diffuser or absorption panels, which would you choose?


If you could only use one acoustical treatment in a room and you’d have to cover most of the walls and leave ceiling untreated, would you pick all diffuser or all absorption panels?
 

 

emergingsoul

That’s really just a silly either/or question.  Use what works best for the sound of your room.  I’d recommend diffusers behind your speakers and absorptive panels at first reflection points and possibly between your speakers along with maybe bass traps in the corners, but that’s just spitballing.  Contact GIK and see what they recommend.  I will say I intend on using these diffusers behind my speakers because they seem to work well, aren’t expensive, and look pretty cool…

 https://www.theabsolutesound.com/articles/2022-golden-ear-gik-acoustics-gotham-n23-5-quadratic-diffusers/

@soix

Those diffusers look like a good deal. That is a 3D diffuser and according to Anthony Grimani 3D diffusers work best in the back half of the room. Behind the speakers he recommends combo panels (absorbers with scatter plates.)

See the :39 minute mark in this video:

 

Not sure I like those gik diffuser panels, don't like the way they look.

I don't think anyone really knows what they're using and why. Some say use diffusers behind the speakers and some say use absorbers and for those who lack conviction, use a combo deal.

Truth is many rooms may not need acoustical treatment due to all the furniture, and pictures in the room already, which serve as diffusers.

Unless you're using diffusers in a large area in the room, most often they are probably a waste of time.  
 

The biggest challenge people tend not to focus on is what the hell you do with a ceiling. A wide open flat space the tends to be problematic, incredibly difficult to mount panels on.. Who wants to put holes in their ceilings? 
 

I'll put up a few absorption panels, behind speaker and at first reflection points and call it a day. I guess first reflection points are a bad thing. As Sound waves spread from a speaker the first reflection point is fairly big.
 

if I ever see a diffuser panel thats unique and really nice looking I'll get it.

 

 

Kota1

Thank you for the YouTube link

The video about diffusers is over an hour. What the hell are they talking about for an hour about diffusers?

The Stillpoints Aperture 2 do both and don't require as many to treat a room.

ozzy

Like most things audio , diffusion is not a simple or cut and dry subject. That’s why folks can go on and on about it lol

You can buy a book about diffusion if you prefer. Lots of folks build quadratic diffusers, as they can be a bit more simple to diy if you go that route.

 

If you have echo issues, use Corning 703 sheets covered in fabric of choice on the walls on either side of listening space. Never use the black foam used in recording studios.

That’s the wrong approach. You first have to identify the problem before implementing the solution. The first step should be an analysis of the listening room. Acoustic companies offer that service. Best to contact them directly.

Is there an iPad app that I can use to evaluate my room? I have a acoustical microphone I can plug into my ipad so that's not a problem.

Check around your area to see if you can find a local builder. I found a guy via FaceBook (which I never use for such things) and he built panels and bass traps for a fraction of the cost of some of the ones you'll see offered. Granted, there's nothing wrong with those services, room correction, etc. Please don't hear me dismiss that. But I was able to build, add, and add a few more, finally with 2 diffusers for several $100 vs. thousands. And custom made, same insulation options, and I was able to get the precise sizes for my room. 

There is no such thing, you need both. Any research you do will tell you that. Wish it was that simple.

OP

Diffusers behind the speakers on the front wall. Absorbers on the front wall will close the stage, speakers will not disappear as the stage will be behind the speakers; don’t believe, try it. Diffusers on the front wall will disperse the reflections and you will hear an improvement in both depth and width, and speakers disappear, at least that’s my experience. Putting a few random panels up on the front wall or only behind the speakers will not help much; best is as a large panel between the front speakers.

Multi diffusers/absorbers best on the side wall at the first reflection. You don’t want to kill the room but you do want to control it so the sound from your speakers will  hit your ears before the first reflection of the sidewalls. I do nothing on the back wall as you want reflections from the room. Speakers need a room for many reasons… it’s about controlling the reflections. Simple test, is take your system outside and hear how horrible it will sound. 

Can’t just do one or the other. Vicoustic is another manufacturer that make both products, which is what I use. Every room is different, and everyone has their opinion what’s right, so buy both types of panels and return what doesn’t work for you.

I suggest watching the hour long video because a lot to learn, and maybe watch others as you’ll probably discover they all support it each as it’s science/physics and can be tested and proven. Lastly pull your speakers into the room and same with your listening seat off the back or unlikely any treatment will help much.

Have fun and good luck.

Really depends. Assuming the room is mostly reflective, absorption.

You can kind of, poorly, simulate diffusion with absorption by using relatively small abosrbers (2’ x 2’ or smaller) and scattering them instead of making large solid areas.

So, I'd chose absorption over diffusion for this sake.

My experience matches what others have said.

Too much absorption will make the music sound dead, but some absorption is likely necessary. I tried the GIK Diffusor/Absorbers behind my speakers to start with and found the sound to be kind of flat. Replaced them with QRD diffusors and this made a big improvement. Deep, wide sound stage with a lively sound. 

Absorption or a combination of absorption and diffusion for the side walls (and ceiling), particularly at first reflection points, also helps a lot. I like to use "art panels" like those offered by GIK and others, with scatter plates which provide a mix of absorption and diffusion, and can be fairly attractive. 

If you have a small room and have to place your listening position close to the rear wall, absorption with a bit of diffusion (such as the GIK panels mentioned above) can make a big difference to the clarity of the music since your ear/brain has a hard time distinguishing the reflections from the direct sound when they are spaced so closely in time. 

Don't let anyone tell you that some rooms can get away without acoustic treatments, at least if you are striving for the best sound. In my experience, targeted acoustic treatments offer the best sound quality improvements for the money spent than anything else I've done to my system.  

Both I have bass busters in the corner then acoustic foam panels behind the speakers 2x4 panels as well as behind above, and first reflection panels on the side and a carpeted floor , it makes a Big difference no slap echo and still lively sounding.

The answer would depend entirely on a measured room response taking into account the on-axis response of the speaker. If the speaker has a flat on-axis response and room response mids-highs are elevated, I would pick absorption. If the room response is good, I would go for diffusion.

I would also consider the music I am listening to. A lot of "near live" stereo microphone recorded music and I would want broadband absorption because I cannot get a wide enough frequency range with diffusion. If I am listening mainly to studio, I would not be as concerned.

I see others have gone beyond the simple request in their answers. There is no single solution. Front wall treatment varies depending on what speaker to wall distance you are targeting. Room dimensions come into play, angles between speakers, walls and listening position, and as noted, your starting position concerning room response. Also, whether you will equalize / use DSP.

Is there an iPad app that I can use to evaluate my room? I have a acoustical microphone I can plug into my ipad so that's not a problem.

The sofware you are looking for is called Room EQ Wizard. I dont think it will run on an iPad, but it will run on any computer. Watch the instruction videos because it is not self explanatory but very informative if you use it correctly.

As already suggested, watch the YT videos mentioned.

I used a combination of absorption and diffusion, alternating panels, and keeping 1-2 feet between them. I went with only absorption panels on the front wall and diffusion/absorption on the back wall.  Alternating diffusion and absorption on the side walls.   Bass traps in the upper room corners.  None on the ceiling. It’s made a huge difference in my 12’ x 20’ x 8’ room. Used only for home theater. There is much better clarity in movies, better dialogue, much tighter bass and overall a more immersive experience.

If you were only to do one thing to a room it would be big bass absorbers on each side wall, cover the wall with them. Not the corners, the side walls. Getting bass under control is job 1, always.

I'll take the bait. I would use only absorption.

Why? Because I can control how much I use.

I would treat the front 1/3 of the room first to deal with first reflection issues. Then I would proceed with caution.

Having said that, I don't use specialized products. I use furniture and wall hangings and thick Persian rugs with heavy felt underlayment.

Has anyone listened to a room with the old concrete acoustic ceilings? They were the first gen version before the softer asbestos version came out it the late 60s and 70s. I had a house built in the late 50s and no room has sounded as good from a clarity and bass perspective.

My thinking is that bass goes right through and is reflected back with softer absorptive/diffuser materials but that the concrete material has a small but noticable effect on all frequencies.

Ceilings with this material cannot be scraped. The whole ceiling needs to be cut out...that's why they're still around. Flipping a house with this ceiling is not cheap.

I've never seen concrete ceilings? Is this for a bomb shelter? 

I have a basement with a cement finished wall which have a rough surface and Nice acoustically but the basement ceiling is so damn low it's a pointless exercise. But the ceilings in these basements tend to be fiberboard tiles versus plaster and this is quite nice actually. But still the ceilings are so damn low. 
 

 

As you see, lots of contradictory advice making a basic understanding  difficult to grasp. The solution is to educate yourself by reading the science and then proceed with some confidence. It is a science but you can start by addressing the most important treatment which will get you a long way in the right direction.

I have posted a fair bit on this so you could read some older posts of mine. Once you have heard the amazing improvement you can then decide if you want to take it further by measurement which is inexpensive. For the cost of a beer and hamburger you can get a microphone and then download REW for free.

Know also that every room needs treatment. It does not depend on your type of furnishings etc. Ignore those that say: "I just use a rug and drapes and my sound is fantastic."  All that tells you is that they have never heard a properly treated room.

Whether you use absorption and/or diffusion depends on the size of your room as does the required time for the sound to decay. This decay should be as near as possible across the spectrum and is known as RT60, being the time it takes for the sound to decay by 60dB usually about 300ms.   All this info is on the net.

If you approach a professional acoustician and they don't ask for room dimensions just run away.

Small rooms require mostly absorption

Mid sized rooms require both

Large rooms require mostly diffusion

And all rooms require bass traps. In fact if you only do one thing then put bass traps in the corners. A floor to ceiling BT in the 2 front corners will have a huge effect.  Google super chunk DIY BT's    You will unavoidably have some nasty peaks and nulls. This is where  the BTs help, they smooth out the room response. Get this right and you no longer hear the room, you hear the recording venue.

  Next:  Add broad-band absorbers at first reflection points.

The problem with a small room is the inability to place the diffusers far enough from your ears.

 

 

I use both absorbtion and diffusion. Agree with those who stated it was best to place diffusers behind speakers. I have combined quadratic diffusers, large bass traps and have absorbing panels at first reflection points. That's the front half of my room. Behind the seated position is wide open. The sound is beyond the capabilities of the equipment alone. Extremely important to treat the room.

In my case, in my room and my equipment,  the result using diffusers is 3D imaging, separation between instruments, clear sound. I encourage you to try with N7 panels at the back of the speakers. It’s a kind of magic in the image sound.

Later, when music is clarified, if you need to treat bass reflexions, you can use absorption, but  using absorbers, carpets, corners …

 

I have chosen diffusion in the form of artificial Ficus trees.  My room needed help from the lower midrange up.  The artificial Ficus trees, layered sometimes two or three deep, broke up the sound in the room giving only the sound produced directly from the speakers to my ears.  The difference was well worth the small expense. I discovered that the deeper the trees were layered, particularly BEHIND the speakers, the more the impact on lower frequencies.  6 feet deep effectively damped frequencies a little below 200hz.  

And the added benefit was a big increase in WAF. 

The ones I picked up were 5 foot tall models U$60 each from "At Home" home decorating store.  

@lemonhaze Very interesting info.  Thank you.  

@bpoletti Who knew fake ficus trees could be an audiophile tweak?  I wonder if real ficus trees sound more natural and provide more air?  Heh heh. 

@soix 

I first saw them used at T.H.E. SHOW at CES maybe 10 years ago.  There is a very prominent high end electronics manufacturer that uses them in his listening room to help control reflections and give him a more accurate reference system.  My room has a lot more problems than his room, so I have a lot more deadening needed.  And that requires MORE artificial Ficus trees scattered around the room perimeter.

I think the effect is more about the number / density of the leaves more than natural vs. artificial.  

 

 

I made an error in describing the artificial Ficus trees I'm using.  They are 6 feet tall, not the 5 foot models.