Ferrofluid tweeter

You should always fill the air gap with the recommended amount of ferrofluid.  Under-filling is a leading cause of poor performance in a driver.  Under-filling can actually cause problems related to overheating - the fluid will be stressed and thicken prematurely, leading to loss of signal clarity and shortening the usable life of the driver.  Good luck!  - Vanessa

When you clean out a tweeter you need to remove the voice coil and diaphragm assembly carefully, then remove the old ferrofluid using absorbent material.  Coffee filters work well because they don't have dust like paper towels can.  Use  strips of filter paper that you insert into the air gap and soak up the fluid.  Use enough so that when they start to come out sort of clean you know you have gotten most of it.  Then soak a strip in acetone or heptane and wipe the gap well.  Also use heptane or acetone to wipe down the coil itself to get the residue of the old fluid off.  Once this is done, allow it to air dry for a few minutes.  You can then put the new fluid in and re-insert the coil assembly (or put in the new one).  When properly filled, the fluid should bulge slightly over the top of the gap.  Under-filling is a common cause of poor performance in fluid filled speakers.  Hope this helps!    -Vanessa