2. misc-audio
  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
viggen
838 posts
 
Face it, most racks such as Target and such that uses hollow tubing and a mixture of materials from metal to wood to plastic is not going to "drain" anything but the life from the music. Those kinds of racks are designed to be filled with sand to minimize unwanted resonance and mechanical vibration. The rubber footing further reduces vibration in this kind of set up.

If you want to drain vibration, first make sure you got the right rack ie. Sistrum then worry about the right spike that further enhances vibration draining. Otherwise, the spike is only good for isolating the rack from the earth.
stehno
1,453 posts
 
IMO, Theaudiotweak and Viggen are both right on the money.

Theaudiotweak mentions some of the many variables that come into play which reminds me what one very knowledgeable individual said not too long ago regarding this hobby:

"The best thing one can spend on their system is time."

Ain't that the truth?

-IMO
viggen
838 posts
 
Oops, it is more correct to say vibration is "altered" not "minimized" in my thread above. Only resonance is minimized.
inpepinnovations1e75
395 posts
 
Eldartford, a little knowledge is a dangerous thing. I don't know about bicyclists using pressurized tube frames, but I bet you that if they are, they are using helium as the gas and that is what is making the frame lighter, through bouyancy. Again, seriously, one doesn't "pre-stress" tubes with gas pressure. Also, CO2 would not be a good gas to pressurise the tube, since the pressure necesary to have any effect on the structural stiffness of the tube would cause the CO2 to solidify, even at room temperature! BTW, make sure that you completely dry the inside of the tube before introducing the CO2. CO2 and water make a nice corrosive atmosphere. At least it is not an explosive atmosphere.

salut, Bob P.
eldartford
4,262 posts
 
inpepinnovations@aol.com..You are right about the CO2, (a careless afterthought on my part) but wrong about internal pressurization stiffening up a structure. There are many examples. I picked the bike example because it somewhat resembles the tubes we are talking about. Blimps, Atlas ICBMs, and children's inflatable toys are others that come to mind. Heliocopter rotor blades are pressurized, but this is mostly done so that the pressure can be monitored for evidence of cracks.
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