disapears. I think it is typical of a direct drive TT and that one driven by a strap shall not have that situation.