Cabinet and floor coupling : sound behaviors...

[Eldam]

Hi,

Well an old subject, always a question of trade offs and not always universal solutions... but let's try to talk about trade offs or our owns expériences !

I'm not even sure we can talk of this subject alone, without some other subjects as : room modes, tonal balance equilibrium of speaker AND electronics (these last seen as a whole result)... even wires can interfer and change the results !

Can we start about myths, then trade offs, then own expériences to adapt to the environment which is subjectiv for sure ?

I have some interrogations first :

- most is about coupling the cabinet to the floor and the vibration behavior of the said cabinet !

- if the cabinet is on smooth coupling : bass are mellow, mid-trebles can be precise (at least in my room)
- the opposite if solid coupling with the floor (cabinet which like very solid but at the price of Something transmited to the floor... (at least at home with traditional plain wood floor not direct putted on mortar)...


Any thoughts ?

 

[Eldam]

as a first empiric input : it seems to me than if the coupling interface is not rigid : speakers less diseaper in the soundstage...odlly not at the price of less deepness in the soundstage (but at least the speakers becomes..visible !)

 

[Eldam]

When I test an other coupling interface for less cabinet rigidity (soft decoupling with floor like rubber coupling) : It's less tight (we all know that with spikes !) , articulation is less hearable (it's more liquid as some say!) but there is more détails at home in the low end (like bass pedal of a piano...)

At least in the trade offs (at home) more tight decoupling with the floor gives less floating soundstage, i.e. more focused sources (singer, etc).

What about piece of wood or stone between the speaker nd the floor with which sort of coupling ?

Two directions : the speaker has a solid interface and seems rigid but there less transmission to the floor ?

Speaker ->spikes->piece of wood or very heavy stone->smooth interface like rubber-> floor ?

Seems to me bass unit and treble should be in the same cabinet with same panel damping ! I can't test but maybe rubber cabinet for mid-tweeter and very tight solid cabinet for mid-bass and bass units could make sense !

In an other way some brand like Living voice have sucees with not too much rigid cabinet like the well regarded (at ears) OBX speakers (chip boards cabinet iirc !) !

One thing is sure at home, not only the soundstage but also unluckilly the tonal balance change with the way speakers are coupled to the floor...

Trade offs possibilities ?

 

[Eldam]

This time and without knowing if I can abstract a rule (and with the damned collection of albums I listen from more than years for all my tweaks and benchmark... and yes with knowing all is subjective regarding the hifi owner, the listening room, the aesthetic tastes) :

If i take the same rubber isolation pads I puted between my MDF planar speaker stand and the speaker than NOW I putt just between those OEM stands and the floor....... :The sound subjectivly improves : more than with some mods with dacs !

So subjectvly at home : this set up gives me a good trade offs : speakers with no spikes : 25 mm MDF panel : 3 cms side rubbers then wood floor (traditional : non directly coupled to mortar) :

Subjectivly :

more détails in the mid! less harchness
a Little less détails in the bass than then rubbers are between speakers and wood floor (have to hear bass piano pedal to understand at home).
treble seems smoother but not at the price of less bass transcient of less tighness in the bass all things being equal...)


It's like if we change of speakers, nears speakers but defintly different ! Enough to say : this one is sounding much better in this room (mine at least !).

I was septic when I readed the review of the Living Voices OBX speaker and its coupling box between the floor and the speaker itself !

Well , yes it's important, but my experiments with my speaker gives opposites results :

For myself the best coupling is : solid and tight with the wood interface (at least mine is an MDF panel and not a square empty box as Living Voice is makink with chip boards) and very smoot (= rubber) with the floor (wood for my floor) ! So totataly the opposite but the conclusions : YES it is very important in the result and a good headroom of improvment !

 

[Eldam]

At least, when listening gems such as : http://www.amazon.com/Bernstein-Century-Copland-Appalachian-Spring/dp/B0000029XG

it makes all the difference ! Coupling matters with the room ! At least at home !

 

[Zuhl]

My speakers are mounted on a 2" thick paving stone. It removes the last layer of 'mush' compared to spikes
through the carpet and into the wooden floor.

 

[Eldam]

thank you for your testimonial !

I'm listening right now Erik Satie from one of the guy who is having the best tempo according to me : https://www.amazon.fr/Satie-Gymnopedies-Gnossiennes-Erik/dp/B00004VSB4

Monsieur Varsano.

I mod a lot my DACs and the speaker and the coupling between speaker and floor ! The surprise is this last has more importance than I believed in relation to the speakers and whole electronic hifi system...

Btw I believe there is a difference between the living experience and hifi at home : each has its force to make short ! Same for Jazz I even prefer, having listened a lot live in all the good old Paris's places

At the moment you can fix more or lesss the sweet point and equilibrium from left and right speakers, then playing with room mods and triangle deepness with speakers, it seems to me coupling between speakers and rooms IS very important !

Maybe I'm wrong, want more inputs from experienced guys (I think I am with live non amplified (unpluged) music )

 

[Octavia]

I took a 1/4 inch plate of aluminum and used some car window gasket seal to firmly attach it to the bottom of speaker cabinets which then sit on a carpeted floor. Seems to clean up the bass and make it more distinct and tuneful.

 

[Eldam]

Octavia,

Verry interresring. Thanks
It seems to me and at least from my readings than metals are easy coupling the vibration at surfaces (being a no-go material for cabinet speaker but maybe the lead): so being an Accelerator at the surface of plans (cabinets ! = no good) ! Defintly have to try as coupling with the floor !

Have to experiment in real life

I try to understand the behavior of spring behavior between light and heavy materials between the speaker cabinet and floor ! (I said I try as there are too much datas : rooms, etc !)

 

[eriksquires]

It's not just about the floor-contact surface and geometry though. It's also about the rigidity of the speaker in the 3 dimensional space. To move, drivers must apply a lot of force to the entire speaker via the front baffle. I do believe that fixing that baffle, and therefore the speaker, in place so it is unable to move relative to the rest of the room enhances clarity and bass. You can experiment with this by leaving your floor coupling alone and adding 20-50 lbs on top. Of course, some speakers will be more or less susceptible than others.

Let me know if you hear anything.

Best,

Erik

 

[Eldam]

Yes I hear A LOT of DIfferences :

Speakers : Boston Lynnfield 400
amp : Chord SPM 1000B
pre-amp : Yamaha CX-2
wires : Cardas & Oyaide
DAC : AYA2 2014 with Ian Canada Front-end and.... 2 years of modding (al in the détails in relation to room).

So yes : I HEAR a lot of difference (and not poor ones so my thread....30 years of modings !))

It seems to me, all in the trade offs, than bass and mid and treble should not made of the same material !

Oddly : a lot of things can be hidded in the mid-bass medium aera !

Any thoughts ?

 

[nigelwright7557]

Care has to be taken with panel resonances.
I use plenty of bracing to get over this.

I have designed a few folded horn enclosures and they can sound a little wooden at higher powers.

I need to move my speakers so they mostly sit on rubber castors.

 

[Eldam]

???

 

[Eldam]

what the relation between internal bracing in outside pannels resonance ? (but coupling eac time outside panels are coupled with 160° bracing pannels ?

 

[nigelwright7557]

Bracing will damp any resonances and/or change the resonant frequency.

 

[Bon]

Getting back to the OP question about the effect of floor coupling, I recount the experience of a large pair of diy 3-way floor standers ~140kg on a carpet/concrete floor. The speaker uses twin 10" woofers and were initially used unspiked to make sliding them into position possible. If you think such a large mass is immune to floor coupling effects, think again. The enclosure fed prodigious amounts of bass into the room structure. The carpet provided no vibrational damping to speak of. This had a negative effect on bass clarity. When the cabinets were spiked to the concrete with sufficiently beefy spikes, the floorbourne transmission completely ceased. The effectiveness could be felt by comparing the vibration at the top of the spike and mounting plate with the vibration near to the spike tip, which was undetectable. Naturally the concrete slab underneath the spike was also completely unresponsive, compared to previously strongly vibrating right across to the listening position. Based on this experience, spikes can greatly reduce the structural transmission from the speakers. Dealing with the residual box vibrations is a different set of problems though, dealt with by good design (bracing/panel damping/materials)

 

[sippy]

It's not just about the floor-contact surface and geometry though. It's also about the rigidity of the speaker in the 3 dimensional space. To move, drivers must apply a lot of force to the entire speaker via the front baffle. I do believe that fixing that baffle, and therefore the speaker, in place so it is unable to move relative to the rest of the room enhances clarity and bass. You can experiment with this by leaving your floor coupling alone and adding 20-50 lbs on top. Of course, some speakers will be more or less susceptible than others.

Let me know if you hear anything.

Best,

Erik

Been doing this 'weight up top' thing for 20+ years.

My 'stands' employ a pair of 2nd hand 'Atacama' stands filled with Sharp Blackpool Sand (Cornwall's Blackpool), these are raised to height by 6 paving bricks on on 75mm thick baltic birch and marine ply spiked plinths.
Patches of thin cotton fabric separate the bricks.
Atop this pile sits the speaker, atop the speaker are 3 paving bricks and cloth betwixt.
This lot sits / spiked on the foundation slab.
This pile sways like rushes in the wind from side-to-side BUT are stable front to back, there is a 'slight' amount of give which is down to the bottom of the speaker enclosure flexing as it is some form of 'filled plastic'.... which is under quite a bit of tension, raising that panels resonance up some where where it cant be heard or whatever.

Taking the bricks of the top of one speaker de-foucuses the soundstage... people ask about them, they get the removal demo and explanation of the 'theory' and leave convinced that I am on to something Not on something.

 

[Eldam]

All the inputs are interressants to me, unluckilly I can't work on some as th internal bracing or remaking the speaker enclosure ! I find it quiet when I putt my hand on in in relation to some others speakers I know ! A cabinet is 37 kg if I'm correct, twice deeper than width !

What is not rigid is the coupling : because it's true non floating wood floor (so not so rigid coupling)

But sure the stand on which is the speaker and the way the cabinet is coupled to this stand and then thi slast to the floor change totally the result...

I don't know if I can't measure this with swept sine waves ? I should come back with measurement made at the sweet point maybe, then describe with more precision the results !

It's true a further discussion could be about the coupling between the drivers to the cabinet and in relation to each others if several cabinets to make one speaker (for instance like Dynaudio is lake in the most expensive range with front bafle glued with elastiic material on the main cabinet...)

For the moment the best result is a NOT rigid coupling between the stand and the wood floor (thick rubber for washing machine decoupling sold by panel) and rigid coupling but no spike between the speaker and the MDF stand (2 cm thick)

 

[Adhoc1]

I have installed 5 vibration dampers for (usually) industrial use on my speakers. Each damper has a specified max load of 9 kg and the speaker weighs 44,5 kg, so about as close to optimal as one can get.

When loaded to its specified max value, the vibration damper reaches its lowest possible natural resonance. (In my case about 14 Hz.) This means the vibration dampers (and the supported cabinet) are in a "floated" condition and will isolate vibrations from and to the cabinet from 14 x (root 2) = about 24 Hz and upwards. If the speaker can play lower than 24 Hz, those frequencys will actually be amplified and transmitted to the room structure. Worst case will be at the resonance frequency 14 Hz. A lower load will render a higher natural resonance frequency and worse isolation frequency wise, as the rubber gets "stiffer" versus a lower load. Too high a load and the rubber "bottoms out" and the isolation performance gets worse too. So optimal load is important for best performance. Like: If too low a load gives a natural resonance at 30 Hz, all frequencies below 42 Hz will be amplified and transmitted to the room structure. Good or bad ?

(So no, I do not believe metal spikes giving a stiff, rigid connection to surrounding structure are the best solution, if you do not want the room structure to rattle along. This may mean a less rich bass is felt when say 25 m² / 269 ft² of wooden floor don't vibrate along with the bass driver and the cabinet, but for more balanced bass I prefer some additional subs.)

Pictures of the dampers and some diagrams on similar ones for higher max load.

 

[sippy]

Eldam,
Is the room on the ground floor?
In that condition now?
If it is, there's plenty of basic things that can be done that'd make the floor a better structure 'just as a floor':
Noggings, doubled up sections of joists and packed sharp sand spring to mind.