Are Floor-borne Vibrations Really the Enemy?

[Cellcbern]

I've been thinking about the significance of floor vibrations too, especially after reading all the accolades for putting speakers on springs. It occurs to me that since E=M*V^2, the problem of the speaker cabinet being mechanically vibrated by the woofer is greatly negated if the cone velocity is reduced for any given output, such as by using multiple large woofers instead of a single smaller woofer that requires higher excursion. Of course it's possible that there are other vibrations happening, such as flexing of the speaker box.

Actually doesn't require much thought (or math). Asumming you trust your ears, all you have to do is try isolating components from floor borne vibrations and listen for the results.

 

[Tim Link]

Actually doesn't require much thought (or math). Asumming you trust your ears, all you have to do is try isolating components from floor borne vibrations and listen for the results.

I do trust my ears to do what they are capable of doing. I'd be happy to try putting my speakers on springs and having a listen but I'll have to figure out how to do it. They weigh 600lbs each and have less than an inch clearance to the ceiling, so I don't have much room to work with. Very short action, stiff springs are called for. Even if I didn't notice a difference I'd be tickled at the fact that my speakers were actually spring floated in such a tiny wiggle space. I've already got an idea - pieces of thin gage 1/4" steel tubing laid sideways. Any tendencies towards a roller effect could be eliminated by placing pieces at 90 degree angles. The tubing will try to squish under the weight but enough pieces should be strong enough to ovalize in a spring like fashion without permanent deformation.

 

[Cellcbern]

600 lbs. is a special case. Good luck with that.

 

[MarkusBarkus]

...the mass of your speakers will make most thin devices or soft materials behave more like a solid, reducing isolating characteristics. I think product search would be in a machinery or architectural category, but even there, the one-inch constraint is tough.

 

[Blackmorec]

...the mass of your speakers will make most thin devices or soft materials behave more like a solid, reducing isolating characteristics. I think product search would be in a machinery or architectural category, but even there, the one-inch constraint is tough.

I do trust my ears to do what they are capable of doing. I'd be happy to try putting my speakers on springs and having a listen but I'll have to figure out how to do it. They weigh 600lbs each and have less than an inch clearance to the ceiling, so I don't have much room to work with. Very short action, stiff springs are called for. Even if I didn't notice a difference I'd be tickled at the fact that my speakers were actually spring floated in such a tiny wiggle space. I've already got an idea - pieces of thin gage 1/4" steel tubing laid sideways. Any tendencies towards a roller effect could be eliminated by placing pieces at 90 degree angles. The tubing will try to squish under the weight but enough pieces should be strong enough to ovalize in a spring like fashion without permanent deformation.

With that sort of space limitation I would think that the optimum approach would be constrained layer damping using finite element analysis SW to engineer the appropriate CLD model.

 

[Gjo]

They weigh 600lbs each and have less than an inch clearance to the ceiling, so I don't have much room to work with.

I'm intrigued to know how the speakers were installed considering 1" vertical clearance. They must be in sections, yes?

Still...a challenge.

 

[Tim Link]

I'm intrigued to know how the speakers were installed considering 1" vertical clearance. They must be in sections, yes?

Still...a challenge.

Yes, they are made up of 5 sections - four are bass horn cabinets and the 5th section in the middle is the mid and high cabinet. We calculated for an inch of clearance at the corner. In reality the ceiling sags a bit coming out of the corners and things aren't quite square so the speakers almost didn't fit. Installing the top segment is tricky because it's heavy, up high, and can't tilt much while it's being slid in place. Plus the cable has to get hooked up.

 

[Tim Link]

I don't know if this has been said before but I suspect that what's happening with spring loading a speaker is that the speaker with its spring suspension is actually acting as a floor damper. I don't think the self generated cabinet vibrations are all that significant, and in most cases what there are of them are not going up and down much - unless the speaker has an upward or downward firing driver. I think it's the sound pressure in the room, which is highest near the speaker, that's pushing the floor up and down. If I'm right it would also be potentially helpful to spring load the equipment rack and other furnishings, especially stuff toward the middle of the floor area, away from any support pillars on the floor's underside. My corner placed speakers would probably do less to damp the floor than me and my listening chair, which is much easier to spring load. So I'm going to start with spring loading myself. This might prove annoying and I suspect I will have to learn to sit very still. On second thought, maybe I can just find some other heavy thing to spring load and move around the room. I'll have to figure out my phone's accelerometer function and see if there are particularly vibration prone areas of the floor and then decide if it's practical to put something there.

 

[dbeau]

Just a thought: Have you considered isolation such as EVP Platforms? 1" thick and can be made to support 600#

 

[MarkusBarkus]

...actually, I could second the EVP idea. An email to Norman Varney might be useful. They are very knowledgeable.

At your service,
Norman Varney
AV RoomService, Ltd.
www.avroomservice.com

 

[Tim Link]

...actually, I could second the EVP idea. An email to Norman Varney might be useful. They are very knowledgeable.

At your service,
Norman Varney
AV RoomService, Ltd.
www.avroomservice.com

An inch is a bit too much but I am interested in Norman's take on my situation. I left my contact info and a short description of the situation on their web site.

 

[Gjo]

An inch is a bit too much but I am interested in Norman's take on my situation. I left my contact info and a short description of the situation on their web site.

Clearly, the solution is to cut holes in the ceiling above the speakers to create ceiling trays to accommodate the added height.

Just kidding.

Maybe.

 

[Tim Link]

Clearly, the solution is to cut holes in the ceiling above the speakers to create ceiling trays to accommodate the added height.

Just kidding.

Maybe.

I can't cut any holes in the ceiling, but I could remove the Pergo under the speakers to gain a little more room.

 

[Tim Link]

I checked in with Norm and he said they could engineer for 600lbs at 1/2" thick! That might just work. I'll have to think about it some more. I'd like to have an idea of what I should expect to achieve sonically from this. If my cabinets are really vibrating significantly enough to transmit that vibration into the floor to audible effect - that's what I'm not convinced of. If it's actually working according to my hypothesis, that the airborne sound is what is actually vibrating the floor and that suspended speakers are just acting as floor dampers, I should try to figure out how much floor vibration I've got and at what frequencies before I try to start controlling them. Damping in the corners where my speakers are doesn't seem like the right place. None of these measurements will tell me for sure what I'll experience upon hearing, but this is a fairly difficult and potentially expensive experiment for me to tackle a sonic issue I'm not convinced I currently have. If I decide to go for it, first experiment will be to see if I can still slide the top cabinet in with 1/2" less room.

 

[BlueFox]

Can you provide pictures of these 600 pound speakers in your room? Thanks.

 

[Cellcbern]

I don't know if this has been said before but I suspect that what's happening with spring loading a speaker is that the speaker with its spring suspension is actually acting as a floor damper. I don't think the self generated cabinet vibrations are all that significant, and in most cases what there are of them are not going up and down much - unless the speaker has an upward or downward firing driver. I think it's the sound pressure in the room, which is highest near the speaker, that's pushing the floor up and down. If I'm right it would also be potentially helpful to spring load the equipment rack and other furnishings, especially stuff toward the middle of the floor area, away from any support pillars on the floor's underside. My corner placed speakers would probably do less to damp the floor than me and my listening chair, which is much easier to spring load. So I'm going to start with spring loading myself. This might prove annoying and I suspect I will have to learn to sit very still. On second thought, maybe I can just find some other heavy thing to spring load and move around the room. I'll have to figure out my phone's accelerometer function and see if there are particularly vibration prone areas of the floor and then decide if it's practical to put something there.

Not exactly sure what you mean by "spring loading". Is that the same as "floating"? My understanding of the devices like the Townshend platforms and the Isoacoustics Gaia and Wellfloat feet that allow speakers to "float" (i.e., to deflect/move in response to the movement of the drivers) is that this movement dissipates vibrations that would be both absorbed by the cabinet and fed back into the drivers creating distortion, and reflected by the floor back up into the speaker cabinet with a similar distorting effect. That is why such "floating" devices (decoupling) have overtaken spiking speakers rigidly to the floor (coupling) as the preferred approach. Racks and other components may benefit from being isolated from floor borne and air borne vibrations but do not generate them internally the way speakers do.

 

[Tim Link]

Can you provide pictures of these 600 pound speakers in your room? Thanks.

This is the latest incarnation, with some damping material applied to the upper and lower bass cabinet horn mouths, and a large waveguide taking over for the tweeter horn located in the center of the mid-horn. Originally there was grill cloth completely down the middle so only the wooden pillars and grill cloth were visible. That looked really nice and clean but unfortunately I wasn't happy with the sound quality. The wooden pillars are essentially a grill frame - not part of the rest of the structure and not included in the stated weight. I've also attached an earlier picture before the waveguides and damping material were added. The grill cloths had come off already because of a houseplant watering accident.

 

[MarkusBarkus]

@Tim Link how do those babies sound, because they look all-kinds of awesome.

 

[Cellcbern]

This is the latest incarnation, with some damping material applied to the upper and lower bass cabinet horn mouths, and a large waveguide taking over for the tweeter horn located in the center of the mid-horn. Originally there was grill cloth completely down the middle so only the wooden pillars and grill cloth were visible. That looked really nice and clean but unfortunately I wasn't happy with the sound quality. The wooden pillars are essentially a grill frame - not part of the rest of the structure and not included in the stated weight. I've also attached an earlier picture before the waveguides and damping material were added. The grill cloths had come off already because of a houseplant watering accident.

Would Corian (which is not supposed to transmit vibrations) instead of wood under the speakers help?

 

[Tim Link]

Not exactly sure what you mean by "spring loading". Is that the same as "floating"? My understanding of the devices like the Townshend platforms and the Isoacoustics Gaia and Wellfloat feet that allow speakers to "float" (i.e., to deflect/move in response to the movement of the drivers) is that this movement dissipates vibrations that would be both absorbed by the cabinet and fed back into the drivers creating distortion, and reflected by the floor back up into the speaker cabinet with a similar distorting effect. That is why such "floating" devices (decoupling) have overtaken spiking speakers rigidly to the floor (coupling) as the preferred approach. Racks and other components may benefit from being isolated from floor borne and air borne vibrations but do not generate them internally the way speakers do.

Yes, I meant floating the speakers or other components in some fashion, springs or otherwise. Your description of what the Townshend platforms are doing is more complicated than I had heard before. So you're saying the suspension helps absorb vibrations in the cabinet as well as preventing vibrations in the floor from getting back into the cabinet rather than preventing cabinet vibrations from going out of the cabinet and into the floor. It all sounds plausible to me but still I'm not convinced that there are significant vibrations in the cabinets of most high end speakers that are causing major sonic issues. I'm not saying I'm sure there aren't, just that I'm not sure there are. I am convinced that airborne sound does cause the floor and other room surfaces to vibrate considerably, which can be quite audible. The floor, walls, and ceiling can be damped in various ways, and suspending a speaker on the floor could possibly end up doing a decent job of damping the floor. Or not. Which might explain the apparent hit or miss success of these products, depending on the situation. Some find after trying all kinds of suspension methods and spiking too, the best sound they could get was to just set the speakers on the floor.