Foam insert inside soft domes

[Swarky]

What is this for ? I am fitting new voice coils to the Audax tweeters on my Heybrook HB2s and was wondering about the best way to make or buy suitable stuff as the original was just a pile of dust when I opened them up. Also what kind of foam ?

 

[AllenB]

Most of the sound that goes behind the dome is not needed. Especially the tube behind the dome can cause problems. The foam should be open so the sound can pass through it, but fit firmly enough that it doesn't move.

 

[moray james]

I use stacked layers of (1/8") S.A.E. rated F-11 Acoustical Felt. Vary the disk diametres so the resulting profile is dome shaped. These eliminate the cavity resonance and they reduce reflected output off the poke piece. Acoustical felt is made from natural wool and will work better than any synthetic material. Best second choice is high density fiberglass third choice is cotton or kapoc fiber. Hope this is of interest. Best regards Moray James.