Speaker De-coupling

[Wombat]

You are saying that the coupling resonance between speaker and floor is causing spurious vibrations of the drivers which is heard as the harmonic buzz? And it is not just a resonant vibration (due to the coupling with floor) of the cabinet walls themselves that is audible?

I agree with all the posters that it is likely due to resonant coupling with the floor, as the OP himself said. I just wanted to point out the bare possibility of something loose in the speaker itself.

No. I doubt that the drivers are having spurious vibrations. I would think the spike to floor contact is the most likely cause of the problem.

 

[Siwel]

I'm not sure precisely what dynamics are at play here, that is exactly where/how this phenomenon originates but I've concluded it is in the interface of the speakers to the room (floor) and not a flaw in the speakers themselves. I will have more to report this evening.

 

[Siwel]

Well, what transpired last night you ask? Let me explain. But can I?

First I ran tone again to reacquaint myself with the level and sound of the issue. This time I was careful to see if any particular frequency seemed to stand out or excite the resonance(s) more than another. I rediscovered that the harmonics were strongest between 50 and 60 Hz and that above 60Hz the noise tailed off and by 90Hz was all but gone. Same thing below my crossover point of 40Hz.

Then I taped some references on the carpet and speaker so I could realign it with confidence when the time came.

Then I laid the right speaker on its side to take a look at what was going on. Like so:

Next it was time to check the condition of the spikes and also hunt for anything loose or obvious. Three of the four spikes were looser than I expected although they were not so loose as to move laterally under any reasonable pressure I could apply to them by hand alone. I tightened them fully home and then decided to check the torque on the four bolts that go through the "stand-offs" and into the speaker itself. The bolts are visible in the photo below.

Although they weren't loose enough to be budged by finger power alone, I decided to re-torque all four equally, to 45 lb/ft, an arbitrary number that felt right in the hand and aligned with typical specs for bolts of their size. I rechecked the collars surrounding the spikes, put the speaker back where it wanted to be and settled in to listen again.

The spurious noises were significantly reduced almost, but not quite to inaudibility. I rocked the speaker on its plinth to see if helping it to "settle in" made any difference. It did. It seemed that the more I could "decompress" the carpet under the speaker, the better the result. That is, after rocking the speaker, it made no audible buzz but letting it sit there and work on the carpet, some minor vibration returned. In other-other words, while gently rocking the speaker, the noise was modulated slightly between "inaudible" and "just barely there". I decided to take a break from all the futzing around and tried to decide what had been learned and how to present this to you.....what conclusions might we draw from this so far?

The experimenting will continue Tuesday which will coincide with the arrival of the "damping" materials Kal linked to and that I ordered a few days ago. Time will tell but there is already substantial improvement even though the speakers have been landed back exactly at the point on the floor where they were making so much trouble initially. Interesting? It is to me!

 

[Wombat]

Try them with the spikes removed.

 

[fløyen]

Russ Andrews has some advice - funny, matches what your wife suggested. I was reading, hoping some one would suggest this then had to have a chuckle when and how it was suggested.
https://www.russandrews.com/understanding-your-room/
Some magazines in the UK used to suggest using cross head screws screwed into the carpeted floor onto which the spikes sit.
We're all concrete slabs these days in this part of the world, though the 5.8 we had last week did make me wonder if that's such a good thing.

Strong earthquake occurred 30 km north-west of Levin: [http://geonet.org.nz/quakes/2020p391429]

 

[JustAnandaDourEyedDude]

Some good detective work there! It seems that any looseness in the spikes might at most have contributed to the buzz by exaggerating it a little. But now that you have tightened spikes and bolts, any potential issue there has gone away. Your experiment strengthens the case for the buzz coming from the tapping of the spikes on the bare floor by penetrating the carpet. Still unclear whether relative elasticity or rigidity of the floor is a factor, and whether any coupling resonance is involved or what you hear is just the natural thudding sound of spikes striking the floor like mallets striking piano strings. Or perhaps the floor acts as a mallet and the cabinet as a piano string, and the buzz you hear is the natural sound of the cabinet when struck. Decompressing the carpet likely decreases the spike-floor contact force, a large part of the carpet under the speakers may have been sufficiently decompressed during your experiments that the spike-floor contact force is now less even with the spikes back in their exact previous spots on the carpet (were there holes in the carpet?), and therefore only minor vibration returned. This would encourage one to think that rubbery dampers might even do the trick and remove the buzz entirely, and a complex spring-based heavy slab isolator may not be needed.

Well, what transpired last night you ask? Let me explain. But can I?

First I ran tone again to reacquaint myself with the level and sound of the issue. This time I was careful to see if any particular frequency seemed to stand out or excite the resonance(s) more than another. I rediscovered that the harmonics were strongest between 50 and 60 Hz and that above 60Hz the noise tailed off and by 90Hz was all but gone. Same thing below my crossover point of 40Hz.

Then I taped some references on the carpet and speaker so I could realign it with confidence when the time came.


Then I laid the right speaker on its side to take a look at what was going on. Like so:

Next it was time to check the condition of the spikes and also hunt for anything loose or obvious. Three of the four spikes were looser than I expected although they were not so loose as to move laterally under any reasonable pressure I could apply to them by hand alone. I tightened them fully home and then decided to check the torque on the four bolts that go through the "stand-offs" and into the speaker itself. The bolts are visible in the photo below.

Although they weren't loose enough to be budged by finger power alone, I decided to re-torque all four equally, to 55 lb/ft, an arbitrary number that felt right in the hand and aligned with typical specs for bolts of their size. I rechecked the collars surrounding the spikes, put the speaker back where it wanted to be and settled in to listen again.

The spurious noises were significantly reduced almost, but not quite to inaudibility. I rocked the speaker on its plinth to see if helping it to "settle in" made any difference. It did. It seemed that the more I could "decompress" the carpet under the speaker, the better the result. That is, after rocking the speaker, it made no audible buzz but letting it sit there and work on the carpet, some minor vibration returned. In other words, while gently rocking the speaker, the noise was modulated slightly between "inaudible" and "just barely there". I decided to take a break from all the futzing around and tried to decide what had been learned and how to present this to you.....what conclusions might we draw from this so far?

The experimenting will continue Tuesday which will coincide with the arrival of the "damping" materials Kal linked to and that I ordered a few days ago. Time will tell but there is already substantial improvement even though the speakers have been landed back exactly at the point on the floor where they were making so much trouble initially. Interesting? It is to me!

 

[Kal Rubinson]

and then decided to check the torque on the four bolts that go through the "stand-offs" and into the speaker itself. The bolts are visible in the photo below.
-----------------------------------------------------------------------------------------
Although they weren't loose enough to be budged by finger power alone, I decided to re-torque all four equally, to 55 lb/ft, an arbitrary number that felt right in the hand and aligned with typical specs for bolts of their size. I rechecked the collars surrounding the spikes, put the speaker back where it wanted to be and settled in to listen again.

I have found those bolts that attach the base to the speaker body are often not tight as the speaker arrives. It has been my policy to check and correct that when I install the spikes although, in one case, it was not possible to tighten a bolt and the speaker was returned for replacement.

 

[pozz]

@Frank Dernie So a product like this would be inappropriate for bass frequencies despite the 7Hz rating? https://www.coleparmer.ca/i/speirs-...latform-sorbothane-isolators-40x50-cm/1150005 There are 25Kg and 100Kg versions.

Pointless for turntable rumble as well?

 

[Frank Dernie]

@Frank Dernie So a product like this would be inappropriate for bass frequencies despite the 7Hz rating? https://www.coleparmer.ca/i/speirs-...latform-sorbothane-isolators-40x50-cm/1150005 There are 25Kg and 100Kg versions.

Pointless for turntable rumble as well?

Doesn't look like it to me.
95% at 50 Hz isn't bad, don't believe much isolation at 7Hz though.
As I have written before a damping "short circuits" an isolator. It does depend on what you want, absorb or isolate.
An isolator working down to lowest audio frequencies will deflect about 1" when the item to be isolated is placed on it - this platform will not, by the look of it.
A low damping steel spring system is best for isolating but upsets some because the handling and impact response is unusual for the uninitiated.
I would only buy a turntable where a competant maker has engineered isolation in as many degrees of freedom they can into their product, personally.
I have a Goldmund Reference with excellent isolation, a B&O 8002 with very clever and effective isolation, a Roksan Xerxes which isolates well at mid frequencies, less good at lowest and an EMT designed for a studio which has rudimentary isolation.

 

[Siwel]

Resonances! Can't live with them, can't live without them! I should probably try to wrap this up.

I ran tone again today to reestablish my aural baseline. I realized that below 92dB SPL a 60Hz tone resulted in no obvious harmonics at the sweet spot. Above that level and at any frequency below about 90Hz, resonance could be distinctly heard rising in level in concert with the loudspeaker output. Just as with any LF tones in small spaces, the resonance(s) behaved like a standing wave, rising and falling in level depending on position in the room. You could feel pressure changes as you walked, but of course we expect that. It was harder to actually locate where the source of the resonance was.

Moving the experiment forward, I installed the layered rubber mats from Supply House. I drilled them at my press with no difficulty. Here you see the centers marked for drilling.

I slipped the pads over the extended blunt ends of the Revel supplied footers and returned the speakers to their marked positions. Oy! My bursitis! And yet, still with the vibes! I'll spare you the image of my confusion but I eventually realized the recessed lighting can 5 feet above the speaker was ringing. Yeah, that was surprising but gratifying. Adhesive tape (nearest to hand) fixed it. Yet to annoy more, there was still that noise, perhaps from a different direction? The other speaker is buzzing now? Finding that one of the windows was rattling out a decent imitation of a Revel loud speaker was a happy ending but underscored how hard these noises have been to track down and isolate. I shoved some matchsticks into the window frame. For now.

What did I learn? Well, I think the speaker(s) actually may have been "vibrating" at the start of this. Perhaps initially disturbing their relationship to the floor (a couple of days ago) was to good effect but then again, with rattles remaining in the room it's possible that I only thought I heard the sound coming from the speakers. But I don't (or prefer not to) think so because the first and most significant improvement came from simply tipping them over, tightening them up and returning them to their initial locations. There were no other changes but in retrospect, I think that stopped them from humming. I can't say definitively if the rubber feet are doing diddly or diddly do but it does sound lovely in here with all the sympathetic vibrations banished. I guess my rig puts out a lot of low end and my room wasn't properly rigged for the job and maybe that's the real conclusion.

I'm confident my floor is still a bit of a weak link. I can feel it moving with the music when the action gets heavy, and it has some soft spots just where they seem to do me the least good. I don't know if that's anything I can change but I am happy with the sound here regardless.

And now, for the "psycho" acoustic part, the windup and the pitch. I think the speakers may sound a bit clearer with the new feet. I can't swear to that and won't. In fact, I have no idea what really happened here except for me bubble-gumming everything that rattled. I didn't actually use bubble gum, but maybe bubble gum IS the real good stuff! What a hobby!

 

[JustAnandaDourEyedDude]

Congratulations on tracing and silencing all the primary and sympathetic vibrations. Now you can relax and enjoy only good vibrations.

Resonances! Can't live with them, can't live without them! I should probably try to wrap this up.

I ran tone again today to reestablish my aural baseline. I realized that below 92dB SPL a 60Hz tone resulted in no obvious harmonics at the sweet spot. Above that level and at any frequency below about 90Hz, resonance could be distinctly heard rising in level in concert with the loudspeaker output. Just as with any LF tones in small spaces, the resonance(s) behaved like a standing wave, rising and falling in level depending on position in the room. You could feel pressure changes as you walked, but of course we expect that. It was harder to actually locate where the source of the resonance was.

Moving the experiment forward, I installed the layered rubber mats from Supply House. I drilled them at my press with no difficulty. Here you see the centers marked for drilling.

I slipped the pads over the extended blunt ends of the Revel supplied footers and returned the speakers to their marked positions. Oy! My bursitis! And yet, still with the vibes! I'll spare you the image of my confusion but I eventually realized the lighting can 5 feet above the speaker was ringing. Yeah, that was surprising but gratifying. Adhesive tape (nearest to hand) fixed it. Yet to annoy more, there was still that noise, perhaps from a different direction? The other speaker is buzzing now? Finding that one of the windows was rattling a decent imitation of a Revel loud speaker was an happy ending but underscored how hard these noises can be to track down and isolate. I shoved some matchsticks into the window frame. For now.

What did I learn? Well, I think the speaker(s) may actually have been "vibrating" at the start of this. Perhaps initially disturbing their relationship to the floor (a couple of days ago) was to good effect but then again, with rattles remaining in the room it's possible that I only thought I heard the sound coming from the speakers. But don't think so because the first and most significant improvement came from simply tipping them over, tightening them up and returning them to their initial locations. There were no other changes but that stopped them from humming. I can't say definitively if the rubber feet are doing diddly but it does sound lovely in here with all the various sympathetic vibrations dealt with. I guess my rig puts out a lot of low end.

My floor is still a bit of a weak link. I can feel it moving with the music when the action gets heavy, and it has some soft spots just where they seem to do me the least good. I don't know if that's anything I can change but I am happy with the sound here regardless.

And now, for the "psycho" acoustic part, the windup and the pitch. I think the speakers may sound a bit clearer with the new feet. I can't swear to that and won't. In fact, I have no idea what really happened here except for me bubble-gumming everything that rattled. I didn't actually use bubble gum, but maybe it's the real good stuff? What a hobby!

 

[Siwel]

Russ Andrews has some advice - funny, matches what your wife suggested. I was reading, hoping some one would suggest this then had to have a chuckle when and how it was suggested.
https://www.russandrews.com/understanding-your-room/
Some magazines in the UK used to suggest using cross head screws screwed into the carpeted floor onto which the spikes sit.
We're all concrete slabs these days in this part of the world, though the 5.8 we had last week did make me wonder if that's such a good thing.

Strong earthquake occurred 30 km north-west of Levin: [http://geonet.org.nz/quakes/2020p391429]

I remember the news about Christchurch's quake a few years ago. I was unaware of your recent experience, but I trust you're ok? We lived on the west coast and experienced a few earthquakes but have never been in a truly devastating quake. Likewise, we were out of town here just 3 months ago when a tornado tore through much of middle Tennessee (tornado prone area), including our immediate neighborhood. It was our last travel, just before covid-19 struck our collective consciousness and we just missed actually sitting through it in the cellar. Our house was untouched and out of power for less than a day. They're very capricious storms. The photos below were taken starting barely a few hundred meters from our house. I have more like them.

Quite devastating. The thing can suck the insides out of a building.

 

[fløyen]

I remember the news about Christchurch's quake a few years ago. I was unaware of your recent experience, but I trust you're ok? We lived on the west coast and experienced a few earthquakes but have never been in a truly devastating quake. Likewise, we were out of town here just 3 months ago when a tornado tore through much of middle Tennessee (tornado prone area), including our immediate neighborhood. It was our last travel, just before covid-19 struck our collective consciousness and we just missed actually sitting through it in the cellar. Our house was untouched and out of power for less than a day. They're very capricious storms. The photos below were taken starting barely a few hundred meters from our house. I have more like them.

View attachment 67082





View attachment 67083View attachment 67084

Quite devastating. The thing can suck the insides out of a building.

That shake was nothing in comparison to the destruction in the images you've shared above. Minor cracks, and the like, 20km from the epicentre in these notoriously "Shaky Isles". The West Coast is a beautiful part of the country - what a great place to experience NZ. Stay safe!

 

[Kal Rubinson]

I can't say definitively if the rubber feet are doing diddly or diddly do

Not surprising since they are sitting on top of carpet.

 

[Siwel]

^No doubt. Apologies if my crudely worded attempt at humor didn't fly. The carpeting has its own issues along with some benefits. A solid footing would be ideal. Maybe some sort of hard "plinth" would be nice.

 

[Angsty]

They don't look like isolators as much as absorbers.
Basically a set of correctly specified steel springs will isolate.
Expensive housings with bits of lossy polymer will absorb.
I think the Townshend isolators are absurdly expensive for what they are but they work correctly in an objective sense.

I finally got around to watching the Townshend video on isolation. Does this really help with music reproduction or are they measuring effects that just don’t matter? I’d imagine the answer might be different for turntables than for loudspeakers or CD players.

 

[MattHooper]

I finally got around to watching the Townshend video on isolation. Does this really help with music reproduction or are they measuring effects that just don’t matter? I’d imagine the answer might be different for turntables than for loudspeakers or CD players.

I should be able to give my own answer to your question soon. I recently ordered the Townshend Audio Isolation Bars for my speakers.

The reason can be found in my own thread on trying springs beneath my speakers:

https://www.audiosciencereview.com/...ings-under-my-speakers-whats-happening.20446/

As I mention in the thread, the Townshend spring pods very obviously killed major floor born vibrations to my turntable, measurably.
Did it help the sound? Well, it did to the extent the records no longer skip when my Godzilla-sized son stomps across the floor. Other than that
who knows? But they sure stop big sources of vibration.

And as indicated in my thread, cheap spring based footers made some amazing changes to the sound of my speakers. I've put them in occasionally since the thread and continue to be taken aback. My only issue is I get a bit less body to the sound. But they also raise the speakers up so that's another factor.

The Townshend product is made to keep the base of the speaker as close to the floor as possible, so it won't significantly alter the height of your speakers when employed, which is supposed to ensure the same sound (frequency balance) but cleaner from the decoupling. So that's what I'm going to find out.

Here's a video I posted in my thread. It's a video from the swiss speaker manufacturer Credo, explaining the effects of isolation vs a speaker sitting on a floor or spiked, demonstrated with measurements.

It includes measurements of a Townshend isolation platform along with their own platform measurements. They also measure the effects of such isolation in terms of the speaker sound in an actual room. It seems to map quite well to the effects I heard in my room:

 

[Purité Audio]

Actual audible differences?
Keith

 

[Thomas_A]

Audible depends from case to case

https://www.audiosciencereview.com/...-couple-your-speakers.8636/page-9#post-219070

 

[MattHooper]

Actual audible differences?
Keith

In my case, yes.