Lamb's Wool Tweak - Modification Technique

This tweak must the easiest and cheapest tweak to make directly on a tweeter. Well, I suppose that the dome-rotation-to-distribute-ferrofluid is really the cheapest, but it's results are varied. Good tweeters don't benefit as they do from the wool tweak. The cost of material is about $4.50 for enough wool to modify at least two dozen tweeters. As soon as I saw the results from one test I applied it to all tweeters which can be modified this way. Here is the first caveat. Don't try to modify a tweeter which either doesn't need it (such as Scan-Speak units) or for which you can't easily (or at all) get to the vent without possible damage (as is the case for the Vifa XT25). Modify at your own risk.

Have the Right Tools

Don't do anything until you have all of the right tools for the job, which isn't much. You'll likely need a small Allen wrench to remove the faceplate for the tweeter. The Dayton requires a 2.5mm while the MDT-30 required a 2mm. You may find that there is an English near-equivalent, but I would recommend buying a small cheap set of metrics. They come in handy.

You may also need a standard sized straight screwdriver, this to carefully pry up the faceplate. Many faceplates fit tightly around the motor top plate. This is when care is most advised. You should slowly pry it up all the way around, moving it a small amount each time. It may suddenly come free, so be sure to hold it so that it won't fall away if this happens.

Other items you'll need are a pair of scissors to cut the wool, a very small square piece of aluminum foil and something small (preferably non-magnetic) to use to hold/push the wool in the vent (I used a wood-handled pen).

Getting Started

Now that you have all of the tools and materials, start by removing the driver faceplate. This is an easy task, but care must be taken primarily with the voice coil. Remove all of the screws which hold the faceplate (and dome/voice coil in some cases) onto the motor frontplate. Now you'll need to lift this assembly off of the motor. You may need to use the screwdrive to slowly pry it up all the way around. Just do it slowly and a little at a time.

When removing the dome/voice coil assembly always be sure to lift it directly away. Don't allow it to slide sideways as this could damage it. In addition, some drivers (Morel and Dayton amoung them) have a felt ring on the motor top plate. Care should be taken to avoid contacting it with the voice coil during removal, so proceed carefully and slowly. You also will want to avoid wiping off any ferrofluid by dragging it across any felt.

Take care also to prevent any foreign matter from finding its way into the magnet gap. Fuzz from wool or felt or any other contaminant may cause damage later when the tweeter is used. It's not likely to be a problem from my experience, but just be aware that it could be. Anything which comes in contact with the gap will stick, since most of the ferrorfluid (if your tweeter has it, that is) will remain in the gap. Most contaminants can be carefully removed, however. Use a toothpick or tweezers. I have just run my finger over the top of the gap which pulls away most fuzz and fibers. The fluid is usually recessed just enough to keep you from making contact with it.

You may insert the wool however you choose. My method works easily and reliably, but it is certainly not the only way. I cut a small square of aluminum to wrap the wool, since it is a very loose weave. It takes quite a bit of the wool so it has to be compressed before insertion. I also found coincidentally that about half of the width of the felt worked best, so you'll get enough for two tweeters with each cutoff.

Cut about 1-1/4" or less from the wool. Wrap the wool with the weave length-wise into a roll. Insert this roll of alumimum and wool as far as possible into the vent as shown in the picture below.

The aluminum foil must now be carefully removed. I used a small (mostly) wooden mechanical pencil which happened to be handily nearby. Just use something not very magnetic. Use it to hold the wool in position, but don't press it in hard as this will make it more difficult to remove the foil.

Pull the aluminum up slowly, pulling it from different points around the top while keeping the wool in position. Once you've pulled it out completely, lightly press the wool further down into the vent until it's about even with the vent or felt ring top. Then use scissors to trim the small strays which are sure to be hanging out. Blow on it while doing this as the cutoff will float around and want to go into the motor gap. This will be a little tricky since most scissors are magnetic. You'll have to work out the best way for you to hold the scissors and keep them up since the magnet will be pulling them down. I leave that to you.

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