It is too bad that whether adhesives were used or not is unknown.emgcr wrote:Ah, many thanks. The reason I asked to see both sides is because we have an ongoing and unsolved mystery regarding some of these (later ?) diaphragms which have an extra section with annular rings on the reverse side. If you would like to look at the following thread you can see what I am talking about (scroll down on page 3):
viewtopic.php?f=11&t=33157&hilit=Meltrope&start=20
So, the diaphragm with the added section therefore has four parts---one large and one small with annular rings and one "spider" or "dished washer" on either side. They were pressed and then riveted together. To date, nobody has quite been able to explain why they did this or what the effects might be. Additionally, it is unknown whether or not any form of glue or anti-rattle material was interposed. From investigations to date it would appear that they were just pressed and riveted---job done !
Looking at the photos, yours does not seem to be in this category and should, therefore, only have three parts.
However, if these still sound nice without any, it shouldn't matter anyway!