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In Reply to: Anyone try Herbies Big Black Dots under floorstanders...instead of spikes... posted by AAG on April 12, 2007 at 07:27:18:
What would lead you to that conclusion?-Pete
Follow Ups:
I thought it was a 'rule of thumb'? if speakers are able to physically rock back and forth, the opposite of securely spiked, it does affect the performance since the drivers are held in place securely.I'm pretty sure its a YMMV thing, but i notice a change when my speakers are spiked compared to just sitting on the carpet.
The trade off is to isolate the speaker from the floor in order to remove resonance from the system.
This can produce a huge improvement especially on a suspended floor.
The amount of the degradation from the "instability" is tiny.You are putting the mass of the whole speaker against the mass of the cone and it overwhelms it completely.
If you ever try this you will be amazed (or rather you may be amazed) how much leaner, faster and deeper your speakers can get.
Agree absolutely. Anything compliant will stop the speakers from working properly and cancel out the movement of the bass driver.
This is a very simple analysis: compare the mass of the moving portion of a driver to the mass of the cabinet. There is more than an order of magnitude difference.This is why for some implementations people can get away with hanging speakers.
Now, if you're going to isolate speakers (generally by using compliant materials, but there are other methods), you need to be wise about how you achieve the isolation. You don't want an isolation system that has a resonant frequency in the audible range - the resonant frequency of the system needs to be well below 20Hz - preferably less than 5Hz.
I can see how people might get confused when considering the 'laying flat on the carpet' vs. spiked example. When you lay speakers on a carpet, unspiked, the speakers are neither well coupled nor well isolated from the floor. This creates opportunities for things to go wrong. If you instead spike the speakers to the floor (thru the carpet), you've now effectively coupled the speakers to the floor. Depending ont he floor type, room layout, etc, this will generally increase the apparent bass output at certain frequencies, and there is also a good chance the speaker was voiced to sound best when set up this way.
On the other hand, if you effectively decouple the speakers from the floor (placing the speakers on roller bearings and the roller bearings atop a constrained-layer platform is one such way), you are preventing a lot of the cabinet's vibration from mechanically coupling to the room structure. Particularly with old, wooden floors, this can be a great advantge since the mechanical coupling of the speaker to the floor can have a few very bad effects. For one, mechanical coupling is much more energy efficient than acoustic coupling, so the chances of sending the floor or larger portions of the room structure into resonance are much greater, and this can naturally muddy your bass response (sometimes a contributor to 'one-note bass'). Second, since sound travels much more quickly thru solids than gases, this also allows bass waves to reach the listener via the structure more quickly than thru the air, and thus can have a smearing effect on the sound.
In short, one cannot say for all systems whether coupling speakers to the floor is the best approach or if isolating them instead is better, but both approaches have merit and the entire set of variables needs to be considered for proper analysis. Of course, trial and error usually leads you to the best result most quickly, but my overall point is that you can't say with a blanket statement that decoupling speakers from a floor is bad.
-Pete
I think you are right. After years of coupling the speakers with spikes to the wooden floor, I experimented a BIG imporvement adopting Atacama spike bases (made of hard ruber and metal).
Based on the fact that I have a suspended wooden floor (80 years young!) - no carpet under speaks, just area rugs in center of room, I was thinking it might be best to decouple...but was worried about the "rocking" of compliant material smearing the imaging. Although the Herbies literature seems to differentiate their products from other compliant materials in this regard...which is what had me thinking about them.However, the roller balls on a constrained layer seems interesting.
I have some BDR's and FIM roller bearings...will play around with and see what works in my situation.
Also, will get the Herbies and play around with them...
What kind (make up) of constrained layer are you using? Did you countersink the rollerball plates into the platform?
My roller bearings and platforms are all DIY.The rollers were made from good quality stainless steel soup ladles (spherical section ones) cut down and set in a brass base via an epoxy/sand/brass shaving mix which provides a very non-resonant cup (the main purpose of the brass base is to assure the bottom of the bearing surface is the same height for all three cups in a set).
The platforms consist of, from top to bottom:
.25" oak ply
.5" MDF
1" PE foam (my memory is failing me as to whether it was closed or open cell - if you search for contrained-layer paltforms on here you'll find out which is the right type to use)
.5" MDF
.25" oak plyThe platforms are of course spiked to the floor. They are also not rectangular - since I was putting the speakers on three bearings, two in the front where the bulk of the weight is, and one in the rear, the platforms are trapezoidal shaped (nearly triangular).
This isn't the most effective platform design - if altering the speaker height weren't an issue, I would have used a layer of .25" birch ply between the oak and MDF both top and bottom, and also added 6061 T6 aluminum as the outermost layers.
I did not countersink the bearings into the platforms, but to assure they are well coupled to the platforms, I added three feet to each bearing base by countersinking and epoxying three 3/16" brass balls into them. In order for the bearings to be effective with the speakers, I needed to epoxy three small squares of polished stainless steel to the bottom of the speakers - I was able to do this without covering the speaker spike threads, in case I ever sell the speakers or decide to go back to spiking them to the floor.
This setup is not for everyone - floorstanders on rollers are VERY unstable and easy to knock over. I get away with it due to my living arrangement, specifically lack of pets and children.
One of the techniques that has worked well for me in addressing vibration is that wherever I'm not trying to achive isolation (such as between the roller bearings and the platforms), I try to achieve effective coupling. In my scheme, the rollers provide very effective horizontal isolation, but provide very effective, rigid coupling to the vertical isolation devices: the platforms.
-Pete
and some directions to explore...And it will be some worthy experimentation on coupling/decoupling.
If your wooden floor is above an unfinished basement or other space that would allow you to set up jacking posts beneath the floor, I highly recommend it. When I did that in my previous house, it was one of the best tweaks I ever did.Have fun,
Pete
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