REW Beta Release Superpoze room simulation modal distribution to measurements

[Silverprout]

Hello,
Is there any way to superpoze the room simulation frequency response and modal distribution to measurements please ?

 

[John Mulcahy]

Not the simulation response, but you can show the mode locations by ensuring "Show modal frequencies" is checked in the graph controls and entering the room dimensions in the Modal Analysis section of the EQ window.

 

[Silverprout]

Not the simulation response, but you can show the mode locations by ensuring "Show modal frequencies" is checked in the graph controls and entering the room dimensions in the Modal Analysis section of the EQ window.

The modal frequencies don't appear, could you tell me what i'm doing wrong please ?

 

[John Mulcahy]

Did you do this?
...entering the room dimensions in the Modal Analysis section of the EQ window

Note it is the EQ window the dimensions need to be entered in, not the room simulator.

 

[Silverprout]

Did you do this?
...entering the room dimensions in the Modal Analysis section of the EQ window
Note it is the EQ window the dimensions need to be entered in, not the room simulator.

Thanks
The first spike is damped by a very large cupboard full of clothes in the right side of the room, could you explain me why the calculated spikes are slightly offseted of the spikes of the measurement curve ?

 

[John Mulcahy]

Room surfaces are often not quite parallel, not rigid and not uniform, and rooms have things in them, all of which shift the actual response compared to the simplified theoretical response.

 

[Silverprout]

Room surfaces are often not quite parallel, not rigid and not uniform, and rooms have things in them, all of which shift the actual response compared to the simplified theoretical response.

I can modify the "surface absorptions" in the "room simulation" window in order to have more accurate results but the most important parameters are the room dimension and the mic position.

Could you explain why there is no mic position in the modal analysis section of the EQ window please ?

 

[John Mulcahy]

Because the frequencies at which the modal resonances occur don't depend on the mic position, that only affects their amplitudes.

 

[Silverprout]

I try to reach the full potential of your software, but i'm still a little bit lost, since i can't modelize the wavelets propagation in my brain.
There is a zone of cancelation in the center of the room and the more you go away from this zone, the more the spikes have amplitude, the distribution is also affected by difractions and delays.

Is there a way do define graphically a "safe zone" with measurements in the room that is less disturbed by room modes ?
Instead of only thinking about trying to stay near the center of the room and run fastidious matrix measurement for each identified (by measurements) room mode.

 

[John Mulcahy]

There aren't any safe zones as such - the centre of the room is usually quite poor, as it is at a null for odd axial modes. There are plenty of suggestions about how to position yourself and your speakers to get the best balance of sound though, here are a few:

http://www.hifiportal.co.uk/Articles/Article0034-SettingUpSpeakersInARectangularRoom.pdf
http://arqen.com/acoustics-101/room-setup-speaker-placement/
http://rtaylor.sites.tru.ca/2013/05/08/loudspeaker-placement-in-small-rooms/
http://realtraps.com/art_room-setup.htm
http://www.acousticfrontiers.com/room-modes-101/
https://www1.crutchfield.com/Learn/learningcenter/home/speakers_roomacoustics.html

 

[Silverprout]

There aren't any safe zones as such - the centre of the room is usually quite poor, as it is at a null for odd axial modes. There are plenty of suggestions about how to position yourself and your speakers to get the best balance of sound though, here are a few:

Thanks, for these very interesting readings.
All my room reflections are at less than 6ms of delay, so i'm working on louspeaker lobing and active room mode damping, wich seems to be perhaps possible at low listening levels IMHO.

It should be usefull to implement a tool to calculate and plot first reflection delay times as a function of listener and loudspeaker placement.
http://rtaylor.sites.tru.ca/2014/11/03/lateral-reflections-in-rectangular-rooms-code/