Vibration damping obvious makes sense (in speakers just as well as in cars).
That involves 'killing' (converting into heat, through typically internal friction) kinetic energy. So any sort of elastic material (rubber has lots of internal friction) makes sense.
And then there are spikes. Using a pointy hard object and pair it with a softer, elastic material (to deform, and kill kinetic energy) can work; think metal sharp spike into carpet or wood floor.
But what is the idea behind pairing fairly unelastic metal (brass for example) with similarly unelastic (brass, stone, etc) material (example photo provided)? Only thing I can come up with: LOOKS good and makes owner feel good thinking its an improvement (works only for Audiophiles though),
Even more curious: are they ENGINEERED "spikes" (vibration dampers or shock absorbers) for speakers that are TUNED for the frequency (and mass) that needs to be dampened? Can piston style fluid dampers be designed for the high frequencies (100, 1000, 10000 Hz) using geometry, nozzles size and viscosity of the fluid?
FWIW, in one if Paul McGowen’s YouTube videos there was a question related to this and he said, spikes (in whatever speaker) produce a more audiophile type bass that many people like, but he likes the more natural bass from eg isoacoustics (or some cheaper similar product).
Just re-read this one: "Rubber has a lower internal impedance than say wood which is lower than concrete. The highest internal impedance I think is Diamond.". That is the reason why they are now building all Stradivaris from receycled tires :-)
@kraftwerkturbo Really? You thought I meant that a tweeters motion is moving the cabinet. I reread your question and my response and I suppose that I should have said that the bass drivers in the speaker cabinet would cause a slight motion, enough to blur the image coming from the tweeter, and possibly midrange because of the pistonic motion of these drivers are so short. So the spikes are there to keep the speaker from moving, hopefully, not at all. Not a millimeter if possible. I thought that this was obvious. And the Linn demonstration of loosening a single spike on each speaker stand was to introduce this rocking motion, and then pressing down on top of the speakers was to stop that rocking motion. That's it! Nothing else. All that blather about vibration control and dampening is something else for another topic. The stuff I discussed were simple explanations, examples that anyone in the room could hear. Not poor or wrong science applied or applications of physics.
I suspect that the less the structure housing a transducer moves/resonates during use.. the better it can sound.. or at least the less it would influence the sound (although this wouldn’t seem to be a linearly proportional relationship). It might have a negative effect if it’s within the operating range of a particular transducer. If the structure is perfectly motionless at any frequency or amplitude (regardless of what the transducers are up to), that would seem to be a perfect enclosure as a foundation for audio reproduction. No energy loss. Exhibit A.. Acora speakers. I think I remember one of the Acora’s (or a presenter?) saying the reason for the granite enclosures was so the kids or dog couldn’t knock the speaker over, but they were probably half joking.
If the footer technique merely transfers the resonance of the entire structure above or below the operating range of the tweeter/midrange, then that may be acceptable (much like we find second-order distortion acceptable with amplification in our electronics). Of course that assumes the entire structure is rigid.. if the panels or sub-components independently move to their own resonance frequencies.. then that is another problem and it’s unlikely what you place underneath will help as much as you hope.
I’d also suspect that a speaker with a large monopole woofer being driven by a high current amplifier (at high levels) and it’s cabinet is resting on ceramic balls or springs or any soft material with a range of motion.. that can’t be good for the impulse response or phase continuity of the other drivers. Coupling with a large mass might be a better solution (vs decoupling), if done well.
(Disclaimer: I’m not a materials specialist or a physicist.. just an audiophile who used to like physics once).
Spikes result in a massive reduction in standing wave energy. My first speakers were Dahlquist DQ-10's and when I spiked them they really stated to shine. The lower midrange and upper bass cleaned up immensely.
OCD Audiophile Mikey has posted several interest discussions on vibration control with an emphasis on high quality brass cones and LiveVibe stands as his preferred method of vibration control.
this one is an interesting explanation is in line with Audiopoint’s posts I believe. I have my speakers and electronics on LiveVibe stands and I have been very satisfied with their performance
Spikes are $1.00 a piece and have been used to raise speakers off the flooring since the early seventies. They should “not” be driving, hosting, or used as a methodology in any conversation comparing modern vibration management techniques or theorems.
You cannot kill 100% of energy by converting it into heat. In most formulas, a portion of energy converts to heat. Where do the remaining percentages of resonance go? Does the remaining resonance mechanically ground or propagate on surfaces and form additional resonance?
Then there is the newer “ballistic resonance” theorem published and earning many followers. Ballistic resonance takes all existing vibration-damping theorems to a new level of understanding or function.
Metal originates within the Earth. These materials provide natural damping factors. These factors are taken into consideration when designing a product for musical reproduction. The damping is within the material chemistry itself.
Only thing I can come up with: LOOKS good and makes owner feel good thinking its an improvement (works only for Audiophiles though), Is the above meant to be SERIOURS? the crazyness in audiophildom has reached a new level of nonsense.
Ouch! - I am serious. Talk about craziness? You appear convinced that isolation and decoupling exist in a world governed by the laws of physics and Earth’s gravity. Equipment floating in the air, just like your responses to a topic where further education is required to comprehend.
Resonance Energy Transfer is an adaptable and scalable technology that mechanically grounds resonance formed by vibrations. The proof is built into products, public acceptance, and managing operational temperature, and aligns with current-day physics.
Parts manufactured for violin, cello, upright bass, and vibraphone are a few musical instrument sonic upgrade products accepted by musicians. Musicians and sound/recording engineers know resonance transfer delivers an improvement.
The technology of Resonance Energy Transfer uses hardened metals that work for musical instruments, structural studio environments, compressors, transformers, fan motors, and many other devices.
Audiophiles also know it as a newfound remarkable sonic.
The vibration absorbers, dampeners, springs, pucks, and cones have been here for thirty years. Giving them a modern-day look, construction, or new definition creates little change in the outcome. They are all based on age-old isolation, presently termed decoupling theorems.
Decoupling is a descriptive adjective established by the audio industry in the interest of selling more products.
Working with Resonance Energy Transfer for the past thirty-four years tells me that natural damping factors and material science provide function, dynamics in sound quality, and temperature reduction without using or combining elastic materials clogging up the electric, electro-mechanical, mechanical, and acoustic signal pathways.
Have you ever listened to what rubber-infused products do to musical reproduction?
@audiopointYeah, right. And all is on top of the fact that 'hard' spikes do nothing except 'hold' the speaker. And no: even solid gold spikes don't do more (except are high on pixel dust content).
Is the above meant to be SERIOURS? Or a nicely done bot generation. Otherwise, the crazyness in audiophildom has reached a new level of nonsense.
We would first like to point out a few items on the OP’s brass cone examples and will follow up with a functionally proven theorem that has taken the first steps to qualify as a science.
Cones (spikes) - the Shape is rarely talked about. Using the image from the OP exposes so many fallacies that the product would never work.
1 Take the machined knurled rings with uneven edges. These establish notches in the body that create rough surfaces and shear waves. The energy has an unsymmetrical travel pathway that makes a lot of noise and distortion. With an uneven medium, the energy flows back into the speaker's chassis.
Reflected sound is like light reflection. It is ten times more evident on rough surfaces. The nuts on this cone design produce a lot of noise.
2 If you take a horizontal view and discover an exposed thread, the system becomes dysfunctional by establishing a separation in the mass and shape of the material. Using a separate nut for leveling the speaker breaks the transition of resonance flow. This designer needs to learn how a cone works before selling fancy-looking parts. Most spikes manufactured have zero capability of function other than raising speakers off the flooring.
3 The disc receptor has ninety-degree angles. Ninety-degree angles add noise and distortion—the same with wall, ceiling, and flooring angles. Ninety-degree angles limit performance in speakers, inside and outside of chassis, pucks, springs, etc. They are not beneficial for energy flow and sound.
The examples shown do not work, so you need to upgrade the designs before they qualify for analysis purposes.
Adding rubber or any material between the device and the floor other than an engineered coupling disc adds to the soup sandwich attempting to correct something doomed from the outset.
Impurities in the material also generate shear energy. There are hundreds of types of brass. Cheap brass means minimal attention to chemical manufacture and less performance. Chemistry is essential to the functionality of any cone shape.
@vitussl101 do OSCILLATING tweeter membran REALLY MOVE a 50 lb speaker? Remember, those milligram 'pistons' go back and forth (SAME force or better, same impulse in EACH DIRCTION) about 5000 time PER SECOND. that 50 lb MASS is way to slow to move. To move the entire speaker i suspect the required accel and decel would SHRED any speaker to pieces.
IF that test was done (hand on speaker) and actually had (not perceived) results as described, the only explanation would be that the hand DAMPENED the vibrations of the respect speaker PANEL; and yes, they DO move/flex. The WALLS of the cabinet, not the speaker.
Geez! For the last forty years, I've followed Linn's maxim that the speaker should not move a millimeter. In other words when I place my hand on the speaker it should not move side to side, back and forth, not rock at all! Time and time again I've heard demonstrations of this by simply loosening/tightening one spike allowing the speaker to move just a little and notice a smearing of the signal. I remember one demo where Linn did this to a pair of speakers by loosening a spike on each speaker stand a bit and as I listened, persons standing next to each speaker pressed down hard on the tops of them to keep them from rocking. Everyone heard the difference easily. The reason? Simple, the tweeter and many midrange drivers' pistonic motion, throw, is tiny, and just a small amount of movement of the cabinet will blur the signal from them. How a device like the Townshend or Sorbothane (useless), or any products that introduce a rocking motion to the speaker helps. I understand where an entire floor of a room floor on a suspension system helps isolate it from the outside but that's it. I've heard Townshend's devices a couple of times. Once under a large heavy pair of floor standing active ATC's and a pair of Proacs. They did nothing but screw things up and I'll bet both companies wouldn't recommend them in any circumstance.
@amtprodExactly! Sometimes it's hard to describe your scenario and experience, but pictures tell it all. For someone just starting into the decoupling arena like my wife I can highly recommend them. I've read the Townshend's take things a step further, but for $200 I'm happy to start here. I'll be trying components next.
@j-wallOh now I see what you are working with. You are actually possibly helping two areas and items: the sound reproduction IN the music room, and trying to reduce the impact on the living space BELOW.
I have a few of the Herbies rubber things under my equipment and under bookshelf speakers so no real major differences, but just 'good practices'.
It's good to see/hear that the pucks are helping a lot in suspended floors and two room considerations.
@j-wallCan you post images when you get a chance? Just to see visually what you were dealing with before and after now that you have logged some sound signature changes. Thanks!
So just an update on the Herbie's spike decoupling gliders I picked up, they're fanatic. Upper frequencies are cleaner, more detailed and have much more depth and nuance to them. Mid frequencies didn't change much for me. Lower register bass notes seem to have lost a ton of flab and vibration and are a lot more detailed and sharp. I did lose a ton of lower end grunt, but it's replaced with more detail from the bass notes and it sounds like instruments are being played rather than frequency loading a room with vibration. I would highly recommend anyone on a second story with carpet over wood subfloor try these out. They've increased detail, decreased bass flab and my wife downstairs doesn't hear the bass frequency vibrations nearly as badly. Speakers are Focal Sopra's in a small room.
There are undoubtedly a variety of methods and configurations for devices and materials being used in bespoke permutations to assist with controlling energies generated within a Cabinet.
If Cabinet produced energies are not being transferred these energies are in many many cases going to have a impact on the sonic being produced, as the drivers will be affected by transferral of Cabinet produced energies into the drivers.
Fortunately for the Speaker user, if Cabinet produced energies are transferred away from the drivers especially to the level its presence has minimum impact, the use if bespoke Cabinet mounting or sandwiching of a Cabinet has been very worthwhile as a practice.
It is also known that in many cases, the bespoke methods for a Cabinets produced energy management can come with costs that for some will be seen as a substantial investment.
The last electronic device downstream of the Source that has the role of processing the Sources produced electrical Signal is the Speakers Xover. As the Electrical Signal moves from the Xover, it is only the Umbilical between Xover and Driver that has the final influence on the Electrical Signal to be delivered to the Driver.
Note: The following will be most suitable as a practice to be put in place, for a Speaker that is out of its warranty period. As many Speaker owners have owned their selected models for quite a few years, and some buy used to get access to the more affordable options, it will be quite common for Speakers to be out of a warranty period.
There are substantial improvements awaiting for the produced sonic, that can be attained by working with Xover and internal Xover - Driver Umbilical. Working with this element of the Speaker is not for everybody as it commonly requires a practice of working with a Soldering Iron, not all have the confidence to do this.
This as a method will entail exchanges of parts, where new parts selected will have the same measurements used that at the ones belonging to the circuit for the Xover. For the more confident in such practices this method can be taken a little further where the Speaker owner may choose a different measured value for a component to replace a insitu Xover component.
From a personal experience I have encountered Speakers having undergone this type of modification. I have been demo'd how a replacement part on a circuit, especially selected as a part, for being one that far excels the Manufactures selection made, as a result of their budget constraints, has transformed a Speaker produced sonic, to the point a the sonic produced leaves the perception a new speaker is seemingly in use.
More recently I was demo'd a Cabinet Speaker I am becoming familiar with, that is mounted on Townshend Podiums, has a modified Xover (expensive parts selected) and uses PC Triple C wire as the Speaker Cable.
As I am a advocate of PC Triple C wire, and have been quite encouraging to others to experience it in use. The recent demo'd Speaker now has the PC Triple C in use as the internal umbilical as well the external Speaker Cable. The reports back are that something quite new is being detected, not night/day, but enough to strongly suggest the small cost and time allocated was more than worthwhile.
Tread carefully on the subject, but an investigation should prove if a practice such as exchanging wire used for the internal umbilical is reasonably easy to achieve. This as a practice is one I will strongly suggest as being a worthwhile undertaking, the suggested wire to be used for an exchange is already stated.
Ok , so set me straight. I have uber thick shag over extra heavy Gortex type padding. My house is a 35 year old cement slab build. I have a couple styles of speakers. Zu omens on spikes and JBL 4312A monitors on 3 leg Sound Anchor stands, both run spikes. Even with what a Sound Anchor stand weighs , I had to press them down to penetrate my floor covering and hit the cement. My floor covering is so thick and dense that without spikes the JBL & Sound Anchor combo rocks at the slightest touch. There’s no way I could run springs or pads. I purchased 4” think walnut slabs from Timber Nation and spiked them to use as footers under my Zu’s. They sounded like crap. I had conversation with the man himself in Utah and tried all his suggestions for spacing the Omens, nothing worked. The Omens on spikes leave maybe a 1/4” gap over the shag and have substantial bass, even with modest tube watts. I must admit I’ve yet to try stacking 2 completely different systems to make an Odd Couple ( pun intended ), but my spikes work pretty well. I think there’s some solid information in this thread, but it’s overloaded with theory based on reading articles Vs actual testing. I’m not saying people are wrong, but I’m saying some are being too absolute in their opinion. So I guess there’s more than one way to catch a fish. And please understand that my words are not meant to offend anyone, we have too much of that here. Happy Listening, Mike B.
@OP Carpet and underlay will not act a mass-spring-damper system. Locating the bottom of the cabinet in free space will not "change" the sound of the majority of speakers since they are designed to be set up in that way.
This is why i was using with springs under and above my damped speakers by a load a sandwich of materials : plate of shungite or quartz feet , oak plate, sorbothane plate,bamboo plate, cork plate granite plate all together...
The alternating coupling and decoupling work the best to isolate the speakers , and the springs work best to decrease the speakers resonance ...
The granite plates (high mass) in conjuction with the carpet/rubber (bottom of carpet) and foam (under carpet) under the puck act as another ’swinger’ (mass, spring, damper) to further modify the fequency and amplitude transmitted into the floor.
@yoyoyaya"but they also stop the bottom of the cabinet from coupling directly to the floor". Yes, that crossed my mind as well. The spikes only couple the motion of the speaker assembly to the floor (undampened if made from just metal) and put on bare floor, or ’spiked’ (penetrating carpet) to wood underneath. .
But putting the speaker flat floor on the carpet rubber/foam underneath may actually help to reduce the vibrations of the cabinet bottom in the frequency range damped by the carpet/rubber/foam. Or looked at it the other way around: ’raising’ the bottom of the cabinet up from the floor may allow it to vibrate more freely and "change" the speaker sound.
@ditusaVandersteen on spikes:just came across this exmaple, and below in that same thread someone who put granite plates under the spikes. Those pucks seem to use rubber to quell speaker vibrations transmitted to the floor.
The granite plates (high mass) in conjuction with the carpet/rubber (bottom of carpet) and foam (under carpet) under the puck act as another 'swinger' (mass, spring, damper) to further modify the fequency and amplitude transmitted into the floor.
My Vandersteen speakers have 3 cones under them, and have just installed recommended discs under the cones.....made an improvement on my tile over house foundation.
@tcotruvoYes! I mentioned this as a case study because there can be a mistaken assumption that just because something is very heavy, it won't move around. However, at the risk of provoking the ire of the OP, the spikes not only stop reactive movement of the loudspeaker cabinets arising from the motion of the drive units, but they also stop the bottom of the cabinet from coupling directly to the floor and turning the floor into a giant resonator/soundboard. In the specific case, the floor is actually quite well damped as it composed of two different layers of wood, a linseed oil based composite and carpet. But...
@yoyoyaya Wow! 400 pounds! I would guess once you have those on spikes you wouldn’t be moving them around. Interesting that even with that weight and thin carpet the spikes still were an improvement in sound quality.
@tcotruvo- to further amplify your point (no pun intended), I originally had my Wilsons (which weight 400lbs each) directly on my carpeted floor (with thin pile carpet). I subsequently spiked them once I had their position optimised and the improvement in sound quality was significant. What surprised me was the degree of improvement in resolution in the midrange as well as the bass.
I have a pair of tall, thin B & O ‘pencil’ speakers. I have rubber feet on them as they’re on a concrete floor. But if I move them onto an area rug, they easily rock and could be knocked over. I think the purpose of spikes is to concentrate the weight to a thin point that can penetrate between carpet loops or piles. This would bring the weight to bear on the firmer surface of the carpet backing. The plusher the carpet, the more they are necessary and effective.
I had fine tuned the compressive and damping load of concrete on top of my speakers acting on the two set of springs near 100 grams of fine tuning by ears with near 80 pounds of concrete ...( this was with my big speakers, with my actual very small speakers nothing had changed bu t i dont need springs now )
In my experience a sandwich of various materials is necessary under them and not only springs ...My speakers were relatively isolated by coupling/ decoupling using various materials not only damped....The two set of springs were powerful because compressed with different weight force they were able to decrease internal resonace in a way one set will not do ....
@mahgister I can see from your description about mounting a Speaker Cabinet you take your investigations into tidying up a sonic quite seriously.
I have a substantial supply of Cork Pads, they regularly find a place as a additional tier in an assembly. My interest in Granite has a 30ish year history of using it in multiple configurations in a support structure.
On my Cabinet Speakers my the Top Weight is a Large Lead Metal Block rested onto four 1/6" Cork Pads. The Lead Blocks then has approx’ 20lb of Steel Dumb Bell Weights sat upon it. Moving this weight around to different resting positions on the Top of the Speaker does have an impact where sonic or box coloration are able to be impacted for the better/worse.
I am a ESL Speaker user as well, so the Cabinet / Driver issues are easily by passed if wanted.
@mahgister I can see from your description about mounting a Speaker Cabinet you take your investigations into tidying up a sonic quite seriously.
I have a substantial supply of Cork Pads, they regularly find a place as a additional tier in an assembly. My interest in Granite has a 30ish year history of using it in multiple configurations in a support structure.
On my Cabinet Speakers my the Top Weight is a Large Lead Metal Block rested onto four 1/6" Cork Pads. The Lead Blocks then has approx' 20lb of Steel Dumb Bell Weights sat upon it. Moving this weight around to different resting positions on the Top of the Speaker does have an impact where sonic or box coloration are able to be impacted for the better/worse.
I am a ESL Speaker user as well, so the Cabinet / Driver issues are easily by passed if wanted.
I used concrete block as damping Masson top...Fined tuned mass ...With 2 set of springs, one set under speakers+load and one set above the speakers compressed only with the load ...
Under the speakers in my sandwiches of materials (cork-Oak-Bamboo-granite-shungite) i add in between one plate of sorbothane patches duro 70 ...One of the best damping materials...Then i use decreasing vibrations materials and also decreasing resonance devices and method and coupling/decoupling principle...
I used it also inside my 2 headphones +FoQ tape as damping materials ...
@mahgister Aside from mass (and materials wilth likely different resonance frequencies), what did you use to DAMPEN (sand filled for example (friction between sand corns converts energy), rubber (ditto), foam (? not sure)).
@j-wall the Herbie's really didn't have any affect on the sound, and in fact my audio buddy thought they made the sound worse than just having the speakers resting on the carpet. I was hoping this would improve the issue I was having, but it wasn't solved until I installed the Townsend podiums.
Once you are wedded to stereo systems it is like any other marriage - you have to try lots of things to keep it going, and even if you think you have it finally settled you will keep tweaking anyway because the great unknown is always beckoning. It's kind of beautiful really if you can stand being miserable at times.
There are a vast range of very very affordable options that can be selected from, as a means to experience an alternative method for supporting a Floor Standing or Stand Mounted Speaker.
Spending a little money to have a new experience will certainly show a change to the sonic being perceived.
For some this one change might be the cut off point for a improved - 'tidied up' presentation. For others the addition may have been less that what was before.
Either way if no alternative methods for mounting are undertaken, not much will be learned apart from what descriptions are being read about alternative methods of interest being used by others in their environments that are most likely very very different from ones own.
The thickness of a Carpet used a Floor Covering can have a substantial impact on the sonic being perceived from a Speaker.
A friend who I assisted with investigating Speaker Footers, with the end result being they now used Townshend Weight Match Plinths under their Speakers, was so impressed with improvements their interest moved to experiencing other Speakers.
At a later date of visiting the friend to hear newly acquired Speakers purchased as a used item sale, I was to point out that the New Speakers were not as projected in the Upper Mid's and Highs as the previous in use speakers had projected.
Initially it was made known to me the Original Owner/Importer of the Speakers had a experience not like too many and was inclined to Speaker Roll. Over the course of approx' 3 Years the Vendor had owned a selection of Speakers that had amounted to close to £100K.
The Vendor had somehow chosen the route of a very cheap Glassy Hard CD Player to push on the Speakers Upper Frequencies.
My friends whole instinct and knowledge of the Speaker Designer knew much more was able to be achieved, they took on the idea of having a punt and made a offer which was close to the Drivers Value only, and the offer was accepted.
The follow up explanation given, was quite interesting and reinforced by the description also given from the designer / builder of the Speaker to my friend.
Simply put, the earlier used Speaker is a design intended to be used in Countries such as the UK where Carpets and Soft Furnishings with Heavy Fabrics are the norm. A Speaker designed for this type of environment will have a Xover design that allows for the Upper Mid's and Highs to be present and not absorbed.
In comparison the New Speakers were a Bespoke Built design Import from Scandinavia. The new owner was aware of the upper frequency roll off and had already made an inquiry to the designer. The description given, being that the Speaker is designed primarily for usage in Scandinavian homes, and if the Xover had a design to suit the UK, the Speakers sonic will be bordering on Glassy Hard in a Scandinavian Home. The designer has a Xover design in place for when such inquires are made. The initial guidance being allow the drivers further time to settle in.
My friend who is a EE and Engineer by career has no concerns about tweaking the Xover. Also they are very aware of the influence of PC Triple C Wire. I encouraged them to use this wire type on the Mid Range and Tweeter, we both agreed that a further presence of these frequencies may be perceived as being achieved iif this method is adopted.
Additional Footers in use may have also been able to lift the projection of the frequencies?
Changing a wire is very cheap to do, adding a footer in conjunction with the Townshend is only adding a little more expense, removing the Townshend? Experimentation is the only way to truly find out?
All ideas are doable before any electronics are exchanged.
For the record, prior to any suggested changes having been made to the Scandinavian Import Speakers being demo'd. I made it known to my friend that these were the best speaker I have been in front of in his room, and possibly the best Cabinet Speaker I had heard using recollections as the judge.
Not bad as an assessment when something else for the sonic is still on offer and earlier Speaker in use Speakers will have been a much more substantial in value retail purchase and the Scandinavian Speakers were acquired for much less than £5K .
@zo6akSorry, didn't see that you were trying to quote someone (i.e. missing "quote marks". It was aactuall @viridian who said "Spikes are cheap, try them and they will either enhance your listening pleasure or they won't." and thus promoting the idea of trial and error for 'cheap' things instead of logic/research/physics to narrow down the field.
@yoyoyaya The point of using spikes as anchors, anti slip, or 'keep level' is not disputed (even so much simpler/cheaper methods are plenty), rather their ineffectiveness as a "decoupler", "damper", or otherwise reduce vibrations.
i would even argue that putting a subwoofer for example totally flat on a carpet MAY even reduce the amount of sound emitted from the vibrating (bottom) panel (while it still couples the sub to the floor accoustically).
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