Problems with Drop Ceiling

[burke111]

Hello,

I moved into a new studio space with drop ceilings and concrete walls. I was fully expecting to have to add absorbers but when running pink noise I am seeing a dip around 4kHz. I am suspecting it is the drop ceiling.

Is there a reflector tile I can put in the drop ceiling? I can't really take the drop ceiling out although I would like to.

Anyone faced this?

Thank you.

[jdg]

RPG skylines are drop in fit for 2x2 ceiling grids

[jwl]

I don't think adding reflectors will help you. Most standard ceiling tiles are reflective at higher frequencies. I'd remove some of the ceiling tiles and add good absorption.

I'm not a fan of diffusion in a ceiling, unless the ceilings are very tall (and even then I still prefer absorption on ceilings).

[Glenn Kuras]

Originally Posted by jwl

I don't think adding reflectors will help you. Most standard ceiling tiles are reflective at higher frequencies. I'd remove some of the ceiling tiles and add good absorption.

I'm not a fan of diffusion in a ceiling, unless the ceilings are very tall (and even then I still prefer absorption on ceilings).

Every room is going to be a bit different in its needs, but yes most of the time absorption is better for the ceiling reflection points. Diffusion though will work pretty darn well a lot of times in the back 1/3rd of the room on the ceiling.

Glenn

[Ethan Winer]

Originally Posted by burke111

I am seeing a dip around 4kHz.

That could be the response of your speakers, or it could be comb filtering from nearby reflections. Try moving the microphone one foot in any direction and see if the frequency changes. If it does not change, it's your speakers. A loudspeaker dip in the "harshness" range around 2 to 4 KHz is common, and some manufacturers do that intentionally to make their speakers sound smoother. I don't agree with that! But it's common anyway.

--Ethan

[burke111]

Thanks for the advice.

It certainly isn't my speakers. I know them very well and have been using that model(NS-10s) for twenty years.

I did move the calibration mic around and saw a similiar response of a dip in the 4kHz region.

Can you give me a little more information about the diffusers? Something I can install in the drop ceiling?

Why would absobers work if I am already seeing a reduction of 4kHz? Wouldn't that just soak up more?

Thanks again. I appreciate it.

Best,

[Glenn Kuras]

Wouldn't that just soak up more?

Nope absorption will help it.

Glenn

[burke111]

Hello,

In the interest in learning...how can more absorbtion give me more high freq?

It soaks up waves that are cancelling HF and stops them thus allowing more HF?????

Wow acoustics are complicated!

[jdg]

it would just even out the other peeks in the high freqs first, so your peaks around your 4k dip are more even.

realtraps.com sells drop in absorbers for ceiling grids too.

im a huge fan of trapped ceilings after i did mine. the whole room is so even now.

[jwl]

burke11,

The phenomenon that produces these counterintuitive dips and peaks is called "comb filtering." When a reflected sound bounces around the room, it interferes with other sound waves that are just now leaving the speaker (or other reflections). These reflections are all out-of-phase with one another, and comb-filtering is the result. Some frequencies show peaks, others show nulls, such as yours at 4k.

By using absorption, you reduce the number and intensity of waves bouncing around the room, which reduces comb filtering, which reduces the nulls (and peaks) you are experiencing.

For more on this idea, see this article: RealTraps - Acoustics Fact & Fiction

Or watch the "Comb Filtering" video, about halfway down our videos page: RealTraps - Videos

Also, JDG is referring to our ceiling tiles: RealTraps - Ceiling Tiles