Any acceptable acoustic tiles for drop ceiling?

[JWZ]

I'm in process of finishing a mixing room with 18 inches thick of R30 pink fiberglass between ceiling joists. Room details noted below.

I wish to finish with a drop ceiling tile that will not compromise absorption potential of R30 ceiling treatment.

Are drop ceiling tiles with NRC rating .55 acceptable for this purpose?

More specifically:
1. Is NRC 0.55 acceptable above mix position where reflection free zone is critical? If not, what (if any) tile is acceptable here?

2. Is NRC 0.55 ok for remaining zones of room where 18 inch R30 ceiling treatment is intended as bass trapping?

My last resort is to use a fabric ceiling as recommend in other threads.

Thanks in advance!

Room Details (plan):
-7.25' x 10' by 16.5' room dimensions (basement)
-superchunks in wall to wall corners (rockwool 6 pounds per cubic foot)
-15 panels 4' x 2', 4 to 6 inch thick (703 rigid fiberglass)
- drop ceiling system attaches directly to joist only consuming 1 inch headroom

[Ethan Winer]

Since this is a DIY project, make your own tiles from 1- or 2-inch thick 703 or 705 for the ceiling reflection points. You can use almost any standard type of ceiling tile everywhere else. Bass waves go right through ceiling tiles.

--Ethan

[ejsongs]

i'd listen to ethan on this.

i put 18" of r30 in my drop ceiling and still had to build a crap load of bass traps and buy stuff. if i had to do it all over i'd put a layer of 703 up there and call it a day. not sure if the the r 30 was that effective.

ej

[Glenn Kuras]

Ceiling tiles will work as long as it is OC, but when placing them in the early reflection points (What Are Early Reflection Points. SPOTLIGHT:Bob Ebeling - Revolution Studio) it is best to remove any kind of facing on them.

[JWZ]

Thanks for feedback.

For reflection zone above mix position I will make custom ceiling tile out of fabric. To be cautious, I will also put 1 inch 703 between fabric tile and R30. Hence, 18" R30 and 1" 703 above mix position finished with reflection free fabric.

[avare]

Originally Posted by JWZ

To be cautious, I will also put 1 inch 703 between fabric tile and R30. Hence, 18" R30 and 1" 703 above mix position finished with reflection free fabric.

There is no need and actually a slight disadvantage to the 703 in your application. Just use the R30.

Andre

[sailor]

Originally Posted by avare

There is no need and actually a slight disadvantage to the 703 in your application. Just use the R30.

Andre

Can you elaborate? I'm planning to do something similar -- an array of clouds overhead. First idea was 1" 703 backed by R30 or R11. Some suggested, as you do, that 703 is perhaps unnecessary....but their recommendation was that basic ceiling tiles in front of the insulation would be sufficient for a modest-budget installation. What is it about 703 or any semi-rigid face that you feel would be detrimental?

[avare]

Originally Posted by sailor

Can you elaborate? I'm planning to do something similar -- an array of clouds overhead. First idea was 1" 703 backed by R30 or R11. Some suggested, as you do, that 703 is perhaps unnecessary....but their recommendation was that basic ceiling tiles in front of the insulation would be sufficient for a modest-budget installation. What is it about 703 or any semi-rigid face that you feel would be detrimental?

It is an application specific, and to a lesser extent 703 deficiency point. Working the second one first, 703 has an absorption deficency in the upper midrange.

First piont second, 18" of "regular" insulation is flat in absorption down to below 50 Hz in diffuse field. The layer of 703 is doing nothing acoustically and adding to cost.

Andre