Wednesday, December 19, 2012

The Tape Worm Method, (How to shim a subwoofer with no dust cap)

I've been fielding questions lately about how to assemble subs using one of our AudioPulse cones.

15" is $75 shipped, 12" is $65 shipped, only 3" adapters are available at this time.
We're working on 4", 2.5" and 2" adapters.

Once we got our hands on the Audio Pulse cones, I asked Thilo about it, he just smiled and told me I'd figure it out.  He was right, and I want to share my discovery so everyone can enjoy these great cone assemblies and build fantastic looking subs for pennies on the dollar!

Building with the Ti frame, (Eclipse Titanium), or other detachable top assembly is easy.  Build the sub normal, leave the shim in while you build.  When cured, remove the top assembly to remove the shim, reassemble and test. Adjust if needed and you're done.

The tricky part was wanting to use these great cones with traditionally, non removable frames like the 12 spoke, (694), or 4 spoke, (689), frames.  Thilo, (TC Sounds), did make an adapter when he wanted this feature for the Eclipse Ti's 8 series, (TC9 motor).  But it was a bit expensive with the machine work and material.  It worked great though but after Eclipse decided China was the solution, I didn't see any use of it with any other TCS clients.  It was granted a patent on the idea as seen HERE.

Thanks to the help of Dan Wiggins, he'd already put us in the habit of using PTFE, aka Teflon®, sheets as shims back when we acquired much of the Adire Audio inventory. PTFE sheets are strong, non stick to CA or epoxy and last for hundreds of builds.  As you may have seen in the video on YouTube of the Hill Recone. For that method, we learned from an old, (now gone), video that Image Dynamics posted to support their ID MAX series drivers.  They sell re-cone kits and the coil is shimmed from the outside using standard plastic sheeting strips. (You can use manila folder or other paper strips as we did in our video... However, what we found works even better for our application is to shim inside the coil.  The outside of the coil is not usually linear, (for many reasons that are natural and do not affect performance), but are inconsistent when using our app in this case.

Once you have the coil assembly ready to mount into the frame assembly, you cut the appropriate thickness shim into aproximate 3/8"-1/2" strips.  The strips need to be long enough to touch the table you're working on yet stay in place, in the gap and not fall out when you're inserting the coil assembly, (Coil with spider).

Build as normal and make sure that all contact surfaces have been prepared and are coated with our Devil's Jizz epoxy or other quality thermal / impact resistant epoxy.

40cc Devi's Jizz kit here for $30 shipped----> 

We do not recommend CA glue in the triple joint area as it cures with micro crystals that can eat away at a spider over time.  CA is fine on the surround as well as the outer spider assembly in most cases.  Builders like REDC and Fi have and still use CA for the triple joint in many of their products. (Fi also builds for the Ascendant and SSA brands.)  I personally I think that the added expense is worth it to me in the long run and I hate seeing a driver come in for that reason and our Subwoofer Library is over flowing with the guts of dead subs.

"Let's Go Shimming!"

The minimum points needed are only 3 to shim but I recommend 4.  More than that and it gets a bit crowded.  Once you have the surround clamped into place and a mass weighing the the cone down, (a bit), so that it makes good contact with the adapter, allow it to cure over night.  We use large washers wrapped in electrical tape to mass.

Remember to use something that will not damage your brand new cone! You can use a piece of paper towel, paper or PTFE to go between  if needed.

Remove the clamps and review your work.  Turn the sub on it's side and using either a tool like needle nose pliers or a pair of forceps, pull the shims out one by one like you would a tape worm from your dirtiest child.

Once all the, 'tape worms', have been removed, run the sub free air with some low frequencies to make sure there's no rubbing or rocking through the excursion of the driver.  At first you'll hear some ripping, that's the breaking in of the spider.  That is normal.

If everything is good, your sub is ready to top off with a nice new gasket and ready for use!

Thanks again for your support and keep the questions coming.
Patrick Chandler
Co-Founder Robot Underground
 - Worldwide Revolution -