strong peak @400hz

Hellooooo :D Maybe someone of you could help me little?!.... I´ve got to narrow peaks coexistence @400Hz making together a big peak of 6 db on the analyzer with 1/6 resolution; 5db with 1/3 octave resolution. I tried almost everything to find out what could be the cause for this reflection. ( i moved some porous absorver around the speaker, the mic and some surfaces but at the peak nothing really changes.) I´v calculated for the 400hz peak a wavelenght of 86cm. (or a latency of 2,58ms) If i ad that distance with the way between me and the speaker (1,10m) can i take it that the reflection path must have a lenght of 196cm to reach the mic? Or are there any other possible solutions or ways to calculate? The speakers are placed on the mixing desk. thanks a million;)

Could it be, that insulation is causing this reflection? The only surface, that fits to the wavelenght is the ceiling cloud...

There is an announcement at the top of the forum about what to do to assure getting as many responses as possible. The announcement leads to this post. Actually, several people, who are experts on this forum, will not reply if you do not do what is written the post. Although some points in the referenced post are significant to you, several still are. If you read it, you can figure out pretty well which ones apply to you. Obviously budget, music type, nieghbours are some that do not. Andre

it would be helpful to know much more detail about the room near these speakers as well as the console etc. to determine if there are potentially other factors at play...