few q's about corner absorbers

i'm really determined to make DIY wall units by Mr. John Sayers n have few newbie q's about corner absorbers. 1) what material should i use to make bevelled ? 2) what thickness should the insulators be (ideal thickness for best lo absortion) n how should i place them inside (should i glue it to the MDF's or just stuff them inside the absorber) ? 3) does corner slot resonators work best when it's ceiling height ? can i just make 2 which adds up to ceiling height n put one on top of the other. if so can i still expect the same performance ? 4) do i just glue the cloth to the bevelled ? also can i glue the cloth on the outer side of the slats (for better appearance) ? 5) i want my corner absorbers to be portable. do i just use 1" MDF's to seal the top n bottom of the absorbers ? 6) do i glue the slats onto the side MDF's or to the clothes ? 7) n finally, what's the best adhesive to stick the MDF's, slots, etc together ? i know some of the questions r stupid, sorry :) thanks for sharing all this info w/us. i think it's awsome !!

) what material should i use to make bevelled ?

it's just normal pine 2" x 1" - one edge is bevelled to take the slats evenly.

2) what thickness should the insulators be (ideal thickness for best lo absortion) n how should i place them inside (should i glue it to the MDF's or just stuff them inside the absorber) ?

just stuff it inside. It's a good way to use up all your insulation off-cuts.

3) does corner slot resonators work best when it's ceiling height ? can i just make 2 which adds up to ceiling height n put one on top of the other. if so can i still expect the same performance ?

yes - you can make two and stack them - not a problem.

5) i want my corner absorbers to be portable. do i just use 1" MDF's to seal the top n bottom of the absorbers ?

yes - that's fine.

6) do i glue the slats onto the side MDF's or to the clothes ?

the slats are nailed to the bevelled strips down the side. You place the cloth on first and then put the slats over the top of the cloth.

7) n finally, what's the best adhesive to stick the MDF's, slots, etc together ?

standard wood glue for the MDF and the slats are nailed. cheers JOhn

thank-you John :) so the trim has to be glued on the last , right ? also can i put cloth on the outer side of the slats ?

also can i put cloth on the outer side of the slats ?

yes but why?? the bright timber and the slots create diffusion - the cloth will soften the extreme high end defeating the purpose. cheers john

ok i understand, thank-you :wink:

would these corner units still work effectivly if they were..say 4 foot high instead of flor to ceiling?

Yes John - height is not part of the formula but it is half as effective as say an 8' version. cheers john

Thanks for the great info. A couple more questions if you don't mind. The dimensions in the drawing are 22 x 24 inches. Is this just so that it isn't a 45% angle? Are bigger resonators better? When MDF is specified for the back of the units, can any cheap plywood be substituted? How air tight must the seal at the top/back of the triangle be? How is the cloth suspended? Do you staple it to the bevelled strips? Thanks, jim

I have another question about absorbers... Reading old posts, i found advice to not build corner absorbers for small control rooms (like mine!), let´s say 2,9mts x 2,4mts., because with just some rigid fiberglass placed on corners, it would be just fine. I know that my room is small, but i would like to have a good sounding room... so, should i build corner absorbers or not??? Thanks!

Either one will work to absorb low frequencies. Just putting rigid fiberglass across the corners will absorb full-range sound, down to a fairly low freq, but as a side effect will deaden the room overall. The absorbers John Sayers designed (that you're talking about here) are helmholz resonators, which will absorb lower freq sound, but have a narrower piece of the sound spectrum that they'll work on (they can actually be tuned) and because of the wood slats on the face will reflect mid and high freq sound, thus brightening your room. In your case, with a smaller room, you'd most likely be better served by just using rigid fiberglass across the corners. When you don't have much wall space to treat the room sound, use it to cover as much of the spectrum as you can. Now, if you're using one of John Sayers' rear-wall absorbers as well, then I'd recommend the slat-type corner unit. And to be honest, with a small room, the next recommendation would be to put a lot of absorption on the back wall anyway... Hope this helps!

Thank dymaxian (again) here´s the design i came up... but i dont know if a room that small deserves all the work and the money... I really appreciate your opinion...

John Sayers wrote:

Yes John - height is not part of the formula but it is half as effective as say an 8' version. cheers john

John, I was wonderign what freq. range your corner absorbers effectivly cover?