[youngho]

Howdy,

I've heard Ethan say several times that recording studios can use up to 3-foot-thick layers of fiberglass on the rear wall to help with bass trapping, although one article that's linked on his website seems to suggest that this may be undesirable. It mentions a ceiling "fiberglass cloud overhead," and Ethan also refers to the benefits of an absorbant ceiling here.

I assume that the studios just have the drywall in front of a 3-ft layer thick cavity stuffed with fiberglass?

How does one make a "fiberglass cloud" and suspend it from the ceiling? Clearly, a dropped ceiling would allow one to put fiberglass above the ceiling tiles, but wouldn't this result in absorption of only the low frequencies and reflection of mid- and high-frequencies?

Thanks!

Young-Ho

[Ethan Winer]

Young-Ho,

> one article that's linked on his website seems to suggest that this may be undesirable. <

Where does it say that? I just took a (quick) look at saw this, which is what I've always said:

Note that having bass traps in the four wall-wall corners as shown is the minimum we recommend. With bass trapping, the more you have, the flatter and tighter the low end will be.

[edit:]Wait a second, I realize now that my quote above is from the article I wrote with Wes Lachot who wrote the article you linked to. But still, where is it said or implied that you can have too much bass trapping?

> Ethan also refers to the benefits of an absorbant ceiling <

A ceiling cloud serves two purposes: 1) it absorbs first / early reflections off the ceiling, and 2) if it's thick enough it can also offer some bass trapping for the floor-ceiling mode.

> a dropped ceiling would allow one to put fiberglass above the ceiling tiles, but wouldn't this result in absorption of only the low frequencies and reflection of mid- and high-frequencies? <

It depends on the type of tiles you use! However, you are correct that the majority of commercial ceiling tiles are not absorbent enough at higher frequencies to use at the first reflection points.

--Ethan

[youngho]

Sorry about the delay. I was out of town.

Wes Lachot wrote:

"So, what's the solution? First, avoid locating deep bass traps just behind the couch position. [EW note: Wes is referring to fiberglass bass traps that are physically deep. Not wood panel bass traps meant to absorb "deep" bass frequencies.] They eat up valuable real estate, and they create the impression of missing bottom end for those in the back of the room."

and

"If the 19 foot-deep room has good modal dimensions and a moderate amount of bass trapping (a fiberglass cloud overhead and a maximum of 8 to 12 inches of fiberglass on the rear wall), the bass should sound pretty even at the back of the room..."

Although the article discusses control rooms, there are many situations where the listening position is placed relatively close to the rear wall, and I would have thought that several feet of fiberglass behind the listening position would have been beneficial in reducing rear wall boundary effects. I interpreted his statesments above to mean that Wes did not recommend a several-feet-thick layer of fiberglass at the back of the room.

From a private message that I got, it sounds like the phrase "fiberglass cloud" is meant to refer to a layer of fiberglass traps placed at a set distance from the ceiling. Reading the word "cloud," I had envisioned a large fluffy mass of fiberglass suspended from the ceiling and thought "WTF?"

Young-Ho

[Ethan Winer]

YH,

> Sorry about the delay. I was out of town. <

No probem because my Internet was out from Thursday until late Sunday. To say I was frantic is an understatement...

> Wes Lachot wrote: <

I disagree with Wes's conclusion and advice in that case. For all I know, Wes might also disagree today. We've both learned a lot over the past few years, and I think that article is pretty old. But I had nothing to do with that article (other than host it), so maybe you should email Wes from his site weslachot.com. If he answers you, let us here know what he said.

--Ethan