[rbbert]

Like at least some here, I try to isolate or decouple my RM -40's from my listening room.  Right now I'm using a home brew concoction of Herbie's Giant Fat Gliders, Dynamat, hockey pucks and Blutack.  These also raise the speakers about 1-3/4", which I have found beneficial.

After some research, I'm thinking about changing to ball/cup (e.g., FIM or Rollerblock II's) with some kind of platform (e.g., a multi-element stone/wood or perhaps just stone or wood) between the ball/cup and the speaker bases.

My floor is a concrete slab with oak hardwood over it (with the standard sort of plywood & felt between the slab and the hardwood.

I'd welcome anyone's experience or knowledgeable comments before I take this plunge (which I figure will cost about $400/speaker, or a little more if I use tungsten balls instead of steel).

[John Casler]

This question comes up on occasion and there is no "exact" answer since it depends on your room, and the structure of the floor.

Essentially coupling and decoupling are used to reduce the transference of vibration in your room.

Coupling causes the speaker vibrations to be reduced by adding the mass of the floor to the speaker so that the speaker is less affected by the more powerful bass vibrations.  This reduction is due to increased stability, meaning that as the woofer moves back and forth, the speaker cabinet itself does not since it is anchored (coupled) to a large mass (the floor).  This gives a cleaner launch and return of the woofer cone and CLEANER  more impactful BASS.

Decoupling is just the opposite.  Its function is to insulate the floor from the vibration (kinetic energy) of the speaker cabinet.  This does not add mass, nor stability.  In fact, it reduces stability and relies on the actual mass of the speaker to be sufficient.  Since the RM40 is at least 240# or so, it will often yield a good result when decoupled.

That said one needs to determine what and why to use either.

As a general rule, the only reason to use "decoupling" is when you have a wooden floor that is so unstable (like a second floor on floor joists) that the vibrations of the speaker actually cause the floor to make a sound that muddies bass.

It is preferable to employ "coupling" for most other circumstances as it will offer the better bass definition overall.

I employ coupling to the floor and even add additional mass (usually 50 - 100#) to each  of my RM40s.

Your description of a wood floor with concrete slab underneath might mean you should also investigate "coupling" means, unless your floor is suspended and making noise.  Best results will be had if you select the appropriate system for your floor.

[Shear Bliss]

THANKS MR CASSLER FOR THAT RESPONCE, HAVING A POURED CEMENT BASEMENT FLOOR CIRCA 1954 WITH UNEVEN SPOTS FOR DRAINAGE, IF EVER REQUIRED, I TOO HAVE ISSUES WITH COUPLING MY RM-1 SPEAKERS. LEFT SPEAKER IN A TROUGH OF SORTS, LEANING WITHOUT SPIKES. BIG B IS PRETTY ADAMENT ABOUT NOT USING SPIKES, BUT I FEEL I HAVE TO, CANNOT HAVE A SPEAKER LEANING ONEWAY OR ANOTHER. BASEMENT FLOOR IS GLUED OVER TILE, THEN CARPETED WITH INDUSTRIAL TYPE CARPET (DOCTORS/DENTIST OFFICE CARPET. SPIKES USED ARE ROUNDED, SO NO POINTS. RAISED TO A MINIMUM HEIGHT TO GET THE SPEAKERS LEVEL. BASS INROOM IS AWESOME, 20 X 13 BI-AMPED.
MEGAWOOFER UPGRADE, WAVE GUIDES, ADDRESSING THE PASSIVE, RAISED THE PERFORMANCE OF THESE CONCIDERABLY BEYOND ANYTHING THATS BEEN IN ROOM. I AM IN SHEAR BLISS.

[John Casler]

Shear,

I can't speak for Brian, but I think his aversion to spikes is that they raise the speaker off the floor.  This places an air space beneath the speaker which causes a pressure release to bass frequencies and pressures that would normally follow a "solid" speaker boundary to the floor and out to the listener.

That is why he also suggests a "beard" for the standmount 626 models.

However, if you cannot get around using spikes for any number of reasons, you could reduce much of that problem by placing a solid "beard" (or maybe since it is going to be so short we should call it "stubble") in the front of the speaker between the bottom of the cabinet and the floor.  It would be even better if you also "stubbled" the sides.

This should allow you to spike without sonic degradation.

[rbbert]

Beard or no beard, I wasn't particularly happy with the sound of spikes.  I have access to an excellent scientific analysis of coupling/decoupling speakers from the room.  If I can get permission I will post it here.

Speaking of the beard, I honestly can't tell a difference with it or without it.  I was using 1/4" plywood just on the front of the speaker.

[rbbert]

...
Coupling causes the speaker vibrations to be reduced by adding the mass of the floor to the speaker so that the speaker is less affected by the more powerful bass vibrations.  This reduction is due to increased stability, meaning that as the woofer moves back and forth, the speaker cabinet itself does not since it is anchored (coupled) to a large mass (the floor).  This gives a cleaner launch and return of the woofer cone and CLEANER  more impactful BASS. ...

In all likelihood, though, you want  your speaker cabinet to move back and forth in reaction to driver movement in the opposite direction, but to always return to the same place.  That is, vertical coupling and horizontal elasticity.  Think about an artillery cannon or battleship big gun.  If your speaker is heavy enough and your floor is stable enough, that is what ball/cup devices can do.

[Linkwitz Riley]

In all likelihood, though, you want  your speaker cabinet to move back and forth in reaction to driver movement in the opposite direction, but to always return to the same place.  That is, vertical coupling and horizontal elasticity.  Think about an artillery cannon or battleship big gun.  If your speaker is heavy enough and your floor is stable enough, that is what ball/cup devices can do.

I thought that the best sound would be obtained when the enclosure was as rigid as possible and is not contributing to the cone movement due to panels flexing.  Are you saying that speakers should be designed to account for a known amount of panel flex and use it to produce more output?  But if that is your thinking wouldn't the initial energy that flexed the panel have been put to better use by producing more clean output in the first place?

I am very perplexed by your statement...it seems to fly in the face of the known principles of speaker design.
Please explain your theory.

[rbbert]

Not my theory, BTW.  NOLA Baby and Grand Reference speakers do this, for example.

When the speaker elements move air (as a piston), it's generating a horizontal force (pushing the air).  The speaker enclosure is going to absorb this force one way or another.  It has an easier job of it if it can move horizontally to accommodate this; otherwise all that force is absorbed by the enclosure, and no matter how well designed and built it is that's not likely to work out as well as if at least some of that force is absorbed somewhere else (e.g., by "elastic" movement of the enclosure).

Exactly as you mention, you don't want parts of the enclosure "flexing".

[John Casler]

In all likelihood, though, you want  your speaker cabinet to move back and forth in reaction to driver movement in the opposite direction, but to always return to the same place.  That is, vertical coupling and horizontal elasticity.  Think about an artillery cannon or battleship big gun.  If your speaker is heavy enough and your floor is stable enough, that is what ball/cup devices can do.

In the Physics and related Acoustics the only time you would want the whole cabinet to somehow react to the forces of the woofer would be if the designer took great pains to design that reaction into their speaker.

In the wave launch of a driver, you have the reactive forces into the cabinet.  If those forces encounter significant resistance then the accelerations of the driver are more precise.  This means that the stiffer and or more stable the cabinet the less it will "soften" the leading edges/impact of the waveforms created by woofers.

The examples of artillery and battleships only serve as examples of HUGE reactive forces causing a reaction, but don't have an association with the wave launch of a woofer.  If the artillery and or the Battleship was anchored and were able to take the HUGE forces, the shells would accelerate faster and travel farther.  Actually that is also why a Battleship always fires sideways, since the resistance to moving the ship is greatest in that position. 

That all said, as mentioned earlier, the sheer mass of the RM40 makes it highly resistant to reactive softening of woofer frequencies.  But unless your wooden floor is suspended to the degree it is audibly resonating, you might get a better sonic results via coupling and or additional mass, but the perceived gains might be small.

Are you hearing resonance from the floor?  If so, then decoupling might be the soultion.

[rbbert]

I'm not hearing any problems per se, just wondering about implementing some ideas about speaker isolation put forth by some fairly successful high-end speaker designers, specifically from NOLA and Genesis.  As I said, these are not my ideas, but they make a lot more sense to me than conventional spiking or nothing at all.  NOLA and Genesis both have excellent sounding large (& expensive) speaker systems that are "isolated" or partially decoupled via rollerball/cup rather than spiked, and as I mentioned I have much preferred the sound of my speakers on the Herbie's Fat Gliders (a so-so decoupler) than "raw" or spiked.

[JP78]

In my experience with VMPS speakers the best sound I had achieved was fully coupled; to do this once I had a permanent position for the speakers we adhered them to the floor with a very thin layer of silicone (peels right off the floor, speaker when done, though bottom of RM2 required a little bit of touch-up paint) and then a thick slab of granite on top that was roughly 12x12 and added ~40lb per side.

Of course, if you're very into tweaking, it may not appeal to you for not moving the speaker very often. That's what a stand-mount system is for!

[Hipper]

Brian comments on spikes on the VMPS site in FAQ:

http://www.vmpsaudio.com/faq.htm

I would guess that the passive bass radiators and slot loading also have a part to play in these considerations.

My RM30Ms sit on pieces of wood to incorporate the 'Tallboy' tweak that John Casler suggested. These in turn sit on carpet tiles, rubber sonic insulation then sprung wooden flooring. I get bass, and the rest of the frequencies, that sounds good to me!

[rbbert]

Reading Brian's comment in the FAQ was one of the things that led me to my current system; it certainly sounds like he prefers isolation if it can be done in a way to not interfere with bass propagation along the floor.  That is the whole idea of having the platform above the ball/cups; it should still allow that propagation to occur.

So far, from all the comments posted, I'm still strongly tempted to go ahead and try this, despite the cost.

[John Casler]

Without a doubt, the best path is the one of preference and sound.

It is just valuable to know the physics and acoustics involved to help you a long.

And again, the RM40 lends itself to both methods quite well due to its large mass.

[rbbert]

...It is just valuable to know the physics and acoustics involved to help you a long...

I was hoping for some more practical experience too, I guess.

The physics and acoustics clearly suggest that a platform over ball/cup is the way to go with a hard stable floor and a heavy speaker.  However, as we all know, the actual implementation may not match our theoretical analysis.

[John Casler]

I was hoping for some more practical experience too, I guess.

The physics and acoustics clearly suggest that a platform over ball/cup is the way to go with a hard stable floor and a heavy speaker.  However, as we all know, the actual implementation may not match our theoretical analysis.

 

I think somehow along the way I (or someone) has confused you and I see from your first post, that it will cost you $400 per speaker to go forward, so to be simple and succinct:

Physics and Acoustics tell us that a "stable" (coupled) platform will provide the cleanest and most precise dynamic wave launch.

The only reason to explore "unstable" (decoupled) is if the floor itself is unstable and producing reasonance.  Actually there is a secondary reason to decouple and that is to reduce sound transmission to other rooms in the house.  For example if your downstairs neighbor complains

Also, I noticed you said you had an article or text and wanted to get permission to post it.  You can certainly post it (or a link) here (for further exploration of the subject) unless the permission you were seeking was from the authors who wrote it.

Maybe this January we will get a chance to hear your set up when we come to Vegas.

[rbbert]

I live in Reno, not Las Vegas, but anyway...

It's difficult or impossible to couple the loudspeaker to the floor both vertically and horizontally; just think about the different force vectors acting on the front and the rear of the loudspeaker enclosure.  It doesn't matter whether you use spikes or just depend on the weight of the speaker and something like Blutack, you have different forces acting on the front and rear of the speaker and the response of the support needs to be different for complete coupling.  Furthermore, with complete coupling you are asking all the forces reactive to the speaker elements to be absorbed in the enclosure and whatever it is coupled to.  You can make this unit very rigid and absorptive, but those forces still need to go somewhere, and almost certainly there will be effects on all the drivers in that enclosure.

Read here

http://www.whatsbestforum.com/showthread.php?4253-Understanding-Coupling-Decoupling-with-particular-reference-to-loudspeakers

[John Casler]

I live in Reno, not Las Vegas, but anyway...

It's difficult or impossible to couple the loudspeaker to the floor both vertically and horizontally; just think about the different force vectors acting on the front and the rear of the loudspeaker enclosure.  It doesn't matter whether you use spikes or just depend on the weight of the speaker and something like Blutack, you have different forces acting on the front and rear of the speaker and the response of the support needs to be different for complete coupling.  Furthermore, with complete coupling you are asking all the forces reactive to the speaker elements to be absorbed in the enclosure and whatever it is coupled to.  You can make this unit very rigid and absorptive, but those forces still need to go somewhere, and almost certainly there will be effects on all the drivers in that enclosure.

Read here

http://www.whatsbestforum.com/showthread.php?4253-Understanding-Coupling-Decoupling-with-particular-reference-to-loudspeakers

I have read through the material at this link and while I have written a quite long post to some of the errors and misinformation, I think it best that I not post it as I don't want to sound disrespectful to another industry member, especially since I can tell he is sincere in his efforts to provide his opinion.

But I will say that there are numerous issues with a few of the scientific points he wants to make.  I was going to post to the thread, but I also thought it better not to since even though I am an independant dealer, someone might interpret my post to represent VMPS or Brian and it might not.

I can see now where you got some of these ideas and the confusion  that information can cause.  I have studied the physics, pshychoacoustics, and acoustics of sound for over 30 years, and find it challenging and interesting.  I could engage in addressing the subject for weeks if I had time, but hesitate to say something that might sound disrespectful to the fellow who you got the info from.

If others view that thread and have questions, they can ask them there, or bring them here for discussion.

But to answer your direct questions;

It's difficult or impossible to couple the loudspeaker to the floor both vertically and horizontally; just think about the different force vectors acting on the front and the rear of the loudspeaker enclosure.

You are correct, for practical purposes the couple takes place at the floor where the mass of the speaker couples the bottom of the speaker to the floor which in theory has an even greater mass.  In theory, depending on the strength of the couple the speaker then takes on the mass of the floor, and even the earth if the floor/room/house is coupled to the earth (as in not a houseboat )

I pretty much understand what fundamental forces (driver reactive forces) occur.

It doesn't matter whether you use spikes or just depend on the weight of the speaker and something like Blutack, you have different forces acting on the front and rear of the speaker and the response of the support needs to be different for complete coupling.

In most cases the woofers and the COM (center of mass) and COG (center of gravity) are low.  Because of this and the fact that the woofer's reactive force is low, the coupling would be quite significant and adequate.  Even with the RM40 and RM50 with an upper woofer, the MASS is pretty sufficient for this task.  If you are a tweaker (like myself) you might add weight to the top front of the cabinet.

I think what is being asserted is that the speaker actually becomes a second class lever and that the rear spikes become the fulcrum.  In order for that to happen the power of the upper woofer would need to lift virtually the whole weight of the speaker.  In this case 240#.  Not likely, but if one is an eternal tweaker like I am, you put an extra amount of weight on top (I use 40-50#)

Furthermore, with complete coupling you are asking all the forces reactive to the speaker elements to be absorbed in the enclosure and whatever it is coupled to.  You can make this unit very rigid and absorptive, but those forces still need to go somewhere, and almost certainly there will be effects on all the drivers in that enclosure.

Not exactly.  You are not really looking for the cabinet to "absorb" reactive forces.  You are looking for it to be rigid and NOT absorb them.  That is, you want the speaker driver to meet a resistance to its reactive forces stronger than they are.  The more rigid, and stable the more clean and accurate bass frequencies.  And I might add that you need to also keep all the various forces separate in your mind to understand them. 

I am used to studying multiple forces since I also study biomechanics of dynamic and athletic actions, and the myriad of forces and what they are acting on is mind boggling.

There are active and refractive pressures within the cabinet related to the backwave and backside of the active drivers. Those forces are also important, but are not related to the reactive forces from accelerations of the cones except they are caused by the same moving parts, but to a different effect.  The reactive driver forces need to be stabilized by a rigid cabinet, high mass, and coupling to cause the best bass.  The active/refractive internal cabinet pressure variations are somewhat damped inside the cabinet by fiberfill, but not completely.  And here's why.  The Passive Radiators react to these changes in internal pressure to add to the bass regions of the sound.

The other drivers (tweeters and neopanels) are housed inside a separate and equally damped chamber so that they are not exposed to those internal pressures.  As well the Highs and Mids are not leaked into the main cabinet to escape through the PR (wouldn't that sound funny to have highs coming out the bottom slot for the PR

Hope this all makes sense and I know it seems I am contradicting someone who should be an authority, but actually we are not as far apart as it may seem, it is just that he worded some things in a way that can cause confusion. 

It is a very interesting subject, and is right up there with Room Conditioning as far as the Physics involved.  So you can see you have several very significant sciences involved in our hobby.

[rbbert]

And the fact of the matter is that there is still some disagreement among speaker manufacturers about whether coupling or decoupling is preferred, realizing that in either case the goal is to keep speaker generated forces from affecting the cabinet (resonances) or the physical behavior of the other drivers.  From reading the VMPS website FAQs, though, I had thought that Brian preferred decoupling, which has agreed with my own experience with my RM-40's so far.  You seem to be indicating a preference for coupling, though?

[John Casler]

And the fact of the matter is that there is still some disagreement among speaker manufacturers about whether coupling or decoupling is preferred, realizing that in either case the goal is to keep speaker generated forces from affecting the cabinet (resonances) or the physical behavior of the other drivers.  From reading the VMPS website FAQs, though, I had thought that Brian preferred decoupling, which has agreed with my own experience with my RM-40's so far.  You seem to be indicating a preference for coupling, though?

What are you doing up so late?

Yes, you are correct there will always be disagreement to methods to our madness.

However, as I mentioned earlier, the path you choose is (or should) be based on the goal and the issues you have to work with.

The ultimate goal is to make the speaker sound as good as possible on the surfaces you have to deal with and you may have to measure trade offs.

I would let Brian speak for himself, but I think he is generally of the same opinion, that if your wooden floor is making noise (due to the cabinet resonances) then you need to decouple.  But he makes his speakers heavy enough that the mass reduces most any negative effects (such as softer flabby bass).

His aversion to spikes is more due to the fact that it raises the cabinet off the floor and this space under the cabinet reduces bass pressurization slightly.

I too do not use spikes, but do move toward mechanical coupling by adding additional mass, which produces a greater force to the floor, without raising it.

I have no preference except to a goal within those parameters.  However if I want the most accurate bass freqs, I would add mass and move toward a couple.  If I had a floor resonance problem, I would add mass and decouple if possible.

Since my RM40s sit on carpet, they start out more decoupled than not, but after adding the weights they are moving towards a greater mechanical coupling.

Sometime ago, I visited a friend of mine who had like $15k Montana speakers.  He had them in an older house on a suspended wooden floor.  They were unlistenable as the 15" woofers made the floor resonate.  He purchased some type of decoupler, which actually had them floating on like an air pocket or pockets sitting in big sand boxes.  If you pushed lightly on the top of the speaker they would even bobble a bit, like a tall building in an earthquake.  It cured the floor resonance, but the bass was pretty flabby and soft.

It is all simple physics, but so many get it wrong or slightly distorted.