[Jonas_h]

Hello,

My room currently has a absorbing ceiling, but there are many reflective walls. I have bought some cheap 2" foam to test if treatments on walls will be a good choice. Would you say, that the improvement is worth the "trouble"? I would cover the walls with compressed mineral wool (Ecophon/Rockfon) which is made for wall panels.



ETC before extra foam treatment

ETC with new extra treatment.

My RT60 graph is shown here:

The 2" panels are not very effective below 250hz which is clear from the graph above.

I am afraid that the sound will be too "dull" if walls are made absorbing. I did some listening tests with music, and it sounded good. But because I was not able to do quick A/B listening tests with and without foam, it is difficult to compare.

Would appreciate some input and advice

 

[SAC]

Just a few quick comments.

First, forget the RT60's. ...wrong calculation in the wrong space. You do not have a reverberant soundfield for which the statistical calculations assume and are applicable. Saver the RT60 for large acoustical spaces - generally generated by driving the space with an omnidirectional dodec speaker - not a directional source...

Instead for modal behavior you use waterfalls/cumulative spectral decays (convolved from a frequency response with NO smoothing applied...).



First, regarding specular reflections, you need to resolve the existing reflections to their paths and points of boundary incidence. This determines the surgical placement of absorption.

As far as the foam....hmmm....Something is amiss.

I am curious as to why you are damping the reflection at ~4ms. Note your reflections are already down ~47 dB!!!! This is already an EXTREMELY DEAD room! My first question is how/why?

And then after applying 2" foam, the result from what we can tell is a damping of arrivals at ~2, 4, 10, 17.5, 23 & 25 ms, and with an increase at ~1 and 7ms.:gulp: ALL from applying some 2" foam? Something else is going on.

So, as far as the reflections, I am curious as to how you chose which to address and why... and how you managed to address so many at different times (and a few new ones appearing - unless they are reflections from the absorption - but at different times?) without something else having changed.

 

[Jonas_h]

Just a few quick comments.

First, forget the RT60's. ...wrong calculation in the wrong space. You do not have a reverberant soundfield for which the statistical calculations assume and are applicable. Saver the RT60 for large acoustical spaces - generally generated by driving the space with an omnidirectional dodec speaker - not a directional source...

Instead for modal behavior you use waterfalls/cumulative spectral decays (convolved from a frequency response with NO smoothing applied...).



First, regarding specular reflections, you need to resolve the existing reflections to their paths and points of boundary incidence. This determines the surgical placement of absorption.

As far as the foam....hmmm....Something is amiss.

I am curious as to why you are damping the reflection at ~4ms. Note your reflections are already down ~47 dB!!!! This is already an EXTREMELY DEAD room! My first question is how/why?

And then after applying 2" foam, the result from what we can tell is a damping of arrivals at ~2, 4, 10, 17.5, 23 & 25 ms, and with an increase at ~1 and 7ms.:gulp: ALL from applying some 2" foam? Something else is going on.

So, as far as the reflections, I am curious as to how you chose which to address and why... and how you managed to address so many at different times (and a few new ones appearing - unless they are reflections from the absorption - but at different times?) without something else having changed.

Thanks for your input! I will generate the waterfall later.

The treatments in the room consists of an absorbing ceiling (3" mineral wool), two 3 feet 11¼ inches by 3 feet 11¼ inches 2" mineralwool panels behind the listening position and one 3 feet 11¼ inches by 1 foot 11⅝ inches 2" mineral wool on the sidewalls. Thats the green graph.
The reason I have the room so "dead", is because I want to replicate the sound from the cinemas. I dont think it is too dead at all.

The "extra" foam-treatment I am testing covers the whole side wall (10 feet by 7 feet) and and covers a big window in the room. I used many foam-panels when testing which explains how I treatet so many reflections.

Would you say the before graph is good enough?

 

[SAC]

Assuming you like a dead space, I would have surgically absorbed the sparse reflections at ~1 & 3ms (on the chart) and diffused the various sparse returns at ~ 10, 17.5, 23.5 and 25 ms.

Also, you could experiment with diffusing the first significant return at ~4ms to see if you could not make it a bit more temporally spread out while not losing too much gain.

But I would not indiscriminately add yet more absorption. I would personally be removing all but what is absolutely needed for surgical treatment specifically to solve problems.