Greg Weaver

August 1997

Part III - A Ten Dollar Isolation Platform?

Fellow SoundStage! (and Positive Feedback) contributor Doug Blackburn seems destined to earn a doctorate in isolation and damping research. While I am in complete agreement with his direction and feel that he has been quite thorough in his quest, I have a slight suggestion as a modification to his inner tube isolation work that I feel offers improvement in two areas, performance and utilization of space. The first part of this tweek, just using an inner tube, will afford you about 50% of the results of the "Higher Priced" Isolation products for an investment of about $3.00! Can you live with that? I thought so. Going all the way with it will take you into isolation heaven for about $7.00 a platform!

The work from many writers, most notably Doug, suggests the use of boat trailer or wheel barrow type inner tubes, sized at 4.00/4.80 x 8 (about 15" round and 4 1/2" tall when inflated), partially deflated under your components. For some time now, I have used a very thin walled, narrow diameter tube under my Linn LP 12.

My original intention was to improve the resolution of the 'table/arm/cart synergy by helping to isolate both air and floor borne vibration. It just seemed to make sense that floating a sensitive device like a turntable on a cushion of air would provide an effective isolation platform. When I saw these tubes for next to nothing (I found 6 of them at a clearance price of just $.79 each while shopping for inexpensive scoopable cat litter for Katana the audiophile feline!), I decided to give it a shot. It worked. It worked VERY WELL. With the proliferation of all the isolation devices from the likes of Townshend (starting at $149), Bright Star (starting at $99) and Vibraplane (starting at $1695!!!), I have followed the lead and applied this very affordable process to just about every component in my system. And with wondrous results.

After reading about the use of the larger tubes, I had to experiment. To my surprise, they seemed WAY too rigid and stiff, even when placed under the heaviest of components, not appearing nearly elastic enough in comparison to the smaller diameter ones I had been using. To me, it seemed as if this was a step away from, rather than a step towards, improvement. So, I abandoned this direction and went back to my original sized tubes.

Head on down to your local discount mart or hardware store and make your way to the bicycle maintenance section. Search out some 14 x 2.125 (about 14" round and 2 1/8" tall) bicycle inner tubes. The apparent advantages to the smaller tubes are that 1.) the walls themselves are comprised of MUCH thinner rubber offering a higher compliance (i.e., less stiffness) and 2.) they don't take up as much rack height when installed.

The advantage of the higher compliance of the thinner tube walls is that the tubes bleed energy better. The thicker walled ones are more rigid and can be very stiff. This makes them less effective at the dissipation of energy. The second advantage is a more shallow isolation device, allowing better use of a probably already over taxed space. More efficient energy bleeding/less wasted space. If this isn't the perfect example of a Win/Win scenario, I don't know what is.

The best way to install the tubes is to completely inflate one so that it takes its full round shape. Place it centrally on the surface on which you plan to install the audio device. You should prepare the equipment by removing any feet from the bottom of the device, as well as any other obstacles which may interfere with the units ability to sit completely level on the tube. Also make sure that any sharp edges such as screws and cabinet corrugations, which might cut or puncture the tube, are covered with electrical tape or something similar.

Place the suitably prepared device on the tube. Now, deflate the tube slightly until it gets very squishy. I do mean very squishy! You may have to adjust the position of the unit on the tube as you deflate it in order to keep the unit level as the tube settles. Continue to deflate the tube until you get a very low system resonant frequency, something on the order of 2-6 Hz. Proper deflation (or inflation?) is achieved when the unit rocks between twice to six times a second when pushed. To test it, just push down on a corner and watch it rock back to stable. It should cycle (rock up and then back down to the point where it began) about 2 to 6 times in one second. Generally, the lower the system resonant cycle the better, but don't be afraid to experiment.

As I have indicated, this alone yields about half the performance of the much more costly devices for isolating source components and electronics from foot falls and both air and floor borne acoustic feedback. Best results were obtained with my digital and analog front ends, but every time I isolated another device, the system performance increased. This tweek provides outstanding improvement of clarity, space, resolution and dynamics and uncovers a much more rhythmic presentation to the music.

If you want to go to the limit (you don't know what you are still missing), follow Doug Blackburn's recipe of damping the component as well as just isolating it (first detailed in the Spring 1997 issue of Positive Feedback, Volume 7, Issue 1). To go the distance, you'll need to fashion some Mass Loading Devices - bags full of sand - and acquire some free floating shelves, preferably MDF (Medium Density Fiberboard). Doug's suggestion of using Zip Lock style freezer bags for the sand is excellent. Pick them up (if you don't have any now) at the grocer. Then, once again, head to your local building supply store (the guys know me by name at my favorite one!) where you can get a 50 pound bag of sand for less than $3. You can either buy pre cut shelving for the free floating shelves, or you can have someone cut some to your specifications. You are looking at as much as $5 a shelf for the nicely finished, pre cut jobbies, and less than $1 a shelf if you have a sheet of 3/4' MDF cut to order. Let me tell you that cutting a sheet of MDF will provide you with a whole lotta' shelves!

Fill the freezer bags with sand. You may want to use a measuring cup to get exactly the same amount of sand in each bag. Sound anal? Not really, keeping the bags identically full helps with the leveling process later. You will want to remove all the air from the sandbags before sealing them completely. It sounds odd, but just give it a try. It really helps. Once the bag is filled with the amount of sand you want, zip the bag about nine tenths closed. Lightly suck the air out by placing your lips over that last one tenth of the open seal. Suck slowly and deliberately and you will be able to remove all the air and not pull any (or certainly very little) of the sand into your mouth. Now completely seal the bag. Fold the zipper over onto the bag itself and secure it with some packing tape. This not only holds down the zippered edge, it also prevents it from accidentally opening and dumping sand everywhere. Repeat as necessary to get as many bags as you need. You're ready to proceed.

First, place the inflated tube on the chosen shelf. Next, place one of your free floating shelves on top of the tube. Now place sandbags on top of this shelf so that they will support the entire bottom of the component you intend to isolate. This should require more than one bag. The more mass you are able to add the better, so don't be shy. Place the prepared component (remember to take off the feet and cover any sharp protrusions with tape) on these sandbags. Finally, add more sandbags atop the component covering as much surface as is feasable (you obviously will omit this with turntables and any other top load devices) to complete this Dagwood of an Isolation/Damping Sandwich. Be careful with amplifies not to block critical ventilation slots or to place them on the heat sinks. Deflate the tube to the proper pressure, just as above, and you are ready to experience the sonic nirvana of this project. THIS PROVIDES STUNNING IMPROVEMENTS!! You will be witness to an almost magical increase in focus, clarity, inner detail and harmonic purity. You will discover more stable imaging, a greater sense of space, a larger yet more defined stage, greater dynamic contrasts, electron microscopic resolution and a revelation of musical pace and rhythm! In short, the music sounds more like music.

We are talking about achieving 80% of the performance of the previously mentioned VERY EXPENSIVE devices. To recap, all you'll need is 1.) tubes at about $3 each, 2.) shelves anywhere from $1 to $5 a piece, 3.) mass loading for about $.50 a bag, including sand, with four bags average per unit - and you're at a cool $10.00 a shot! What a bargain! This mass/isolation sandwich produces improvements which cannot be achieved any other way! Quite honestly, even replacing your components with mega buck gear may not get you anywhere near this level of performance enhancement. Those of you out there with mega buck gear, guess what? It will do the same thing for you! This isolation method gives any unit the chance to sound its absolute best.

Give it a try and be prepared to save a BOAT LOAD of money! The better to spend on software, my friends! This hobby/sport/disease is, after all, about the music, isn't it? Till next time.

...Greg Weaver
gregw@soundstage.com