Springs Under My Speakers: What's Happening?

[Thomas_A]

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.

I use the Sonic Design feet which comes in different variants depending on mass.

I believe the material used is called "sylomer".

 

[Chromatischism]

Speaking of subwoofers, eliminating all tactile feedback using pads, etc leaves a lot to be desired when watching movies.

 

[DavidMcRoy]

Speaking of subwoofers, eliminating all tactile feedback using pads, etc leaves a lot to be desired when watching movies.

If by "tactile feedback" you are referring to structure-born vibration shaking your body through the your chair, that's certainly true and there are bass shaker drivers specifically intended to be attached to your chair or sofa. I've played with those and they're fun. The ones I tried boost everything around 40Hz.

If one is just looking for close fidelity to the signal as opposed to modifying it in that way, (not that there's anything wrong with that...home audio is part of the "entertainment industry" after all) you can just turn them off. As far as strictly airborne waves, Note that your abdomen resonates at bass frequencies around 50Hz give-or-take depending on how heavy your are, and different organs at various frequencies, the liver being the heaviest. I've read of some subwoofer manufacturers putting a 3dB boost at 63Hz to goose-up the gut punch feel. I guess they reckon that specific frequency is a good one, but I don't know. For me personally 56Hz seems to do the trick. (I'm a 5'11"/180cm, 190lbs./86kg male.)

 

[Chromatischism]

Home audio subs don't have that.

 

[Thomas_A]

If by "tactile feedback" you are referring to structure-born vibration shaking your body through the your chair, that's certainly true and there are bass shaker drivers specifically intended to be attached to your chair or sofa. I've played with those and they're fun. The ones I tried boost everything around 40Hz.

If one is just looking for close fidelity to the signal as opposed to modifying it in that way, (not that there's anything wrong with that...home audio is part of the "entertainment industry" after all) you can just turn them off. As far as strictly airborne waves, Note that your abdomen resonates at bass frequencies around 50Hz give-or-take depending on how heavy your are, and different organs at various frequencies, the liver being the heaviest. I've read of some subwoofer manufacturers putting a 3dB boost at 63Hz to goose-up the gut punch feel. I guess they reckon that specific frequency is a good one, but I don't know. For me personally 56Hz seems to do the trick. (I'm a 5'11"/180cm, 190lbs./86kg male.)

I would like to try a serious bass shaker sometime. I have s dedicated output for shaker with slight delay and volume knob on my active sub filter. Those who have tried good ones (going to infra LF) say they add a new, previously missed, dimension to music and movies. Despite having competent subs.

 

[Triliza]

So I got one of this laying around, and I'm thinking to give it a try and make some diy speaker stands (from MDF as I have some spare available). Would it be a good idea to put a piece of this between the speaker and the stand or is that pointless?

https://www.amazon.com/Xavax-00111362-mat/dp/B00ECUFNCE

 

[fineMen]

... is that pointless?

Depends! With soft couplings, and that includes even 'spikes', the mass of the suspended thing and the spring forces consitute a resonator. Below the resonance frequency the strength of the spring rules, above the inertia of the mass--to put it simply.

Most probably one would consider a quite low resonance frequency a success. It would mean, that the coupling is low, and the forces are counter-acted by the mass alone. The transfer of motional "energy" to other things, e/g the floor is somehow minimised.

Another talking-point is the 'damping'. It wouldn't help too much with the above mentioned transfer. Basically it's pointless to try to dampen the resonances of a piece of floor with felt put below the speaker (stands). If the floor would be as soft as to make it effective, I would rather leave the house for security reasons and never come back. One only prevents rocking / rattling which, on the other hand is the most annoying thing to begin with.

So, some felt may act as a spring. Check the resonance frequency by pushing against the speaker, best at the height or aotherwise close to the mounting position of the bass driver. If ith box wobbles, o/k, resonance is obviously very low. Done.

These explanations may 'feel' simple. But they are true. I've got some education in this field. I say this as to make you trust me. I don't want to sell to you anything.

 

[Triliza]

Depends! With soft couplings, and that includes even 'spikes', the mass of the suspended thing and the spring forces consitute a resonator. Below the resonance frequency the strength of the spring rules, above the inertia of the mass--to put it simply.

Most probably one would consider a quite low resonance frequency a success. It would mean, that the coupling is low, and the forces are counter-acted by the mass alone. The transfer of motional "energy" to other things, e/g the floor is somehow minimised.

Another talking-point is the 'damping'. It wouldn't help too much with the above mentioned transfer. Basically it's pointless to try to dampen the resonances of a piece of floor with felt put below the speaker (stands). If the floor would be as soft as to make it effective, I would rather leave the house for security reasons and never come back. One only prevents rocking / rattling which, on the other hand is the most annoying thing to begin with.

So, some felt may act as a spring. Check the resonance frequency by pushing against the speaker, best at the height or aotherwise close to the mounting position of the bass driver. If ith box wobbles, o/k, resonance is obviously very low. Done.

These explanations may 'feel' simple. But they are true. I've got some education in this field. I say this as to make you trust me. I don't want to sell to you anything.

Nothing simple about what you wrote, I have read it at least three times, I don't have a clue about any of this, so thanks for explaining it. I don't understand though how to check the resonance frequency manually, and I don't have any kind of instrument that can measure such things. Speakers are Elac DBR62 if that helps, to be or not to be?

 

[fpitas]

So I got one of this laying around, and I'm thinking to give it a try and make some diy speaker stands (from MDF as I have some spare available). Would it be a good idea to put a piece of this between the speaker and the stand or is that pointless?

View attachment 262868

https://www.amazon.com/Xavax-00111362-mat/dp/B00ECUFNCE

FWIW, a friend and I glued carpet samples under his DIY speakers to protect the wood floor. They also seem to isolate vibration nicely. Now, the speakers in question weigh about 90 pounds each.

 

[cicastol]

Speakers are Elac DBR62 if that helps, to be or not to be?

Hi, my DBR62 are mass coupled with 3 point spike glued to a 30 mm granite slabs the same size as the speaker and then decoupled with 35mm height poliester sandwiched between two books (temporary ) works really good with tighter bass (probably due to rigid mass coupling with granite) and no vibrations on the desk... !!!!
Under the granite there are 5 feets of Sylomer SR42 elastomer for further decoupling purpose .

 

[fineMen]

So, some felt may act as a spring. Check the resonance frequency by pushing against the speaker, best at the height or aotherwise close to the mounting position of the bass driver. If ith box wobbles, o/k, resonance is obviously very low. Done.

These explanations may 'feel' simple. But they are true. I've got some education in this field. I say this as to make you trust me. I don't want to sell to you anything ...

a) prevent rattling
b) suspend the speaker in some sort of spring; the more weight the speaker has, the stiffer the spring could be

Practical example: I use a bass module of about 20kg weight. The speaker rests on a single-folded towel. Perfect. No mysteries, nothing else to be optimized.

 

[Triliza]

Thanks everyone, I guess I'll just use it and hope it does something beneficial, one way or another.

 

[Sokel]

I was always wondering,and as some of you have worked in studios or are pro installers:
Are the in-wall flush mounted speakers in studios have some sort on "air" so they can work with the same principle springs work or are hard mounted as stiff as they could be?

 

[fineMen]

I was always wondering,and as some of you have worked in studios or are pro installers:
Are the in-wall flush mounted speakers in studios have some sort on "air" so they can work with the same principle springs work or are hard mounted as stiff as they could be?

I'm not that professional you asked for. Anyway, everthing is a spring. There isn't a thing that wasn't elastic. The only thing to be relevant is the relation of mass to the spring force, because that determines the resonant frequency You want the resonant frequency to be lower than the lowest operation frequency of the transducer. Nothing else, really.

With quite heavy loudspeakers, with the driver mounted more towards the top of the enclosure, the relations are so that even with the common 'spikes' with their pointy, hence springy end one ends up at a resonace of, say 40Hz. You cannot 'feel' that resonance, but it is there.

Maybe someone else is willing to explain the workings of the spring suspension graphically.

By the laws of nature (physics, Isaac Newton) every force implies a counter force. The counter force could originate in the stiffness of the floor. If you want that, screw/glue the box to the floor. If you do not want it, what other counter-force could be used? It could be the sheer mass of the speaker, its inertia. In order to come to this, make the mass 'fly'. To do so, suspend it softly. That is what I'm talking about.

 

[Sokel]

I'm not that professional you asked for. Anyway, everthing is a spring. There isn't a thing that wasn't elastic. The only thing to be relevant is the relation of mass to the spring force, because that determines the resonant frequency You want the resonant frequency to be lower than the lowest operation frequency of the transducer. Nothing else, really.

With quite heavy loudspeakers, with the driver mounted more towards the top of the enclosure, the relations are so that even with the common 'spikes' with their pointy, hence springy end one ends up at a resonace of, say 40Hz. You cannot 'feel' that resonance, but it is there.

Maybe someone else is willing to explain the workings of the spring suspension graphically.

By the laws of nature (physics, Isaac Newton) every force implies a counter force. The counter force could originate in the stiffness of the floor. If you want that, screw/glue the box to the floor. If you do not want it, what other counter-force could be used? It could be the sheer mass of the speaker, its inertia. In order to come to this, make the mass 'fly'. To do so, suspend it softly. That is what I'm talking about.

Thank's for tthe explanation,it makes sense,though my question refers to how studios deal with it.
I have seen (in some installations) that even if the speakers are flush-mounted to the wall their internal bracing consists of spring-like brackets (excuse my poor english if I say it wrong).
Is that the norm or some kind of special use and in other cases are mounted stiff in the wall enclosure?

 

[MattHooper]

Hi folks,

Dropping in again for an update on my shenanigans.

As I think various conversations on this thread have indicated, it is difficult to say the least to predict the results of trying to damp resonances/isolate/couple etc with any particular speaker in any particular room. As Frank D. pointed out to me, even just moving the speakers to different spots on a sprung wood floor is likely to change the resonant character/frequencies involved.

So I'm down to, as I've said, throwing spaghetti at the wall, trying things to see what if anything alters the sound in a way I like.

The new thing that has changed is that I now have my Joseph Audio Perspective floor standing speakers back in the system (replacing the Thiel 2.7s referenced in this thread). They are responding slightly differently than the Thiels.

First using them with their supplied outriggers and spikes, they sounded quite nice. The bass is actually a bit more controlled (through some of the spectrum) than the Thiels in this room. But I had the Gaia footers and wanted to see if I could still tighten things up. Unfortunately the Gaia footers fit fine on the back of the speakers, but I could not remove the front spike/cones from the outrigger to install the Gaia (the cones won't come off as apparently they have a stopper - some glue - holding them to the bolt that would separate them from the outrigger).

So I had to just screw the front Gaia in to the existing speaker cone like this:

Results: It just didn't work.

I found no real benefits to the sound, if anything things seemed to get a tad more mushy and diffuse sounding. Directly coupled to the floor sounded more firm and in control.

But I did kind of like the slightly raised soundstage so I thought what the heck, try something else to raise the speakers. I left the Gaias on the back of the speakers, but took them off the front outriggers, put in the bottom 1/2" spike on the speaker cones, then a hockey puck, which was held more firmly in place on the rug by placing the Isoacoustic carpet spike cup beneath the puck (buried in the rug). Since that raised the speakers a bit higher, I also shoved the carpet spikes under the back Gaia, raising the speakers up about another 3/4" vs the previous all Gaia set up:

Well, that the heck? This sounded terrific! First of all it sounded a bit more tight and solid vs the full Gaia set up.
But also the soundstage was raised even a bit higher which increased the subjective sense of scale too. Also the sound
took on an even more pleasing (to me) tonality - a more lush, thick lower midrange especially giving nice richness and heft to the sound.

Now we are cookin' !

My sense from this is that I would like to raise the speakers more, get something under there because I like that raised soundstage and lushness I
was hearing. But I wondered what my options were. So I bought a bunch of other stuff to try. Among them 2" thick cedar fence end caps that replaced the hockey pucks with. Didn't sound as good, went back to more mushy.

Next I tried constructing a make-shift base for the speakers. I used two sheets of 1/2" thick MDF layered together with sound damping material in between.
Felt pretty solid for the knuckle-rap test. The thing is I have TWO important goals for anything under the speakers: Improve sound quality AND it MUST help the speakers be moved more easily along my carpet. The reason is I have a big projection screen and if I can easily shove the speakers a foot to the side, it allows for a larger image.

SO...I drilled holes so I could use some Herbie Audio Lab slider feet, which I'd used under my Thiels for sliding them around:

Ok, so now I had the speakers on that quickly built platform, with the slider feet at each corner.

Results: Not good. Did nothing good for the sound, if anything again a bit more mushy.

Hmmm.....what to do now?

Then for the heck of it I replaced the Herbie footers with the spring footers - the footers mentioned in the beginning of this thread, that look like this:

Well...what do you know?.. that was interesting. The bass did seem to tighten somewhat and loose some boom particularly for the lowest problematic bass torture tracks. But unlike the Thiels, which when raised on those footers became a bit too lean and bright sounding for my taste, it didn't seem to have the same detrimental effect when raising the Joseph speakers. This was promising. But the Joseph speakers do best with some tilt, so I then added the hocky puck under the front spikes. Here's the photo (you can't see the spring footers under the platform because of the high shag rug):

And ...BAM!!!....the sound just clicked in! The speakers just "disappeared" more, got that lush rich sound again, and yet bass test after bass test showed some of the tightest bass I've had in the room. So many of the torture tracks in which well known bass notes would jut out in a bloated manner were now significantly more laid back and in control. And the speakers are raised even a bit more, making for an even more massive sense of soundstaging. Yay!

SO...here is my dilemma and goal:

It looks like I've found a speaker height and angle that I really like. Something has to go under the Joseph speakers to keep them in this position.
But it's still hard to know for sure how much of what I'm liking has to do with JUST the raising and angling I've introduced, vs what is holding the speakers up.
I am quite certain the spring footers are playing a role. As before, unlike using all the other coupling or decoupling stuff, with the spring footers I can feel much less floor vibration when the speakers are playing heavy bass.

The last thing I'd like to try, to strike it off my list, is just sheer mass - some heavy stone, granite perhaps, under the speakers. Ideally a really dark black marble would beautifully match the black parts of the Joseph speakers. But I understand Granite is more solid/heavy.

However, I have a feeling that springs will end up being involved in my final design.

Any thoughts welcome.

 

[MattHooper]

Just thought I'd post some crude measurements using a vibrometer app on my iphone...with some follow up questions.

First of all, as detailed above, I've tried various things under my speakers (which sit on a sprung wood floor covered by carpet) to see if there are any interesting results. I built a fast MDF base with added damping material. The things that have worked best so far in terms of a sense of the bass tightening up and better imaging have been speaker spikes set atop hockey pucks, but most "obvious" was putting springs under the MDF platform on which the speakers sit. That seemed to produce the most obvious alteration in sound in terms of more focused base and imaging.

It seems so far in my experiments that I either like the speakers more fully coupled to my floor with spikes OR as decoupled as I can get them. In-between seems to make things more mushy.

Anyway, here are some screen shots from the vibrometer app where you can see the obvious reduction in the transmission of vibration between the wood floor and the speakers. So I would place my iphone with the vibrometer app running in various spots, and thump the floor or speaker to measure vibrations.

This is with the iphone on the floor, with my foot thumping the ground nearby. You can see the obvious spikes of vibration with each foot thump on the floor:

Here's placing the phone on my left stand mounted home theater speaker in the same room, and stomping the floor near the speaker. That speakers is on a stand which is spiked to the wood floor. Still obvious spikes of vibration transmission:

Here's with the iphone on top of my Joseph Audio speakers, which are sitting on the MDF platform decoupled from the floor with the spring footers. Me stomping the floor right near the speakers. Obvious reduction in the amplitude of vibration:

Also to do a check of vibration from the speaker to the floor, I placed the iphone on the floor right near the joseph speakers and banged on the speakers. Again, with the spring footers, there is very little transmission from the speaker back to the floor:

So clearly using the spring decoupling significantly diminishes the amplitude of the vibrations between the floor and speaker. Which I think suggests that my hearing sonic changes is quite plausible.

Though a question arises: When speakers are coupled to the floor (e.g. my HT speakers) the amplitude of the vibration spikes are high, but they stop ringing quickly. With the speakers on the springs, the amplitude is quite low, but there is more sustained ringing in the vibration pattern.

So the question is, which would be more important or "better?" A high amplitude but more quickly damped transmission of vibrations? Or a low amplitude but longer ringing pattern using springs?

A further question: There was discussion about what, at least in principle, would reduce vibrations from the speaker. At one point it was suggested that hard coupling the speaker to high mass - e.g. coupling the speaker directly to a slab of granite - COMBINED with decoupling - decoupling all of that from the floor with springs, should be the most potent approach. So the idea is sort of increasing the mass of the speaker by coupling it to the granite to reduce vibrations (or change the resonant frequency) and then further stopping vibrations getting to the floor via the springs under the granite.

Does that make the most sense? I think it was actually disputed as well?

 

[Frank Dernie]

So clearly using the spring decoupling significantly diminishes the amplitude of the vibrations between the floor and speaker. Which I think suggests that my hearing sonic changes is quite plausible.

More than plausible IMO, pretty well guaranteed!
Changing mass and/or stiffness basically changes the frequency of the filter.
More mass added at the speaker side will reduce the frequency from which isolation is effective as will reducing the stiffness of the springs.

In handling terms using a heavier speaker or mass loading it will give the better isolation without ending up with a floppy feeling installation so is probably “nicer”.

OTOH there are 6 degrees of freedom so the reality is very much more complex than people think, mode shape dependant and probably cross coupled too.

 

[MattHooper]

More than plausible IMO, pretty well guaranteed!
Changing mass and/or stiffness basically changes the frequency of the filter.
More mass added at the speaker side will reduce the frequency from which isolation is effective as will reducing the stiffness of the springs.

In handling terms using a heavier speaker or mass loading it will give the better isolation without ending up with a floppy feeling installation so is probably “nicer”.

OTOH there are 6 degrees of freedom so the reality is very much more complex than people think, mode shape dependant and probably cross coupled too.

As I think I mentioned before: if I construct a more serious base under the speakers- and perhaps screw the speakers tightly to it for 'mass loading,' I'm curious about the consequences of using one thick slab of material - e.g. 1 or 1 1/2" thick solid granite slab - vs doing a sandwich - two 1/2" granite slaps with damping material between them (sorbathane sheets or wall damping...or including a sheet of metal). So would adding the damping in between two thinner sheets have more integrity for mass loading/damping? Or is a solid piece of granite better in that respect?

Also, you spoke to an "either or" approach, mass loading or decoupling with springs. What about the "use both" approach I mentioned - bolting a high mass base to the speakers, but sitting that all upon springs? (And even using Isoacoustic Gaia footers between the speakers and bass, since I have those too).

I understand that this is complex stuff and ultimately, in a situation like mine, it's a try-it-and-see scenario. But just asking in terms of general principles, is it "either mass loading OR decoupling" or can those two things be combined for further effectiveness?

 

[Frank Dernie]

Also, you spoke to an "either or" approach, mass loading or decoupling with springs.

Don't remember that, both more mass and/or softer springs lower the filter frequency as do a combination of both. I obviously wasn't clear enough.

The effect of lossy damping sheets would be speculation from me - the mass and spring effects are absolute.