Room Gain

Does anyone actually know some sort of mathematical relation(s) that describe room gain?

Assuming a room is a rectangular prism, it shouldn't be that hard to calculate room gain for a given location. I just don't have the faintest idea what sort of relations can describe it. Has anyone actually researched this to the point of developing some solid details?
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Ignite:

Here is a chart:
http://www.speakerbuilding.com/content/1020/rge.gif

Here is another chart that seems to show that room gain applies to high frequency sounds as well, because of the size of the speaker baffle:
http://www.speakerbuilding.com/content/1020/rge-bafl.gif

Here is the article that accompanies both charts:
http://www.speakerbuilding.com/content/1020/

I must admit that I am somewhat surprised by the second chart. Anyway, this gives you an idea.

Pyle once told me that at 16 Hz, room gain commonly amounts to 9 dB. By this chart, it is about 7 dB. Since I am sure that any given room will likely vary from either chart, I think that is accurate enough.

[Edited by kelticwizard on 11-25-2001 at 09:52 AM]
 

CarMan

Member
2003-03-12 1:18 am
Reno
Couldn't get your link there kelticwizard, but it seems that room gain depends on the size of the room a lot once it gets smaller than about 10 feet square on each side (I did some listening in a closet with a subwoofer while testing it there to see how it sounded, which incidentally was the 2nd best place in the room). Smaller cars also seem to enjoy an increased effect as well. For example;

2 door 5 seater, sport coupe
flat response down to at 20 hz, windows closed

Same box in a van

0db at 30hz
-5db at 25hz
-7db at 20hz

I think the lower frequecies start to raise volume faster as the cabin size decreases, but this is all based on personal experiences, using an analogue db tester and a test disc with synthed sine waves. Sorry only the very low end is given, didn't have problems with the higher frequencies.
 
kelticwizard said:
I must admit that I am somewhat surprised by the second chart

I think that you're right kelticwizard. The second chart looks like a 6dB drop due to diffraction, with the room gain from the first chart added.

I suppose that it's a bit strange to call the second chart "room gain" as this would be the response in an open field and in fact a room would act against these diffraction effects, depending on the distance between speaker and wall. I haven't read the article though, so ...

Steve
 
You are right CarMan IMO. Room gain is usually 6dB/okt with dropping frequency. The point where the gain starts depends on the size (volume?) of the room. The smaller the room, the higher the starting point of the 6dB/okt curve. But up to now I did not find a proper formula for it.