The TNT-BulletSpike

A Killer Spike

Product: TNT BulletSpikes - Equipment Spikes
Manufacturer : not for sale, a free TNT-DIY design
Cost: Free (well, really cheap anyway)
Author: Scott Faller
Published: October, 2001

Ramblings

I don't know about you guys, but when I walk through a store (any store) I find myself looking at things a little different. I look at the items on the shelves and think to myself "Can I use that in my audio system as a tweak?" Especially when it comes to the area of vibration isolation.

In my quest for the perfect DIY vibration isolator, I've collected some pretty bizarre items over the past few years. Suction cups (yuck), domed rubber door stops (decent), makeup removal pads (OK no jokes) not to mention some homemade concoctions like "Gloop" which uses Elmers glue mixed down to create this gelatinous type substance similar to Sorbothane. I could never get that to work very well......but I did end up with a lifetime supply of glue out of the deal :-)

Lets fast forward to last week. I was wandering through WalMart (AKA WallyWorld). With the change of seasons they brought out some of their seasonal gear. I was there to pick up some points (the screw on arrowheads used as floor coupling spikes) that I am going to use for an upcoming TNT DIY speaker project.

I was wandering around the sporting goods department on the prowl for tweaks and stuff when a bolt of lighting hit me (well maybe it was my wife poking me in the back, but it was an idea none-the-less). I found myself standing in front of the Black Powder and re-loading section.

Barnes 50 caliber mussleloading hollow point bullet

I was mesmerized by a package of 50 caliber muzzleloader bullets manufactured by Barnes (did you just read what I just typed? now that's scary). As you can see they are almost ½" (10mm) in diameter, 7/8" (23mm) long and have a hollow point that measures ½" (12mm) deep and 3/8" (7mm) across. After scratching at one I think they are solid copper. They come 10 per package.

Now, I had spikes on the brain, so I started thinking. We've all seen the reviews and ads for spikes and we know their advantages. Trouble is, spikes have to be used carefully otherwise you'll end up with huge gouge marks in your fine wood furniture. I kind of like the idea of those machined ball bearing type spikes but boy are they expensive.

I moved a little further down the death and dismemberment isle and saw BB's. You know, like the ones for your Red Rider BB gun you had when you were a kid. It all started coming together. Why don't I take the 50 caliber hollow point bullets, fill them with something and stick a BB in the tip? Voila, cheap spike!

Cool, I'm most of the way there, but the bullet is going to be pretty wobbley so I had to come up with some way to stabilize it. Well, gluing the bullet to a fender washer should do it. So I picked up some two part epoxy to use as the glue and also grabbed a small tube of Silicone and Latex caulk to use in the cavity of the hollow point bullet.

So I had a plan, now to see if it works.

Theory and Design

The reason I grabbed both the Silicone and Latex caulks was when they harden the Latex seems to be a bit more flexible than the Silicone. I thought Latex might do better in absorbing the vibrations than the Silicone. More on that later.

I'm not going to bore you with the physics of vibration isolation so I'll give you the Cliff Notes version instead. The basic concept of a spike is to concentrate a particular piece of equipment's weight into the smallest area possible (three points preferably) therefore reducing transmitted vibrations generated by standing waves introduced by your stereo speakers and migrating into your equipment via your equipment rack. Hmmm not perfect, but then again, not bad for a forty five word definition :-)

A close up shot of the bearing surface

These nasty little vibrations end up shaking the hell out of your gear. All of those small signals going through all of those electronic gismos (that's a technical term) inside your equipment casing end up coming out smeared and inaccurate. Or in other words, vibrations equal sonic disaster. Enough with the physics lesson (if you could call it that).

My thoughts for the design are very simple. Fill the hollow point bullet with caulk (flush with the end of the hollow point) and stick a BB dead center of the caulk. Buried it about halfway into the caulk (to keep it from popping out of the caulk) then glue the bullet to the fender washer. Pretty darned simple, if I say so myself.

So that's exactly what I did. I made up a batch of nine TNT Bullets.

I tried the Latex caulk in several of them to see the difference but after three days of drying time, the Latex had only formed a crust, shrunk and never really dried inside the bullet casing. On the other hand, the Silicone was dry, retained it's original form and was very resilient.

The reason I chose BB's instead of something different is that a BB is round rather than pointed. That way it will be far less abrasive on your equipment racks plus it gives us a very small contact point with your rack.

Listening Test

After letting the caulk dry for a week, I decided it was time to try them out. I grabbed my handy roll of rope caulk and pealed off about 1 ½" of caulk, applied it to the backside of the fender washer then I smooshed the TNT-Bullets to the bottom of my Arcam CD Player. Blue tack will work just fine too. In theory, the rope caulk should also provide yet another layer of vibration damping above and beyond the Silicone caulk.

Big Note Here. Let these things dry for a full week. If you don't and you put these under a load prematurely, the BB's will get pushed up inside the caulk, never to be seen again (trust me 'cause that's just what happend to me).

First things first, the test music. I picked out the most brutal tracks I could think of to test these little baby's out, Blue Man Group and Kodo. From the Blue Man Group, Audio CD I picked track 7, Mandelgroove. This is a killer for making my equipment rack vibrate at really high SPL's. At 1:09 the Drum Wall (essentially a group of drummers all playing the same notes) kicks in, then at 1:23 a kick ass bass track comes over the top of everything. At 3:40 the song they start beating on the Big Drum (it's a 9' diameter drum)....whoa! From Kodo, Tataku CD I picked track 5, The Hunted. Just an awesome track of pure percussion. The acoustic energy created by this performance group playing native instruments is nearly unsurpassed.

Between these two tracks, if pictures aren't falling off the walls, you either A) don't have big enough speakers or B) aren't pushing enough watts.

I started the music, but rather than listening I wanted to feel how much of the vibrations were being isolated, so I put my hand on my equipment rack. The vibrations on the shelf were pretty heavy, but then again I had the music cranked to about 110db hitting 114db on transients (verified with my Radio Shack db Meter). Needless to say my house was a rockin'.
Then I felt the TNT-Bullets, not a single vibration. I touched the fender washer, nothing. So I ran my fingers across the bottom of my Arcam casing, nothing was being transmitted! BINGO !!!!

Secondary isolation shelves

Next, since I use secondary isolation shelves (as you can see from the pic), I decided to remove the shelf under the Arcam and see what I could feel. I repeated the same scenario's and didn't feel a thing.

In a critical listening test I hear all the things we should from a good set of spikes. Clear unencumbered sound. I could go on and on with the usual audiophile hype and language, but I'll spare you all that.

As for the weight it can handle, rather than guessing, I weighed my Arcam. With the additional damping materials I added to the casing (rope caulk) it weighs in at 12 pounds (5.5 kilos). I ended up using 4 of the TNT Bullet Spikes to support it. That compressed the BB into the caulk enough to let me know the CD player wasn't going to dance around on it's own. My Systemdek 2X2 turntable ended up getting 6 of these little gems installed under it. Not being a physics major nor having any serious test equipment, if you have a heavier (or lighter) piece of gear you are setting on these little gems, I'd figure one TNT Bullet Spike for every 3 to 4 pounds (1.3 to 1.8 kilos), YMMV. Have fun, experiment !

Conclusion

Well folks, I think we've got a winner here. Sometimes we get lucky. These may not be able to handle the heaviest of your audiophile components, but they sure do a fine job on the lighter pieces. Plus they are really easy to make.

Now, are these findings scientific? No, it's completely subjective, but I'm here to tell you the TNT-Bullets work. They work so well, in fact, I'm off to WallyWorld to buy enough bullets to retrofit all of my gear and do away with my secondary isolation shelves.

While I'm there I think I'll treat myself to a CD or two since I saved all that money not buying those expensive audiophile spikes. Don't forget, that same logic works for us too guy's. My wife does it to me all the time. "It was marked down so I bought two". Sound familiar? :-)

Note

If you don't have a WalMart near you, just go to your local Gun and Ammo shop and ask the attendant for a 50 caliber hollow point bullet for reloading. He should carry several different styles. Hopefully one of them will have a large enough hollow area to accept the proper amount of caulk. This is the key to success of this project, lots of silicone for dampening those nasty vibrations.

Bigger Note

If the hollow point isn't large enough, you could put the bullet in your vise and drill out the point a little farther. Be careful though. Most of the bullets I looked at were copper coated LEAD. As we all know, mishandling lead can be and is extremely hazardous to your health, so be careful and most of all have fun tweaking.
Remember, we at TNT-Audio want you coherent enough to participate in our forums :-)