Question about a statement made in Ethan Winer's acoustics article

[Geddyleewannabe]

I've been slowly making my way through Ethan's acoustics article. One recommendation he made has me confused. He states:

"Treating a "dropped" grid ceiling is even easier: Simply lay fluffy fiberglass batts on top of the grid, above the ceiling tiles."

If the ceiling tiles are between your room and the fiberglass, wouldn't the sound be reflected off of the ceiling tile and not be absorbed by the fiberglass?

I have a dropped ceiling in my basement, so I am very interested in this seemingly simple solution.

[Glenn Kuras]

You are right, but wrong at the same time.
If the ceiling tiles are solid (very ridged) then yes the mid and HF would reflect off the tiles, which would not be a good thing. But if the tiles are soft then it should help absorb HF.
We just did a room here in Atlanta and the person had very ridged tiles in the grids. All it took was talking into them to find that all of the HF was just reflecting off of them. We replaced the ceiling tiles with our GIK 242 panels and now it sounds great. So it depends on the tiles you have. To test them, stand about 2 feet from them and talk into the tile. If you can hear it coming back on you then you may want to rethink changing them. .

Glenn

[john caldwell]

But it it not also Ethan's point that generic fibergalss tiles in a suspended ceiling act as a low-pass filter? So while the tiles may absorb some HF, LF pass right through the tile to the reflective boundary above the tiles (poured concrete floor of room above, etc.), and then reflect right back through the tile into the control room. Ethan is simply recommending additional material above the tile to increase the LF absorption of the tile-fiberglass batts combination.

As Glenn suggests, if the tile are reflective (imagine a poured concrete ceiling instead of tiles), the fiberglass you place above that ceiling make no acoustic difference whatsoever, because no energy ever gets to the compartment which contains your fiberglass.

John-

[max cooper]

Whatever the principle, acoustic drop ceilings can make for a pretty ok sounding room. Usually on the dead side, but more workable than other materials I can think of.

[NathanEldred]

I believe it acts as a huge bass trap. The ceiling tiles don't seem to be extremely reflective either, just moderately so IME. Where it 'counts' just put some 703 filled panels for HF absorbtion and all is well.

[Glenn Kuras]

Originally Posted by NathanEldred

I believe it acts as a huge bass trap. The ceiling tiles don't seem to be extremely reflective either, just moderately so IME. Where it 'counts' just put some 703 filled panels for HF absorbtion and all is well.

If you mean put the 703 in the first reflections (Where it couts) then yes I would agree 100% on that.

Glenn

[max cooper]

Originally Posted by NathanEldred

I believe it acts as a huge bass trap. The ceiling tiles don't seem to be extremely reflective either, just moderately so IME. Where it 'counts' just put some 703 filled panels for HF absorbtion and all is well.

I had a studio share where the guys had done basically what Nathan mentions above.

One day we pulled out every sixth panel and the room suddenly sounded much better.

[Yiannis]

If the ceiling tiles are solid (very ridged) then yes the mid and HF would reflect off the tiles, which would not be a good thing. But if the tiles are soft then it should help absorb HF.

Glenn, it will also not allow bass frequences to be absorbed,right?

[NathanEldred]

Originally Posted by myfipie

If you mean put the 703 in the first reflections (Where it couts) then yes I would agree 100% on that.

Glenn

That's what I meant. On the ceiling too above the mix position, especially if the drop ceiling tile is extremely rigid. If it's the softer type, I'd still do it because it's not going to hurt anything.

[nathanvacha]

There are ceiling tiles that are made out of rigid fiberglass with a covering on the bottom side that are also the same 2'x4' size as the panels that everyone buys. The grids are 2'x2' or 2'x4' so if you have a drop-tile ceiling, you can wrap 703 panels in cloth and simply drop them into the grid. There are also diffusive panels that are made to drop in and you could add a few flat (or textured) wood panels.

If you already have the ceiling grid, that's one of the easiest ways to help control a home studio room. You probably don't want a dead floor though... but if you have a concrete slab in there with maybe something thin covering it... making your whole ceiling a bass trap isn't going to hurt.

or get some of the frk and alternate that around.

[Ethan Winer]

John,

> So while the tiles may absorb some HF, LF pass right through the tile to the reflective boundary above the tiles (poured concrete floor of room above, etc.), and then reflect right back through the tile into the control room. Ethan is simply recommending additional material above the tile to increase the LF absorption of the tile-fiberglass batts combination. <

Exactly.

Also, some tiles absorb mids and highs better than others. Even "good" tiles based on thick rigid fiberglass often have a thin plastic facing that is too reflective for use at first reflection points.

--Ethan