Equipment isolation and vibration damping.

esldude · July 1, 2015

You would certainly find a lot of interesting things if you read from the beginning. Lots of good posts.

I am sure I will. I wasn't dismissing anyone else's contribution to the thread. I jumped into the end of it, and simply wanted to point out I may be in need of some catching up. So some of my thoughts may have been replication of others.

JohnSwenson · July 1, 2015

On the magnetic levitation topic, besides the instability issues Barry mentioned, it is still just a spring, a very low loss spring, but still just a spring. It suffers from the same issue that all "normal" spring systems have: the spring constant has to be high to support the weight of the equipment, and that high spring constant means a fairly high frequency resonance.

The Euler spring gets around this by being a highly non-linear spring where most of the weight is dealt with in the very high spring constant realm, but when you get past that mode you are in a low spring constant realm which gives rise to very low frequency resonances.

This is also why the partially inflated inner tube is effective, it is the interaction of the spring behavior of the air and the container (the tube) changing shape as the pressure on the tube changes. The result is also a bit of non-linear behavior. (not nearly as much as an Euler spring, but enough that it helps lower the resonance frequency)

John S.

YashN · July 1, 2015

Magnepans are planar *dynamic* speakers, not electrostats.

Right, but for the argument, it's the same: your setup does not need any mass loading as it is technically not subject to a lot of 'cabinet resonance' or 'cabinet vibration'.

But regardless, I would suggest *against* any sort of mass loading. Mass stores energy, releasing it after a delay. The goal isn't mass but *rigidity* combined with *low* mass in order to not be an efficient reservoir for that energy.

No, there are two different goals here:

One is cabinet vibration reduction, and the way to reduce this with bookshelf speakers is to do what I did, i.e. use stands to which the speakers are coupled.

The second one is the seismic events isolation that Townshend speaks about and which we are using the cup-and-ball arrangement to deal with the vibrations and rotational in the horizontal plane only.

However, putting the cup-and-ball in between the stand and the bookshelf speaker breaks the speaker + stand arrangement, thereby annihilating the cabinet vibration reduction. This (speaker cabinet vibration) also colours the sound.

Therefore, one of my next tests will be to move the cup-and-ball to below the stand's bottom platform, and in so doing, benefit from both the seismic isolation as well as the lessened cabinet vibrations.

Hope that's clearer for you (I already explained that in the prior post).

monteverdi · July 1, 2015

I used to develop and do microinjections into the nucleus of a single cell and that system had to be vibration free within less than 1 µm. I used a very heavy cast iron plate supported on large blocks on restrained styrofoam. Later with a much larger expense account I had a floating air table which had extremely good isolation in the horizontal plane and also very good isolation in the vertical axis. The only problem with this fancy table was there was not much damping. My original table had very good damping but also very good isolation but by far not to that degree of the air table and was much more practical for my task.

I think for audio one needs also booth, isolation from structure born/seismic vibrations but also damping of airborne (sound) and internal vibration from power supplies (an advantage of switch mode ones) and optical or disk drives.

Cup and ball based one are mostly isolation devices. But depending on the radius of the cup they reduce their isolation values (in the horizontal plane) but add an damping element to it.

One alternative mentioned by John Swenson is to suspend the equipment on a pendulum from above. With a longer suspension lines one could much more approximate a horizontal plane than with ball and cup. On could vary the elasticity of the line from spectran with close to none to nylon or use TiNi shape metal wire and thus varying the vertical. I can see several problems: WAF, ceilings in many buildings have more vibrations than floors (especially ground slabs) and close to no damping.

Duke40 · July 1, 2015

In my experience, seismic isolation will be most effective when it is placed closest to that which we want to isolate. There really isn't any point in isolating the stands since it is really the speakers we want to isolate. For a stand-mounted speaker, I'd recommend a high-rigidity, now-mass stand with isolation between the stand and the speaker.

By all means, the most educational path will be to try all the variations you can think of. I'll be curious to hear about your experiences. Have fun!

Best regards,

Barry

Soundkeeper Recordings

www.soundkeeperrecordings.wordpress.com

Barry Diament Audio

Barry that echoes my experience.

I have Focal Utopia Micro Be bookshelf speakers with the Focal stands.

Because the stands are filled with sand, I thought if I put the Townshend Stella Stands underneath the stands it would be better. I found it a little bit unstable for relatively expensive speakers, which kind of scared me, bit difficult to relax and enjoy the music.

So I tried the Townshend Stella Stands ... between ... the speakers and the stands.

Not only is it more stable, I found improved results from trying the speaker isolation this way, it was much more effective.

Gave me a bit more freedom on speaker placement as well because what was under the Townshend Stella Stands does not really matter, so I had more flexibility on where I placed them.

JohnSwenson · July 1, 2015

You CAN get low frequency isolation with regular springs, but it gets a little ridiculous. I just crunched the numbers and this is what I found:

a 1Hz resonance can be achieved with a spring with 4 meters (over 12 feet) of extension. That is not total length, but the amount it has increased in length due to hanging a mass off it. Thus if you have a spring that can increase in length 4 times it's "resting length", then the resting spring would be 1M and the total length for 1Hz would be 5M. Getting a 4:1 elongation ratio is not very common, it's usually less, which will make the whole thing even longer!

So it CAN be done, but you will need a high ceiling. So with this you can do both horizontal and vertical isolation with some long springs suspended from the ceiling. You get both horizontal pendulum and vertical spring. One nice thing about this is that the frequencies of the horizontal and vertical a re very different, which cuts down on the cross excitation of the resonances.

John S.

bdiament · July 1, 2015

Right, but for the argument, it's the same: your setup does not need any mass loading as it is technically not subject to a lot of 'cabinet resonance' or 'cabinet vibration'.

No, there are two different goals here:

One is cabinet vibration reduction, and the way to reduce this with bookshelf speakers is to do what I did, i.e. use stands to which the speakers are coupled.

The second one is the seismic events isolation that Townshend speaks about and which we are using the cup-and-ball arrangement to deal with the vibrations and rotational in the horizontal plane only.

However, putting the cup-and-ball in between the stand and the bookshelf speaker breaks the speaker + stand arrangement, thereby annihilating the cabinet vibration reduction. This (speaker cabinet vibration) also colours the sound.

Therefore, one of my next tests will be to move the cup-and-ball to below the stand's bottom platform, and in so doing, benefit from both the seismic isolation as well as the lessened cabinet vibrations.

Hope that's clearer for you (I already explained that in the prior post).

Hi YashN,

Actually from my perspective, they're not the same, aside from being planar. I believe what you mean is "boxless" which the Maggies are. Outside of that, they are worlds apart-- at least to me they are.

I understood about the mass loading the first time. I just disagree.

Adding mass to the cabinet will not make it more clear -- at least to my ears. It will simply move the resonance around, changing one color to another color.

If that is the goal, then yes, that is one way to achieve it.

My preference is to get the speaker out of the way. If the cabinet is singing, I'd get it out of the way literally. ;-}

Best regards,

Barry

YashN · July 2, 2015

Adding mass to the cabinet will not make it more clear -- at least to my ears.

Your speakers aren't low mass.

YashN · July 2, 2015

You CAN get low frequency isolation with regular springs, but it gets a little ridiculous. I just crunched the numbers and this is what I found:
a 1Hz resonance can be achieved with a spring with 4 meters (over 12 feet) of extension. That is not total length, but the amount it has increased in length due to hanging a mass off it. Thus if you have a spring that can increase in length 4 times it's "resting length", then the resting spring would be 1M and the total length for 1Hz would be 5M. Getting a 4:1 elongation ratio is not very common, it's usually less, which will make the whole thing even longer!

So it CAN be done, but you will need a high ceiling.

It would be interesting to see a simulation of a spring + rubber around it, and a spring + rubber + air damping as in the Townshend device.

Are there mechanical simulators we could tinker with?

bdiament · July 2, 2015

Your speakers aren't low mass.

Hi YashN,

Unless I am mistaken, you are talking about *adding* mass to the existing cabinets of your speakers.

I'm not adding mass to the Magnepans.

Also, the Maggies I'm using may be considerably larger than the stand-mounted speakers to which you are referring.

If that is the case, it would be expectable they would have more *inherent* mass.

But we're talking about two designs that are about as different as they could be, from size, to radiation pattern, to driver mass (which is *much* lower on the Maggies, despite their considerably larger size), to how they load a room, etc. etc.

So, the entire body might not be low mass but then, compared to other speakers of similar size, they are feather-weights.

And the drivers will make most tiny shoebox speakers seem quite massive by comparison.

Bottom line for me, is where is the mass (in the frame, in the cabinet, in the drivers, or in some combination) and what it is doing to the sound as a result.

Based on their sound, I am utterly unconcerned with the mass of the speaker as it seems the designer has put it in the right place(s).

This is not at all the same as deliberately adding mass to the cabinet of a box speaker.

Best regards,

Barry

YashN · July 2, 2015

Unless I am mistaken, you are talking about *adding* mass to the existing cabinets of your speakers.

I'm not adding mass to the Magnepans.

To be more blunt and clearer about it: the issues we have with bookshelf speakers are different from what you have in your speakers. Therefore, what you do not want to do with your speakers concerning cabinet vibration, isn't IMO relevant to what I want to do in my setup.

bdiament · July 2, 2015

To be more blunt and clearer about it: the issues we have with bookshelf speakers are different from what you have in your speakers. Therefore, what you do not want to do with your speakers concerning cabinet vibration, isn't IMO relevant to what I want to do in my setup.

Blunt? I thought this was a friendly conversation.

If I was mistaken about that, I'll not reply to any more of your posts.

Do not however, be under the mistaken impression that I am not also familiar with (and do not also have *several* pairs of) box speakers. Or that I am not aware of what happens to the sonics when mass is added. It seems to me you are theorizing about all of this and haven't yet actually tried it. If you've read my other posts, you should know I always suggest folks try everything they're willing to try, so have at it. And have fun.

To be clear ("blunt" if you will), I think you should do whatever you want to do with your speakers.

Never felt otherwise. I speak of my own perspective, not yours.

Barry