DIY speaker isolation base for a wood floor

May I suggest Fastenal for springs (or any number of other industrial suppliers). They have literally hundreds of options and they are dirt cheap. Many diameters, lengths, wire size, and very inexpensive. That let’s you much better match your component to the spring as opposed to a few limited options.

delkal72 posts12-18-2019 10:14pmI always thought you wanted to couple your speakers to the floor (with spikes). Now it is best to decouple them?

There is no right answer delkal, as it depends on your floor and speakers. Those claiming one answer is always right .... and like a broken clock. They are exactly right every once in a while.


Concrete floors and a speaker cabinet not as stiff as one would like, then odds are better to couple to the floor for damping. A springy floor and you likely want to decouple it, but not necessarily. If the cone is going one way, then the cabinet wants to go the other way.

Georgehifi makes a point about sorbathane. It is one of the best energy absorbing substances and absorbing energy you don’t want to turn into sound is a good thing (this is what sand does as well) ... and what the op is trying to accomplish with neoprene. I would suggest sorbathane instead, though more expensive.  The 70D linked would be too dense as a set of 4 for almost any speaker. 50D which they appear to also sell or even 30 would be more appropriate.

Spring based systems don't store energy .... Ooooookay.

The more you try to store energy the worse things get. It’s a vicious cycle. That’s why spring based systems rule the night. They don’t store energy.


What makes Sorbothane the best energy-absorption material are its combination of shock absorption, vibration isolation, and vibration damping properties with its strong, long-term performance in nearly any environment or for any application.

If one was purely trying to isolate than springs make sense but that is based on the assumption that is the best path forward always. It is not. 

If anyone would like a quick refresher on springs, mass, and resonance, they may enjoy this:

https://www.newport.com/t/fundamentals-of-vibration

Newport is a scientific instruments company mainly focused in anything related to optics and light and anything related to that, including vibration control.

i.e. a spring that is 1.5" free length, 1 inch compressed with a 10lb load will have a C of about 0.00029  meters/newton, and a resonant frequency with a 10lb (4.5 kg) load of 4.4Hz.   That  (w) is radians/second in the link.

Nano-K did not start out in audio, that was just a side market. The primary market for Minus-K (Nano-K) is scientific / industrial.


You can be as bold as you want but I am going to say the guy who runs Minus-K with his 10's of patents around shock and vibration isolation knows a few things about the "art" and science of isolation and probably has the numbers down pat as well 


Kinetic Systems (vibraplane) has been around since the 60s.   When did Your company release an isolation platform?

The person with no skin in this game is feeling no angst. The one with angst is the one desperately trying to appear relevant while the rest of us are going "Geoff who?".


I mean why else would someone describe a somewhat simple but effective concept of using spring mechanisms both in compression and extension, the extension implemented as a flexure (the negative term in Minus) as "much more complex"?   The use of the tunable flexure giving significant benefits but not that complex. The whole isolation mechanism certainly has some complexity, but the underlying principle ... Not at all.


I am glad I am your favourite. Everyone needs a muse.

You are right, you don't need a muse, you need an inner voice. You seem to be missing one. Sure, when I want to learn about "negative-K" isolation basics, of course I am going to go to 6-moons, the well accepted authority on vibration isolation .... :-)

How about the actual website of the MFR where the system is broken down to show that conceptually it is very simple. The completed system looks complex due to the multi-axis nature of the completed assembly. The basics ... quite simple:

https://www.minusk.com/content/technology/how-it-works_passive_vibration_isolator.html

The video "lost" me, as in lost any respect I had when they started talking about seismic coupling into the speaker impacting micro-detail. The spectrum of background vibrations is predominantly <10Hz, pretty much nothing >100Hz for starters.  Surface area of a speaker maybe 10 square feet? Surface area of room walls, ceiling, floor = 1000 square feet. If those microvibrations are anywhere near audible, it's too late, your room is already a giant speaker for them. If you think the movement in these frequencies and amplitudes of the cabinet impacts the "detail" of the drivers, then your head is going to explode when you think about that mid-woofer trying to play say a 1Khz tone while that mid-woofer is experiencing comparatively large subsonic and sonic motion from your turntable (let alone from the music itself).

Got a good laugh out of claiming the cabinet does not move in one sentence to claiming large floor coupling the next. Which is it?   Could acoustic coupling be a primary mode of coupling to the floor ... after all, where is the energy coupled, to the cabinet or to the air?

select-hifi246 posts12-18-2019 9:57pm mijostyn

In my humble opinion you are wrong regarding the use of Spikes,

https://www.youtube.com/watch?v=dW9-r83IvhI

A vehicle suspension consists of a spring element AND a shock absorber. The shock absorber portion is not a spring. It moves typically fluid between sections through small channels converting motion to heat. A little research may be in order for you.

It's okay Geoff. I am going to guess most people know the difference between a shock absorber and a spring in a car even if you don't. Here, maybe this link will help you:


https://www.bilstein.com/us/en/technology-and-knowledge/basic-know-how/

Springs and shock absorbers are completely different beasts. If you have just the spring and not the absorber you can get oscillation at the resonant frequency.


Are there any tests w.r.t. frequency response, distortion, impulse response of a speaker on/off an isolation platform to characterize the improvement? 

From Sorbothane.com

• Sorbothane® combines shock absorption, good memory, vibration isolation and vibration damping characteristics.
• Sorbothane® can absorb over 50 percent of vibration energy over most of its temperature operating range at frequencies from 10 to 30,000 hertz.

From me: Sorbothane acts as both a shock absorber and a spring. That is one of the reasons why it is effective. The problem that may arise with Sorbothane alone is getting the resonant frequency. Best to use their calculator and you may need to cut pieces to the size you need and pay attention to the Shore hardness. A very approximate rule of thumb is if the Sorbothane is compressed 30-50% you are getting pretty good isolation (~90%). 50% compression should put you under 10Hz resonant frequency.

That someone would compare Lead to Sorbathane, i.e. a soft metal to a visco-elastic polymer makes me really question what message they are trying to communicate. Lead would be more an analog to granite, SONEX an analog to a GIK acoustic panel.


To experiment properly with Sorbothane, one has to properly implement it, which means using the correct hardness material as well as the correct cross-sectional area for the weight being supported, no different from a spring. Unfortunately, people just say "Sorbathane" or spring, without the required knowledge to properly implement and hence they lead people astray.

SONEX is an acoustic foam, so not sure why you are bringing that into the equation ..... however, just like Sorbothane or a spring, it must be properly implemented to work well.

I am not confused, but someone reading a post mentioning lead and sorbothane in the same sentence like they are directly related may be. I don’t need to hide behind hand-waving explanations and insults on topics I engage in.

Lead can be a very effective sound absorber. That is simply fact. It is regularly used in this application due to density and hysteretic loss. It’s hysteretic loss is also such that it is difficult to make a resonant structure out of it. Like anything else, it has to be used properly.

Unlike lead, sorbothane behaves both as a spring (isolator) and absorber (dampener). Think of that like a combination of the spring and the shock absorber in a car (or truck).

Placing lead between your speaker and the floor could only provide some level of dampening. At bass frequencies, that would be almost none. Contrast that with sorbothane, which provides isolation by acting as a spring, and dampening.  Properly implemented, not just buying some random things off the web, you can isolate something to <20Hz, and even <10Hz.


Your attempts to try to discredit me, embarrass me, or whatever it is you are trying to accomplish are not going to work as that would require the knowledge to know who is and is not technically "up" on the topic.

Hey bdp24,

Do you have experience with ISODAMP. We used some for a project a while back, but my colleague was working on that and I did not have enough time for "info-osmosis". I think the foams are quite interesting, and the availability is good. Thanks for the reminder. I will probably get some in the next week or two to try out. I have more experience with Sorbothane so it becomes a go to.

I like this video:   https://www.youtube.com/watch?v=3HRbjfZUbe8

After the first simultaneous ball drop, listen to how loud the next bounces are from the regular rubber material. The foam absorbs the energy and releases as heat, not sound.

blueranger,

I am assuming each granite slab is about 25lbs, and the sorbathane is between them, so assume a 100lb total load.

georgehifi posted a link above to an Ebay seller. They sell 2.5" diameter disks of 70, 50 and 30 hardness. My rough calcs say that if you cut those in half (so half circle), and use 4 of them, they should depress about 25%.  That is not going to isolate the lowest bass frequencies, but will be a good improvement over what you have now. One area I agree with geoffkait on is that springs are best for low low frequency isolation.

I expect you have lots of cork around, so you can start experimenting. As opposed to single large sheets of cork, cut them into say 2" squares and stack them say 1/2" high, and use 4 stacks for stability. You want the cork supports small enough (and not too small) that the cork is compressing say 10-20%.

1. Does Sorbathane convert motion into heat? ... yes
2. Is turning motion (vibration) into heat as opposed to sound where cabinet motion is an issue a good thing? ... yes
   
3. Do springs store energy? ... well of course yes. The better the spring, the more perfect it’s energy storage.
4. Is isolation always the path to the best sound? Of course not.

Feel free to address 1 to 4 in a cogent manner.

6) The one where you get creative and figure out a way to have the springs and sorbothane between the two slabs at the same time ... or maybe the springs and a stack of lightly compressed cork. That way you get isolation and dampening.


Which springs are you getting? If you have them at the bottom, you need the right springs for 125lbs (spring and two slabs). The resonant frequency of the spring is a factor of spring constant and loading.

If you have large diameter springs and do not overly compress them, you don't need conical spings. Conical springs have better stability the you can make one layer sit within another, but you shouldn't be compressing them that much. It is a bit harder to calculate the operating point for a conical spring.

Blueranger,


Just using springs will be wobbly. If you are targeting 2-3hz resonant on the springs, then most higher frequencies will not be transmitted .. it flops.  If you add dampening in parallel with the spring (ie sorbothane), then you can keep a low resonant frequency, but damp oscillation. Some higher frequencies will now pass (still highly attenuated), but the system will not feel nearly as "floppy" as the resonances are damped.


Wrt Clearthink's post on just adding mass, all that does is change the resonant frequency of the speaker/mass and spring (i.e. your floor). The spring constant, i.e. your floor does not change. As I mentioned above, a wider stiff base (ie your granite bases) does change your floor interface which may transfer weight closer to the joists which will change your spring constant (floor).


Where Geoff and I agree is on a spring loaded floor isolation is better. I prefer damped as that damps out cabinet vibration and isolates from the floor.

If you push down on a mass that’s on a spring and then let go it will oscillate. it’s not a sustained oscillation but it most definitely oscillates. many of us have done this experiment on our car when the shock absorbers were at the end of their life.


I am not trying to turn this into a debate because there is no debate. When you push a mass on a spring it will oscillate at a defined frequency. It won’t sustain those oscillations but it will oscillate. There is no debate it does that. That is literally high School physics. The op doesn’t like his speaker is being floppy. the way to eliminate that floppiness while still having a high level of isolation is to a dampening. A game this is not a debate that is simple fact. There are trade-offs with adding that dampening as I pointed out. That is not a debatable item that is simply fact.

Twoleftears,


Note what I posted earlier in the thread. The primary coupling is acoustic. 

Got a good laugh out of claiming the cabinet does not move in one sentence to claiming large floor coupling the next. Which is it?   Could acoustic coupling be a primary mode of coupling to the floor ... after all, where is the energy coupled, to the cabinet or to the air?

I never said the spring would oscillate with music though with some of the platforms with their rubber springs they actually would. With a well chosen basic steel spring it will not. However as the op stated he found it wobbly and does not like it. Most don't find damped systems wobbly, to that end damping his spread would give most of the benefit of isolation you promote with a system they can live with. 


Granite would be excited by vibrations at higher frequency, but given the mass and relatively low energy at those frequencies it's not going to create audible issues.


The spring only system will not help to damp cabinet vibrations. Damped system will.


Blueranger, you may have a half decent measuring device in your hand right now. Your phone has a multi-axis accelerometer. There are programs for logging / testing. Bandwidth is limited but frequencies are usable.  I have a range of accelerometers in the lab, we can also do non contact, but for a speaker cabinet that is not really needed.

There is a video posted above by select of the Townsend isolation system 4 speakers. That is a good example David damped spring system.  Well I find the video of it cheesy you can see that that system not only isolates the speaker from the floor but also helps to dampen cabinet vibrations.

You will find that Ethan gets 0 respect here from certain people. I am not one of those people. I don’t agree with him on everything he says, but more often than not he is right. Is he completely right here? While I think he did his best to measure, I am not sure metrology is his strong point, and as he admits, it is a difficult measurement due to consistent positioning. A THD or IM measurement would be less sensitive to position and yield more repeatable results. He was only measuring how the speaker behaved, not if floor coupling was at all a factor. For the frequency response, it is just not an accurate enough measurement in his environment. If you look closely at the impulse responses, for which the resolution is very poor in both the temporal domain and the SPL domain, there does still appear to be noticeable differences. Is height a factor? Maybe. I would have like to seen a measurement farther as well to take into account potential floor interaction (or lack thereof).


One serious issue in the Townsend video is they only take into account the motion of the very light speaker cone w.r.t. how the cabinet would move. This is an incorrect model as it only takes into account reactionary mass (sort of like a rocket where you are "throwing" mass so to speak). In a speaker, the air is a mechanical loading. You are not just moving the cone, but moving the air, and in front of the cone, pressurizing it, so the mechanical force is more than just the mass of the air as well. Put your hands on a wall when loud bass is playing. You can feel it. That is the energy that cone is transferring.

blueranger OP636 posts01-04-2020 3:11pmInteresting article from a snake oil sleuth. I have wondered too if the change was somewhat due to speaker height. I swear my DIY speaker isolation base made a worthwhile difference when I played Madonna’s "Erotoica" and Al Stewart’s "On the Border" The bass seemed better controlled and deeper. I dont want to think that the expense of time and 💰 money was wasted. That earlier video of the RMAF show was impressive. So according to the article he didn’t test that guys product did he? So I’m thinking maybe my DIY speaker isolation platform is making a small but positve step closer to audio nirvana.

Can you explain how you have a damped buckling isolator ... and none of the issues damping brings to the table?  I understand what a mechanical diode is.

all you need is a critically DAMPED buckling isolator tuned to an appropriate frequency for isolation
....and a mechanical diode to take care of all the speaker vibrations, and without the phase issues DAMPING brings to the table.

blueranger,

Quick calc says your resonant frequency is about 6Hz. That does not feel right, but perhaps geoff can check my math. I was assuming 134lbs (2x granite + speakers). That do a pretty good job at isolating most stuff over 20Hz (will be down 10x at 20Hz). Another slab of granite is not going to make much of a difference in the isolation.

If the room us vibrating the walls are already enormous speakers.


When the woofer is already moving way more from say turntable rumble and your music is riding on top of that, does seismic motion matter? Seismic motion us predominantly <10 Hz and quickly drops off from their to 200hz, opposite to the Fletcher Munson curves so seismic movement would need to be more substantial to be an issue but again, the giant speaker walls are going to be orders of magnitude more an issue.

Goeffkait, can you use that expertise and review my math wrt the spring resonance for the OP?


Blueranger, what is the spring constant of the new springs (57 lb rated)?   As your platforms are not overly large, shorter springs as well would be "safer" due to less angular movement (say if you bang into them).