Springs Under My Speakers: What's Happening?

[Doodski]

Agreed. I always felt the spike thing was snake-oil, unless your speakers are dancing around the room.



I remember when they used to hang TT's on bungee cords from the ceiling. LOL

I used to make a stereo system stand from cinder blocks. Very heavy and the turntable seemed to have less rumble too.

 

[Emlin]

I used to make a stereo system stand from cinder blocks. Very heavy and the turntable seemed to have less rumble too.

More rubble, less rumble...

 

[Ken Tajalli]

I just discovered this thread.
Seriously ? you put springs under your speakers?
If you wanted to decoupled your speakers from your floor and reduce floor vibrations and its "sound", there was a better way.
I have had this issue, hell most of us in UK have these issues! we mostly have suspended floor boards in UK.
My way of thinking was as follows:
- The speakers need as steady and dead-sounding a cabinet, specially for the front baffle.
- any decoupling under the speakers would cut into the above.
- so how to give the speakers a steady, solid foundation , but be decoupled from my springy floor-boards?
- A heavy slab!
I use a heavy dead slab of granite! 50mm thick, 600mm square slab (remnants bought from a local kitchen manufacturer). The speaker sits on the slab on three stainless steel dome nuts, basically coupled sonically to the slab. The slabs, being natural particle bases, have no resonances.
The slab itself , sits on three raised bolts screwed to the floor-boards. The decoupling is in the form of thick Sorbothane chunks placed between the slabs and the bolts.
- the slabs, can sort of "wobble" on the Sorbothanes. but the speakers and the slabs are coupled together.
Results:
The sheer mass of the slabs creates a high stationary inertia that grips my speakers tight, allowing very little vibration..
the slabs are acting as vibration sinks. Very little vibration is transmitted to the floor-boards and vice versa.
Of course, the floor will shake if I turn up the volume, as sound waves travel through air, but it hardly reaches back to the cabinets.
So I got my cake, and could eat it.

 

[I know (almost) nothing]

Question about isolation feet in general. I live on the 2nd floor of a 150 yr old house with very springy floors. What will adding isolation feet to my subwoofer do overall?

Thanks!
Charlie...

 

[Emlin]

Question about isolation feet in general. I live on the 2nd floor of a 150 yr old house with very springy floors. What will adding isolation feet to my subwoofer do overall?

Thanks!
Charlie...

Make things more springy.

 

[Sal1950]

Question about isolation feet in general. I live on the 2nd floor of a 150 yr old house with very springy floors. What will adding isolation feet to my subwoofer do overall?

Thanks!
Charlie...

Somewhat reduce the transfer of sound into the floor and your downstairs neighbors apartment.
Notice I said "somewhat", they're no miracle worker and may only account for a very minor transfer at that.
The same with the transfer of the sound into your listening room, maybe slightly reducing the excitation of
buzzing, rattling of things in the room, on the walls, etc.
Just don't spend a fortune on them, or make sure you can return if they don't do what you hoped for.

 

[DavidMcRoy]

In my estimation, for highest fidelity to the signal, only the drivers should move, nothing else. If you accept that, a very dead speaker cabinet should be mechanically coupled as best as practical to the planet. Sometimes compromises must be made. If your floor is springy, then you need a surrogate "planet"...like a big, heavy platform. That platform "may" need to be decoupled from the springy floor. Correct me if I am wrong, I'm not a mechanical engineer.

I routinely adhere heavy slabs of concrete to the top and bottom of subwoofers with Blu-Tac, adding tremendous mass to make it harder for the driver to move the cabinet. If my floors weren't on a concrete slab in a basement below earth grade, as they are, I might need to float the whole thing.

 

[Sal1950]

Correct me if I am wrong, I'm not a mechanical engineer.

Your not wrong, I think it's more a matter of the better of evils?
Your in what I would call an near ideal situation with the concrete floors and rigidly coupling the speakers to the floor
will damp things best as possible.
OTOH, the more capable the floor is of moving and transferring vibrations to walls etc, the more important isolating the speakers becomes..
Then in both cases we all have to deal with airborne vibrations. LOL
Mainly just my BS opinion.

 

[Doodski]

Your not wrong, I think it's more a matter of the better of evils?
Your in what I would call an near ideal situation with the concrete floors and rigidly coupling the speakers to the floor
will damp things best as possible.
OTOH, the more capable the floor is of moving and transferring vibrations to walls etc, the more important isolating the speakers becomes..
Then in both cases we all have to deal with airborne vibrations. LOL
Mainly just my BS opinion.

I think concrete reflects the sound and does not absorb nor transfer sound. So if there are concrete walls that would be good is what I read here @ ASR. Much better (enhanced?) bass response in those conditions.

 

[Thomas_A]

In my estimation, for highest fidelity to the signal, only the drivers should move, nothing else. If you accept that, a very dead speaker cabinet should be mechanically coupled as best as practical to the planet. Sometimes compromises must be made. If your floor is springy, then you need a surrogate "planet"...like a big, heavy platform. That platform "may" need to be decoupled from the springy floor. Correct me if I am wrong, I'm not a mechanical engineer.

I routinely adhere heavy slabs of concrete to the top and bottom of subwoofers with Blu-Tac, adding tremendous mass to make it harder for the driver to move the cabinet. If my floors weren't on a concrete slab in a basement below earth grade, as they are, I might need to float the whole thing.

It does not work. You cannot couple the speaker stiff enough, a resonance will appear somewhere in the bass region. With soft feet you can lower the resonance below the lowest frequency that the speaker reproduce. The principle has been used for tonearm-cartridge resonance for many years. A stiff coupling may however be good if you have subwoofers capable of reproducing sound down to DC (closed boxes).

 

[Ken Tajalli]

I think concrete reflects the sound and does not absorb nor transfer sound. So if there are concrete walls that would be good is what I read here @ ASR. Much better (enhanced?) bass response in those conditions.

How can the concrete reflect the sound if it is attached to top and bottom of the enclosure?
Even if it does, is it going to be any worse than anything else in the room?
I think the idea of putting stiff, massive slabs to the speaker is a good idea, but I wouldn't use blutak, I would use metal cones or bolts!
A soft footing between the concrete and floor would then be beneficial, as it would isolate the whole assembly from floor vibrations, to and from.

 

[Chromatischism]

I think concrete reflects the sound and does not absorb nor transfer sound. So if there are concrete walls that would be good is what I read here @ ASR. Much better (enhanced?) bass response in those conditions.

Better bass is found in American homes with drywall, actually, because they are less reflective. Stucco is even better.

 

[DavidMcRoy]

It does not work. You cannot couple the speaker stiff enough, a resonance will appear somewhere in the bass region. With soft feet you can lower the resonance below the lowest frequency that the speaker reproduce. The principle has been used for tonearm-cartridge resonance for many years. A stiff coupling may however be good if you have subwoofers capable of reproducing sound down to DC (closed boxes).

That makes sense to me and I'd like to give it a try. How critical is the "tuning" of the decoupling device relative to the mass of the speaker and anything else that's in the equation? I obviously can't just plop a sub with two concrete pavers down on a slab of foam, it'll just compress. But, I'm sure there is some such solution for that case. Some of the speakers in my "stable" weigh a lot even without modification.

As an example of something I could experiment with, how would I go about tuning an isolation system for my Tannoy System 12 DMTs? They weigh 57.3 lbs. each. I just ordered some 24" tall, open-frame steel stands for them and now would be a good opportunity to get ahold of suitable isolation feet.

 

[Ken Tajalli]

That makes sense to me and I'd like to give it a try. How critical is the "tuning" of the decoupling device relative to the mass of the speaker and anything else that's in the equation? I obviously can't just plop a sub with two concrete pavers down on a slab of foam, it'll just compress. But, I'm sure there is some such solution for that case. Some of the speakers in my "stable" weigh a lot even without modification.

As an example of something I could experiment with, how would I go about tuning an isolation system for my Tannoy System 12 DMTs? They weigh 57.3 lbs. each. I just ordered some 24" tall, open-frame steel stands for them and now would be a good opportunity to get ahold of suitable isolation feet.

Thick Sorbothane pads.
25mm thick, probably 50mm square.
I have used 25mm Sorbo's under my home speaker and granite slab, probably about 40kg total weight, it still wobbles side ways and up and down after many years.
Sorbothane is like a gel plastic, it also acts as shock absorber. Simple springs would just oscillate.
The heavier the mass, the softer the decoupling, the lower the fundamental frequency.
Remember, the blutak compliance also adds to the whole equation, better replace them with metal cones, pointy ends on concrete.
Garden concrete labs do fine! you can even dress the whole thing up, with a thin rug or decorative blanket thrown over, but not between the speaker and the slab.

 

[DavidMcRoy]

Thick Sorbothane pads.
25mm thick, probably 50mm square.
I have used 25mm Sorbo's under my home speaker and granite slab, probably about 40kg total weight, it still wobbles side ways and up and down after many years.
Sorbothane is like a gel plastic, it also acts as shock absorber. Simple springs would just oscillate.
The heavier the mass, the softer the decoupling, the lower the fundamental frequency.
Remember, the blutak compliance also adds to the whole equation, better replace them with metal cones, pointy ends on concrete.
Garden concrete labs do fine! you can even dress the whole thing up, with a thin rug or decorative blanket thrown over, but not between the speaker and the slab.

If I can sort of "bring this home," it sounds like I should be mechanically coupling a speaker to a heavy mass (as I've done with all my subs) with spikes, and then "float" the speaker/spikes/concrete combined mass from the floor at a very low frequency with Sorbothane? And I assume this is still optimum if my floors are concrete?

 

[Ken Tajalli]

If I can sort of "bring this home," it sounds like I should be mechanically coupling a speaker to a heavy mass (as I've done with all my subs) with spikes, and then "float" the speaker/spikes/concrete combined mass from the floor at a very low frequency with Sorbothane? And I assume this is still optimum if my floors are concrete?

If your floors are concrete and full solid, never vibrate, then you don't need the pads! (at least according to me).
If the floors do vibrate, or they are suspended wood boards, then you do.

 

[DavidMcRoy]

If your floors are concrete and full solid, never vibrate, then you don't need the pads! (at least according to me).
If the floors do vibrate, or they are suspended wood boards, then you do.

That's what I was thinking. For all practical purposes a concrete slab built on dirt (with lots of big rocks in it here in southwest Washington state) is a good mechanical ground. I had a hard time trying to wrap my brain around any reason to float a heavy speaker rather than just spike it to the floor If the floor is pretty immovable.

 

[Ken Tajalli]

As you had said before and I agree, the only thing vibrating should be the cones/diaphragms.
Any other vibration, would mingle with the diaphragm vibrations and cause distortion, acoustic distortion.
Mass inertia, keeps the speaker cabinet from vibrating back and forth in tandem with the diaphragm. Your slabs are adding mass to the whole assembly. provided the speakers have a rigid enclosure, the extra mass, would add resistance to movement (through increased inertia).

 

[Ken Tajalli]

That's what I was thinking. For all practical purposes a concrete slab built on dirt (with lots of big rocks in it here in southwest Washington state) is a good mechanical ground. I had a hard time trying to wrap my brain around any reason to float a heavy speaker rather than just spike it to the floor If the floor is pretty immovable.

Don't even need the slabs for that matter!
Just metal cones on concrete floors will do.
Edit: use only three cones, to make sure it sits right.
But do use some carpeting elsewhere, , to stop reflections off the floors.
If you feel like doing something, open the enclosure and see if cross-bracing is required to stiffen any panels, otherwise, you are good.

 

[Natural1]

For subwoofers on floating floors (Ranch on basement) the SVS SoundPath isolation feet make a very nice and noticeable difference, and are not particularly expensive. My subs no longer rattle the contents of my kitchen cabinets. This was true of my previous dual SB12-NSD subwoofers, and now dual Rythmik E15s. There's no way I would go without them in this house.