No need to mistify simple physics - Newton 3rd law has nothing to do with resonances.
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Speaker spikes, pads etc. couple or de-couple your speakers
- Thread starter Snarfie
- Start date
No need to mistify simple physics - Newton 3rd law has nothing to do with resonances.
I am not talking about the structural borne resonances here, but the movement of the speaker due to action-reaction forces, and that spikes/hard coupling causes the speaker to move more. You have a mass of the speaker what it rests on act like a spring. This will have a fundamental resonance frequency that will amplify the movement of the speaker due to the action/reaction forces. This will be in the upper bass region for speaker, unless you decouple them to below the speakers lowest output. This is just one of the effects of hard coupling, which needs to be separated from other effects such as transfer of vibrations.
Now if you like to discuss the transfer of vibrations from speaker to floor. The results will of course be dependent on the floor type. If you have a typical old suspended wood floor you can easily measure vibrations in the floor when resting on spikes compared to if the speaker rests on soft feet. There was a guy, Markku Salonen, measuring this around 2001using a stand-mount Revel speaker and it was clearly evident that hard coupling caused many vibrational excitements of the floor. With soft feet you could only see the effects of the acoustic fundamental standing wave acting on the floor, which naturally was quite large. But many of the speaker-induced vibrations were quite significant as well. The site does not exist anymore but I tracked down the history of it, unfortunately, the images could not be retrieved. And this is just one example of measurements, there have been others as well, but not perhaps published on internet.
http://web.archive.org/web/20030816073958/http://www.mosaic.fi/markku/sweeptest.html
The final question is whether any of the excited vibrations of the floor could be audible. I have no answer to that question, since I have not seen any DBTs of that.
If you have a wooden floor, and heavy speakers on spikes the speakers might as well be nailed to the floor after a short while, there will be no decoupling or isolation going on, they will be firmly joined to the floor.
I used to have a pair of Naim speakers with a crude spring as part of their setup. They were short floorstanders, with an 8" bass mid driver at the top, underneath the front spikes were normal, the rear spikes were either end of a short metal bar, the middle of which was screwed to the bottom of the cabinet. With the spikes set perfectly on a concrete floor pushing hard on them would make them move about 1cm at the top, maybe less, it made them a real pain to know when the spikes were perfectly adjusted. Playing some tracks with big kick drum at high volume caused them to bounce several mm back and forth, in a surprisingly well damped fashion.
From unreliable memory the metal bar was about 8" long, an inch wide and about 1/4 inch thick, it was supported in the middle by about 2" of cabinet, it did not look or feel springy at all.
I wrote out a whole thing that was wrong but I found this guys math that seems correct to me.
Credit to
Len Zenith Jr
of ProsoundWeb
"Newtons 3rd law states that for every action there is an equal and opposite reaction;
force=mass x acceleration or f=ma
so using newtons 3rd law;
mass(cabinet) x acceleration (cabinet) = mass(cones) x acceleration (cones)
Assuming the mass of the cones of a double 18" cabinet is ~210 grams each so mass(cones) = 420 grams for the both of them or mass(cones) = 0.42 kg
and acceleration = 2 x distance / time squared
lets find acceleration of the cones at 60 hz:
time @ 60 hz = 1/60 = 0.0167 seconds
distance of cone travel (x-max) lets assume full bore is 18mm = 0.018 meters
acceleration (cones) = 2 x 0.018 m / (0.0167 s)squared
acceleration(cones) = 129 m/s2
assume the mass(cabinet) = 112 kg
back to newtons 3rd law:
mass(cabinet) x acceleration (cabinet) = mass(cones) x acceleration (cones)
112 kg x acceleration (cabinet) = 0.42 kg x 129 m/s2
gives us acceleration (cabinet) = 0.484 m/s2
now distance the cabinet moves d = 1/2at2
d= 1/2 x 0.484 m/s2 x 0.0167 s x 0.0167 s
d= 0.0000674 m
d = 0.067 mm
So there you have it, hanging in free space with a 60 hz tone playing at full balls to the wall 18mm x-max the cabinets are vibrating back and forth 0.067 mm or less than 3 thousands of an inch.
If you think about it, a driver sitting on the workbench playing at x-max doesn't even move the driver, nevermind the whole subwoofer cabinet. "
I cant see the force of the drivers playing any roll in the force transmitted to the floor. Also by this math spikes and anything "coupling the speaker to the floor" is unnecessary because even teflon coated surfaces will have enough static friction to hold the cabs in space.
The real question would be cabinet vibrations I suppose but I would surmise spending more money damping your speaker would be a better use of time.
Credit to
Len Zenith Jr
of ProsoundWeb
"Newtons 3rd law states that for every action there is an equal and opposite reaction;
force=mass x acceleration or f=ma
so using newtons 3rd law;
mass(cabinet) x acceleration (cabinet) = mass(cones) x acceleration (cones)
Assuming the mass of the cones of a double 18" cabinet is ~210 grams each so mass(cones) = 420 grams for the both of them or mass(cones) = 0.42 kg
and acceleration = 2 x distance / time squared
lets find acceleration of the cones at 60 hz:
time @ 60 hz = 1/60 = 0.0167 seconds
distance of cone travel (x-max) lets assume full bore is 18mm = 0.018 meters
acceleration (cones) = 2 x 0.018 m / (0.0167 s)squared
acceleration(cones) = 129 m/s2
assume the mass(cabinet) = 112 kg
back to newtons 3rd law:
mass(cabinet) x acceleration (cabinet) = mass(cones) x acceleration (cones)
112 kg x acceleration (cabinet) = 0.42 kg x 129 m/s2
gives us acceleration (cabinet) = 0.484 m/s2
now distance the cabinet moves d = 1/2at2
d= 1/2 x 0.484 m/s2 x 0.0167 s x 0.0167 s
d= 0.0000674 m
d = 0.067 mm
So there you have it, hanging in free space with a 60 hz tone playing at full balls to the wall 18mm x-max the cabinets are vibrating back and forth 0.067 mm or less than 3 thousands of an inch.
If you think about it, a driver sitting on the workbench playing at x-max doesn't even move the driver, nevermind the whole subwoofer cabinet. "
I cant see the force of the drivers playing any roll in the force transmitted to the floor. Also by this math spikes and anything "coupling the speaker to the floor" is unnecessary because even teflon coated surfaces will have enough static friction to hold the cabs in space.
The real question would be cabinet vibrations I suppose but I would surmise spending more money damping your speaker would be a better use of time.
If you put the same speaker on springy feet tuned to a highQ resonance at 60 Hz, what would the movement then be? I am not saying things are audible but the above example relies on a free floating, decoupled speaker, where the is no problem to be seen at all.
restorer-john
Grand Contributor
Clearly, you've never had speakers move backwards, forwards, or fall off shelves when played loud...
Spikes are excellent for securing floor-standing speakers firmly, accurately and they pierce through the carpet, underlay and contact the hard surface (wood/cement) below. The speakers don't rock or move at all, which is good and prevents accidents.
Blutack or double-sided tape holds small standmount speakers on their stands, prevents knock-off accidents and stops them vibrating and falling off.
What kind of physics are you talking about?!?
Most of the energy sent to loudspeaker is radiated as acoustic energy, the rest is converted to heat in the coils of the drivers, same as various friction forces etc. Enclosure will absorb some of that acoustic energy and the result will be vibrations of the enclosure panels and some of those vibrations will be sent to spikes/wheels/pads. Most of the vibrations will not be in the bottom and top panels but at side, front and back panels. In well designed enclosures those virbations will be so small that you will indeed need accelerometer to measure it, like they do it in Stereophile when testing speakers. With well designed enclosures there will be minimal differences with soft or hard coupling and those differrnces certainly won't have any imact on sound nor they will have any impact on the accoustic energy radiated through the walls to your neighbours.
P.S. I will not comment your "practical" proposal to measure vibrations with accelerometer as assuming that any of us have such instrument at home is, well, entertaining. Although some other words are jumping to my mind as well..
I have a bunch of accels. I keep promising to do some measurements so I will do so today.
This whole vibration topic keeps cropping up and there is much mis/lack of understanding.
You got it wrong again - speaker is the source of vibrations, it's enclosure will vibrate because drivers are moving (vibrating). Floor is not the source of vibrations so it cannot give energy to the speaker, it's vice versa that is happening, but not through the speaker/floor coupling but through the air in the room.
Spikes/pads/wheels are certainly not acting like a spring. Spikes/wheels are hard coupling with extremely low surface so vibrations can't pass through them while pads are dampening vibrations due to mechanic proeprties of the material which doesn't transfer vibrations.
I'll be happy to read his research if you provide a link.
Standing wave on the floor? I guess you meant in the floor? Are you aware thathouse floors typically have resonant frequencies of 1-2Hz or even lower?
Oh c'mon, every serious science research is published on the Internet.
Once again, and for the last time - floor, and other room surfaces like walls and ceiling, are excited only because of sound wave energy sent through the air by the drivers. Loudspeaker enclosure is usually "dead" meaning that it doesn't vibrate in order not to affect the drivers and those tiny vibrations that exist in the enclosure are not transferred through spikes because of extremely low surface of the spike/floor connection. Even if you remove the spikes and put speakers directly sitting on the floor with it's lower base those tiny vibrations in the enclosure would be easilly absorebed by such heavy object like floor and there will be absolutely no effect on the sound.
In case you are considering loopback scenario where floor gets exited because of acoustic waves and try to send those vibrations to the speaker's enclosure via the spikes I ahve to remind you that floor accepted only small part of the acoustic energy while speakers enclosure already have to deal with total ammount of the energy emitted from the drivers - and it did that without any issues.
The whole spikes/pads/wheels thing is simply a myth because the problem have to be solved by making the enclosure acoustically "dead". For that reason no wonder there are no researches with DBT on that subject because scientists are aware that it affects the sound pretty much the same as colour of speakers cables.
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LOOL
I take it you're joking, as loudspeakers that are using spikes to secure themselves against moving because of the loud sounds they are producing are of extremely bad enclosure design.
Absolutely nothing. Some tiny vibrations from the enclosure will be transferred to the floor without any effect to the enclsoure nor to the sound, as it is the enclosure that is delivering the energy to the floor in this scenario. Floor, of course, wouldn't be affected in any way as well.
Btw, I hope you at least now understand that energy transfer via vibrations is out of scope of Newton laws.
If you have a wooden floor and heavy speakers on spikes you better not be married as in that scenarion you would be running for your life shortly after installing spikes.
P.S. depends on the wood actually. I had my 17kg Castles spending nearly a week on spikes before spike pads arrived. They manage to dig into the oak parquet for app 1mm which was small enough for the wife to miss it.
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Here you go:
https://www.brown.edu/Departments/E...Notes/vibrations_forced/vibrations_forced.htm
And no, I am not reducing it into a couple of sentences.
https://www.brown.edu/Departments/E...Notes/vibrations_forced/vibrations_forced.htm
And no, I am not reducing it into a couple of sentences.
Carpet over floorboards is very common, and there are no complaints from wives using spikes with that.If you have a wooden floor and heavy speakers on spikes you better not be married as in that scenarion you would be running for your life shortly after installing spikes.
This is a topic that needs a lot less theorising and a lot more measuring.
I've got a small sub-woofer that will scuttle across a wooden floor given little provocation, a couple of volumes of an encyclopedia on top fixes it.
IMHO I really don't see any way how LF vibrations from the floor can affect sound. I strongly believe this is a myth.
It's not the panels vibrating, it's the whole box moving.It fixes it not to move but vibrations within the enclsoure are left there.
That wasn't what I was talking about, that's only part of this thread.
I'd mainly interested in what happens to the front baffle, does it move, and if so at what frequencies.
The low frequency movements in the floor are again something that should be measured if someone believes it impacts the sound, if they are all very low frequency they probably don't matter, but if they are high frequency they might. I'd want to see measurements without music playing, and with it playing with different ways of supporting the speakers.
