need some suggest (broadbandabsorber)

[pm2]

I would like to build a broadband absorber! 10" of 703 glassfiberboard in a wood framework (24"x48") with fabric-covering in the front.
The back/rear is closed with a wood-plate.

For a complete broadbandeffect it is important for me to have also strong absorb in the deep frequencies (30-80hz)!
So
1. How much is the best distance/space between the glassfiberboard and the back/rear wood plate for deep absorption as possible.
2. Is it better to choose the wood plate rigid and thick or is it better to choose a less rigid wood plate to create better values at deep absorption between 30-80 hz. Which diameter/thickness of the wood-plate do you suggest?

Thanks for answers

[knightfly]

pm2, first I'd like you to edit your profile to include your location, as asked in this link

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=4062

For a complete broadbandeffect it is important for me to have also strong absorb in the deep frequencies (30-80hz)!
So
1. How much is the best distance/space between the glassfiberboard and the back/rear wood plate for deep absorption as possible.

This type absorber is velocity actuated, and peaks at 1/4 wavelength for normal incidence; this means that to be highly effective at 30 hZ, the solid barrier BEHIND the absorbent would need to be just over 9 FEET away (1/4 wavelength of 30 hZ) - this is why, for lower than about 100-120 hZ, it's better to use resonant or helmholtz traps.

2. Is it better to choose the wood plate rigid and thick or is it better to choose a less rigid wood plate to create better values at deep absorption between 30-80 hz. Which diameter/thickness of the wood-plate do you suggest?

For reasons stated in (1), it's better to NOT have a back on the absorber at all if you want that low frequency a response. If you really need that much absorption at that low a frequency, you should be designing panel traps for specific locations within the room where they will have the greatest effect.

Because of the nature of your questions, I think we need a LOT more information before we can suggest anything; this type of treatment is NOT a "hit or miss" deal, you need very specific room measurements and floor plan before it's possible to come up with a workable plan.

If you answer all the questions in the above link and post some sort of sketch, we'll be more able to give you good advice... Steve

[pm2]

First thank you for answer knightfly,

i need the absorber as a free standing an mobile absorber
to prevent lateral reflections.
Its for a friend who developed Loudspeakers in different rooms.

When i understand you right,
1. i can not replace a stone wall with
a thick stable wood-plate on the rear of the absorber? and
2. more distance from glasswoll to the wall (maybe 2inch instead of 8") is better for deep absorption at for example 80Hz?

[knightfly]

I'm not sure I understand just what you want - can you possibly draw a basic sketch and post it, showing where speakers, absorbers, walls are located?

If you're on a Windows machine, the Paint program will do enough for this... Steve