[andycsb]

Hi Everyone,

Thinking of treating ceiling reflection points with either absorptive or diffusive (clone styrofoam skyline) panels. Ceiling is 10 feet in height (thought it was 9 feet till last night ). Which would be better....absorptive or diffusive? Will there be any benefits since ceiling is on the high side? Have area rug on the floor.

Thanks!

[Freemand]

In theory it seems both absorption and diffusion would be a good thing cause the ceiling plays a big role as do the other walls.

In Minnesota I had a home theater with skylines and proved very successful. Since moving south I have used a different alternative for the ceiling with excellent results. I found some 1 inch thick 2 feet by 2 feet hvac filters on the cheap for just a buck a pop. They have made big improvements at its cost. They are pleated with some type of fabric so they are probably doing both absorption and diffusion.

I was very fortunate with them cause they are all white and have a totally clean look to them except writing on one side of them, however you install them next to one another which covers it up.

I did not like the look of any of the hvac filters at the big box stores cause they had all kinds of writing and such and would not look as good in the room. Plus they were all thinner.

looking online you could probably find some all white clean 1 inch thick filters.

If anyone is interested I can look at the model name and pass it by.

[paul79]

I think first reflections of any kind are damaging. If the ceiling was say, 12' or so, all diffusion might be a really great thing.

My way of thinking, both mine and your scenario, one should address it same as the side walls. Absorb the first reflection points for sure, then diffuse above your head maybe? Or not? I am contemplating this very thing in my new listening room.

Maybe the experts will chime in soon.

[jk@home]

Diffusion needs a minimum distance between the treatment and the listener, for it to work optimally. So having 10' ceilings, you may be OK, depending on what you use, and the distance you have.  I use absorption on my 8' ceilings, as the panels are only 4' - 5' from my ears. Using 1d QRDs on the front wall, as they are 10' away from the chair.

Some folks will argue that a small room will show little benefit with diffusion, but I noticed an improvement with the QRDs in mine. On the other hand, placing poly diffusers at the side wall reflect points, which worked great with my old Maggies, was too much (think the term is ringing?) with the present KEF speakers.

[Big Red Machine]

Look at my gallery pic. I use diffusion on the ceiling and sidewalls to great effect. Eight foot ceiling.

I like live much better than "dead".

[Hipper]

Before investing any money in ceiling panels I suggest you experiment first to see if it really will make a difference.

It will firstly depend on your speakers and if they have a wide or narrow vertical dispersion. My speakers for example have ribbon tweeters which I'm told have a thirty degree vertical dispersion. When I tried some foam glued on the ceiling at the reflection points I noticed no change, and the dispersion pattern explains that.

If you've already got some absorption material you might be able to temporarily place it on the ceiling, perhaps by jamming a couple of wooden poles between the floor and ceiling. You could also try putting something on top of the speakers so it sticks out enough to prevent sounds going to the ceiling reflection point.

[andycsb]

Thanks everyone for your help. Really appreciate it.

[Glenn Kuras]

If this was a mastering or control room, I would say absorption for sure. The point is you want to hear, within the first 20ms only what is coming out of the speakers. Not the speakers plus the 0-20ms reflection from the sidewalls/ceiling.  In that first 20ms, the brain cannot  separate the reflection from the direct sound so it translates it to sound like smearing.  It makes it harder to pinpoint panning and so on.  Diffusion will decrease that reflection, but not totally, unless your ceiling is really high or your room is wide. Generally speaking to hear the stereo imaging "proper" you want all reflections, in the first 20ms down 20 db.  Now with all of that said, some people like the sound with a bit of the reflection, so in a two channel room it is personal preference.  Some believe (which is not untrue) that it sounds wider with diffusion over absorption, which it does,  but it is not totally accurate with the recording. 

Glenn,
GIK Acoustics

Diffusion needs a minimum distance between the treatment and the listener, for it to work optimally. So having 10' ceilings, you may be OK, depending on what you use, and the distance you have.  I use absorption on my 8' ceilings, as the panels are only 4' - 5' from my ears. Using 1d QRDs on the front wall, as they are 10' away from the chair.

Some folks will argue that a small room will show little benefit with diffusion, but I noticed an improvement with the QRDs in mine. On the other hand, placing poly diffusers at the side wall reflect points, which worked great with my old Maggies, was too much (think the term is ringing?) with the present KEF speakers.

plus one!

[oneinthepipe]

I didn't have diffusion, and I used absorption panels hanging from the ceiling.  to determine placement, I held a panel over my ex-wife's head and in front of and behind her, and the panel's placement had a significant effect on the sound.

[poseidonsvoice]

I use alternating rows of GIK GRIDFUSORs along with 242's on my 10.5 ft ceiling for both the 1st and 2nd row of seats. Basically the area between your speaker and your listening positions is where you want to treat and like others said the vertical dispersion, off axis response (and how that compares to your on axis response) along with your ceiling height and hence distance from the acoustic treatment, will determine how much and what kind of ceiling treatment can help. If you have line sources it won't help as much. The most important criteria though is to have these measurements at hand, so unless the manufacturer provides you with them or if it is done by a reputable 3rd party, i.e. Sterophile's Atkinson or the National Research Council of Canada, Harmon/JBL's lab, etc...you may be shooting in the dark. Many manufacturers will not provide you with "raw" vertical off axis response curves because they don't consider it important (so they haven't measured it) or it may be truly atrocious looking (at which point you should put absorbers on your ceiling!). If you do enquire, try to get ones that are not overly smoothed, so no 1/3 octave smoothing. 1/10th octave would be great above 300 Hz (Schroeder frequency), but not commonly offered.

Best,
Anand.

[jk@home]

...The point is you want to hear, within the first 20ms only what is coming out of the speakers. Not the speakers plus the 0-20ms reflection from the sidewalls/ceiling.  In that first 20ms, the brain cannot  separate the reflection from the direct sound so it translates it to sound like smearing. ... 

Glenn,
GIK Acoustics

plus one!

At an average room temperature and humidity, this is around 17 feet, correct? Asking cause I stink at math.

In my case, the speakers are 3-1/2' to 4' off the front wall QRDs, and the listening chair is 13' off that wall.