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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
bigpoppakrell
30 posts
 
At the risk of stating the obvious, why not just set your system up on a less rigid/damped rack/table to see if the difference in sound warrants removing the sand ?
Years ago, when a certain Scottish t-table ruled the world, many people were setting them up on simple TV dinner type table stands !! The concept was that a simple rigid stand provided less intrusive detrimental effects than a large mass loaded one.
When in doubt ... try it out !
There are merits in both methods of isolation. Mass loading works in some instances, and lossy decoupling in others. The bottom line is if you like what you're hearing don't fret about it.. just enjoy your system.
theaudiotweak
2,797 posts
 
You now have stored and impeded the exit of resonant energy when you added the sand to your rack..You have a conflict of mechanics within the rack itself. You say the rack is designed to couple and then you filled it with dampening material. One will work better without the other! The fill material mentioned by TWL was chosen to aid in the retreval of resonant energy, and with coupling, the noise now has a point of exit. I am a total coupler, no dampening allowed in my system..This concept is hard to accept. This concept takes much time and effort to implement. This concept I feel brings me closer to the truth of the music..Tom
unhalfbricking OP
15 posts
 
I guess I should have pointed out in the beginning that I live in New Zealand. While I would very much like to try out some of the devices suggested they are not available here. I have found NZ sources for Black Diamond Racing Cones and Polycrystal Cones. The BDR Cones I am able to audition before purchase but the PC Cones I would have to source from another city. Any comments on the effectiveness of these devices? The PC Cones are twice the price of the BDR Cones, are they twice as effective?
theaudiotweak
2,797 posts
 
Changing one thing will not eliminate the problem.Changing one thing will only mask and fail to eliminate the inherent problem. The root cause of the problem still exists. Dampening is another storage medium. Tom
eldartford
4,262 posts
 
NZ has earthquakes that are of low intensity but more frequent than anywhere else on earth. How near to Rotorua (SP?) are you?
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