Room gain and Me... (1 Viewer)

[Seth_L]

I'm attempting to compute my room gain for my room. Currently I have my full 7.1 setup in a 14x13x8 room. I used the Room Modes.xls spreadsheet to compute the various frequencies. It seems the lowest two frequencies are at 40Hz and 43Hz which seems to agree with what I've observed with my SPL meter.

My question becomes what happens below that point. Some people have said that you get a 12dB per octave increase in the SPL below that point. Some information I've come across seems to indicate that room gain has a 'Q' of .6. This gives a different approximation of the room gain than the 12dB per octave rule of thumb.

Which is correct?

Seth

 

[Richard Greene]

You do get 12dB/octave rise below the lowest room mode in a sturdy well sealed room. If there are many open doorways and other leaks you may get less than 12dB/octave.

I once attempted to measure this at home by hauling a heavy subwoofer outside for a 2-meter ground plane measurement in my driveway... my numbers showed a room gain starting at

about +9dB per octave and then increasing to about +15dB/octave. I've seen measurements posted on the internet ranging from +9dB/octave to +15dB/octave by people who used much better measuring equipment than me.

Forget about room gain -- you've got stacked room modes at near 40Hz. and that usually means a big room boom ... save up $130 for a Behringer Feedback Destroyer to reduce output at 40Hz.

 

[Seth_L]

Forget about room gain -- you've got stacked room modes at near 40Hz. and that usually means a big room boom ... save up $130 for a Behringer Feedback Destroyer to reduce output at 40Hz.

I've already got two of them. I'm well covered on that front. My current sub doesn't seem to excite them too much, but my front mains had nearly a 10dB spike at 40Hz. I switched them over to small and set the crossover to 40Hz which took care of the problem.

Seth