Slot absorber

Hello forum members,... i want to build some slat/slot absober from the structural drawing from Johns index site. Perhaps you could help me with some questions about it... 1)Is it possible to build them flat to a wall; not as shown there? 2)Is it necessarily to have a plywood backwool or can i use the stone wall if i seal it with silikon for an airtight space? 3)Can i alter the height or the widht of the entire dimensions? I would like to build them from the floor to the ceiling(3,5m) thx a lot for your help... :)

i'll take a crack at it. 1) if you mean parallel to the wall, yes. . .it all depends on the frequency (range) you are trying to absorb. in a sticky on top of this forum is a slot resonator calculator. that will help you understand a lot more. 2)it can be plywood or MDF or anything else that will make it airtight. i'm not sure about stone. my guess would be to put some sort of sealer over it first ie: paint or drylok or something. and you'd really have to work at sealing the sides. you'd have to get pretty crazy with a jigsaw to get the sides of it to match up with the stones. and still caulk the crap out of it. 3)refer to answer 1 about the calculator. you can go as high or wide as you want/need

Hello dynamike thx a lot for your help. I found a calculator from the sae side. Is that the one you mentioned? In this calculator there isn´t an option for the entire dimensions of the slat absorber. I mean for example the lenght of the slats? How would it affect the frequency if i´ll build it with longer or shorter slats and what about the height of the entire absorber....is it different if i build it with 20 or perhaps 50 slats and build it 2m or 3m height? I thought the air volume in the absorber is changed... thx... kind regards

if i remember correctly the calculator on the sae site is wrong. there is a ton of info here on these things, since just about everyone uses them. find the sticky about the calc too, make sure you use the right one.

the length of the slats would in some ways be related to the amount of open space in the overall absorber. so depth and width of the slots, the percentages of slat-to-slot, cavity depth, insulation etc. all play a role. if you do a search on google for Chris Whealy's Porous Absorber calculator, its a very nice tool. also the Excel Helmholtz calculator on this site has the corrected formula. for some reason the SAE site just isn't getting updated lately :)

gullfo wrote:

the length of the slats would in some ways be related to the amount of open space in the overall absorber. so depth and width of the slots, the percentages of slat-to-slot, cavity depth, insulation etc. all play a role. if you do a search on google for Chris Whealy's Porous Absorber calculator, its a very nice tool. also the Excel Helmholtz calculator on this site has the corrected formula. for some reason the SAE site just isn't getting updated lately :)

Hello firneds I´ve reading the John´s DIY Wall Units, Isaw the images, I´v have some doubts. The page says 50x20 mm ,75x20 mm,&100x20mm slats. alternating with gaps from 6mm-12mm. A) My q is: must the gaps just be 6mm and 12mm,? or .... B) should I alterntae 6mm , 7mm, 8mm etc to 12mm gaps?. Sorry may be is to obvious. C) If question A is the correct, then I guess I should construct the device this way. From ceiling to floor: 1-) 50x20 mm slats 2-) 6m gaps 3) ,75x20 mm,slats 4) 12mlm gaps 5) 100x20mm slats. 6) 6m gaps 7) 50x20 mm slats 8) 12mlm gaps 9) ,75x20 mm,slats 10) 6m gaps 11) 100x20mm slats. 12) 12mlm gaps etc..etc...that`s right? The DIY Wall Units page says I've kept the box to a straight 8" box but you may vary width at the left end and follow the slat shape if preferred. D)does it mean if I built a widther slat resonator supporting the slat size an gaps relations it will also absort from 150 to 500 hz ? E) I saw slots resonator mounted over plywood, Could it be mounted over drywall? That´s all. Thanks and sorry about my english I speak spanish.