In our continuing story about trying to figure out why isolation bases mattered, how they worked and what we could do to perhaps make our products less needy of their services, I endeavored to build my own. It’s been my experience that the best way for me to learn is to jump in, roll my sleeves up and get dirty with the work. In this way I make a lot of failures and failures are the most important aspect of design. When we fail we learn. When we succeed we stop trying and stop learning as we move on to the next project. I had a lot to learn and that meant a lot of failures.
I can see a few of my engineering readers rolling their eyes at me. ”You should do this by measuring the vibrations levels and minimizing them”. The problem is/was we didn’t really understand what it was we were trying to eliminate and why – so measuring for some elusive parameter that may or may not have the desired effect would have been pointless – at least for me, the consumate tinkerer.
My first attempt showed promise. I used a 1/4″ steel plate mounted on some rubber feet as a test base and that worked well. The next step was to test the steel plate as a given – I swapped it out for a 1″ piece of MDF (medium density particle board) – worse. I swapped it out for a 1″ thick piece of HDF (high density particle board) – even worse. Wait a minute, I was going backwards.
I took one of the particle boards and added a ring around the outside and filled the inside with sand – a trick my friend Barry at Bright Star had shown me. Interesting indeed. Better than just the particle board but worse than my original idea of the steel plate. I went back to the steel plate and after all that decided it was clearly head and shoulders better than anything else I had tried.
So the obvious next step was the feet. I scrapped the rubber feet for cones. Yuck. I swapped the cones for Sorbothane feet (a branded polyurethane product) that I had around and instead of going backwards, went forward. Better for sure. Sorbothane is available in many different durometers and sizes (durometer refers to hardness) and I got a kit from the distributor and went to town.
I soon discovered something interesting and counterintuitive: the larger the diameter of foot the better the sound. I would have thought the opposite because it seemed to me that by limiting the contact area (as we would with a cone) the amount of vibrations would be reduced. Yet the opposite was happening which made me quite happy I wasn’t on a mission of measurement and tuning to an unknown goal. By simply listening and observing the results with an open mind I discovered this interesting twist.
So, if bigger and broader was best, how big and how broad? Might a Sorbothane pad covering the entire area of the plate be the key? Turns out no – it was worse. The sound more open between instruments but the muddled effect worse.
I discovered that a Sorbothane foot close to a couple of inches in diameter and at a specific durometer, coupled to the heavy steel plate, worked best.
And interestingly enough my results now matched the original wooden base! I was on to something but wanted more.