Question: Placing the filling into a Helmholtz resonator

Hi, I built several broadband absorbers. The holes have 8mm diameter, 14mm from center to center, 25,6% of the panel are holes. The panel has 4mm thickness. I calculated a range from ca. 312 HZ to 1.5kHz cause of the increasing modul depth. My question: Should I place the basotect (or glaswool) right behind the frontpanel or should I mount it on the backpanel, so theres some space between the holes and the absorbing material? John has in his reference material some air gap in the slat-absorbers.

I may be wrong here, but as far as I know you should put the wool at the back of the box, or at least away from the front panel. IIRC, if the wool is up against the front panel, then it interferes with the motion of the air plugs in the holes, basically destroying the resonance characteristics. But like I say, I may be wrong about that. Hopefully one of the experts can comment. - Stuart -

Stuart is right :)

Thanks. I love this forum! and next time I am in Vitacura I will come over. promised!

Don't forget to add a fine black cloth backing to the front panel so when you look through the holes you don't see the insulation inside the cavity.

I have a question about this. I thought that with the slot absorbers, you would place the absorbent right up against the slats. Since both the perforated and the slot absorbers are working under the same principle, why would you place the absorbent differently? Thanks, Seamus