Isolation/decoupler platforms vs. speaker spikes

[Pyrrho]

I have noticed quite a few posts lately touting the supposed benefits of using isolation platforms to "decouple" a subwoofer from the floor, with the idea being that it is bad to have a speaker directly vibrate the floor. This is an interesting contrast to the idea of using spikes on speakers and speaker stands to "couple" a speaker to the floor.

My question is, what should be made of these sorts of claims?

 

[adwilk]

I have noticed quite a few posts lately touting the supposed benefits of using isolation platforms to "decouple" a subwoofer from the floor, with the idea being that it is bad to have a speaker directly vibrate the floor. This is an interesting contrast to the idea of using spikes on speakers and speaker stands to "couple" a speaker to the floor.

My question is, what should be made of these sorts of claims?

A lot of subwoofer frequency material match the resonant frequency of structural parts of the home. Decoupling the sub can help avoid nasty sounds from your substrate. It should be pointed out that its the sound waves that create the vibrations and not the enclosure. The enclosure should not vibrate. Dampening material keeps these waves away from the structural part of your home, ie the Gramma...

Speaker stands and spikes help stability but I've never heard them being "coupled" to the floor in terms of wanting to make sure vibrations are coupled. They shouldnt be vibrating.

 

[MatthewB.]

For years I have been using my SVS NSD 12/2 in my great room just sitting on tile floor and the bass was tight and well controlled and I loved the sound. Then a buddy over at Sound and Vision was selling his two Aurolux Grammas at a price I couldnt turn down. I have Mopads on all my speakers (inlcuding computer power monitors) and love the "angling"and the tighter sound it brought. So I was open to the sub decoupling idea.

Wow was I surprised, I mean jaw dropping surprised at how takingt the sub off my tile floor tightened up the bass the Nth degree, I thought it was good before, but now it's friggin great. My pictures on the wall and my huge bay window no longer vibrate, it raised my sub about 2" which sitting next to my couch was just enough to really increase the tactile effect of the SVS.

My GF suffers from severe asthma, and some movies (Cloverfield) will set her asthma off pronto quick, so I had to turn the gain down to help elleviate her problem. With the Gramma pad in place, I can now turn my sub up at a "Matt Level" of bass and really enjoy the stomping of creatures and explosions without it setting her asthma off. She says the pressure has lessened on her chest even though the volume has increased, all by adding a simple decoupler Gramma pad under my sub.

Now I placed one under my master bedroom sub and that made no inherent difference at all, but that room is heavily carpeted with thick padding, so the "gains" where not as noticable as the sub sitting in the tiled great room.

So for me, it was worth it and I highly recommend a Gramma pad and Mopads to anyone who wants tighter control of their sound.

 

[lsiberian]

I have noticed quite a few posts lately touting the supposed benefits of using isolation platforms to "decouple" a subwoofer from the floor, with the idea being that it is bad to have a speaker directly vibrate the floor. This is an interesting contrast to the idea of using spikes on speakers and speaker stands to "couple" a speaker to the floor.

My question is, what should be made of these sorts of claims?

I can only speak from experience.

With the Gamma pad I can't hear my sub in the other rooms of my apartment.

Without it I can.

The bass does sound tighter as well. I've never ABXed my claims, but I paid for the thing and have no desire to prove myself a fool. Ignorance is bliss on that part.

 

[mtrycrafts]

A lot of subwoofer frequency material match the resonant frequency of structural parts of the home. Decoupling the sub can help avoid nasty sounds from your substrate. It should be pointed out that its the sound waves that create the vibrations and not the enclosure. The enclosure should not vibrate. Dampening material keeps these waves away from the structural part of your home, ie the Gramma...

Speaker stands and spikes help stability but I've never heard them being "coupled" to the floor in terms of wanting to make sure vibrations are coupled. They shouldnt be vibrating.

You have resonance issues whether it is sitting on the floor or not. things in the room will vibrate at some frequency unless it is tightly anchored regardless of spikes or not.

 

[mtrycrafts]

A lot of subwoofer frequency material match the resonant frequency of structural parts of the home. Decoupling the sub can help avoid nasty sounds from your substrate. It should be pointed out that its the sound waves that create the vibrations and not the enclosure. The enclosure should not vibrate. Dampening material keeps these waves away from the structural part of your home, ie the Gramma...

Speaker stands and spikes help stability but I've never heard them being "coupled" to the floor in terms of wanting to make sure vibrations are coupled. They shouldnt be vibrating.

The AH University here has an article on spikes but mainly on stands:

http://www.audioholics.com/education/loudspeaker-basics/speaker-spikes-and-cones-2013-what2019s-the-point

Room structures can pick up vibration from subs just fine from the airborne vibrations from playing the sub.
One issue in the reference in that article not mentioned is at what level of structural vibration if carried from a sitting speaker is audible.

 

[adwilk]

You have resonance issues whether it is sitting on the floor or not. things in the room will vibrate at some frequency unless it is tightly anchored regardless of spikes or not.

I wasn't implying that you wouldn't have issues, I was just saying that the "decoupling" helps avoid immediate harmonic resonance, at least it reduces it. The pressure level CAN be high very near the enclosure, thus higher chance of structure resonance. That doesnt mean it wont rattle the dishes in the kitchen.

 

[just-some-guy]

i used to be a spike man. not any more. i want "me" to feel to sound, not the structure. makes a difference.

 

[FirstReflection]

I know I'm at least partially to "blame" for some of the decoupling talk. I am a HUGE supporter of decoupling speakers and subwoofer from the surfaces upon which they sit. I honestly believe it would be GREAT if every sub in the world automatically came with a GRAMMA

It's the principle of decoupling that is important though, not the device. I happen to think that $50 for an Auralex GRAMMA or SubDude is a fair price, but you certainly aren't limited to only those Auralex products.

A lot depends on how heavy the subwoofer is and how pointy its "feet" are. Basically, you just want to stop the vibrations of the subwoofer from reaching the hard structure of the floor. So if the subwoofer isn't terribly heavy and it's using wider feet (or no feet), then a nice, thick carpet pad will likely decouple that subwoofer just fine!

Spikes though can literally penetrate right through a carpet and its pad. In that sense, they "couple" the subwoofer or speaker stand to the solid structure of the floor.

There are a few principles to consider when it comes to sound transmission:

First - what we normally think of as "sound" are just vibrations travelling through the air. Molecules "bump" into each other and in this way, energy is passed along from molecule to molecule.

In the air, the molecules are fairly far apart, but they are also very easy to move and there is essentially nothing dampening their movement.

So eventually the air molecules meet a wall. The wall's molecules are much closer together and thus, the wall is much more dense than air. It will take more energy to get those wall molecules moving. But if they DO move - at all - they very easily "bump" into each other because they are so close. Sound actually travels faster through a solid than through a liquid or a gas. And if the solid doesn't really dampen the vibrations at all (wood, sheetrock and concrete aren't really the best dampeners), then the sound can actually travel further while retaining more energy (loudness) than it could through the air.

So adding a lot of mass helps to soundproof a space simply by virtue of making it harder to get the molecules moving in the first place. But once they DO move, the sound travels VERY well - better than through air, in fact!

So the other principle to consider is that of dampening. "Squishy" materials are dampeners. They are "shock absorbers". They move, but they do not "snap" back into position. The rebound much more slowly by being visco-elastic or semi-liquid.

So we put it all together. We WANT to hear the vibrations that are travelling through the air. But we do NOT want to hear the vibrations that are travelling through the solid structure of our homes! So we use a dampening material in between to "cushion" the vibrations.

I've seen several people question whether or not a decoupling pad beneath a subwoofer really makes a difference. I've seen people question why it would be equally important to decouple a subwoofer from a concrete floor as it is to decouple it from a wood frame floor. I've seen people use intuitive logic to say that it shouldn't matter as much on a concrete floor. The problem is that intuition is mostly wrong in this case.

Sometimes, science isn't about predicting what you think ought to happen. Sometimes, science is about explaining why something you don't intuitively think should happen DOES happen. You observe what is happening and then use science to figure out WHY - when intuition tells you that it maybe shouldn't happen.

The heavier, denser concrete floor does require more energy than the wood floor to get it to shake. But if the concrete floor shakes AT ALL, it transmits that sound energy extremely well. Wood is actually a better dampener than concrete, but neither are very good dampeners. So the wood floor WILL shake more easily, but that doesn't mean that you don't still need a decoupling device with a concrete floor!

Observation tells us that there is still a whole lot of shaking happening with a concrete floor! It might go against intuition, but the observation is correct and I hope I've explained clearly WHY the observation is correct and intuition is incorrect. So decouple the subwoofer, stop the shaking and enjoy the benefits of hearing (for the most part) only the sound that is travelling through the air rather than the distortion of your whole house shaking in sympathy to the movements of the subwoofer's driver!

 

[Tomorrow]

I'll point out, as I did in the other thread, that I agree with what you're saying...that cleaner, more distortion free sound can be had with isolation platforms. (Though distortion at near subsonic frequencies is quite difficult to hear.) While a positive role can be assumed for the use of pads for critical music listening, it is still my contention that you will be losing the tactile "earth moving" effects during home theater emulations of large impacts (car or aircraft crashes, train rumblings, bomb explosions, etc.). Having the structure (your home/floor) actually move in those situations seems a desirable trait. The event mimicry in the case of a coupled subwoofer/floor can be a good thing.

 

[FNG212]

I can only offer my ideas from an Einsteinian "thought experiment" perspective.

Some amount of mechanical energy will be transmitted through the enclosure into floor if in direct contact. The amount of this energy will depend mostly on the type of media. Obviously the more massive the enclosure (higher inertia, more stability) and the type of material (low transmission medium) will dampen much of the energy before it has a chance to interact with the floor or anything else in the room.

If we go to one extreme and create a very low mass enclosure with a high transmission/conduction property (such as most metals -- think tuning fork) with a high power driver, it will bounce around on the floor comically like a child's toy. Even if we create a high mass highly conductive enclosure it will still transmit a large amount of the mechanical energy into the floor. The only result of this would be resonance or distortion.

If we go to the other extreme and create a massive non conductive enclosure (such as some fantasy material like super ridge soft rubber) and were able to suspend it in free air (some awesome anti-gravity star trek device), all of the extra energy would be absorbed or lost in the enclosure. The only negative effects of resonance or distortion would come from the driver itself or the natural resonance of the material in the room affected by the sound pressure levels. This can be remedied by room treatments before the waves can interact with the walls, floors, and ceiling.

Please pick this apart but I think the best bet would be to decouple the sub, and really any speaker, from the floor if possible to eliminate any minute negative effects.

EDIT: FirstReflection kind of stole my thunder =(

 

[Pyrrho]

I can only offer my ideas from an Einsteinian "thought experiment" perspective.

Some amount of mechanical energy will be transmitted through the enclosure into floor if in direct contact. The amount of this energy will depend mostly on the type of media. Obviously the more massive the enclosure (higher inertia, more stability) and the type of material (low transmission medium) will dampen much of the energy before it has a chance to interact with the floor or anything else in the room.

If we go to one extreme and create a very low mass enclosure with a high transmission/conduction property (such as most metals -- think tuning fork) with a high power driver, it will bounce around on the floor comically like a child's toy. Even if we create a high mass highly conductive enclosure it will still transmit a large amount of the mechanical energy into the floor. The only result of this would be resonance or distortion.

If we go to the other extreme and create a massive non conductive enclosure (such as some fantasy material like super ridge soft rubber) and were able to suspend it in free air (some awesome anti-gravity star trek device), all of the extra energy would be absorbed or lost in the enclosure. The only negative effects of resonance or distortion would come from the driver itself or the natural resonance of the material in the room affected by the sound pressure levels. This can be remedied by room treatments before the waves can interact with the walls, floors, and ceiling.

Please pick this apart but I think the best bet would be to decouple the sub, and really any speaker, from the floor if possible to eliminate any minute negative effects.

EDIT: FirstReflection kind of stole my thunder =(

That is an interesting thought experiment. Wouldn't suspending the speaker mean that all of the energy that would have been transmitted into the floor would then being absorbed by the cabinet and speaker itself, so that it would vibrate more than if it were firmly attached to the floor? And given that it has less mass than your house, wouldn't that mean that the cabinet would vibrate more than the house would, and thus make a louder noise than if it were firmly attached?

Also, if the speaker were suspended in air, whenever the woofer moved in one direction, it would push the entire enclosure in the opposite direction (for every action, there is an equal and opposite reaction), thus introducing even more distortion? And, indeed, any decoupling is going to allow the cabinet to move more than if it were firmly fixed to the floor, thus introducing distortion.

But what I would really like to see is some actual scientific experiments on all of this, so that we could see what is really happening, and see what matters and what does not.

As it is, what I find striking is the fact that the posts that I have been reading lately are directly contradicting posts I have read in the past. Decoupling is the opposite of using spikes, which couple the speaker to the floor. If the one story is right, then the other must be wrong and must be harming the sound. If spikes are good, then isolation is bad, and vice versa. Of course, if each one is sometimes good and sometimes bad, then that would go against what most people say who love one or the other, and it would mean that it would be bad advice to simply tell everyone to use one of those.

 

[FNG212]

You are correct that a free floating unit would be subject to the action-reaction effects. My example meant to explain a situation where it was somehow held solid but in free air (enter star trek anti-matter containment unit or some such nonsense; anyone who has taken a mechanics/physics class has seen the following first part of a problem: "given a totally frictionless enviroment, calculate......).

I think this will be one of those topics that will go back and forth forever since it will be impossible to fully suspend/isolate a speaker/woofer. But we can try!

 

[MatthewB.]

pyyrho, adding distortion and movement to the free flaoting sub would be true if using a sealed sub, but since most subs have ports, the energy dispersed would be output via the port plugs (hence giving you greater output) since the majority of bass is actual output via the port plugs and not the drivers themselves.

The sub wether on the floor or on a subdude will still output the same amount of pressure (the sub has no idea what it is sitting on) it's just the energy that was being exerted to the floor is no longer there and your floor is no longer dispersing that energy along the floor and walls and pictures and windows. That energy is being directed elsewhere (either the subs floor face plate or if no plate then along the subdudes surface and then outwards in open air.

It is this decoupling from the floor that is easing distortion that the room itself introduces. Hence tighter bass.

 

[FirstReflection]

Actually, with a decoupling device in place, the energy that used to shake the floor is now being turned into heat!

A decoupler is actually taking kinetic energy out of the room - obviously not "destroying" that energy, but just converting it into heat.

I can see Tomorrow's point. I've had quite a few people light up at the idea of actually making their whole room shake as opposed to stopping that from happening and only having the sound from the subwoofer travel through the air. As I say, with a decoupler, we are actually taking energy out of the room.

With something like an explosion in a movie soundtrack - it's unlikely that we're going to be able to tell distortion from the actual recorded sound. The recorded sound itself is OF distortion And having the floor and walls and ceiling shake does add excitement to the experience!

But I contend that there is also a lot of music in movies and there are many low bass sound effects that are meant to be clear and distinct and precise and quick. So I simply prefer detail and accuracy over raw energy and tactile shaking - but I can see Tomorrow's point

 

[walter duque]

Would these isolation platforms be needed on downfiring subs and what kind of benefit would I get. One more thing: Without spikes how do you keep a front firing sub from walking all over the livingroom.

 

[FirstReflection]

Actually, with a decoupling device in place, the energy that used to shake the floor is not being turned into heat!

Cripes! That should have read, "is now being turned into heat!"

Yeesh - HUGE difference in meaning there with that typo!

 

[mike c]

Cripes! That should have read, "is now being turned into heat!"

Yeesh - HUGE difference in meaning there with that typo!

fixed you're welcome