Best Isolation Device for Speakers?

Rtn1, I also have suspended floor. I have tried both coupling and isolation. For my room, isolation is essential. When vibration from the speakers gets into the floor, a lot of terrible sounding grunge obscures the music. My existing rig sounds very nice, and the difference (compared to bare speakers sitting on floor) is astounding - the largest single improvement I have made to my system.

I started with points, then cones. I was astounded at the improvement these made (over no devices). I could still feel some vibration on the floor.

In effort to isolate further I tried sorbothane pads. Floor vibrated less, sound stage was deeper (than cones or points) background was a bit quieter. Down side is music was smeared somewhat and lacked "PRAT" and excitement.

Convinced that I needed a more linear device than sorbothane, I tried sash springs. Smearing was gone, but not soft enough to decouple - floor still vibrated.

Better that all of these as isolation device (which I have been using for about a year now) are bicycle inner tubes, partially inflated. These float the speaker off the floor, in a manner similar to turntable suspension.

My speakers are fairly heavy (about 100lb) and dead, so coupling is somewhat less important for me. If you need to couple (ground) your speakers *and* isolate them from the soft floor (two oposite concepts) you could try this: Use a heavy, stiff slab or platform (maple, granite, concrete, etc). Ground the speaker to the platform with cones (under speakers), then isolate the platform with innertubes or springs (under the platforms). Down side of innnertubes is you need to re-inflate them every few months, and some design consideration may be required to keep them from being "tippy."

Have fun experimenting, and tell us what worked for you...

Cheers,
Charlie

Zargon,

I think you are on the right track to isolate your speakers from the floor. You might find better results with a platform which is more massive that MDF - granite, marble, or custom poured concrete (decorated with something of course). Your speakers should sit on this platform on three pointed feet. If you wish to get adventurous, do what I have done: use bicycle tires to float the platform (isolate) above the carpeted floor. I can give you details if you are interested.

Here are the issues, in order of importance as I see them:

1) You do not want your floors and walls vibrating. If they do, they will radiate sound which is very bad. You cannot avoid exciting floor/wall vibration from acoustic excitation, but you can reduce speaker mechanical vibration from exciting your floor. Please note we are not talking concrete slab floors here, we are talking about wood floor over joists.
2) You do want the mechanical connection, between speaker and floor (or for that matter, all the rest of your system) to be linear. Rattles must be avoided as they destroy music and generate unwanted noise. Also you do not want the mechanical connection to be modulated by the music (or associated speaker vibration). If the connection is through a squishy or rubbery material, this is also less than optimum because the material is not linear, and music loses its pace and timing.
3) You do not want the speaker box to vibrate - only the driver diaphram(s). This of course is a distinguishing feature of loudspeaker designs, the degree to which cabinets vibrate and radiate sound, or excite the floor beneath them.

If you have a concrete floor, anchoring the speakers to the floor addresses item 3. If your floor can vibrate, then item 1 is likely of much greater importance.

Using cone or points under the speakers can actually help all three of these. Transfer to the floor (1) is reduced because the interface points of contact are limited to corners and edges of the cabinet where box modal vibration is minimized. The linearity (2) of the interface is improved. And this usually reduces at least the lowest frequency motion of the box (3)to greater or lesser degree.

In my experience, while using cones under my speakers provided a huge improvement in sound quality (over speakers on bare floor), there was still significant floor and wall vibration which I could hear and also feel with my hands and ear (against the floor). The sound improved even further when I isolated the speakers from the floor. I tried sorbothane, rubber feet, stainless steel sash springs, and finally bicycle tire "air springs."

In your case, you could get some of the best of both worlds ("coupling" vs "isolation") if your speakers sit on cones on (coupled to) a massive platform. The platform (isolated from the floor) sits on soft linear springs.

If you have children or pets, or concern over the 5As being "tipsy", then maybe the air springs are not for you. In my case, after hearing the difference, I am more than willing to explain to visitors why my speakers are "floating" like a turntable and bounce or rock at a few Hertz when you bump them.

Please report your experiences so we all can learn from them.

Cheers,

Charlie

Tom,

I agree with you that one would like the speaker box to not move, and that the reaction force on a woofer (or other driver) motor/basket can be very large - many pounds. This force must be reacted by the cabinet and possibly the floor. But the cabinet is not only a mass at audio frequencies, but has stiffness and modes of vibration. While the cabinet-to-driver mass ratio can be perhaps 1000:1, the cabinet can still end up vibrating significantly at certain frequencies.

This is not a simple problem, and there is not one solution which is best for everyone. For me it did help a lot to "ground" my speakers on points to the floor - but isolation worked even better. I have a flexible wood floor. Perhaps you have a concrete floor?

Charlie

Charlie

Tom,

That is a good point about tweeter motion. This is why some speaker designs decouple the tweeter from the rest of the cabinet, rather than hard mount it to the front baffle.

Still, due to cabinet modes of vibration, even with base of cabinet "fixed" to floor, there could still be a lot of vibration of the tweeter (due to woofer-induced cabinet motion). We cannot guarantee that for all speakers, on all floors, that this product or that product will provide the best solution. Also, many times one thing gets better while another thing gets worse! That is what makes this hobby so interesting...

Cheers,

Charlie