Question regarding volume/distance calculations

Hello everyone, What a great resource this website is for someone like me. Thanks to everyone who works so hard on it! I believe I have an important question, but I have not been able to find an answer in the archives. When calculating the room modes in a room that contains a broadband wall absorber (such as Johns rear wall design), what is the effective distance between the walls? For example, if two such units were used on the front & rear walls of the control room, their total depth would equal 16"(or more). Do you take this depth into account when performing distance and volume calculations, or do you ignore their presence in the room for the calculations? Are the slot resonators treated any differently? Do you measure from the front of the slat or from the wall behind them for modal calculations? Thank-you very much for your time! Sincerely, Daniel

You've read enough to have the information, just have not yet absorbed it. If the absorber is absorbent at the modal frequency range, then there is no standing wave coming from the wall. If the absorber is not effective at that frequency, then use the distance to the partition htat the absorber is mounted on. Same criteria for volume calculations. That is if the material is not absorbent, then include the volume of the absorber. Have fun! Andre