Quote Originally Posted by Jonas@Psychedelic View Post
I have built my cabinet from 15mm birch plywood according to the original plans.

Since you built yourself, you should have really used 19mm or 3/4 ply Minimum.As you can control every aspect of your build, a solid thick (Void Free) ply is preferable. 15 mm is only what 9/16" or 5/8" correct.They are too flimsy IMO, no matter how much you brace it, they will still resonate much more than a thicker ply.

But anyway diagonal bracing should be employed on all sides IMHO.Good Luck, and we all Love to see Pictures Here of peoples Altec projects (Builds) ! :2thumbsup: