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Confusion on speaker stands versus floor standing

WillVT said:
I know there are different theories on this, but I've never quite understood the idea of spikes with rubber cups. Other than issues with uneven floors, how is that different than just rubber feet? Is there something about the cone shaped spikes that affects vibrations? My understanding was that spikes were to penetrate carpet to couple with the floor, and not "float" on top of the carpet. Or to kind of grab onto something like a wood floor to prevent sliding and ensure coupling, that imperfections in the floor and speaker base might prevent.
Spikes AND rubber cups seem like opposing ideas. Rubber would seem to decouple and absorb vibrations, whereas spikes couple? What am I missing?
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For carpet .. yes pierce it or the speaker is rocking on the carpet fibers in response to the drivers moving back and forth.. blurs the sound ..
To every action there is an equal and opposite reaction .. driver pushes out and pushes speaker frame and box back ..

Spikes is mass loading .. all of the weight of the speaker on one tiny point which results in a very, very high psi on that small point ..
With a rubber cup it's still mass loaded, but with a rubber cup it's a lot easier on the floor .. the weight on that point in the cup compresses the rubber flat but the point doesn't penetrate the rubber or floor ..

We sandblast granite headstones with a rubber mat over everything but the letters .. always dumbfounds me that the sandblaster cuts in to the granite but the sand just bounces off the rubber mask .. kinda hard to penetrate that stuff ..
 
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rothwellaudio said:
And what's the benefit of that?
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Lifting the bottom of the speaker off of the floor decouples it from the floor so that it doesn't and can't audibly resonate the floor ..
Mass loading via spikes lowers the frequency range of the speaker box's vibrations below audibility ..
The vibrations cannot and will not be contained or eliminated ...The energy that's being pumped in has to, and will dissipate somewhere ..
The spikes are channeling the box vibrations into an ultra low frequency vibration out of the speaker system and in to whatever the speaker is sitting on ...

Kinda makes sense that removing some of the box's vibrational resonances would improve clarity by removing a resonant blur ..
 
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Akustic said:
Study some physics ..
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I have a degree in physics.
If we consider a simple weight and spring analogy, the resonant frequency of oscillation depends on the mass of the suspended object and the elasticity of the spring. If the elasticity of the spring remains constant the resonant frequency of the system can be lowered by increasing the mass of the suspended object or raised by lowering the mass of the suspended object.
In the case of a loudspeaker sitting on the floor, the loudspeaker's mass doesn't change by putting spikes between it and the floor, nor does the elasticity of the floor change.
Or are we considering the resonant frequency of the panels which make up the loudspeaker enclosure? Certainly the resonant frequency of the panels can be lowered by adding mass to them, but I don't understand how spikes will change any frequency.
Please explain. If you have an explanation, I'd love to hear it. I certainly don't claim to know everything and I never want to stop learning.
 
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Sgt Shultz said:
One of the funniest Top Gear episodes.
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Yup, one of my favs (along with the ones with the hover van, the vehicle for the elderly and the info spot on bicycle safety - and quite a few more...).

JoeESP9 said:
I've seen the Top Gear episode that shows exactly how easy it was to roll a Robin.
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According to Wikipedia they cheated a bit, though. I.e., the Robin was somewhat modified, so that it would roll over even easier.

Greetings from Munich!

Manfred / lini
 
Akustic said:
Good ... then simplify the explanation..
That's as simple as I can make it ...

Obviously you didn't need to ask me then did you ??
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Yes, I needed to ask because I don't understand. Why can't you give me an explanation? :dunno:
I'm not asking for simplification, I'm asking for elaboration.
 
rothwellaudio said:
Yes, I needed to ask because I don't understand. Why can't you give me an explanation? :dunno:
I'm not asking for simplification, I'm asking for elaboration.
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Apologies..

Energy seeks a path to ground or stasis .. The speakers are being energized ..
Mass loading provides a low frequency path in to other objects and out of the system for higher frequencies ..
The panels of the cabinet are resonating at higher rates with the energy input ..

High frequency energy is weaker than low frequency energy so a low frequency path absorbs higher frequencies ..
Best that I can do is explain it as a resonant energy drain .. that subsequently changes the box's resonating, not resonant frequencies ..
 
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Call the spike a vibration capacitor for the speaker box and it starts making sense ....

The other advantage to the spikes is that the box is much stiffer in the horizontal plane .. can't be so easily pushed back and forth if the spike penetrates the surface below ..
Back to removing a potential blur ..
 
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All materials are elastic to some extent and have some "springiness". Compressing a spring stores some energy in the spring which is released as the spring returns to its rest position. That's how the spring in a clock or watch stores energy which is released to turn the hands.
Capacitors too store energy, so an analogy between a capacitor and a spring isn't too far-fetched.
So, both spikes and rubber feet could be viewed as analogous to capacitors, but if they were they'd be at opposite ends of the spectrum with rubber being something like a 10,000 microfarad capacitor and a metal spike being 0.1 picofarads. (They're just numbers plucked out of the air to illustrate a point.)
Still, in my opinion that's over-thinking things and speculating about mechanisms at play for which there is no measured data.
I still have no idea what "mass loading" is supposed to mean in this context.
Spikes simply form a rigid coupling between a loudspeaker and the floor and I don't think there's anything more complicated than that at play.
 
GChief said:
Thats is all I was going for ;)

That said they did help a lot in the Tiny House listening loft. that floor was like a giant guitar body, the spikes and supplied rubber feet really helped.
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And every bit that the speaker energized that floor with sound- is an induced error in the frequency and transient response. That's something that could be easily seen in a waterfall plot, if someone had been inclined to make that measurement.

By making it small point contact as opposed to area contact- especially when the spikes or feet are generally in the stiffest areas of the cabinets (the corners), the transmission of vibration to the floor can be reduced by an order of magnitude, in many cases.

Regards,
Gordon.
 
GordonW said:
And every bit that the speaker energized that floor with sound- is an induced error in the frequency and transient response. That's something that could be easily seen in a waterfall plot, if someone had been inclined to make that measurement.

By making it small point contact as opposed to area contact- especially when the spikes or feet are generally in the stiffest areas of the cabinets (the corners), the transmission of vibration to the floor can be reduced by an order of magnitude, in many cases.

Regards,
Gordon.
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I also ended up putting studio monitor isolation pads under them. That even helped some. Took a lot of tweaking to get that space sounding good.
 
One other thing that spikes and threaded feet offer- is the ability to level the speakers, or to at least insure that both speakers have exactly the same rake angles (forward-to-back tilt from bottom to top). This CAN DEFINITELY have a PROFOUND effect on the uniformity of frequency response and timing, relatively between the speakers, at the listening position.

I've had cases where speakers simply would not image properly in a room, sitting flat on the floor. Take the same speakers, put ihem on adjustable feet, and adjust the cabinet attitude so that both were identical- and voila- the soundstage just opened up. Just because both speakers were "launching" sound at the listener, identically, in terms of where one was in the frequency response dispersion pattern.

EDIT: Actually, I can remember one case, when a friend of mine and I were measuring some of our own project speakers using LEAP/LMS- and we were getting some weird results. We even tried to duplicate a test we had done a week before, on the same speaker, in the same point in the room- but got a subtly different curve.

This was in a climate-controlled basement room- same temperature and humidity as before. What could be the issue?

Discovered there was a small pebble, sitting under the back of the speaker, lifting the back of the cabinet about 1/8" off of the floor. So, the speaker was facing downward, very slightly.

Took the pebble out- and voila- we got a curve that virtually laid right on top of what we had done the week before.

Really was remarkable, that just that change in rake angle, could cause such a different response effect. I never specifically investigated why- my strong suspicion was that it was due to cancellations due to floor bounce (the Allison effect), being affected by a different part of the "response lobe" hitting the floor in a different place, relative to the speaker... different comb filtering from the reflections...

Regards,
Gordon.
 
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