QuietCoat

I successfully used this to coat the outside surface of Altec 511B horns to stop the infamous ringing. After a few coats, the bell-like ringing was reduced to a dull thud. In use, the difference before and after is very noticeable, especially on music that would tend to excite the ringing, but there's an improvement in detail and clarity on almost everything.It goes on like paint and dries to the touch in a few hours, although it takes a few days for the full damping effect. Unlike some of the spray-on damping compounds this is water-based and doesn't have an obnoxious smell, so it can be applied indoors without worrying about fumes. Before it dries it cleans up with water, and your brushes, rollers etc. can be cleaned in water. I used an ordinary paint brush to apply it, although the manufacturer claims it's also sprayable. Despite being water based it sticks OK to painted surfaces, but may not adhere to bare metal without priming. I applied a primer coat of Quiet Kote (the black rubbery stuff in the spray can) to places where I was worried about adhesion, and when that had thoroughly dried painted the QuietCoat over it.For best effect you'll want to apply several coats, repainting once the last coat has dried to the touch. It sticks best to itself, so the most expedient way to apply it is to paint a thin layer on first and let that dry, then paint on thicker layers.For the product I received, the color after drying is a medium grey.