I would start with filling the tubes with lead shot. Then if you add spikes make sure you use cone rest between spike and floor. I think butcher block would be a waste.
How thick are MDF shelves and are you sure they are MDF and not particle board? MDF really should deaden vibration which is why speaker manufactures love the stuff.
I think these measures would be a good start and possibly the solution.
I've got a Billy Baggs rack of similar construction and I find thick maple platforms contribute very positively to better sound. Not all components respond equally well to sitting on maple, but that's true of every audio proposition. MDF is a dull sounding poor excuse for shelving IMO. Manufacturers use it because it's cheap and performs reasonably well, pure and simple. Better sounding shelving and speaker construction panels cost a lot more than mdf. I also find Golden Sound ceramic cones between gear and mdf shelving are a good thing. I'm sure there are many other good choices. You just have to find what sort of sound you like. Galen Carol Audio's website has a good summary of the sound characteristics of various footers & cones which I've found accurate. If you want to spend more, Neuance, Gingko, and others make good isolation platforms. Basically, the money you save on a less expensive rack with MDF shelving forces you to spend more money to correct the crummy sound of MDF. Think carefully about filing the rack with lead shot or putting spikes on it if you ever want to move it to change equipment, clean, etc. Your idea to use damping material on the bottom of the shelving will help to ameliorate vibration, but it will still sound dull and lifeless.
Actually, MDF can work well when used properly, but its use in lesser designs has given it a bad name. What you should be careful of is mixing different design philosophies in regard to vibration control. Basically, you can either attempt to drain vibration as directly as possible or attempt to damp it at each stage. I prefer the first but I have used the other successfully. But a combination of the two is seldom successful. It also depends on the components you are using. Suspended sub chassis tables like dampened platforms much better than rigid tables. I have noticed this with VPI. The new tables have different requirements than the older ones. I would consider Kitty litter if you wanted to fill the tubes , I prefer it to lead or sand, Use of good cones under the shelf system or the individual units will help. You can combine this with use of maple blocks, Timbernation and Michigan Maple Block are good sources. Controlling vibration is a very critical element of good sound and there are several approaches , just keep track of what you expect each element to do.
The MDF itself is on the verge of providing to much damping,all that saw dust and glue. I once had a Michael Green stand which came with steel all thread rods that made the shelfs adjustable. Replacing the steel with brass made for a dramatic improvement in stage and dynamics,the rods where grounded/coupled with Audipoints. As Stan suggested I would not shut your system down with the use of sand or lead shot. Steel or brass bearings would be much better but costly. The kitty litter maybe the best value. I would fill the tubes only 1/3 at a time and then listen to the same familar recording at the same volume level, adding more each time until you hear the stage dynamics begin to shut down...and then stop. You may not get to fill the rods to the top. You will hear a difference with each additional pour. Tom
I filled the vertical tubular columns with sand. They used to ding like a bell when tapped, now it's a thud.
The shelves are relatively thin, and transmit vibrations easily. I'm going to try some dampening sheets under each (Dynamat Extreme)
How can I tell if the shelves are MDF or particle board? They're completely painted smooth flat black. How does that make a difference in my strategy?
I see many put their equipment on top of butcher block or other thick wood platforms with some isolators (cones, etc.)
Can you supply the manufacturer and model name/ number?
Just looked at the specs, says its medium density fiber board.
Wondering how much a low end rack is really affecting the sound..
What type of sand did you use?
Home Depot "natural play sand" They had another, much thinner, called leveling sand, but I was afraid of the mess.
Ordered Dynamat Extreme 10435 door kit ($50). Trying to increase the mass on each shelf to reduce vibrations, and also it should give some EMF shielding between components because it has an aluminum sheet.
We'll see what happens.
With your additional choice of materials you are now trapping more vibrations and .....over a longer period of time. Instead of allowing for and providing a path for vibrations to naturally migrate away fom your components you have provided a greater storage reservoir. Have you provided a way for self induced component vibrations or those that travel thru the air a method of retreat? Tom
Im not sure I understand. Am I going to get negative results by adding mass to the rack with sand in the steel tubes and dynamat to the shelves? Floor is concrete, sub is on vibrapods, so I believe most vibration felt on the shelf is via the sound waves over the air. Other than getting the shelves made out of birch or another material, what else can I do?
I just bought the Studiotech PS-3 with the optional high mass cone feet for my TV/tube system. It replaced a flimsy rack with glass shelving that was clearly not made for audio at all.
The HF-4 is similar but I went with the PS-3 because of the added bracing. Its very rigid and with the cone feet on my carpeted floor and a 80lb plasma on the top shelf it doesnt move at all. I can tell you it is a huge improvement sonically - the bass is tighter with more separation, the mids became more lush and the highs seem to have smoothed out a bit too. Now certainly, this isnt a high end rack, but it was a very noticable improvement in my system for not much money.
I have my CDP and tube preamp sitting on the middle shelf and my Power Plant Premier sitting on the bottom shelf. My amps sit on Timbernation maple stands with brass cones to each side of the rack. Im ordering up some Black Diamond Racing cones for further isolation on the 3 rack components but so far Im happy with it.
Adding mass is not all bad. Choosing the right material for that added mass is different than what we all were LEAD to believe. Mixing and matching materials and geometry is like trying to eat a soup sandwich. If the brass is doing such a good job as a conductor why use rubber products or carbon fiber? Why jumble up the phase coherency and transfer speed by using dissimular material and geometry? Transfer methods are the opposite of damping/storage methods.
Alex you need to ground that rack first to the floor. Audiopoints are what I would recommend and the only coupling device I use and sell. What size, well call Robert at Starsound. Whatever size fits then also use the APCD coupling discs under each Audiopoint for surface protection as well as an increase in surface tension, resonance capture and release. As your budget progresses apply the same ideas and methods to the components shown on the rack ..and also your speakers. Resonance transfer is the method of my choice ..no such thing as isolation. One method one singular coherent voice.
Installed Dynamat Extreme under each shelf, took about 20 minutes total. Shelves feel much more solid now, and has definitely reduced vibrations for each piece of equipment.
Problem is at the same time I upgraded the power amp to a McIntosh mc7200, and upgraded the Oppo 980 by bypassing the opamps with better caps, and installing cardas RCA connectors.
Does the system sound better? Yes. How did the rack dampening with the sand and dynamat make a difference to the sound? I have no idea.
Instead of messing around with your rack to dampen vibration, you instead might want to try using the Herbies Audio Lab Component Top Weights to lessen the vibration. I put two of his Super Sonic Srabilizer(s) on top of my pre-pro. Without them, when I tapped on the chassic I could feel vibration. With them, the vibration was gone. They cost only $20.00 each so you won't break the bank.