The science of neutrality

[psychotropic]

The science of stands and racks etc.,

I've read a lot of people talking about stands and racks and concepts like resonance, isolation, coupling, decoupling, etc., while talking about their quest to achieve the highest level of neutrality and the best performance from their systems.

While I've gotten a broad and very simplistic understanding of these things, I would be really grateful if the experts around here could give the noobs a bit more serious and in depth gyan on these concepts.

My specific questions would be.

1) What are the objectives when you are getting/building stands or a rack? What are the various types of resonances that we are trying to address, and how do we address each of these individually and collectively? What is isolation? what is coupling? what else do we need to know?

2) How does each component of a stand (such as the spikes, the base plate, the tube, the sand filling, the top plate, the washers, etc.,) help in achieving these objectives, and similarly how do the various components of a rack help in achieving these objectives?

3) what are the best materials for achieving these objectives, and how do they need to be used?

4) suri mentioned somewhere that just using a slab (say 12mm) of granite will not be useful. Assuming that granite is not resonant (i've seen the discussion on this, and i am just assuming here), then wouldn't a slab of granite be good in providing isolation to the speakers? why not?

5) what are the tools and implements that we can use to achieve neutrality? i've heard of cones and feet and blu-tack and squishy balls and stuff like that...which of these have you guys tried and how effective are they and for what components? How do these things achieve their objective of furthering the neutrality of your systems?

6) do we approach the neutrality of the output of our system keeping both the room as well as the stands/contact points in mind, or are room resonances and other resonances to be dealt with separately?

There are a 100 more questions in my mind, but I will stop now. I am hoping that this thread can become a useful reference point for people like me who are interested in understanding these concepts but can't find any basic information around (and i have searched a fair bit).

 

[rallynut]

nice goin psychotropic,good topic for discussion.cheers

 

[square_wave]

Isolation from mechanical vibrations helps you extract that last 5 percent out of your gear.

If neutral sound is your goal, more can be gained by investing in the best loudspeaker and source one can afford and then some decent amplifier and cables. Good placement of loudspeakers and a good room will take you to 95 percent of the system's potential

If you want to discuss Isolation from mechanical vibrations
There are 3 types of vibrations to be taken care of:

1.Airborne vibrations (typically caused by the vibrating cone of the loudspeakers)

2.Vibration that travel through the floor into the platform holding the gear.

3.Vibration that originate from the equipment itself. It travels into the platform holding the gear.

 

[Asit]

Hi Psychotropic,

I am not an expert, so do not have much "gyan" to offer. But because of my background (both musical and scientific) and a long experience of listening to stereo separates, I can tell you some of the basic stuff. The experts can take it from there.

The basic purpose of all this is to minimize any unwanted mechanical vibrations or movements.

Any physical object has a natural frequency where it resonates. Driven by some external influence, if the frequency of the vibration of that physical object reaches near that resonant frequency, the amplitude of vibration (extent of the vibration from equlibrium position of the object) becomes very very large. Bridges are nowadays built so that any undulations of the bridge cannot reach that resonant frequency, otherwise because of large internal stress at large amplitudes of vibration, the bridge will literally break. This has happened in the past and videos of such a thing happening live are available.

As a result of the above discussion, it is now clear that the cabinets of the AV equipments first need to be built in a way to avoid this sort of resonant vibration. Good designers take care of this. Many of the rattles inside a car (sometimes even new cars) you hear is because of lack of proper finish and also because of the phenomenon of resonance.

Audio equipments are kept on racks, tables, shelves etc. Now one needs to make sure that any forign movements and vibrations do not reach the equipments. The shelves etc are "coupled" to the floor through the legs or spikes. So people try to minimize the contact areas by using spikes or inverted cones so that the contacts are pointlike. However, I feel that while having these cones are ideal, they may not be absolutely necessary in the Indian context, because in India mostly we have concrete floors and they absorb a lot of the vibration-noises. On the other hand in the US and most Western countries, residential buildings are mainly built from wood and any body walking on the floor or going down the stairs creates a vibration which is not easily damped and may reach your audio equipments through the legs of the shelves.

In addition, the shelves themselves may have some vibrations of their own.

So basically you want your audio video equipments to be housed in racks/shelves where none of these vibrations (including the vibrations due to poorly designed or too light cabinets of their own) can bother these equipments. You want to "isolate" them from all kinds of vibrations.

Naturally, the most vulnerable ones are those euipments which for their own operation need some mechanical movements, for example a CD player or transport and the turntable and also the speakers (with the diaphragms physically moving in and out to make the sound). One needs to make them more isolated than others.

In Indian conditions, I find with my set-up (which is mid-fi) that having heavy shelves and stands (well secured in their positions) is the most important issue. Speaker stands should always be heavy and steady. Once in the US long time ago (1992-94), I had my speakers (the same ones I have now) on some light stands (bought from Best Buy), and the sound became really strange and poor, as if all the wind was knocked out of the musicians. I did not immediately understand why it was so, there was no forum to discuss these things at that time. I learnt that part with time just by trying.

Note added later: After my post, I noticed that square_wave also has posted. Obviously there are quite a few things common in both of our posts.

 

[psychotropic]

Thanks Asit and Square_Wave, can i repeat a couple of my more specific questions, and some follow up questions on your poasts.

1) For instance, if there is a non-resonant material between your speakers and the surface of say your desk or table, should that not be sufficient to contain the external vibrations being trasmitted between your desk and your speaker (or vice versa)? Say for instance you keep a 1 s. ft. square of one inch thick granite joined to a 1 s. ft. square of MDF with say blu-tack, and keep it on your table and place your speakers on it, in what ways would this be inferior to a proper 'speaker stand' ?

2) you said that you need to protect the equipment from extraneous vibrations, is it also necessary that we ensure that the speakers vibrations are not transferred to the the rack or the floor? which of these is more important?

Square Wave - I have some questions on your points in bold


1.Airborne vibrations (typically caused by the vibrating cone of the loudspeakers). how are these taken care of? by treating the room?

2.Vibration that travel through the floor into the platform holding the gear. are stands the only way to achieve this for speakers?

3.Vibration that originate from the equipment itself. It travels into the platform holding the gear. will not something that achieves objective 2, also achieve this objective 3?

 

[gobble]

I had posted some links and explanation in another thread - granite is resonant.

Regards

 

[psychotropic]

hey gobble, i had read your links, which is why i said 'assume' in my first post, instead of granite say we use 12 mm glass. so 12mm glass + blu tack + MDF.....how would this perform worse than a speaker stand?

one more scenario, the above combo with spikes, and those spikes resting on the table/desk/platform/whatever.....how would this perform worse than a speaker stand?

I had posted some links and explanation in another thread - granite is resonant.

Regards

 

[psychotropic]

no one else wants to give out some gyan?

 

[square_wave]

It depends. I have a very strong feeling that in our pursuit for 'neutrality, we look at the wrong end of the horse. The weakest link in the audio chain is usually the room, the speakers, the listener and the source/source material, in that particular order. The effects of the amplifier and the fiddly bits are IMO secondary, and should be investigated after the first set of problems is mitigated (and that can take a lot of money). Blu-Tack ain't gonna do diddly squat if your room is one large reflective mess, or the speakers have no space to the sidewall. Those are more urgent problems.

This is more or less what I have tried to say in my earlier post. Unless these critical issues are addressed, the rest of the tweaks will not get anybody anywhere.
The title science of neutrality seems to be misplaced in the context of the discussion here

 

[square_wave]

Cranky,
I have heard of two type of designs. High Q and low Q designs in loudspeaker cabinet design system.
A high Q indicates that for the amount of energy stored in a resonant system, the mechanisms that dissipate that energy
are small. So a high-Q system will tend to have a resonance that decays slowly, because the amount of resistance
available to dissipate the energy is small compared to the amount of energy stored. A low-Q system will tend to dampen
the resonant motion quickly, because the energy is dissipated quickly and removed from the resonant system.

I have heard that these two types of loudspeakers need to be handled in different ways when you try to marry them to a stand. De-couple, couple, Isolate etc
For example, Merlin recomends blu tack under the speakers and no spikes. while some others prefer spikes.
Any thoughts ?
I have seen many a fight over at AA over this

 

[psychotropic]

hey cranky thanks a ton, i realise that the title of the thread is a bit misleading i realise, as "neutrality" is not exactly the objective over here. My bad!

Quick replies, Asit and SW's posts cover most of what you need to know.

1) What are the objectives when you are getting/building stands or a rack? What are the various types of resonances that we are trying to address, and how do we address each of these individually and collectively? What is isolation? what is coupling? what else do we need to know?

Energy flows from a point of excess (source), to a place of shortage (sink). Coupling increases the rate of flow, and isolation reduces the rate of flow. SW has outlined the sources of energy and all one needs to do is figure out the source and nature of all vibrations in a system. A speaker with flexing sidewalls will require dissipation through the length of the stand, but very good coupling at the mount point, whereas a speaker with well-behaved resonances can be coupled with the minimum of dissipation.

Stands are usually coupled to the floor, I know of very few speaker stands (well-designed) that are designed for isolation. Equipment racks should usually be exactly the reverse of the above, and add protection from airborne vibration if any. The two schools of development in speaker stands is light and rigid, or massive and rigid, but both are rigid. I guess you can figure out why.

2) How does each component of a stand (such as the spikes, the base plate, the tube, the sand filling, the top plate, the washers, etc.,) help in achieving these objectives, and similarly how do the various components of a rack help in achieving these objectives?

See above for hints. You're not going to let me do all the work, are you?

3) what are the best materials for achieving these objectives, and how do they need to be used?

This is a tough one really. Most metals exhibit ringing and most natural products have less rigidity. Composites are very promising, though (Carbon Fiber). For argument's sake you need no part of the stand to have it's natural resonance within the audio band. This is easier said than done. Very heavy glass works, but is prone to damage. Aluminum is a no-no, unless it's 14 inches thick. Stone is non-resonant only when it's a composite. Natural stone rings horribly, ever been to a quarry? I prefer to build/buy speakers with controlled resonance (a stethoscope is a wonderful tool to check speaker panels) and have light and rigid stands, such as common in studios. These usually consist of steel rods with excellent transmission. They ring a bit, but they work very well. Some studios prefer to put the speakers on custom racks of 4" steel bar construction. Those things could dent a truck.

4) suri mentioned somewhere that just using a slab (say 12mm) of granite will not be useful. Assuming that granite is not resonant (i've seen the discussion on this, and i am just assuming here), then wouldn't a slab of granite be good in providing isolation to the speakers? why not?

Granite is heavy. It is very good at being stable. Beyond that, however, I am skeptical of its properties. It is difficult to work with, requires lots of additional hardware for adaption to floors and speaker bottoms. Apart from that, it rings with a pretty wide spectrum of noise. Isolation is not related to weight, FWIW.

5) what are the tools and implements that we can use to achieve neutrality? i've heard of cones and feet and blu-tack and squishy balls and stuff like that...which of these have you guys tried and how effective are they and for what components? How do these things achieve their objective of furthering the neutrality of your systems?

It depends. I have a very strong feeling that in our pursuit for 'neutrality, we look at the wrong end of the horse. The weakest link in the audio chain is usually the room, the speakers, the listener and the source/source material, in that particular order. The effects of the amplifier and the fiddly bits are IMO secondary, and should be investigated after the first set of problems is mitigated (and that can take a lot of money). Blu-Tack ain't gonna do diddly squat if your room is one large reflective mess, or the speakers have no space to the sidewall. Those are more urgent problems.

Tennis balls are a good start for under equipment, and Blu-tack can help if your speakers wobble on the stand (should not be used otherwise). Spikes almost always help under speakers, or stands. They may make a highly resonant speaker sound very aggressive though, so some experimentation is key, really.

But i still don't know what this has to do with 'Neutrality'. I don't understand the relationship between the topic title and your specific question, so would be good if you could enlighten me... You can't get rid of energy, only convert it into various forms. In the case of audio, every piece of equipment is generating some kind of energy. The mechanical energy of vibration may or may not affect neutrality. This is very individual by nature.

6) do we approach the neutrality of the output of our system keeping both the room as well as the stands/contact points in mind, or are room resonances and other resonances to be dealt with separately?

I didn't understand this one, sorry.

 

[psychotropic]

Oh it looks like I can't correct the name of the thread, only the title of the first post....where I was coming from was that i was under the impression that eliminating unwanted resonances and reflections and so on were all steps to attaining a perfectly neutral sound.

 

[stevieboy]

psychotropic,

this is an extremely open (read never ending) discussion point. basically spikes versus something soft/damping will have different effects on the sound so try both types and see what you like. this is very equipment and ear dependent. i have my cd player on spikes and two round weights on top of it. tightens up the sound considerably, makes it more solid. a good primer would be to go through acousticsounds.com and go through all that they have on isolation equiment. the writeups for each product will give you insights on the various ways one can control vibration.

also some people use two layers of different material together to better damp different frequencies. eg cork board and plywood. slate which is a layered stone is good for turntables. check out slatedeck.com and plywood is better than mdf. you could use granite as one base slab but use blutak or squash ball cut in half or something similar and a plywood sheet on top. or you could use spikes and place a granite slab on top and speakers on top. you might find differences you might not find too much difference!

regards

 

[Asit]

1) For instance, if there is a non-resonant material between your speakers and the surface of say your desk or table, should that not be sufficient to contain the external vibrations being trasmitted between your desk and your speaker (or vice versa)? Say for instance you keep a 1 s. ft. square of one inch thick granite joined to a 1 s. ft. square of MDF with say blu-tack, and keep it on your table and place your speakers on it, in what ways would this be inferior to a proper 'speaker stand' ?

I think other people, especially Cranky, have effectively addressed this. All I can say is that I have kept my speakers at times on top of heavy stools and got very good results. But my speakers are very special, I guess. They do not seem to care too much about anything except that they are kept on a rigid, firm and heavy base.

2) you said that you need to protect the equipment from extraneous vibrations, is it also necessary that we ensure that the speakers vibrations are not transferred to the the rack or the floor? which of these is more important?

Do your speakers vibrate as a whole? I find that very strange. Of course the diaphragms vibrate to make the sound, but the effect of that on the speaker cabinet should be negligible. I guess this may have to do with the material of the speaker cabinet. Mine is made of solid wood and I have touched the surface when music is being played and I do not feel very much. Okay, I'll try it again this evening and let you know. Sometimes, with the previous HK amp (which has a bit of Rotel amp like charateristics, I guess), especially when some music was being played with heavy bass content, I could feel the air throw even at my listening position which is not less than 10 feet. But with the Leben (obviously a much better amp), music is never thrown at me. But in neither case, I do not think there is a significant vibration of the speaker cabinets as a whole. Hence I cannot answer your question what to do in such a case.