Why are vibration isolation products still considered accessories?

Testy Troll

Well-Known Member
Dec 29, 2015
10
0
81
#21
DaveC,
Once again, can you provide me data on the deleterious use of concrete floors?
I did a brief search and found nothing.
I recall J. Gordon Holt used concrete floors when he set up his listening room.

Please, educate me....
 

DaveC

Industry Expert
Nov 16, 2014
3,132
1,037
390
#22
DaveC,
Once again, can you provide me data on the deleterious use of concrete floors?
I did a brief search and found nothing.
I recall J. Gordon Holt used concrete floors when he set up his listening room.

Please, educate me....
I'm just relating my own experience. I have not measured vibrations in floors as I don't make isolation products and have plenty of other stuff to do. Maybe check with manufacturers of isolation devices? Or simply experiment for yourself?
 

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
8,886
2,671
770
#23
Actually, Mike, we can generalize. Either a method and its principles work consistantly throughout or something is wrong with the method and/or its principles.
i see it differently. in my experience i try things and listen over time. it sounds better......or not. it's my approach. and i've found that the same method is not ideal for each piece of gear.

As for turning your active devices on and off and hearing sonic differences, which source of vibrations do you suppose they are addressing? More importantly, which sources of vibrations are the mfg'ers telling you they are addressing?
i'm a listener, and the what and why are not important to me. in fact, i realize that my techie knowledge is limited so since i can only understand the surface aspect of science, i don't get caught up in that side of things. i only care whether it makes the music more real.

I've no clue about your devices but as for "real science", hasn't everybody claimed real science has been behind vibration isolation for maybe 30 years now?
i'm sure you could teach these guys about your perspective. but.......maybe not. they provide products to industry and research facilities. scroll down to learn some real science about vibration attenuation.

https://www.herzan.com/resources/tutorials.html

I agree about approaching any subject blindly is misguided. I think I've sufficiently described that's exactly what the isolationist has done these past 30+ years. Even if they hear nice but limited improvements along the way.
and i have no reason to doubt your experiences and if they work then enjoy them. i like my own for myself too.
 
Likes: Stbo

Testy Troll

Well-Known Member
Dec 29, 2015
10
0
81
#24
I'm just relating my own experience. I have not measured vibrations in floors as I don't make isolation products and have plenty of other stuff to do. Maybe check with manufacturers of isolation devices? Or simply experiment for yourself?
I'm glad to see you changed your original reply to me as it did not reflect well on you.
Not itching for a fight, but when you claim cement floor resonances are a factor then some explanation/proof is required on your part. If all of your evidence is anecdotal, then you must have felt the concrete floor vibrate at some point since no measurements were taken. I have no doubt that the floor has a resonant frequency, but an 8", steel reinforced floor would likely not resonate with enough power to affect the speakers mounted upon it or isolated components within the room. And what great, large source would be required to get the massive floors a-resonating?

I have experimented for myself. I've owned/rented three homes with concrete floors and three with wood floors.
The concrete floors win hands down.
There are methods that I've used to beef up wooden floors to improve their performance.

I've never used a bare concrete floor.
Currently, I employ a 1/2" pad under a wall to wall rug.
Also lots of diffusion/absorption devices on the walls and ceiling.
The floor is the least of my worries...
 
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Hear Here

Active Member
Feb 14, 2020
111
51
30
76
Portsmouth, UK
#25
Thanks Dave. In fact I bought Gaia IIs for the Martin Logan 13As I now have for sale and I've tried them on the older AG Duos that I'm currently using. These were fixed as per attached photo, but I really should use Gaia Is on these heavier spreakers. When the subs are on the Gaias the cabinets are isolated from my floor (timber on screen on concrete) but the mid and top tubes are further isolated from the sub cabinet by using vibration bushes and Sorbothane isolation pads - the 3 chrome thumb-bolts go into vibration-absorbing rubber bobbins.. I feel that the mid and top tubes really do need isolation from the sub cabinets (which they do in my present AG arrangement), but I'm less convinced at the need for isolating the sub from the floor. AG recommend spikes.

When I look carefully at the Duo XD design, I see that the base frame is standing on spikes, but the sub cabinets are "floating" as they are bolted to the uprights using vibration-absorbing rubber bobbins. The midhorn tube is also connected to these uprights with similar bobbins. This leaves the subs and midhorn tubes isolated from the floor to some extent and the mid-horn tubes double-isolated from vibration generated by the subs.

In view of this I'm disinclined to use Gaias or other isolation devices with the new Duo XDs The only IsoAcoustic option would be the Gaia Is that are rated at 100 kg per set - good for these 95 Kg speakers.

If isolation is important with some installations, are we not best off using air cushions rather than Gaias or alternative "audiophile" devices? I use simple air pumps (pump wedges) to lift my heavy speakers to change spikes etc. When pumped up, it would appear that even more vibration isolation could be achieved compared with Gaias, etc. And they cost a few bucks each! Thin-walled air filled balls or an air mattress IMG_5957.JPG would be a more attractive alternative unless we want to suspecd our speakers from the ceiling with elastic/ bungee cords. Wouldn't these forms of isolation be even more effective and much less coatly? Peter IMG_5960.JPG
 

DaveC

Industry Expert
Nov 16, 2014
3,132
1,037
390
#26
Not itching for a fight, but when you claim cement floor resonances are a factor then some explanation/proof is required on your part.
No, it is not.

I'm here casually chatting and sharing observations and experiences. Folks who DEMAND these kinds of things are taking the conversation WAY too seriously, and my answer to that is: Do your own research if you're interested in it. I'm not an expert, never claimed to be an authority on anything, and have absolutely no obligation to provide you with any additional information on anything.
 

DaveC

Industry Expert
Nov 16, 2014
3,132
1,037
390
#27
If isolation is important with some installations, are we not best off using air cushions rather than Gaias or alternative "audiophile" devices? I use simple air pumps (pump wedges) to lift my heavy speakers to change spikes etc. When pumped up, it would appear that even more vibration isolation could be achieved compared with Gaias, etc. And they cost a few bucks each! Thin-walled air filled balls or an air mattress would be a more attractive alternative unless we want to suspecd our speakers from the ceiling with elastic/ bungee cords. Wouldn't these forms of isolation be even more effective and much less coatly? Peter
Agreed, many of these solutions can work very well.

I know of at least one commercial design that has the speaker hanging from a stand and know a couple people who do indeed hang their speakers from the ceiling, they all claim it works very well. I think an air bladder may work well too. The issue is you don't want the device to have resonant peaks in it's frequency vs attenuation performance, and it needs to keep the speaker steady. I have heard from an expert here who has done measurements and sells vibration control products that many soft materials like sorbothane do indeed produce very non-linear results with peaks and this may be responsible for making the sound seem dead and lifeless when implemented in an audio system, although I hear those results mainly from using soft footers on component chassis.

I think the vast array of devices sold and solutions espoused are an indication that we lack some knowledge as far as how vibration control relates to user preference in audio systems.

P.S. I think you'll be VERY happy with your new XDs, IMO they are a massive leap over the older designs. And it's nice to hear they have paid attention to vibration controls in the design as well. :)
 

Maril555

Well-Known Member
Jun 27, 2014
131
42
235
#28
Thanks Dave. In fact I bought Gaia IIs for the Martin Logan 13As I now have for sale and I've tried them on the older AG Duos that I'm currently using. These were fixed as per attached photo, but I really should use Gaia Is on these heavier spreakers. When the subs are on the Gaias the cabinets are isolated from my floor (timber on screen on concrete) but the mid and top tubes are further isolated from the sub cabinet by using vibration bushes and Sorbothane isolation pads - the 3 chrome thumb-bolts go into vibration-absorbing rubber bobbins.. I feel that the mid and top tubes really do need isolation from the sub cabinets (which they do in my present AG arrangement), but I'm less convinced at the need for isolating the sub from the floor. AG recommend spikes.

When I look carefully at the Duo XD design, I see that the base frame is standing on spikes, but the sub cabinets are "floating" as they are bolted to the uprights using vibration-absorbing rubber bobbins. The midhorn tube is also connected to these uprights with similar bobbins. This leaves the subs and midhorn tubes isolated from the floor to some extent and the mid-horn tubes double-isolated from vibration generated by the subs.

In view of this I'm disinclined to use Gaias or other isolation devices with the new Duo XDs The only IsoAcoustic option would be the Gaia Is that are rated at 100 kg per set - good for these 95 Kg speakers.

If isolation is important with some installations, are we not best off using air cushions rather than Gaias or alternative "audiophile" devices? I use simple air pumps (pump wedges) to lift my heavy speakers to change spikes etc. When pumped up, it would appear that even more vibration isolation could be achieved compared with Gaias, etc. And they cost a few bucks each! Thin-walled air filled balls or an air mattress View attachment 66593 would be a more attractive alternative unless we want to suspecd our speakers from the ceiling with elastic/ bungee cords. Wouldn't these forms of isolation be even more effective and much less coatly? Peter View attachment 66594
Fort what it's worth.
I have Avantgarde Duo Omega G2, and the supplied spikes are the worst option in my experience.
I have ended up using Stillpoints Ultra 5s with ebony wood in b/w them and Symposium platform the speakers are sitting on.
Admittedly, and for obvious reasons, I haven't tried every option available, but I stopped trying after implementing the above solution.
 

Blackmorec

Well-Known Member
Feb 1, 2019
312
400
68
67
#29
Like most things in audio, vibration control is not as straightforward as it may first appear, but understanding a few important characteristics can be very helpful in building a well executed strategy to control vibration.

Firstly lets list a few components known to be negatively affected by vibration:
  • Crystal oscillators, the heart of digital systems and present in many components of modern digital systems really don’t perform well when vibrated....so vibration can be a source of jitter and noise in digital systems
  • Printed circuit boards
  • Circuit board connectors
  • Capacitors
  • Connectors, sockets and plugs....
Then let’s list a few types of vibration that can affect audio systems:
  • Seismic
  • Structural
  • Airborne
  • Internal, component generated (motors, transformers, rectifiers etc)
There are literally thousands of different devices designed to ameliorate problems related to vibration...the correct approach can bring major improvements, while ill thought out approaches can cause coloration or distortion and rob the music of its vibrancy, naturalness, pace, rhythm and timing (PRaT). A perfectly well engineered device, used in the wrong setting (for the wrong reason) is just as bad or worse than a poorly designed device, so it can be a minefield unless you understand a few basic principles.

Firstly, energy can neither be created nor destroyed and that goes for vibrational energy too....so vibration can’t just disappear and you have to do something with it. It can be converted to another form of energy like work or heat, or it can be grounded and lead away from a component. You can stop a component vibrating by removing the source of vibration or by isolating the component from the vibration, however different strategies are often in conflict with one another and you need to resolve these conflicts as part of your strategy. For example, if you isolate a component from external vibration using high compliance footers for example, at the same time you lock in the internal vibration that the device itself generates. Similarly, if you use hard footers to couple the component to its base, you essentially ground the internal vibration but couple the device to external vibration. This is exactly why your strategy needs to be well thought through!

Let‘s look at the phenomena of coupling and isolation. Vibrations pass easily between materials of similar compliance (density, stiffness, elasticity) and very poorly between materials with widely diverging compliance, so hard footers like aluminium, steel or carbon fibre under a steel or aluminium component housing will couple, while soft footers like Sorbothane will isolate. We can call these low impedance coupling (well matched compliance) and high impedance coupling (highly differentiated compliance).

Another phenomena I have observed is that different support materials tends to imbue the music with tonal characteristics similar to their resonant frequencies I.e the frequency at which those materials naturally vibrate...so a glass shelf under a component may make the music sound slightly hard with a ’glass-like’ emphasis or ringing in the treble. This is likely to do with vibrations from the glass entering the component, so ideally you want component vibrations to pass into the support (grounding), while your want the component isolated from its support (isolation)....a clear conflict that’s going to take some clever engineering to solve.
So how can this dilemma be resolved?
Essentially what you want are supports that isolate your component from Seismic (ground borne), structural (most usually energy from the loudspeakers) vibration and the resulting support structure resonances, while at the same time providing the component with a grounding path to lead away its internally generated vibrations....in other words you need multi-functional supports that provide both grounding and isolation, providing the correct impedance s at exactly the right points to achieve your 2 goals. This sounds like a conflict, but its exactly where carefully thought through technology and implementation are requireD to solve the problem.

Products like `Sorbothane’ provide excellent isolation, but inhibit grounding. If you isolate your component from it’s support structure, you also prevent any internal vibration from grounding into the support. Products like BDR cones provide excellent grounding by coupling the component to its support, but that coupling is bi-directional, so if you ground the internal vibration you also couple the component to any support structure borme vibration.

So hopefully, you see some of the problems associated with implementing vibration control ‘accessories’ that only ground or isolate. This is a good point to discuss the third strategy that we mentioned at the beginning of this post, namely conversion. In order to solve the dilemma of needing to ground in 1 direction and isolate in another, a device may incorporate a mechanism to convert vibration to heat or work. In this way, the device can be configured to ideally couple to the component, then convert the component’s vibrational energy to heat or work. The same component can then isolate the component from its support structure.
The structure of such a device would be as follows.....well matched, low compliance, low impedance interface to the component, followed by increasingly compliant layers designed to convert the component’s vibrational energy to heat. At the opposite base end of the device, where it interfaces with the support structure, you’d want a high compliance, high impedance interface to prevent support structure vibration being transmitted into the footer and on to the component. Devices like the Centre Stage Footer are constructed in this manner. Component vibration flows into the footer and is converted to heat, while the soft layer in contact with the support structure isolates the component from structural and seismic vibration.
When you implement any combination of vibration controls, you really have to look at the situation bidirectionally and figure out; ‘How and where is my component being isolated from Seismic and structural vibration and how are internal vibrations being removed from the component by grounding and/or conversion. When you can clearly answer those questions and the answer is non-conflicting and logical, you have a good strategy for managing vibration.
I hope the above is reasonably understandable o_O
 
Last edited:

Blackmorec

Well-Known Member
Feb 1, 2019
312
400
68
67
#30
Just as an aside on the subject of concrete floors

There are concrete floors that are layered directly on the earth....basements for example. Here very low frequency seismic vibrations would be the issue

Then there are concrete floors made from reinforced concrete linked to the building’ s walls Seismic and structural vibration would be the issue here

Finally there is the so-called ’Estrich’ which is a thin layer of concrete, not connected to the walls, usually placed on top of insulation and designed to insulate the floors below from footfall noise etc. As the concrete is sufficiently thin and floating (unsupported) the issue would be mainly vibration generated by the loudspeakers.
 

DaveC

Industry Expert
Nov 16, 2014
3,132
1,037
390
#31
Like most things in audio, vibration control is not as straightforward as it may first appear, but understanding a few important characteristics can be very helpful in building a well executed strategy to control vibration.

Firstly lets list a few components known to be negatively affected by vibration:
  • Crystal oscillators, the heart of digital systems and present in many components of modern digital systems really don’t perform well when vibrated....so vibration can be a source of jitter and noise in digital systems
  • Printed circuit boards
  • Circuit board connectors
  • Capacitors
  • Connectors, sockets and plugs....
Then let’s list a few types of vibration that can affect audio systems:
  • Seismic
  • Structural
  • Airborne
  • Internal, component generated (motors, transformers, rectifiers etc)
There are literally thousands of different devices designed to ameliorate problems related to vibration...the correct approach can bring major improvements, while ill thought out approaches can cause coloration or distortion and rob the music of its vibrancy, naturalness, pace, rhythm and timing (PRaT). A perfectly well engineered device, used in the wrong setting (for the wrong reason) is just as bad or worse than a poorly designed device, so it can be a minefield unless you understand a few basic principles.

Firstly, energy can neither be created nor destroyed and that goes for vibrational energy too....so vibration can’t just disappear and you have to do something with it. It can be converted to another form of energy like work or heat, or it can be grounded and lead away from a component. You can stop a component vibrating by removing the source of vibration or by isolating the component from the vibration, however different strategies are often in conflict with one another and you need to resolve these conflicts as part of your strategy. For example, if you isolate a component from external vibration using high compliance footers for example, at the same time you lock in the internal vibration that the device itself generates. Similarly, if you use hard footers to couple the component to its base, you essentially ground the internal vibration but couple the device to external vibration. This is exactly why your strategy needs to be well thought through!

Let‘s look at the phenomena of coupling and isolation. Vibrations pass easily between materials of similar compliance (density, stiffness, elasticity) and very poorly between materials with widely diverging compliance, so hard footers like aluminium, steel or carbon fibre under a steel or aluminium component housing will couple, while soft footers like Sorbothane will isolate. We can call these low impedance coupling (well matched compliance) and high impedance coupling (highly differentiated compliance).

Another phenomena I have observed is that different support materials tends to imbue the music with tonal characteristics similar to their resonant frequencies I.e the frequency at which those materials naturally vibrate...so a glass shelf under a component may make the music sound slightly hard with a ’glass-like’ emphasis or ringing in the treble. This is likely to do with vibrations from the glass entering the component, so ideally you want component vibrations to pass into the support (grounding), while your want the component isolated from its support (isolation)....a clear conflict that’s going to take some clever engineering to solve.
So how can this dilemma be resolved?
Essentially what you want are supports that isolate your component from Seismic (ground borne), structural (most usually energy from the loudspeakers) vibration and the resulting support structure resonances, while at the same time providing the component with a grounding path to lead away its internally generated vibrations....in other words you need multi-functional supports that provide both grounding and isolation, providing the correct impedance s at exactly the right points to achieve your 2 goals. This sounds like a conflict, but its exactly where carefully thought through technology and implementation are requireD to solve the problem.

Products like `Sorbothane’ provide excellent isolation, but inhibit grounding. If you isolate your component from it’s support structure, you also prevent any internal vibration from grounding into the support. Products like BDR cones provide excellent grounding by coupling the component to its support, but that coupling is bi-directional, so if you ground the internal vibration you also couple the component to any support structure borme vibration.

So hopefully, you see some of the problems associated with implementing vibration control ‘accessories’ that only ground or isolate. This is a good point to discuss the third strategy that we mentioned at the beginning of this post, namely conversion. In order to solve the dilemma of needing to ground in 1 direction and isolate in another, a device may incorporate a mechanism to convert vibration to heat or work. In this way, the device can be configured to ideally couple to the component, then convert the component’s vibrational energy to heat or work. The same component can then isolate the component from its support structure.
The structure of such a device would be as follows.....well matched, low compliance, low impedance interface to the component, followed by increasingly compliant layers designed to convert the component’s vibrational energy to heat. At the opposite base end of the device, where it interfaces with the support structure, you’d want a high compliance, high impedance interface to prevent support structure vibration being transmitted into the footer and on to the component. Devices like the Centre Stage Footer are constructed in this manner. Component vibration flows into the footer and is converted to heat, while the soft layer in contact with the support structure isolates the component from structural and seismic vibration.
When you implement any combination of vibration controls, you really have to look at the situation bidirectionally and figure out; ‘How and where is my component being isolated from Seismic and structural vibration and how are internal vibrations being removed from the component by grounding and/or conversion. When you can clearly answer those questions and the answer is non-conflicting and logical, you have a good strategy for managing vibration.
I hope the above is reasonably understandable o_O

Good post!

Isolation and transformation are always one and the same, all soft viscoelastic materials have a hysteresis curve. What was explained to me in another thread is that some materials have very uneven frequency vs attenuation curves, some with spikes in the curve where it can make some resonances worse, and this is an issue that can cause the lifeless sound many of us are familiar with when using soft footers on components.

Vibration is well understood wrt most scientific equipment, but correlating that knowledge to preferences in audio systems is the issue.
 

DaveC

Industry Expert
Nov 16, 2014
3,132
1,037
390
#32
Just as an aside on the subject of concrete floors

There are concrete floors that are layered directly on the earth....basements for example. Here very low frequency seismic vibrations would be the issue

Then there are concrete floors made from reinforced concrete linked to the building’ s walls Seismic and structural vibration would be the issue here

Finally there is the so-called ’Estrich’ which is a thin layer of concrete, not connected to the walls, usually placed on top of insulation and designed to insulate the floors below from footfall noise etc. As the concrete is sufficiently thin and floating (unsupported) the issue would be mainly vibration generated by the loudspeakers.
I think people underestimate how much energy from loudspeakers can get into housing structures, including concrete floors.
 

Hear Here

Active Member
Feb 14, 2020
111
51
30
76
Portsmouth, UK
#33
Fort what it's worth.
I have Avantgarde Duo Omega G2, and the supplied spikes are the worst option in my experience.
I have ended up using Stillpoints Ultra 5s with ebony wood in b/w them and Symposium platform the speakers are sitting on.
Admittedly, and for obvious reasons, I haven't tried every option available, but I stopped trying after implementing the above solution.
I think my present Duos are just pre-Omega as they could have been upgraded to Omega - but haven't been.

What do you think of my mods to their looks? I've never liked the "scaffolding" so had an F-shaped frame made locally that supports the horn tubes. It's mounted to the back of the sub using left-over rubber bobbins and thumb-bolts. Many years ago I obtained from Avantgarde a set of 8 curved shims that they use in the Trio to securely support the treble tube from one side only. Using these and Sorbothane pads and the rubber bobbins, these tubes are vibration-isolated from the subs - in fact more so than the original design.

I fitted nice outrigger feet to the sub cases and can attach either spikes or something like IsoAcoustic Gaias to suit. I'm currently on spikes. The outriggers add to stability and, together with ditching the scaffolding, thus slimming their appearance, modernise the look of these old speakers - IMO! They've taken on a new lease of life, all for a couple of hunded quid and a bit of careful planning.

Favourable comments from Holger Fromme ("Your modification looks absolutely cool. Can we publish these on our website") and Jim Smith ("I Like!!!") were amongst those received for these changes.

Drawings on request - equally applicable to Unos. You could easily amend so the horn tubes hang from (rather than be supported by) the frame. IMG_0106.JPG IMG_0102.JPG IMG_5954.JPG Either way, the original scaffolding can easily be restored with just 2 small holes (easily stoppable with M8 bolts) in the back panel of the sub. Peter
 
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Testy Troll

Well-Known Member
Dec 29, 2015
10
0
81
#34
I think people underestimate how much energy from loudspeakers can get into housing structures, including concrete floors.
I'm willing to believe energy from loudspeakers (especially subwoofers) can be transferred to walls and ceilings (and this is why one needs to treat them). But IMO, a massive structure like a steel reinforced foundation would need a lot more than loudspeakers to get it resonating/vibrating.

I'm dead serious. If you have some analysis that indicates concrete floors can be significantly stimulated by your average (or above average) stereo system, I'm more than willing to weigh such evidence.
All you have to do is provide it...
 

Testy Troll

Well-Known Member
Dec 29, 2015
10
0
81
#35
Just as an aside on the subject of concrete floors

There are concrete floors that are layered directly on the earth....basements for example. Here very low frequency seismic vibrations would be the issue

Then there are concrete floors made from reinforced concrete linked to the building’ s walls Seismic and structural vibration would be the issue here

Finally there is the so-called ’Estrich’ which is a thin layer of concrete, not connected to the walls, usually placed on top of insulation and designed to insulate the floors below from footfall noise etc. As the concrete is sufficiently thin and floating (unsupported) the issue would be mainly vibration generated by the loudspeakers.
I enjoyed your previous post and the one above.
My situation is your 2nd example (concrete floors made from reinforced concrete linked to the building’ s walls). My outer foundation walls only rise around 3 ft above the ground (with another 1-2 ft underground).
In some spots the wall is 2 ft thick. My home was built in the early 60s and with 60 yrs of age the concrete has become QUITE HARD. I used sledge hammers, jack hammers and serious diamond tip gas saws on certain sections when I did some house additions a couple of years ago.
I can assure you that my concrete was like granite.

You mention seismic activity in your post.
I've lived in CA since 1983 so I'm well aware of the power of shifting plates!
I'm no expert on the subject so please enlighten me.
Obviously, when an earthquake (minor or major) happens, any foundation would vibrate/resonate.
Are you saying that seismic activity affecting the foundation is a constant 24/7 occurrence?
If so, is it really of a magnitude that would be deletarious to a stereo setup?
 

BlueFox

Member Sponsor
Nov 8, 2013
1,435
151
285
#36
My house has concrete floors, and they sit directly on the ground. My house was built in the 50s, so I suspect it is settled by now. The floors are covered with wooden flooring over the concrete. When I added spikes to my speakers there was a slight improvement in sound, but nothing really major. To be honest, I was a bit surprised since putting the gear on brass footers made a big improvement.
 
Mar 14, 2019
27
9
10
France
#37
To be honest, I was a bit surprised since putting the gear on brass footers made a big improvement.
Interesting!
Basic round footers or is there a design quirk somewhere?
 

Blackmorec

Well-Known Member
Feb 1, 2019
312
400
68
67
#38
I enjoyed your previous post and the one above.
My situation is your 2nd example (concrete floors made from reinforced concrete linked to the building’ s walls). My outer foundation walls only rise around 3 ft above the ground (with another 1-2 ft underground).
In some spots the wall is 2 ft thick. My home was built in the early 60s and with 60 yrs of age the concrete has become QUITE HARD. I used sledge hammers, jack hammers and serious diamond tip gas saws on certain sections when I did some house additions a couple of years ago.
I can assure you that my concrete was like granite.

You mention seismic activity in your post.
I've lived in CA since 1983 so I'm well aware of the power of shifting plates!
I'm no expert on the subject so please enlighten me.
Obviously, when an earthquake (minor or major) happens, any foundation would vibrate/resonate.
Are you saying that seismic activity affecting the foundation is a constant 24/7 occurrence?
If so, is it really of a magnitude that would be deletarious to a stereo setup?
Yes, Seismic activity is a round the clock affair, generated within the Earth’s crust and by things like passing traffic, underground trains, wind buffeting buildings etc. Enough to affect stereo systems? Who knows....depends on amplitude, frequency and on the building itself. Given that counter measures usually bring substantial improvements in sound quality, one should probably conclude that isolating stereos from low frequency vibration is generally beneficial. Its certainly one reason hard, precision polished roller bearings work so well under hi-fi gear
 

BlueFox

Member Sponsor
Nov 8, 2013
1,435
151
285
#39
Likes: Gregm

tima

Industry Expert
Mar 4, 2014
1,792
1,289
390
the Upper Midwest
#40
Wrt concrete: Everything vibrates and every thing has a resonance frequency. The earth vibrates around three cycles per second. Resonance occurs when the frequency of excitation equals the natural frequency of an object - the so-called critical frequency. When resonance occurs, the amplitude of the vibration increases; it is limited only by the damping or abatement available to the object.

What is the resonant frequency of concrete? According to this site, the resonant frequency of concrete is 100Hz - 200Hz. At what frequency do subwoofers operate?

How well does concrete transmit vibration? How well does rebar transmit vibration?
 

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