Ceiling Clouds (For Tom treitz3 and others)

[sbnx]

Hello all,

I met Tom at LSAF this year. (I was the OCD person with the blanket stuck to the door with magnets to suppress the first reflection point.). We had a discussion about ceiling clouds and their effectiveness. He asked how I knew what they did and I didn't have a good answer since I never measured my room without them in place. When I built my room I suspended 5/8" plywood angled panels per plan from Rives much like what many of you have seen in Mike L's room. I could see the general idea of having multiple ceiling heights spreads out peaks and valleys in the frequency response. However, giving this more thought I realized that this was insufficient and better would be absorptive panels hanging from the ceiling. I got six 5'X2' 244 panels with scatter plates from GIK and hung them this last weekend. (Thanks to Scott for the help hanging them). The measurement data is pretty compelling and the listening also bears out the BIG improvement in sonics. I pasted the data below for your perusal.

In the Wavelet plots you can see the weird phase "blips" at 400Hz and 1.5kHz. In the post data these are gone. You can also see the "tree" is much skinnier. The "branches" don't go out as far which means less resonance. In the filtered impulse response it is clear that the ringing at 250Hz is greatly reduced. It is also reduced at other frequency filters. I just give 250 Hz as an example.

For those of you who have not explored ceiling clouds I highly encourage it. The ceiling is free real estate. And if done properly can look good to your non-audiophile spouse.

Thanks,
Todd

 

[Ron Resnick]

Very interesting, Todd. Thank you for posting about this.

How is your floor treated? Do you have carpet and padding under the carpet on your floor?

I ask because I wonder how different the results would be with a wood floor versus a carpet and carpet pad on the floor.

 

[sbnx]

Hello Ron,

My floor is Hardwood over a concrete slab foundation. I have a large, thick wool rug between my listening seat and the speakers. Carpet and padding is not going to do much for mid and low frequencies. 10kHz and above will be damped. I have a paper on the acoustic properties of carpets if you want a copy. I pasted a graph showing the absorption of 1" high density fiberglass with no gap between it and the floor which would be more absorptive than carpet at lower frequencies.

Thanks,
Todd

 

[Ron Resnick]

Interesting, thank you. Do you think the ceiling cloud achieves greater efficacy when the floor also is made less reflective with carpet of some type?

 

[heihei]

Can you share photos?

 

[Bobvin]

The cloud topic is interesting... and like everything wrt room acoustics is likely easy to f_up. When I was having my room acoustically designed, I had mentioned I'd like to have some kind of cloud, and was thinking of something visually interesting but not as crazy as the SMT bubbles. Sadly, I never did get a detailed explanation of this particular aspect of the room design--which ended up being, if I remember, a particular model of hard fiberglass insulation that was suspended from the ceiling (after a frame had been constructed and then wrapped in fabric.) The "cloud" is about 10' x 12' and really isn't noticeable visually. Since it was part of the overall acoustic plan there is no way to determine what the individual effect of the cloud is because it can't be removed and reinstalled to take individual measurements. Bear in mind this is hung from the ceiling, so there is an gap between it and the sheetrock, and of course behind the sheetrock is a layer of heavy mass loaded vinyl and "blue jeans" insulation. It is obvious as you walk around my room there is a difference in how voices sound under the cloud vs. not -- certainly more damped under the cloud but not in a "just lost all the liveliness' way.

So, while the "cloud" I ended up with is less interesting in terms of diffusion/absorbtion, or treatment of any particular frequency anomoly, and less visually interesting, the room as a whole sounds amazing. It seems to me a cloud has possibility to have a big impact, so should be part of an integrated, engineered solution.

 

[MTB Vince]

A ceiling cloud forms a significant portion of the room treatment strategy in our dedicated music and theater room as well. The 4'x10' frame is 5" deep and open top and bottom. Broadband absorption is courtesy of the ten 2'x4' sheets of 2" rigid Manson OC703 fiberglass contained in it stacked 2 sheets deep. It is wrapped in Guilford of Maine AT fabric. The frame hangs from threaded screw eyes as close to the ceiling as we could manage. It is positioned to intercept the first reflection from the front speaker trio.

 

[sbnx]

Hard to say the effect of clouds with and without carpet in the room as one would have to install the clouds -- measure. Then install the carpet and measure again. Carpet is good for helping with echo and helping with the HF floor reflection from the speakers but isn't doing much of anything with the low to mid frequencies. If a room is measured with and without carpet the most obvious place to look to see the effect is the RT60 number. A carpeted room will have a lower RT60 meaning the room will sound more "dead". More dead is not necessarily a bad thing. If you have an RT60 above 0.5 then it is too lively. Most normal living spaces with carpet and furniture have an RT60 in this range.

It will lower the absorption frequency if there is an air gap between the panel and the ceiling so suspending them (as opposed to flush mounting them to the ceiling) is a good thing to do. I have mine suspended and angled. Angling them does two things. -- It spreads out the absorption peak so there are no "gaps" in the absorption frequency response. And if a scatter plate is used on the front then it acts like a sloped ceiling in that it pushes the HF reflections over your head to the back wall. I put a picture of my ceiling with the hard clouds below for reference. I only changed the 6 in recesses in the back of the room (closest to me in the pic).

I posted the impulse response and wavlet data above as I thought it was pretty easy to see the impact of the change. But I was very surprised to see an improvement in the waterfall plot from 45-55 Hz after I installed the absorptive clouds. Pics below for reference. Honestly, I should not have been too surprised since the first height mode of my room is 48Hz. That is the necessity of clouds IMHO. How else can we treat the vertical room mode? Nobody wants to put a bunch of bass absorbers flat on the floor so hanging them from the ceiling is the way to go. Just a note on the frequency response below 40 Hz. This trough is due to SBIR from the speaker distance from the front wall. I am not worried about this as I fill in with subs for the bottom octave.

As an extension of the clouds idea, building a hollow soffit around the perimeter of your room and filling it with fluffy insulation is also a huge thing for helping with LF absorption. (Hollow means that at least one side has to be fabric covered so air can go in and out.) You can see this in the pic of my ceiling. The soffit is 3'X3' on the side walls and 3'X4' in the front and back. The side is covered with GoM fabric. I posted a picture of the absorption coefficient of a 2 foot deep cavity filled with fiberglass batts. It is still absorbing 40% at 20Hz, which is awesome.

Going with Bobvin's comment regarding messing up the room acoustics. I have noticed that as you start out big improvements happen quickly and don't mess with anything. You just get improvement in sound. We all know these -- bass traps in the corners, dealing with first reflection points etc. But once you make it a little farther down the path there seems to be a push/pull effect. Making changes to room treatments usually will result in the need for either a listening position change or small tweaks to the speaker positioning. I thought for sure that going from a hard cloud to an absorptive cloud I would have to adjust me seating location, but I did not. I will have to adjust my speaker position (toe-in and rake) just a little.

Thanks,
Todd

 

[Al M.]

My ceiling diffusers are shown and their effect described here:

https://www.whatsbestforum.com/threads/my-monitor-subwoofer-system.25101/page-9#post-554228

I chose ASC custom diffusing panels rather than full-out absorbers. I agree, BIG improvement in sonics.

 

[spiritofmusic]

Al, just seen the photos. Why did you group so many? Surely four would have done to cover reflection pts L and R?

 

[Al M.]

Al, just seen the photos. Why did you group so many? Surely four would have done to cover reflection pts L and R?

Because they work better. Ten work better than 6. If you compare the dimensions described by the other posters above, you will see that they are also generous in covering surface.

 

[spiritofmusic]

Al, then why stick at this number, and not more? It's a genuine Q, since I'm thinking of doing the same on my cathedral ceiling eaves. I really thought it would be sufficient to stick w four ceiling panels, as per side walls reflection points.

 

[spiritofmusic]

Al, just read the whole explanation in yr system thread. You have two sitting positions, and need reasonable spread.

 

[Al M.]

Al, just read the whole explanation in yr system thread. You have two sitting positions, and need reasonable spread.

Yes, and on the other hand I did not want to over dampen the room.

 

[spiritofmusic]

Sure Al. The UK dealer of a specialist room acoustics treatments system is suggesting 2x 4' lengths of clg panel absorbers/diffusors at 2' centres, from just behind listening chair, to front wall, in my room a grand total of 20-24 panels. I suspect like yr experience, that would be overkill.

 

[Al M.]

Sure Al. The UK dealer of a specialist room acoustics treatments system is suggesting 2x 4' lengths of clg panel absorbers/diffusors at 2' centres, from just behind listening chair, to front wall, in my room a grand total of 20-24 panels. I suspect like yr experience, that would be overkill.

Probably, yes.

 

[spiritofmusic]

Al, assuming you only had the one fixed seating position, you would have used less than the ten panels you ended up with? How many in total do you think? I remain unsure how far to go w all this. Just trial and error?

 

[sbnx]

I read Al’s post. Very nice. I agree with all of his comments and specifically that high frequency hash gets blamed on gear like dac’s far too often. We are in a great amount of control over what we heat in how we deal with the room interaction — listening position, acoustic treatment and speaker positioning.

I consider what Al did as treating the first reflection point. Just on the ceiling rather than a sidewall. Nothing wrong with that. The panels will absorb down to about 1000Hz before the absoption falls off rapidly. Definitely enough to take the ‘zing’ out of the sound. But they are not doing much for low freq control. To my way of thinking a “cloud” hangs down some and absorbs down to at least 100 Hz or even lower. The same panels if hung down six inches would absorb down to 200 Hz before falling off. The penalty of HF absoption (which gives the dead sound) has already been paid with them mounted to the ceiling. As long as there is sufficient ceiling height then IMHO leaving a space behind the panel is better.

The bad thing with acoustic treatment is there is no try before you buy. You have to buy 10 panels and if you decide 8 is enough then what to do with the remainder? Although i would contend that 99% of people would not take treatment out after they hear the improvements it brings.

Thanks,
Todd

 

[Al M.]

I read Al’s post. Very nice. I agree with all of his comments and specifically that high frequency hash gets blamed on gear like dac’s far too often. We are in a great amount of control over what we heat in how we deal with the room interaction — listening position, acoustic treatment and speaker positioning.

I consider what Al did as treating the first reflection point.

Thanks, Todd, and yes to the last point.

Just on the ceiling rather than a sidewall. Nothing wrong with that. The panels will absorb down to about 1000Hz before the absoption falls off rapidly. Definitely enough to take the ‘zing’ out of the sound.

They mainly diffuse, even though there is also some absorption.

But they are not doing much for low freq control. To my way of thinking a “cloud” hangs down some and absorbs down to at least 100 Hz or even lower. The same panels if hung down six inches would absorb down to 200 Hz before falling off. The penalty of HF absoption (which gives the dead sound) has already been paid with them mounted to the ceiling. As long as there is sufficient ceiling height then IMHO leaving a space behind the panel is better.

This approach may work, but I never worried about treating bass with ceiling treatment. Bass in my room is not a problem at all; I did think of purchasing ASC IsoThermal tube traps for the back of the room (to catch the "back wave" of the low bass, as ASC says), but while this might be icing on the cake, currently I don't see the need for it.

The bad thing with acoustic treatment is there is no try before you buy. You have to buy 10 panels and if you decide 8 is enough then what to do with the remainder? Although i would contend that 99% of people would not take treatment out after they hear the improvements it brings.

Agreed.

 

[Al M.]

Al, assuming you only had the one fixed seating position, you would have used less than the ten panels you ended up with? How many in total do you think? I remain unsure how far to go w all this. Just trial and error?

I would have used eight panels, it's in my write-up.

I'm glad that I went for ten, I think it is of general benefit in my room, even if you use just one seating position. It does add some more absorption though.

For your room you should also take into account that it is much larger, thus probably can take more absorption from ceiling panels without too much penalty. Ceiling height is also a consideration.