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Absorbtion x Diffusion ratio
Posts: 2
June 20, 2016 - 8:58 am


Hi everybody,
beside some ceiling panels on the first reflection point and few rugs on the floor, I´m planning to treat ALL the walls in my listening room with acoustic panels. The question is
- is there a common rule of how much of the wall surface should be treated in % to preserve liveliness in music recordings (I´m 99% of the time in classical music) or it´s better to do measurement from listening position with f.e. REW to find current state of RT60 time and decrease this reverb time with ac. treatment to some value which is common to classical music?

- what´s the difference in treating the first reflection points with absorbtion vs. diffusion?

- if I remember correctly, there´s no given height of quadratic diffusor in any calculator. What is changing with diffusors height? Is there a height-limit after which there´s no larger benefit = the added height is pointless?

What are yours experiences?

Posts: 389
June 22, 2016 - 7:46 am

The first objective you must achieve is a definition of your room usage. Each usage live, voice, mix, mastering, and listening all have different acoustic treatment requirements to achieve the best quality sound within that room size and volume. Treating all the wall surfaces may or may not be desirable.

Diffusion on the side walls is dependent on distance and objective. Diffusion on the side walls creates a broader sound stage with less center image focus. This may or may not be desirable for your needs and requirements. Diffusion height is dependent on listening position height and distance from the diffuser .

RT60 times are subjective and dependent upon the end users preferences. Some like a more "dryer" room that has low times and some prefer a more "live" room with more of the room sound entering into the room acoustic.

Posts: 4
June 24, 2016 - 6:09 am


My experience is most error on too much absorption and not enough diffusion. Excessive absorption and the room is too dry and the music loses the excitement. Rooms need both diffusion and absorption and getting the balance right is the trick. If you are looking to achieve an RT60 of 25-30ms, you could remove all your treatment and add pieces strategically and measure. Make a note before measuring if the sound is improving or not. It's also easy to rely too much on measurement and not enough on our own ears.

I too listen to classical music (and jazz). A very dynamic piece is The Firebird Suite: II. L'oiseau de feu et sa danse (The Firebird) from the Minnesota Orchestra Showcase, Eiji Oue (Conductor), This piece of music is a good test for proper balance of room treatment.

Just my 2 cents.

Posts: 389
June 24, 2016 - 8:34 am

Mark is correct. Use measurements and ratios as starting points. This will assist you with what treatment type, how much to use, and where to place it. Remember, in the end, it is the emotional connection you have with your music that is the most important. Acoustical treatment is just a tool like your amplifiers and speakers to assist you in connecting with your music. Sometimes you need more tools for the job, sometimes less.

With classical music, you want lots of air and space. You want big, full sound at all frequencies. You must manage the low end with classical or you will be disappointed. Everything builds on the low end. Diffusion will be a must for middle and high frequencies.

Lets look at your room size and volume first along with your speaker size and listening pressure levels. Fill out the information in this link and lets see where we need to start.

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