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  3. 1064803157

Why Does A Concrete Floor/Spiked Metal Rack...

suck all the warmth and life out of my system?

I have been thoroughly dissatisfied with my hi-fi system for the good part of a year now and I have been unable to until recently to put my finger on the problem. In a nutshell, almost every CD I would play would sound bright and harsh and bass light. The top end and upper midrange would completely overwhelm the bottom end. I have experimented with all sorts of tweaks and in particular various isolation devices, and although I was able to achieve minor changes to the tone the overall top end brightness and lack of bass was still evident.

I was enjoying (as best as I could given the problem!) a listening session and wracking my brain (for the ten millionth time) for ideas on how to make my system work better, when it suddenly dawned on me that I had these small plastic/hard rubber? cups that might be ideal to place under the rack spikes as a last ditch attempt to solve the brightness issue. With the music still playing I carefully tilted the rack enough to slip the cups under each spike on the four corners of the rack, thus de-coupling the rack from the concrete floor. They were a perfect fit and the effect was both immediate and DRAMATIC. The system was for the first time tonally balanced, the bass response increased, the sound stage widened, the noise floor dropped, there was greater depth, increased clarity, and most importantly the brightness and harshness had completely disappeared!

I was firmly of the belief that audio racks should be coupled to the floor for stability and assist with the reduction of floor vibration eminating from the floor. My rack is a rigid design composed of tubular steel and every cavity is filled with sand in order to reduce any possible ringing. The rack is supported by four large adjustable screw in spikes which penetrate the carpet and couple the rack to the concrete floor beneath. The components are supported on MDF shelving. What I discovered this weekend is that this rack/floor interface was completely sucking the life out of the system. Upper midrange and top end frequencies were being accentuated at the expense of the lower mid range and bottom end, thus producing the fatiguing brightness and harshness.

Can anybody explain to me in laymans terms why this occurs?
unhalfbricking
twl
3,251 posts
 
Geoffkait, I agree that seismic movements will "outpower" any of the typical airborne vibrations in an audio system. However, short of a laboratory type active platform, there is nothing that an audio rack can do about that. No little rubber blocks or grommets are going to absorb and dissipate the energy that is moving your entire building around. They are going to move your rack, no matter what the rack construction is.

The airborne vibrations, however, can be more easily and successfully addressed by the equipment rack.
onhwy61's avatar
onhwy61
5,348 posts
 
I totally agree with Geoffkait. If you couple your rack to your house, then vibrations from the house will be transmitted to your rack. Cones and spikes are not one way devices! If you live within 5 miles of rail tracks, interstates, airports, industrial areas, construction sites or any road that carries truck traffic then your house is being excited (vibrated) by low frequency energy. Research by Gran Prix Audio, the makers of high end racks, indicates that this structural transmitted vibrations is several orders of magnitude higher than both energy transmitted through the air from the speaker or a components' interally generated vibration.

For my specific house and system decoupling is the way to go. I'm floating my entire rack with Aurios Pro devices (the rack is on 3.5" of maple which rest upon the Aurios). Other people living in different locations with different housing structures may have other solutions to the coupling/decoupling question. It's not a one size fits all issue.

One of the observations by Gran Prix Audio is that deep bass from loudspeakers is a major source of vibration being fed back into an equipment rack. It makes me wonder if people with systems that don't produce deep bass (say sub 40Hz) at high levels would have less need to decouple their equipment racks?
viggen
838 posts
 
I think a company such as Sistrum has addressed the directionality of cones/spike. I think it is safe to say most of the mechanical vibration is drained in the direction to the point of the spike.

As for seismic vibrations, that is a physical vibration where its effect on stereo equipment is minimized when attached to solid matter rather than a soft one. Seismic waves will travel right through solid matter. If I remember correctly, seismic waves causes most damage their P and S waves are slowed down and impeded from completing their waves.
onhwy61's avatar
onhwy61
5,348 posts
 
From the Audio Point website:

The unique design of the Audio Point displaces the focal point of the resonant energy to a virtual point below the tip of the Audio Point. Physics dictates that this virtual focal point creates a natural high speed channel through which resonance energy will flow. The result is the relocation of the resonance energy into the surface upon which the Audio Point is resting.

Statements such as this may make sense to some people, but it sounds like mumbo-jumbo to me. Furthermore, as far as the directionality of "resonant energy", if I use an Audio Point the pointy end faces downward, but if I use the same Audio Point in a Sistrum rack some of the points face upward (into the component) and some face downward. Is the rack feeding "resonant energy" into the component? I don't mean to sound obstinate, nor am I disputing peoples' testimonials to the effectiveness of Audio Points/Sistrum, but their explanation of how their product works is weak.
viggen
838 posts
 
Don't forget about gravity.
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