Hello,
Thank you for your responses. I want to be clear: I'm not saying that JBL speakers do ring. They use an interferometer to design their boxes, so if they were ringing, they would detect and correct it.
My question is really genuine:
do they use "dampened braces", or a special glue that adds damping to the construction? The
KEF paper shows that it is very effective.
MDF do ring, so a good box design seem mandatory, and JBL knows how to do that.
The reason why I'm asking this is because I carefully constructed a box following the JBL M2 plans precisely. The result that I get is that the panels do exibit some unwanted resonances that create a 'discomfort' while listening to music. If I put one ear directly on the panels I can clearly hear the resonnances (especialy on the top and on the rear panels).
So I wonder what does JBL that I don't. After having read the KEF paper, I think it could be the glue. I used wood glue, maybe they don't...