[JohnR]

I'm wondering about the early reflections from the floor and ceiling. Representative diagram, with direct sound in blue and reflections in red:



So I'm wondering, rather than try and put something up on the ceiling (and/or floor), why can't the reflections be pre-emptively reflected somewhere else? Like this:



While not terribly attractive, it would be pretty cheap to do... I do realise that it will have no effect on T30 etc, but that's not the aim.

Anyone tried something like this?

[Guy 13]

Hi JohnR and all Audio Circle members.
If it's not attractive, most will walk away from it, even if it improve the sound.
Cheaper: Yes.
Easier to install, again: Yes.

Guy 13

[WireNut]

JohnR,

I love you man, but honestly, I think ceilings need to be treating if you can afford it and don't mind looking at it, I'd do it if I had the cash..Think about it, yeah, it will make a difference in anyone's listening environment.....

Look at the Whisperwave Clouds here:

http://www.acousticalsolutions.com/70~whisperwave-clouds

[JohnR]

Hi Guy, true, but still I think it's worth exploring the options.

Hi Wirenut, thank you, I may end up doing the ceiling but I don't think 2" of foam will do it. I'm lucky that I have beams running along the length of the ceiling that I can fasten something between. But there's a ceiling fan in the way.

I did some measurements, interesting results, the answer so far is that it "sort of" works....

[JohnR]

Here's the impulse response measured with one speaker and bare floor. You can see the strong reflection from the floor at 1.4ms and the reflection from the ceiling at 4 ms:



If I've got the dimensions right, this reflection should cause a dip at 400, a boost at 800, a dip at 1200, a boost at 1600, a dip at 2000. Let's see (1/6 octave smoothing):



So you if track the undulations of the graph, you can see that it's actually going up and down about where the floor reflection says it should. Could just be coincidence, but maybe not...

Next I stacked three bolsters midway between speaker and microphone, total 45cm high, 35cm deep, 60cm wide. You can see the floor reflection is absorbed a lot:



The effect on frequency response:



At 800 (well more like 900), 1200, and 1600, it seems to have not only removed the peaks and dips mentioned above but reversed them. No effect at 400 Hz, but for reasons I don't understand, the peak centered around 270 Hz has been reduced. (I thought that was ceiling effects, but maybe not...)

Then I replaced the bolsters with a piece of wood, 45x50cm in size. I had to put it on the floor. Impulse response:



The floor reflection is reduced although not as much as before. The frequency response now:



Similar effects between 800-2000 Hz, no difference below 800 Hz.

In case you're wondering if a rug makes any difference, here is the impulse response with a woollen rug about 12mm thick laid down between the speaker and the mic:



It does give a reduction in the reflection although not as much as either of the above two. Effect on frequency response:



A bit of effect around 900 Hz, a small amount at 1600 Hz, not much elsewhere.

No specific conclusion at this time. I'm thinking maybe something that is a combination of absorption and reflection that can be placed on the floor might be best. I'll think about how to test the ceiling reflection.

[AKLegal]

I have a drop ceiling in my listening room and, other than adding floor to ceiling bass traps in the corners, treating the ceiling had the biggest effect.   

[youngho]

So I'm wondering, rather than try and put something up on the ceiling (and/or floor), why can't the reflections be pre-emptively reflected somewhere else? Like this:

Depending on the reflector, there could potentially be issues with diffraction around the edges.

However, it's reasonably common to see the ceiling reflections directed towards the back of the room: http://www.theabsolutesound.com/articles/robert-harley-visits-transparent-audio-and-discovers-a-210-miracle-upgrade/, http://www.goodwinshighend.com/facility.htm#osiris (I think).

The wavelengths associated with the floor bounce effect might be a little large to reflect as you propose...

[JohnR]

Depending on the reflector, there could potentially be issues with diffraction around the edges.

Good point.

However, it's reasonably common to see the ceiling reflections directed towards the back of the room:

I guess the main thing I'm wondering is if putting the "whatever" closer to the speaker means it can be smaller. I've a few people coming over tonight for some listening, I'll see if I can convince them to hold bits of wood in the air while I measure 

The wavelengths associated with the floor bounce effect might be a little large to reflect as you propose...

Yes, it seems that it's only effective above a certain frequency.

[nwboater]

I have a drop ceiling in my listening room and, other than adding floor to ceiling bass traps in the corners, treating the ceiling had the biggest effect.

I also have a dropped ceiling and have not done any treatment yet. Would appreciate it if you'd explain what you did.

Thanks very much.

Rod

[plaf26]

Try a line source array.  They are VERY effective in public address applications, why not the home?  See Duran Audio and Newform Research.

[drummermitchell]

I have a drop ceiling with the vinyl coated fiberglass panels and will be replacing them with Realtraps 3"tiles,I believe they have the same absorption qualities of their minitraps,hopefully they will be here end of next week.
Looking forward to hear what they can do for the room.
I had replaced some sidewall panels(first reflections)with some HF mondos and I was shocked at the difference compared to the others.
They literally opened up what was inside the recording whether macro effects such as reverb ect,a lot more layering of the instruments now where before everything was just clearer,a huge upgrade compared to the others.
Here's hoping the RT ceiling tiles will give another big positive.
For the price and what RT's does for the music,for me a no brainer.
Will be slowly selling off my other traps and going Realtraps all the way,wouldn't have believed the difference until I heard it.
I really like it whether it's a component change or panel and you get a huge upgrade musically.
Been a bit of trial and error with some acoustic panels but at least I can sell with minimum loss ..

[Alex Reynolds]

Hey John,

Many studio designers opt for a similar strategy when treating rooms (read up about the Haas effect and a Haas kicker), and I'm quite fond of it too when it's used right. But there are a few things to consider with the way to go about it, and it certainly shouldn't really be done in the way you've shown.

Usually, how redirection works isn't to just shoot it backwards to the front of the room. The problem here is that, say the first reflection distance - speaker to wall to listener - is 8 feet. A reflector that reflects sound to the front of the room would cut it off from the first reflection point, but it can still very easily have a distance that wouldn't be much longer - you could have the reflection that goes speaker to reflector to front wall to listener, and that might only be 10 feet. Granted, this would be a longer distance and quieter reflection, so it'd be good, but not as good as it could be. Also, you have a much larger problem that is MUCH more sound other than the first reflection will be affected by this - you're interrupting a huge angle of dispersion, and also creating problems with diffraction that didn't exist before

Instead, a better idea is usually to redirect sound backwards AT the first reflection point. So, it basically amounts to having angled walls or installing an angled reflector that will shoot the sound backwards. And what you could do from there, is diffuse the sound that gets reflected to the rear wall - that way, no early energy is impeding on your response, yet all of the energy is moved to be dispersed later in an ambient break. This is basically why studio walls are usually splayed at an angle.

[JohnR]

Thanks guys for the thoughts. Alex, the angle would be about the same as something much larger on the ceiling, that's part of the idea - closer to speaker means less size. However, diffraction around the object is what seems to make them not have any effect below a certain frequency. Which wouldn't happen of course with something mounted on the ceiling.

So I've learnt something 

I forgot to do the actual measurement for the ceiling when the guys were over the other evening 

[JohnR]

Try a line source array.

Yes indeed. It's on the list of projects   

[AKLegal]

I also have a dropped ceiling and have not done any treatment yet. Would appreciate it if you'd explain what you did.

Thanks very much.

Rod

Completely missed your question but I'll reply anyway even though the thread is old.

I made frames the same size as my ceiling tiles out of some spare wood and wrapped them with white guilford of maine fabric.  I then stuffed fluffy R-30 insulation above them.  In my ceiling I was able to stuff 14 inches of insulation above each of my homemade panels.  It was alot of work but well worth it.  Alot of the more nasty bass issues I was having disappeared and early ceiling reflections were eliminated.

[tabrink]

Great thread.. Just found it..I actually used 4" foam covered in colorful fabric put up in a geometric and triangular pattern to make it look like it was something other than its intended purpose.
Several area rugs on the hard woods and would never  go back!