Spikes or Isolators under subs?

I have a pair of 10" subwoofers, on an engineered hardwood floor, over slab-on-grade concrete. Currently I have them sitting on Auralex MoPad foam isolators. I have threaded spikes in a drawer.

I am not keen to use the spikes because in the past they have damaged wooden floors, even when mounted in cups. Also, installing them is a pain in the ***.

What does theory say I should use, isolators or spikes? What is your personal experience?
 
Really simple question once you understand the issue.

The purpose of the voice coil is to vibrate the cone in relation to your ears. But if the driver is shaking about because the cabinet is not rock-solid in relation to your ears by way of the floor joists, the critical relationship between ear and cone becomes damaged.

(Just moving your head is on a wholly different time scale and doesn't matter in this analysis. But cabinet vibration - which ordinarily is not worth over-fretting about - might matter here.)

Different ways to make the cabinet rock-solid depending on the cabinet and flooring. Three spikes are good for connecting the cabinet to the building structure through a rug (but might scar a wood floor).

Small thin rubber pads might seat a cabinet nicely and over-ride slight irregularities, provided the cabinet remains essentially rock-solid. Anything rubbery that serves to "isolate" the cabinet also means that it gives the cabinet free opportunity to shake about - which is exactly what you don't want in relation to your ears. Only the voice coil should determine where the cone is.

I used to put heavy cinderblocks on my corner horn and the natural or added weight of the cabinet may be all you realistically need.

B.
 
Last edited:
Anything rubbery that serves to "isolate" the cabinet also means that it gives the cabinet free opportunity to shake about - which is exactly what you don't want in relation to your ears. Only the voice coil should determine where the cone is.

And...why?
Precisely, exactly, any argumentation is valid but bring evidence!
(1 micron of tymphanyc movement produces a stimulus, so you're warned:Pirate:)
 
I think the spikes idea is an alternative to adding mass to the enclosure, by mechanically coupling it to a relatively infinite mass.
...
First, is there a problem that needs to be fixed? Is the driver frame moving in a time-frame and distance extent relevant to music band from that driver?

Lots of ways to fix it, depending on local circumstances. If sitting on a high-pile carpet or shag rug, surface area of base of cab, weight of cab, sub or mains, etc. Can be reinforced by adjacent furnishings or wall? Is the sub driver low in the cab?

You can sit cab on a cement paving stone (like 2 x 2 feet, with a sheet of thin vinyl-stuff to protect the cab and ensure good resting surface.

You can slobber "rubber cement" (not RTV silicone) on bottom of cab which can be peeled off later.

Etc.

B.
 
Thanks all for the replies. I intend to stay with the MoPad isolators. Formerly I had small felt pads under the subs and the MoPads did improve on the sound. I can't feel any motion or rocking when the subs are playing, so I don't think stability is a concern.

The danger of scratching the floor with coupling spikes is definitely a factor in my decision. If there was a clear indication in this thread that spikes are indicated for this application, I would have taken the risk.
 
Really simple question once you understand the issue.

The purpose of the voice coil is to vibrate the cone in relation to your ears. But if the driver is shaking about because the cabinet is not rock-solid in relation to your ears by way of the floor joists, the critical relationship between ear and cone becomes damaged............

Wood floors bounce with the loudspeakers and that may cause equal if not more distortion than the isolating material/pads.

They call them sprung floors for a reason, they have spring like action to them. Couple to them and the speaker bounces with it.

Wood flooring on sleeper furring (or foam rubber strip) on top of a concrete slab will provide some spring, which is why people install them, to reduce the fatigue of walking on concrete floors.

You have to think in 3D, not 2D.

All those speaker frame/enclosure forces are going into the floor, or can be dissipated though mechanical motion/heat. Your choice.

Think horizontal forces to vertical forces to 180 degree dispersion throughout the supporting ground plane. It's more like 45/45 or 90 degree dispersion downward like in a building foundation (spread footing) but you get the picture, right?

What is kinetic energy? (article) | Khan Academy
Kinetic energy can be transferred between objects and transformed into other kinds of energy. For example, a flying squirrel might collide with a stationary chipmunk. Following the collision, some of the initial kinetic energy of the squirrel might have been transferred into the chipmunk or transformed to some other form of energy.

A recent thread in another forum there are some images and GIF's posted that might clear this up, or might not.

An argument for NOT spiking speakers to floor
An argument for NOT spiking speakers to floor | What's Best Audio and Video Forum. The Best High End Audio Forum on the planet!
 
Last edited:
Wood floors... They call them sprung floors for a reason, they have spring like action to them. Couple to them and the speaker bounces with it....

Yes, those floors are moving: every 6 months as the weather changes.

In my posts, I emphasized that the time-frame of motions have to be taken into account.

B.
 
Yes, those floors are moving: every 6 months as the weather changes.

In my posts, I emphasized that the time-frame of motions have to be taken into account.

B.
Good point about thermal expansion/contraction and perhaps humidity conditions, but that is not the time period or movement type we are talking about.

We have two wood floor types under discussion.

1. Floating wood floor of the original poster (wood over concrete).

2. Platform construction of wood framed houses.

In each case there is some movement of the ground plane (floor), but will admit may be insignificant compared to a rubber base (or foam) under the speakers - so many variables.

To be clear I have not experimented with foam or rubber feet with loudspeakers. The closest I came was plastic feet on thread rods that came with my Martin Logan's intended for room location purposes, as per manual once perfect location found to be replaced with the provided spikes.

To be clear, the time-frame of motions you introduced to the discussion focused on lateral motion (2D diagram).

I would like your interpretation of taking that model 3D or at least to a 2D conclusion into the ground plane where possible vertical motions reside.

Are there even more time-frame motion errors as we follow the energy into the actual foundation of the building?

When in college we had to do structural design of buildings for wind resistance and earthquake loads that started at the top/roof, included the floor and wall construction and then finally be able to size the foundation.

Such a top down approach is warranted here I suspect.

The foundation of the loudspeaker is not where it terminates at the floor, we must carry it beyond if we are to be fully comprehensive - in my opinion.

The floor in other words, is part of our speaker system (because it is it's foundation), yes?
 
Last edited:
A few images from another thread that I posted which perked my curiosity.

Our Technology - Alsyvox
[IMGDEAD]https://whatsbestforum.com/attachments/soft-2-disegno8-1-jpg.60804/[/IMGDEAD]

disegno9.jpg



In the below GIF, imagine the building is the loudspeaker causing all the motion (reverse of an earthquake).

giphy.gif
 
...In the below GIF, imagine the building is the loudspeaker causing all the motion (reverse of an earthquake).

Nice graphic and nicely illustrates how wrong it would be to use rubber mounts of the isolation variety whose purpose is just like the graphic shows.*

But thin rubber pads that help seat the speaker more stably against the substrate below act in the opposite manner. And they could do more to firmly connect the cab to the floor compared to pointy little cones.

Construction hint: to make really great form-fitting rubber pads, use dabs of RTV silicone rubber but be sure to have sheets of wax paper or Saranwrap above and below during curing. Or for very thin applications (including mounting drivers), non-silicone-RTV "rubber cement" as previously mentioned.

B.
* Ummm, I must have box of those mounts in my storeroom somewhere that I used under vinyl turntables (with SME arms) decades ago.
 
Last edited:
Somehow one of the Alsyvox images didn't show up.

Try again.

Our Technology - Alsyvox
disegno8-1.jpg


I believe one may conclude that the flat panel speaker maker Alsyvox gave up on trying to be as stiff as a box speaker, threw in the towel and just let it roll with the punches. Alternately one could conclude they are right, and almost everyone else in the industry is wrong.

I'm also going to guess based on bentoronto's comments that enclosure flex is a minimal concern compared to having the entire speaker cabinet move and mess things up.

Sound right?

I recall one forum poster's story of his flooring moving in a wave towards him as his large horn speakers hit a lower octave. I'm not sure if there is a solution there or just an example of energy transference gone astray.
 
Last edited:
Hard to know what extent of motions and period you need to address. So this discussion is unfortunately rather abstract.

Yes, I am skeptical about going too nuts about cab wall stiffness; yes, you can feel cab vibration with your sensitive finger tips but maybe there's nothing too audible really.

But I wonder about the really bad trend today toward heavy cones (mostly due to mega-weight voice coils that can carry an advertised 3000 watts... fantasy-land).

Driving cones that weigh half a pound (no kidding) must have an effect on cab shaking?* Time to go load the cab with a cinderblock?

B.
* bikers and automobile aficionados will understand about "unsprung weight" and vehicle suspensions
 
Last edited:

impuls60

Member
2011-04-07 2:24 pm
I insulated my speakers with thick rubber feet and the glass wall behind the speakers affected the sound less. Also the rattling from the interior on sidewalls also diminished. The floor is a bouncy wooden frame floor so feet had a dramatic effect. I think spikes should be used on floors directly connected to ground. The rattling from interior is usally a much bigger problem than the very small audible difference spikes makes, at least that has been my experience with big speakers.