The actual t60 is 0,28-0,3.
For a room used for speech, that's a little low, but not by a huge amount. It should probably be more in the range 0.4 - 0.45 for a room that size. It would seem that there's just too much absorption overall, and not enough reflection/diffusion. But it might also be the case that the absorption just isn't balanced well across the frequency spectrum.
Without seeing actual acoustic test data from the room, it's hard to give you advice on what to do since we don't know what the problems actually are! If you could run a REW test in there and post the results, that would help.
The room is used for talking and listening to music on 2 or 3 different small speaker systems.
Is this for some type of speaker evaluation system? Or just a music listening room? Also, optimizing for music and also for speech isn't that easy, as there are different acoustic recommendations for each. If you could be more specific about what the room will be used for, and also provide some photos, that would help too.
I think what makes it awkward could be peaks from axial modes or the rining from those modes and the loss of more high end frequency.
That's possible, but getting actual acoustic data would be the only way to be certain. A "boxy" sound is usually due to over-absorption of one frequency range, and/or a lack of reflection/diffusion in another frequency range.
Set up a REW test with the mic in the normal listening position, and using the best speakers that you would normally use in there, set up in their normal positions. The draw a diagram of where all those are in relation to the walls, floor, and ceiling, and post that too.
Where is the best position to place the absorbers to have the best effect in general against the mud.
Corners. Corners are always best, because you get a free "boost" in effectiveness, and you get to deal with the modes from two axes at once, or all three axes if you are covering the tri-corners well.
Would it be centered on the walls to dampen the axial modes...
Axial modes aren't just related to the center of the wall: they are related to the entire wall, from corner to corner, and floor to ceiling. And since all modes terminate in the corners, by putting the trapping in the corners you are assured of hitting all the modes, not just the axial ones.
However, using lots of thick absorption for your bass traps will also kill the high end of the spectrum, and the mids too. You need to compensate for that, by using selectively tuned foils in front of the absorption. The foil will reflect the high frequencies back into the room, to keep it lively, while still allowing the lows through to be damped by the absorption.
And if I measure different locations in the room....after what should I look (the ringing) or more the avareged frequency response?
Both!
In fact, look at everything! There's a lot of acoustic things happening all at once in any room, and the overall psycho-acoustic impression that your brain receives is a combination of all of them. First and foremost is to ensure that your modal issues are damped as much as reasonably possibly, but you also need to be looking at SBIR issues (which can have a big effect), as well as flutter echo, diffusion, specular reflections, frequency response, etc. Possibly the most important view is the ETC data, provided that you understand how to interpret it. But look at everything, then treat the biggest issues one by one, but also making sure that you are not causing other issues in the process.
I´m planning to install some wood or diffusors on the absorber if needed to give some reflections back.
Don't do that until you understand what the problems are! If you don't know what you are dealing with, then how would you decide what frequency to tune the diffusers too?
First do the test, then identify the problems, then decide how to deal with each of them, one by one, or in related groups.
what is more effective to bring down strong axial modes or to give better speach quality
Speech isn't usually affected by strong axial modes. The frequencies are totally different. Axial modes are usually a problem in small rooms up to about 200 Hz, but mostly below around 100 Hz. There's very little useful energy in speech at such low frequencies. Yes, there are some fundamentals down there, but actual intelligibility is much higher up the spectrum. The problem with speech intelligibility is usually more in the mid range and the lower part of the highs.
- Stuart -
thank you....try to answer as best as i can.
), a 1m cat tree, 2barstool